Native Bee Visitation on Florida Native Wildflowers

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Title:
Native Bee Visitation on Florida Native Wildflowers
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1 online resource (99 p.)
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english
Creator:
Buckley,Katharine Denise
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University of Florida
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Gainesville, Fla.
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Thesis/Dissertation Information

Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Entomology and Nematology
Committee Chair:
Ellis, James D.
Committee Members:
Daniels, Jaret
Hall, Harlan G

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Subjects / Keywords:
bees -- native -- pollination -- pollinator
Entomology and Nematology -- Dissertations, Academic -- UF
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Entomology and Nematology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
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Abstract:
Declining pollination services in Florida is a cause for concern as several economically-valuable crops in Florida (blueberries, watermelons and other cucurbits, citrus, avocados, etc.) require pollination to some degree. Declines in bee populations associated with pollinating many of these crops have been correlated strongly with the loss of forage. Consequently, investigators outlining bee conservation programs recommend improving forage availability for bees using several management schemes, the most successful of which has been planting seeds from wildflower species known to attract bees. The goal of my study was to identify and quantify the attractiveness of several native Florida wildflower species to native bees for use in native bee conservation. To that end I surveyed bees on 20 different wildflowers species planted in 5 mixes at 4 different sites to compare bee visitation rates. Ten of the wildflower species (Chamaecrista fasciculata (Michaux), Coreopsis basalis (A. Dietrich), Coreopsis lanceolata Linnaeus, Coreopsis leavenworthii Torrey & A. Gray, Gaillardia pulchella Fougeroux de Bondaroy, Helianthus angustifolius Linnaeus, Monarda punctata Linnaeus, Rudbeckia hirta Linnaeus, Trifolium incarnatum Linnaeus and Trifolium repens (Linnaeus) were significantly more attractive to bees than were the other species. The attraction of these wildflower species to bees was not uniform and varied according to time of year, time of day and tribe to which a bee belonged. Overall, G. pulchella, C. lanceolata, and R. hirta were the most attractive wildflower species to the bees observed in this project. The data I collected highlight what native Florida wildflower species are attractive to bees in general and to some bee tribes specifically. This information can be used by the general public and/or farmers interested in providing forage for local bee pollinator species. Combined with extension and outreach materials and programming, the data provided in this study hopefully will aid the conservation and restoration of native bee habitat.
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In the series University of Florida Digital Collections.
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Includes vita.
Bibliography:
Includes bibliographical references.
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Description based on online resource; title from PDF title page.
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This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Katharine Denise Buckley.
Thesis:
Thesis (M.S.)--University of Florida, 2011.
Local:
Adviser: Ellis, James D.
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RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2013-08-31

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UFE0043415:00001


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1 NATIVE BEE VISITATION ON FLORIDA NATIVE WILDFLOWERS By KATHARINE D. BUCKLEY A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2011

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2 2011 Katharine D. Buckley

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3 To those who knew I was weird and encouraged me to study bugs anyway

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4 ACKNOWLEDGMENTS I thank my advisor, Dr. Jamie Ellis and committee members Drs. Jaret Daniels and Glenn Hall for all their advice and guida nce. I thank Dr. David Jarzen for the generous gift of the use of his laboratory, supplies and expertise in palynology. I thank James Colee for helping me with statistics. I also thank my fellow graduate students Eddie Atkinson, Jason Graham, Pablo Herrera and Dr. J. Akers Pence as well as research technicians Jeanette Klopchin, Mark Dykes, Michelle Kelley, Jonnie Dietz and Ben King for their help and support. I especia lly thank my family for their love and encouragement of my desire to study bugs, including letting me keep a tarantula in my bedroom.

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5 TABLE OF CONTENTS page ACKNOWLEDG MENTS .................................................................................................. 4LIST OF TABLES............................................................................................................ 7LIST OF FIGURES.......................................................................................................... 8ABSTRACT..................................................................................................................... 9CHAPTER 1 INTRODUCTION.................................................................................................... 112 MATERIALS A ND METH ODS ................................................................................ 22General Site Information......................................................................................... 22Site Preparation and Establishment................................................................. 23Site Main tenance.............................................................................................. 24Vegetation Survey.................................................................................................. 24Bee Su rvey............................................................................................................. 25Primary Bee Surveys........................................................................................ 25Supplementary Bee Surv eys............................................................................ 26Pollen Su rvey.......................................................................................................... 27Statistical Analysis.................................................................................................. 293 RESULT S............................................................................................................... 43Overall Bee Attraction to Na tive Florida Wildflowers............................................... 43Principle Overl apping Flow ers.......................................................................... 43Spring Time Period........................................................................................... 44Late Summer/Early Fa ll Time Period................................................................ 44Late Fall Time Period....................................................................................... 45Wildflower Visitati on by Bee Tribe.......................................................................... 45Apini (A pidae)................................................................................................... 45Spring time period...................................................................................... 45Augochlorini (H alictidae)................................................................................... 46Bombini (Apidae).............................................................................................. 46Principle overl apping flow ers..................................................................... 46Late summer/early fall time period............................................................. 47Eucerini (Api dae).............................................................................................. 47Late fall time period.................................................................................... 47Halictini (H alicti dae).......................................................................................... 48Principle overl apping flow ers..................................................................... 48Spring time period...................................................................................... 48Late summer/early fall time period............................................................. 48

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6 Late fall time period .................................................................................... 49Megachilini (Megach ilidae) ............................................................................... 49Principle over lapping pl ants....................................................................... 49Late summer/early fall time period............................................................. 49Late fall time period.................................................................................... 50Xylocopini (Api dae).......................................................................................... 50Principle overl apping flow ers..................................................................... 50Late summer/early fall time period............................................................. 50Pollen Wa shes........................................................................................................ 51Pollen Wash Means......................................................................................... 51Pollen Wash Perc entage Like lihood................................................................. 51Pollen on Bumble Bees.................................................................................... 51Pollen on Hali ctus poeyi................................................................................... 524 DISCUSSION......................................................................................................... 79Benefits of Wild flower Mixes................................................................................... 79Native Bee Use of W ildflower Species.................................................................... 79Developing a Florida Wildflower Mi x That Is Used By Native Bees........................ 81Study Limi tations.................................................................................................... 83Further Inve stigat ions............................................................................................. 84Conclu sion.............................................................................................................. 88LIST OF RE FERENCES............................................................................................... 90BIOGRAPHICAL SKETCH............................................................................................ 99

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7 LIST OF TABLES Table page 1-1 Examples of bee fora ge studies......................................................................... 212-1 Wildflowers assessed in t he st udy...................................................................... 322-2 Wildflower drought toleranc e and months of bloom time.................................... 332-3 Wildflower sources, % pure seed, % germination rate, and ecotype/source of the wildfl owers.................................................................................................... 342-4 Grams of wildfl ower seed per pl ot...................................................................... 352-5 Total bees obser ved and co llected..................................................................... 363-1 Bee visitation of the tested wildflower species.................................................... 533-2 Bee tribe visitation by plant species.................................................................... 543-3 Pollen wa sh data................................................................................................ 543-4 Pollen wash percentage like lihoods.................................................................... 543-5 Bumble bee pollen wash means......................................................................... 553-6 Bumble bee pollen wa sh percentage likelihoods................................................ 553-7 Halictus poeyi pollen wash means...................................................................... 553-8 Halictus poeyi pollen wash percentage lik elihoods............................................. 554-1 Bee-plant associati ons from lit erature................................................................ 89

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8 LIST OF FIGURES Figure page 2-1 Map of University of Florida Plant Science Research and Extension Unit near Citra, Fl orida ....................................................................................................... 372-2 Plot spacing at the wildflower sites..................................................................... 382-3 Layout of plots.................................................................................................... 392-4 Grouped Aster-Like pollen at 400x magnification under a light microscope....... 402-5 Gaillardia pulchella pollen at 400x magnification under a light microscope........ 402-6 Helianthus angustifolius pollen at 400x magnif ication under a light microscope......................................................................................................... 412-7 Chamaecrista fasciculata pollen at 400x under a light micr oscope.................... 412-8 Monarda punctata pollen at 400x under a light mi croscope............................... 422-9 Example frame locations (in grey) for a veget ation survey................................. 423-1 Bee visitation (LS-mean number of bees /100 blooms/minute) on the principle six wildflower species......................................................................................... 563-2 Bee visitation (LS-mean number of bees/100 blooms/minute) on the spring blooming fl owers................................................................................................... 13-3 Bee visitation (LS-mean number of bees/100 blooms/minute) on the late summer/early fall bl ooming fl owers.................................................................... 603-5 Apini visitation (LS-mean num ber of bees/100 blooms/mi nute).......................... 633-6 Augochlorini overall flower vi sitation (LS-mean number of bees/100 blooms/minute)................................................................................................... 653-7 Bombini visitation (LS-mean number of bees/100 blooms/mi nute)....................... 13-8 Eucerini visitation (LS-mean number of bees/100 blooms/minute) on late fall blooms................................................................................................................ 693-9 Halictini visitation (LS-mean number of bees/100 blooms/mi nute)....................... 13-10 Megachilini visitation (LS-mean number of bees/ 100 blooms/ minute).................. 13-11 Xylocopini visitation (LS-mean number of bees/100 blooms/minute)................... 1

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9 Abstract of Thesis Pres ented to the Graduate School of the University of Florida in Partial Fulf illment of the Requirements for t he Degree of Master of Science NATIVE BEE VISITATION ON FLORIDA NATIVE WILDFLOWERS By Katharine D. Buckley August 2011 Chair: James D. Ellis Major: Entomology and Nematology Declining pollination services in Florida is a cause for concern as several economically-valuable crops in Florida (blueberries, watermelons and other cucurbits, citrus, avocados, etc.) require pollination to some degree. Declines in bee populations associated with pollinating m any of these crops have been correlated strongly with the loss of forage. Consequently, investigators outlining bee conservation programs recommend improving forage availability for bees using several management schemes, the most successful of which has been planti ng seeds from wildflower species known to attract bees. The goal of my study was to identify and quantify the attractiveness of several native Florida wildflower species to native bees for use in native bee conservation. To that end I surveyed bees on 20 different wildflowers species planted in 5 mixes at 4 different sites to compare bee visitation rates. Ten of the wildflower species ( Chamaecrista fasciculata (Michaux), Coreopsis basalis (A. Dietrich), Coreopsis lanceolata Linnaeus, Coreopsis leavenworthii Torrey & A. Gray, Gaillardia pulchella Fougeroux de Bondaroy, Helianthus angustifolius Linnaeus, Monarda punctata Linnaeus, Rudbeckia hirta Linnaeus, Trifolium incarnatum Linnaeus and Trifolium

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10 repens (Linnaeus) were significantly more attr active to bees than were the other species. The attraction of these wildflower species to bees was not uniform and varied according to time of year, time of day and tribe to which a bee belonged. Overall, G. pulchella C. lanceolata and R. hirta were the most attractive wildflower species to the bees observed in this project. The data I collected highlight what native Florida wildflowe r species are attractive to bees in general and to some bee tribes s pecifically. This information can be used by the general public and/or farmers interested in providing forage for local bee pollinator species. Combined with extension and out reach materials and programming, the data provided in this study hopefully will aid the conservation and restoration of native bee habitat.

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11 CHAPTER 1 INTRODUCTION Since The Forgotten Pollinators was publis hed in 1996 (Buchmann & Nabhan 1996) there have been an increasing number of published studies on pollinators. This is due, in part, to the decline in the number of managed and feral European honey bee colonies in North America and bumble bee p opulations and range in North America and Europe (Corbet et al. 1991; Watanabe 1994; K earns et al. 1998; Kremen & Ricketts 2000; Steffan-Dewenter 2005; Goulson et al. 2005; Biesmeij er et al. 2006; Grixti et al. 2009; Aizen & Harder 2009). Butterflies also have been the topic of research and media attention due to declining populations of several widely distributed and well-known species such as the monarch butterfly and multiple previously common species in Europe (Van Dyck et al. 2009). Taken together, these declines have prompted discussion about a pollinator crisis. While some scientists are skeptical about such a crisis, many remain concerned (Ghazoul 2005a; Steffan-Dewenter et al. 2005; Ghazoul 2005b; Klein et al. 2007; Kluser & Peduzzi 2007; National Research Council of the National Academies 2007; Murray et al. 2009; among others). To address the issue of pollinator decline in North America the National Research Council investigated the issue, then published a book detailing their recommendations (National Research Counc il of the National Ac ademies 2007). The research presented here touches on a few of their goals for wild pollinator conservation: Conservation and restoration of habitat Basic information on the resource require ments of a wider va riety of pollinator species is needed to improve habitat management Encourage the stewards of a wide r ange of urban and rural areas to adopt pollinator-friendly practices and also to encourage information exchange and outreach

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12 Identify and implement practices that promote the availability of diverse commercial and wild pollinators. Animal pollinators are es timated to pollinate 90% of all flowering plants (Buchmann & Nabhan 1996), and 75% of crop plants either need pollinators or produce better yields when pollinated, accounting for nearly a third of the human diet (Klein et al. 2007). Many animals, including bu tterflies, moths, flies, beet les, birds, bats, mammals, and even reptiles are pollinators. Hymenoptera, specifically bees, undisputedly remain the most efficient pollinators because immatu re and adult bees feed solely from flowers. Honey bees are responsible for providing most of the pollination services in modern agriculture (MacGregor 1976). Unfo rtunately, honey bees in North America and globally are under threat from pests, paras ites, diseases, pesticides, poor management practices, low honey prices, and bad public ity due to Africanized honey bees, among many other stressors (National Research Council of the National Academies 2007). More bee pollinated crops are grown today than ever before, and honey bee populations no longer can meet the demand (A llen-Wardell et al. 1998; Aizen & Harder 2009; Aizen et al. 2009). Fortunately, native bees (non-Apis species of bees) can help supplement honey bee pollination services. In highly heterogeneous landscapes, native bees can perform most pollination services (Winfree et al. 2008). Crop fields close to natural areas can be pollinated almost entirely by native bees in some circumstances (Kremen et al. 2004). Pollination services provided by honey bees and native bees together can increase fruit set in several crops (Greenleaf & Krem en 2006). For some crops, like onions and squash, native bees are more efficient pollinators than honey bees (Parker 1982;

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13 Canto-Aguilar & Parra-Tabla 2000), and can be managed in high enough numbers to pollinate the target crops adequately (Shipp et al. 1994). In many cases however, providing one managed native bee species probably is not the best solution to the ongoing pollination cr isis. A better solution, especially in wild systems, is the maintenance and propagation of a diversity of pollinators rather than one or a few species (Klein et al. 2003; Font aine et al. 2006). High diversity in pollinator species is best because populations of indi vidual bee species have been shown to vary considerably from year to year (Willi ams et al. 2001), making reliance on any one species risky. Bee communities experience vari ations not only during the year (different spring/summer/fall compositions are common), but also year to year with different dominant species in a multiple year cycle (Williams et al. 2001). In the interest of increasing or conserving diversity in native bee populations, it is important to understand bee biology and ecology (Freitas et al. 2009). Bees are very diverse in their life histories, especially t heir food and nesting habits. As such, there are several different issues that need to be addressed in a conservation or pollinator diversity management plan. These include genet ic structure, nest habitat availability, bee health as affected by external factors such as pesticides and various pests/pathogens, and food resource availability. All bees have an unusual genetic structure in common, a stru cture that makes them more susceptible to inbreeding: males are haploid and females are diploid (termed haplodiploidy). Because male bees contain only a single copy of DNA while females have two, males only contribute half as mu ch genetic diversity within the population compared to that contributed by diploid females. Also, the likelihood of a fertilized egg

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14 being homozygous at the sex-determini ng locus increases as a bee population decreases, thus increasing the probability of a diploid male being produced. Diploid males cause female mortality directly (as they would have otherwise been female) and indirectly because their offspring are essentially sterile (Zayed 2009). Haplodiploidy is not the only unusual genetic structure associated with bees. While most bees are solitary, many are social. Higher degrees of sociality decrease the number of reproductively active individuals in the total population as numbers of nonreproductive workers increase. Fewer repr oductives lead to lower genetic diversity within the population, thus increasing the chances of inbreeding depression (Zayed 2009). In bee conservation and management program s, genetic diversity is an indicator of healthy bee populations. The problem with controlling bee genetics is that to date genetic testing cannot replace a pedigree for predicting inbreedi ng (Grueber et al. 2011). Since many bee species of conservation importance oft en have cryptic nesting habits as well as relatively unknown life histories, espec ially mating systems (Zayed 2009), pedigrees for wild bees currently are very difficult to determine. Because of the difficulties associated wit h monitoring genetics, the monitoring of nest sites can be done to give some indicati on of the health of bee populations (Frankie et al. 1998). Creating suitable nesting habitat is one of the three most common methods currently used in bee conservation and m anagement programs (the other two being pesticide use reduction and increasing bee for age plants). Several native bee species are managed successfully for crop pollinatio n by providing suitable nesting habitat. Managed native species include the blue orchard bee ( Osmia lignaria ), the alkali bee

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15 ( Nomia melanderi ), the alfalfa leafcutter bee (not technically native, but a notable managed solitary species) ( Megachile rotundata ), and several bumble bee species ( Bombus spp. ) (Johansen et al. 1978; Peterson et al. 1992; Bosch & Kemp 2001; Velthuis & van Doorn 2006). These bees all are managed by inducing populations of the bees to nest where pollination services are needed. Many other bee species can be trap-nested in bamboo, different sized straws, and holes drilled into wood (Krombein 1967). Ho wever, most bee species nest in the ground (Michener 2007) so other management schemes are necessary. One of the most recommended methods of encouraging ground nesting bees to nest in an area is to keep the ground as undisturbed as possible by limiting tilling (Vaughan et al. 2004). Furthermore, one can create soil mounds or ban ks in a bees preferred nesting soil type since sites with bare soil are encouraged (Vaughan et al. 2004). Keeping a record of where bees are nesting from year to year or how many bees are using trap-nest sites can give one a reasonable estimation of bee populations in an area. Bee health is another factor one must consider when developing a conservation or pollinator diversity program. Bee health is a ffected by many external factors (weather, climate change, pesticides, poor nutrition, pr edators and parasites, etc.) perhaps the most damaging of which are pesticides. Many common insecticides are known to affect native bee populations (Johansen 1977; Kevan 1999; Desneux et al. 2007). Even at sub-lethal levels, some insecticides hav e been shown to cause navigating problems in adult bees, leading to higher forager mortalit y, decreased food availability in social colonies and lower fecundity among solitary bees whose level of reproduction is limited by the amount of food for which they can fo rage in their lifetimes (Desneux et al. 2007;

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16 Winfree 2010). Other pesticides, includ ing some common fungicides, have been associated with direct mortality in honey bees (Desneux et al. 2007), which typically serve as a surrogate for native bees in 50% lethal dose (LD50) tests required by the EPA before a pesticide can be registered (OECD 2010). To a lesser extent (largely for research purposes) bumble bees, alfalfa leaf cutter bees and alkali bees also have been used in insecticide testing (Johansen 1977; Drescher & Geusen-Pfister 1991; Thompson & Hunt 1999). Johansen (1977) showed that all species tested displayed a different LD50 to the same chemicals, thus calling into question the idea that honey bees can be used as a model for the effects of pesticides on other pollinator species and pollinator communities (Thomson & Hunt 1999; Barmaz et al. 2010). Herbicides and weed management also ma y affect bee populations negatively (Johansen 1977). Mowing weedy roadsides c auses a noticeable decline in bee populations because the weeds flowers provide forage when nearby crops are no longer flowering (Benedek 1996). Similarly, herbicide use also can reduce available forage for pollinators in an area. Since m any solitary bees are constrained by the distance they can fly and have foraging seasons that outlast a given crops flowering period, bee populations near crop fields w here intensive weed man agement is practiced often suffer. From the standpoint of pestici des (herbicides included), conservation and management practices for native bees includ e reduced pesticide use as an important component (Vaughan et al. 2004). Though genetic structure, nest habitat av ailability and bee health are important considerations in native bee conservation sc hemes, the availability of food resources (i.e. nectar and pollen) is of major importance, and, therefore, the s ubject of my thesis.

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17 Bees are flower obligates, i.e. bees acquire their food exclusively from flowers. Adult bees use nectar as their carbohydrate source and actively gather pollen which is fed to bee larva as their protein source (Michener 2007). Some bees also collect volatile floral oils, which may be used as mating pheromones (Eltz et al. 1999). This mutualism between flowers and bees has led to the theory that the abundance and diversity of bees in an area can be estimated with a comb ination of pan traps near flowers as well as active netting from flowers (LeBuhn et al 2003, Matteson et al. 2008). Due to bees often cryptic nesting habitat, colle cting from flowers is usually the most reliable method of monitoring bee populati ons (Roulston et al. 2007). Bee dependence on flowers for food also ha s led to the theory that planting flowers that bees actively utilize could improve their populations. Declines in bee populations have been correlated strongly with the loss of fo rage, especially in bumble bees (Benedek 1996; Goulson & Darvill 2004; Bi esmeijer et al. 2006; Carvell et al. 2006; Kleijn & Raemakers 2008; Decourtye 2010). These declines have been especially prevalent with the current tendency towards agricultural intensification (Kim et al. 2006). Therefore a major tool used in bee conser vation programs has been increasing forage for bees using several different management schemes, the most successful of which has been sowing plant mixes known to attract bees (Carvell et al. 2004; Pywell et al. 2006; Carvell et al. 2007; Potts et al. 2009). It has not been conclusively demonstrated that planting wildflowers increases bee popula tions and diversity. It has, however, been shown that bee visitations and diversity withi n a crop strongly increases with proximity to natural habitat, although actual crop production showed only a weak increase (Ricketts et al. 2008). Increasing suitable habitat in agricultural areas has been shown

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18 to increase population of several other groups, so providing flowers for bees would likely increase their numbers as well (Goulson 2003) The subsequent problem that arises lies in determining which flowering plants are benef icial to various local bee communities in attempting to restore th is natural habitat. Researchers in Europe, and especially Great Britain, have pioneered most of the studies on bee plant preference (Carvell et al 2004; Pywell et al. 2005; Pywell et al. 2006; Carvell et al. 2007; Potts et al. 2009). T he majority of these studies include bees and plants that are not native to North Am erica and in some cases are considered invasive weeds (Winfree 2010). To date, the only studies of native bee forage preference in the United States have been in Washington (Patien et al. 1993), California (Vaughn et al. 2004; Frankie et al. 2005), Mi chigan (Tuell et al. 2008), and New Jersey (Williams et al. 2009). Many of these studies, including those in Europe, include information regarding the bees surveyed on specific plants or in a specific area without considering the amount and density of available blooms (Winfr ee 2010). The problem wit h this strategy is that it tests bees use of flowers, but not their actual preference for certain flowers (Winfree 2010). A more attractive but less abundant plant may have fewer visits than a less attractive but highly abundant plant. Consequently, studies that do not include vegetation information such as survey data or standardized plots of plants cannot confirm bee preference of a particular flower, rather only bee use of that flower. There is a solution to this to this dilemma. Plant surveys should be conducted when determining bee preference for a given plant because the information can be used to estimate the relative abundance of fl owers on which the bees are being found

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19 (LeBuhn et al. 2003). There are a few exampl es of investigators who have used this method (Johnson 1980; Kells et al. 2001; Will iams 2005; Williams et al. 2010). Another technique that can be used to estimate bee preference for a given plant is to grow different plant species at standard dens ities and conduct bee surveys on these standardized plots (Tuell et al. 2008). While Patien et al. (1993), Vaughn et al. (2004), Frankie et al. (2005), Tuell et al. (2008), and Williams et al. (2009) did survey a large number of wildflowers native to North America, many of t he plants and/or bees surveyed were not native to central Florida. For concerned Floridians this is a problem because wildflowers native to Florida may support native pollinators better than woul d non-native plants (Frankie et al. 2005). Native plants are less likely to behave inva sively, less likely to support invasive pest insects, and more likely to be adapted to local conditions (Rieff 2011). Consequently these beneficial qualities will make the general public more likely to use native plants, especially since they likely will require le ss fertilizer, pesticides and watering than nonnative plants (Floridas Water Management Districts 2009). Though certain plants are known to be highl y attractive to bees, different plants bloom at different times throughout the year. Furthermore, local bee communities change throughout the year (although eusocial species often ar e found year round, which is why they benefit most from year round forage). As such, anyone developing a native seed mix that would in clude seeds of plants attractive to a wide variety of bee pollinators needs to consider the bloom per iod of tested plants as well as the abundance of bees seasonally.

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20 Despite multiple studies on the compos ition of the bee community in Florida (Graenicher 1930; Pascarella et al. 1999; Deyr up et al. 2002; Hall & Ascher 2010), and publicly accessible keys to Florida bees wit h flower associations (Pascarella 2008; Ascher & Pickering 2010), no comparative study of native bee flower preference has been conducted in Florida, or anywhere el se in the south-eastern United States. Declining pollination services in Florida is cause for concern, as several economicallyvaluable crops in Florida (blueberries, wa termelons and other cucurbits, citrus, avocados, etc.) require pollination to some degree (MacGregor 1976). Conservation in general is also a concern. For example, Fl oridas main ecosystem pine flatwoods, has a diverse plant understory including many wildflower species which require insect pollination to reproduce (Myer s & Ewel 1990; Whitney et al. 2004). Therefore, the conservation of native Florida bees, which likely are a major pollinating group in this ecosystem, should remain a high priority. The goal of the current study is to i dentify and quantify the attractiveness of several native Florida wildflower species to native bees. I hypothesize that different common Florida bee species will exhibit vari ed preferences for a host of wildflower species. Further, I expect bee pr eference for certain plants to change during the year. I hope that this information will contribute to the development of a pollinator seed mixture that would support the greatest number and di versity of bees throughout the year. Such a mix potentially would provide year-round fo rage for native bees in otherwise florally depauperate areas such as agriculture-intense regions. My long term goal is that the information I present herein could be used to develop conservation practices for native bees, thus protecting the pollinat ion services they provide.

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21 Table 1-1. Examples of bee forage studies Location Study Reference California and New Jersey Analyzed native versus non-native bee forage plants bees did not prefer non-native and non-native abundance did not affect bee diversity Williams et al. 2010 California Tested attractiveness of common ornamental plants to different bee groups for bee population survey purposes in urban areas Frankie et al. 2009 UK Tested seven grassland management strategies for bumble bee response responded best to sown flowers Potts et al. 2009 Michigan 43 native perennials tested for bee preference for use in bee conservation Tuell et al. 2008 New Jersey and Pennsylvania Bee visitation rates across organic and conventional farms suggest landscape effects important and bee conservation best focused on intensively farmed areas for best effects Winfree et al. 2008 UK Compared Environmental Stewardship schemes for bumble bee use recommend legume flower mix with greater seasonal bloom diversity and/or diverse perennial forage plants Carvell et al. 2007 UK Comparison of annual and perennial mixes different bee species preferred different mixes Carvell et al. 2006 UK Comparison of seed mixes on bumble bee diversity and abundance wildflower and forage plant mixes performed best Pywell et al. 2006 UK Four management strategies for field margins compared for bumble bees wildflower seed mix significantly better Pywell et al. 2005 Finland Field margin effects on bumble bee diversity flowers over grass, most important are a few flower species' abundance during bumble bee reproduction period Bckman & Tiainen 2002 UK Six flowers planted at various times and ratios, evaluated for different polli nating insect preferences Carreck & Williams 2002 UK Five treatments of field ma rgins indicate sown mixes better than natural regeneration Meek et al. 2002 UK Bees prefer natural re generation over cropped field margins Kells et al. 2001 Washington 21 herbaceous bee forage plants evaluated for planting near cranberry farms honey bee and bumble bee preferences differ Patien et al. 1993

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22 CHAPTER 2 MATERIALS AND METHODS General Site Information Five different wildflo wer mixes were plant ed (Table 2-1) at four sites at the University of Florida Plant Science Res earch and Extension Unit (PSREU) near Citra, Florida (N29'36.28" W82'11.90"). There we re six plots at ever y site: (1) control, (2) basic annual flower mix, (3) basic perennial flower mix, (4) diverse annual flower mix, (5) diverse perennial flower mix and (6 ) a mixture of annual a nd perennial flowers. The wildflower species were selected based on potential attractiveness to pollinators, their status as regionally native or naturalized, seed availability, low cost, similar management, and representing a di versity of bloom times (s pring/summer/fall) (Table 22, Table 2-3). Eighteen species of native Fl orida wildflowers were selected along with three naturalized wildflowers: Phlox drummondii Hooker, Trifolium incarnatum Linnaeus and T. repens Linnaeus (Table 2-1). Coreopsis basalis (A. Dietrich), C. lanceolata Linnaeus, C. tinctoria Nuttall, Gaillardia pulchella Fougeroux de Bondaroy, Monarda punctata Linnaeus, Helianthus angustifolius Linnaeus, P. drummondii and Rudbeckia hirta Linnaeus were also specifically chos en because they are commonly planted along Florida roadsides as part of the Florida Department of Transportations wildflower program. A few of these spec ies either never grew or produced too few flowers to attract bees significantly. The four sites at the PSREU were > 1000 m from one another (Figure 2-1). All sites were prepared during the fall of 2009. Ea ch site was ~75 21 m, containing the six plots which were 15 3 meters eac h and spaced 10 m from one another (Figure 2-

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23 2). The type of wildflower seed mix planted was randomized among the plots within a site. 1) Site 1 N29 24.621' W082 10.828' (Figure 2-3a) 2) Site 2 N29 24.163' W082 10.124' (Figure 2-3b) 3) Site 3 N29 24.610' W082 08.360' (Figure 2-3c) 4) Site 4 N29 24.227' W082 08.912' (Figure 2-3d). Site Preparation and Establishment I followed methods suggested by Florida wildflower experts (Janet Grabowski, USDA, NRCS Florid a state office; M.J. W illiams, USDA, NRCS Florida state office; and Jeff Norcini, Oecohort, LLC) for planting t he 5 seed mixes at each site (Norcini & Aldritch 2004). Site preparation began September 15, 2009. Plots were measured and laid out at all sites following which the plots were treat ed with glyphosate (TouchdownTM) at 3 qt/acre mixed with Induce pH, a non-ionic surfactant, at 1 pt/acre. After seven days, the Bahia grass in the pl ots was cut with a Hinik er 5700 Flail-chopper which cuts the grass to 5-8 cm tall and va cuums up the cuttings. On 3 November, the plots were treated with glyphosate again. Later that week, herbicide resistant perennials, including Mexican Tea ( Chenopodium ambrosioides Linnaeus), Hairy Indigo ( Indigofera hirsuta Linnaeus), Benghal Dayflower ( Commelina benghalensis Linnaeus) and Nutsedge ( Cyperus spp.), were removed with shov els. On 17 November, the plots were burned to remove the remaining dead thatch. Although the thatch burned well, the hard roots of the Bahia grass in many places did not, forming thick mats in some places. It was determined that a Lely Rod Weeder (Lel y USA, Pella, IA) would be able to break up the mats while disturbing the soil as little as possible. Several passes from different directions were necessary to break up the root masses.

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24 Seeds were mixed beforehand at densit ies per acre based on manufacturers recommendations (Table 2-4). Chamaecrista fasciculata (Michaux) and Baptisia alba (Linnaeus) were scarified in tumblers wit h sandpaper to improve the chances of germination. All seeds were weighed carefully and individually bagged in preparation for planting. On 8 December, sites once agai n were raked with the Lely Rod Weeder and rolled with a 16 foot cylindrical roller. The seeds were mixed with 19L sand and spread over their respective plots using Scotts Pr o Turf Professional SS2 Drop Spreaders (The Scotts Company LLC, Marysville, OH). Plot s then were pressed with the roller in an effort to keep the seeds from blowing away. Sites were irrigated with 1.25 to 2.5 cm of water, once a week when < 0.6 cm of rain fe ll. Irrigation aided in seedling establishment. Site Maintenance Little maintenance was necessary once the wildflowers were established. Wild radishes (Raphanus raphanistrum Linnaeus) were weeded from Site 1 early in the season when they were growing in high d ensities. On 10 August, I removed large perennial weeds (most notably Hairy Indigo ( Indigofera hirsuta ) which resembled small trees) from all plots except the control. A few weeks late r, it was determined that Partridge Pea ( Chamaecrista fasciculata ) had established too densely and was shading out the other wildflower species in the annual mixes. Consequently, the Partridge Pea was thinned by roughly 25%. Vegetation Survey Vegetation surveys were conducted the day prior to the beginning of the intensive bee surveys, except for the first vegetation survey whic h was conducted the week prior to the first bee survey due to the length of ti me it took to perform. During the first vegetation survey, all plant stems, percent vegetation cover, and number of blooms in

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25 10, 1 m frames were noted for each plot at all sites. The frames were placed randomly in 10 different areas delineated wit hin a plot (Figure 2-9). This level of replication was necessary because of the pe rformance of varying plant species from one side of a plot to the other, this likely due to different amounts of watering or a slight slope throughout the plot causing differences in soil moisture and nutrients (Elzinga et al. 1998). During subsequent surveys, only t he number of blooms and percent bloom coverage were noted. Bee Survey Primary Bee Surveys The primary bee surveys were conducted at all sites every third w eek. Nine surveys were conducted from 11 May 4 November 2010. Each survey lasted two days, with two teams consisting of an observer and a recorder responsible for one site both days. The surveys involved observing bees on eac h plot at each site for 10 minutes, followed by 10 minutes of collecting bees fr om the plot. This was done once in the morning and once in the early afternoon ever y sampling day. For each plot sampling, the recorder would record all information fo r the observer, leaving the observers hands and eyes free. The recorder also was responsible for noting the weather conditions, and recording time, date, location, and sampli ng data for each survey (Figure 2-7). During the observation period, the observer would walk down the sides of the plot and tell the recorder which bees they saw (T able 2-5) and which flowers the bees were visiting. The recorder woul d write down the flower and b ee type per the observers comments. The observer walked the perimeter of the plot twice during the 10 minute observation period. During the first trip ar ound the plot, the observer would identify every new bee sighted. During the second trip, he/she only noted novel bees (species

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26 not seen during the first trip) or increases in the frequency of a previously observed bee species. For example, if 15 Bombus impatiens were seen during the first trip and 17 during the second, the greater of the two numbers was used. For each ten minute collection period, the observer randomly chose a side of the plot from which to collect in the morni ng, which was alternat ed during the afternoon sampling period. This was due to the possib ility of some of the flowers becoming damaged from the action of netting bees in the morning, so sides were alternated to avoid bias. Bees were captured using standard 45 cm diameter butterfly nets and were placed immediately into kill jars prepared wit h cyanide. After the collection period was over, the collected bees were placed into labeled vials and frozen in preparation for subsequent pinning and identificat ion. At the beginning of t he season, most bees seen on the wildflowers were captured as referenc e specimens. After several samplings, I discovered that many of the bees being captured were one species, Halictus poeyi which could easily be sight identified. After that, only one specimen of H. poeyi was caught during each sampling period, although samples of all other bees were collected for identification and for bee community composition determination (Table 2-5). Supplementary Bee Surveys Supplementary bee surveys were conduct ed every other week except those weeks on which the primary bee surveys fell. These surveys were conducted over all sites in one day by a team of two indivi duals Unlike the primary bee surveys, the supplementary surveys were conducted by su rveying each plant species for visiting bees for a total of 10 minutes at every site across all plots. Similar to the primary surv eys, the team consisted of a recorder and an observer. For ten minutes the observer would walk around all plots within a site containing a

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27 targeted plant species. Any bees seen on that plant during the ten minute observation period were recorded (Table 2-5). During th is time, voucher specimens of unknown species were captured (pinned an d identified) (Table 2-5) as were bees seen carrying large pollen loads (saved for the pollen survey). Bee species were identified using Michener (1994) and Pascarella (2010). All other insects were identified to family using Johnson & Triplehorn (2004). Voucher specimens are maintained at the Honey Bee Research and Extension Lab from both surveys. Pollen Survey To determine pollen use by the bees, I collected and pressed samples from each blooming wildflower species throughout the study. At the end of the study, I created reference slides of the pollen for each spec ies in order to creat e a pollen reference collection. To do this, I us ed the preparation technique for modern pollen and spores as outlined in Jarzen 2008. Permanent reference slides were created using the glycerine jelly techniques also outlined in Jarzen 2008. The pollen preparation method was as follows: The reference material (a single flowe r) was placed in 15 cc centrifuge tubes and half filled with 5% KOH. The tubes were placed in a hot water bath at about 90C for two to three minutes and then removed. The tubes contents were stirred with a glass rod and then poured through a fine meshed plastic screen into a clean 15 cc centrifuge tube. The 15 cc tubes were centrifuged at 1500 rpm for two to three minutes, decanted, and the contents in the tube were washed twice with distilled water and once with glacial acetic acid. To conduct a wash (fro m this point forward), the washing liquid was poured into the tube until the total vo lume reached approximately a centimeter from the top, unless other wise specified. The tubes then were centrifuged and decanted in preparation for the next wash.

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28 Once the washes were complete, the t ubes were half filled with acetolysis mixture (one part concentrated sulfuric acid to nine parts acetic anhydride) and placed in a hot water bath for 3-5 minutes. The tubes were removed and allowed to cool before centrifuging and decanting into a large beaker under running water. The contents of the tube were washed once with glacial acetic acid, twice with distilled water, and once with a 1:1 mixture of glycerin and distilled water. After decanting, the tubes were allowed to drain upside down overnight. The next day, a small cube of glycerine jelly was placed in the bottom of the tube and the tube placed in hot water bath unt il the glycerine jelly was completely melted. The resulting produc t was stirred thoroughly. One drop of the glycerine mix was pl aced onto a pre-cleaned microscope slide and a cover slide was pressed gently on the drop using toothpicks. The remaining glycerine mix was stored in individual vials at room temperature. The slides were allowed to air dry fo r at least 24 hours before they were sealed using Sally Hansen Hard as Nails clear nail polish (Coty LLC, Uniondale, NY). Bees visibly carrying pollen were captured in individual vials during the supplementary sampling for pollen collection analysis. They were stored in individual vials in a freezer until i dentification and pollen wash ing could be performed. The bees were washed according to the pollen washing proc edure outlined by Ellis and Delaplane (2008). A stock solution of 45 parts by volume 70% ethyl alcohol, 3 parts by volume liquid soap, and 2 parts by volume basic fuchsin at 5% concentration was prepared. This was added to the vials cont aining individual bees in quantities as follows: small bees (i.e., Lasioglossum spp.) = 0.125 ml; medium bees (i.e., large Halictus poeyi to Melissodes communis) = 0.250 ml; and large bees (i.e., Xylocopa and Bombus spp.) = 0.500 ml. After the addition of the stock solution, the vials were closed and vortexed for 1.5 minutes. As the pollen was not analyzed immediately following the addition of stock solution, the vials always were stirred using a vortex for at least 15 seconds prior to

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29 analysis. To determine the volume and type of pollen that individual bees were carrying, a drop of the pollen suspension was loaded into a Bright-Line Re ichert hemacytometer (manufacturer, city, state). A ll pollen grains within the c enter square millimeter were identified, counted and reco rded. Four samples were counted per bee. The four samples were averaged and, following the hemacytometers instructions, (1) multiplied by 10,000, (2) then multiplied by the milliliters of stock solution added to the bees vial. The resulting number is the approximate pollen load of t hat bee. Pollen was identified (Kapp et al. 2000) to one of six diff erent categories: Grouped Aster-like ( Coreopsis spp. and Rudbeckia hirta ) (Figure 2-4), Gaillardia pulchella (Figure 2-5), Helianthus angustifolius (Figure 2-6), Chamaecrista fasciculata (Figure 2-7), Monarda punctata (Figure 2-8) and Unknown. These groups of pollen were relatively easy to distinguish from one another. Most were very different shapes. For example, M. punctata pollen was spheroid with six furrows, while C. fasciculata pollen was a flattened oblong shape with two furrows on each side. All Asteraceae pollen in this study was a spiky ball, which is very typical of the family. Some were indistinguishable to me, hence the Aster-Like group. However, H. angustifolius had a significantly larger pollen grain size than the other Asteraceae in the study, and G. pulchella had a very distinctive two part spike. For comparative purposes, all included figures of pollen were phot ographed at exactly the same settings and magnification (Figure 2-4 to 2-8). Statistical Analysis To facilitate data analysis, the bee surv ey data was paired with the vegetation survey data to create the standard unit of measure: # bees/100 bl ooms/minute (number of bees visiting 100 blooms of a particular w ildflower species during one minute) which

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30 was the dependent variable. The overall bee survey data (grouping all bees together independent of bee species) were analyzed using a generalized linear model (GLM) procedure with an exponential distribution ( SAS Institute, 2010), recognizing plant species, the estimated number of blooms for that plant species, and the overall number of species in bloom in the plot as t he independent variables. Furthermore, the GLM procedure was run by morning and afternoon sa mplings as it had been noted previously during sampling that time may affect bee spec ies use of various wildflowers. The overall bee survey data then was analyzed by three ti me periods; spring (May though the first week of June), late summer/early fall (end of Ju ly to mid-October), late fall (beginning of October to early November) and a fourth period when the six longest blooming and most attractive plant species overlapped co mpletely in bloom. These species included Chamaecrista fasciculata, Coreopsis basalis Coreopsis lanceolata Coreopsis leavenworthii, Gaillardia pulchella and Rudbeckia hirta For each time period, only flowers that bloomed throughout the entire period were included in the analysis. Furthermore, I determined which wildflowers were used most by each bee tribe, the lowest taxonomic level that could be si ght identified reasonably during monitoring. Where possible (i.e. when enough data were co llected), bee tribe use of the various wildflower species was analyzed by time period using the GLM procedure already described (SAS Institute, 2010). For the pollen data, the means and standard error are reported; along with the percent likelihood that a bee caught on a species of wildflower will be carrying pollen from that flower species. T he two groups most captured ( H. poeyi and Bombus spp.)

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31 were analyzed separately and their means, st andard errors, and percent likelihood that they carried the pollen from the flower which they were captured were determined.

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32 Table 2-1. Wildflowers assessed in the study Scientific Name Common Name Family Sig. Asclepias tuberosa Linnaeus Butterfly Milkweed AsclepiadaceaeNo Baptisia alba (Linnaeus) White Indigo Fabaceae No Chamaecrista fasciculata (Michaux) Partridge Pea Fabaceae Yes Coreopsis basalis (A. Dietrich) Dye Flower Asteraceae Yes Coreopsis lanceolata Linnaeus Lanceleaf Coreopsis Asteraceae Yes Coreopsis leavenworthii Torrey & A. Gray Leavenworth's Coreopsis Asteraceae Yes Coreopsis tinctoria Nuttall Golden Tickseed Asteraceae Yes Eryngium yuccifolium Michaux Rattlesnake Master Apiaceae No Gaillardia pulchella Fougeroux de Bondaroy Blanketflower Asteraceae Yes Helianthus angustifolius Linnaeus Narrow-leaved Sunflower Asteraceae Yes Ipomopsis rubra (Linnaeus) Standing Cypress Polemoniaceae No Liatris spicata (Linnaeus) Spiked Gayfeather Asteraceae No Monarda punctata Linnaeus Spotted Bee Balm Lamiaceae Yes Phlox drummondii Hooker Drummond Phlox Polemoniaceae No Rudbeckia hirta Linnaeus Black Eyed Susan Asteraceae Yes Salvia coccinea Buchoz ex Etlinger Tropical Sage Lamiaceae No Solidago fistulosa Miller Pinebarren Gol denrod Asteraceae No Trifolium incarnatum Linnaeus Crimson Cl over Fabaceae No Trifolium repens Linnaeus Osceola Clover Fabaceae No Vernonia gigantea (Walter) Giant Ironweed Asteraceae No Osceola Clover is a cultivar of White Dutch Clover. Sig. implies either that a flower could not be used in the analysis (no = the s pecies either did not produce any blooms or did not attract enough bees to be used in statisti cal analysis) or that it could be used in the analysis (yes).

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33 Table 2-2. Wildflower drought tole rance and months of bloom time Bloom Time Plant Drought Tolerance JFMAMJ J A S O ND Asclepias tuberosa High XXXX X Baptisia alba High XXX Chamaecrista fasciculata Medium XXX X X Coreopsis basalis High XXXX Coreopsis lanceolata High XXXXX X Coreopsis leavenworthii Low XXXXX X X X Coreopsis tinctoria Low XXX Eryngium yuccifolium Low XXXX Gaillardia pulchella High XXXX X X XX Helianthus angustifolius Low X X Ipomopsis rubra High XXX Liatris spicata Low XX X Monarda punctata High XX X X Phlox drummondii High XXXX Rudbeckia hirta High XXXX X X X Salvia coccinea Medium XXXXXXX X X X Solidago fistulosa High X X Trifolium incarnatum Low XXX Trifolium repens Medium XX Vernonia gigantea Medium X X X

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34 Table 2-3. Wildflower sources, % pure seed, % germination rate, and ecotype/source of the wildflowers Scientific Name Wildflower Source % Pure Seed Germination Rate Ecotype/ Source Asclepias tuberosa ERNST Seeds 99.61% 80% CA Baptisia alba Florida Wildflower Cooperative 98% 80% FL Chamaecrista fasciculata ERNST Seeds 99.22% 21% FL Coreopsis basalis Florida Wildflower Cooperative 98% 65% FL Coreopsis lanceolata Florida Wildflower Cooperative 95% 65% FL Coreopsis leavenworthii Florida Wildflower Cooperative 85% 55% FL Coreopsis tinctoria ERNST Seeds 93.21% 62% NC Eryngium yuccifolium ERNST Seeds 79.42% 1% FL Gaillardia pulchella Florida Wildflower Cooperative 89% 85% FL Helianthus angustifolius Florida Wildflower Cooperative 95% 55% FL Ipomopsis rubra Florida Wildflower Cooperative 95% 75% FL Liatris spicata ERNST Seeds 87.09% 40% FL Monarda punctata ERNST Seeds 99.89% 87% SC Phlox drummondii Florida Wildflower Cooperative 99% 65% FL Rudbeckia hirta ERNST Seeds 99.80% 93% NC Salvia coccinea Wildseed Farms 99.97% 91% TX Solidago fistulosa ERNST Seeds 14.66% 14% FL Trifolium incarnatum Adams-Briscoe Seed Company 98% 80% GA Trifolium repens Adams-Briscoe Seed Company 99.65% 90% GA Vernonia gigantea Florida Wildflower Cooperative 85% 45% FL

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35 Table 2-4. Grams of wildflower seed per plot Plant AB AD PB PD Combo Asclepias tuberosa 18.00g Baptisia alba 4.01g 10.04g 4.62g Chamaecrista fasciculata 80.70g 40g 70.20g Coreopsis basalis 5.04g 2.52g 2.22g Coreopsis lanceolata 7.57g Coreopsis leavenworthii 1.26g 0.76g Coreopsis tinctoria 0.78g Eryngium yuccifolium 10.04g Gaillardia pulchella 12.60g 6.05g 11.50g Helianthus angustifolius 14.13g Ipomopsis rubra 4.88g Liatris spicata 6.38g 1.79g 1.79g Monarda punctata 0.50g Phlox drummondii 5.55g Rudbeckia hirta 4.70g 2.90g 1.74g Salvia coccinea 7.01g 5.04g Solidago fistulosa 5.04g 5.04g 5.04g Trifolium incarnatum 100.90g 100.90g Trifolium repens 15.20g 15.10g 15.20g Vernonia gigantea 5.42g 0.72g 2.17g Mix abbreviations refer to Perennial Basic (P B), Perennial Diverse (PD), Annual Basic (AB), Annual Diverse (AD), and Combinat ion of Annual and Perennial (Combo) wildflower mixes.

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36 Table 2-5. Total bees observed and collected TribeObs.GenusObs.Coll.Species Obs.Coll Anthidiini1 Anthidiellum 11 Anthidiellum (Loyolanthidium) perplexum (Smith)11 Apini87 Apis 87 9 Apis mellifera Linnaeus 87 9 Augochlorini17 Augochlorella 2 Augochlorella aurata (Smith) 2 Augochloropsis 2 Augochloropsis anonyma (Cockerell) 2 Bombini694 Bombus 694 60 Bombus (Pyrobombus) bimaculatus Cresson 2 Bombus (Cullumanobombus) fraternus (Smith)191 Bombus (Pyrobombus) impatiens Cresson19135 Bombus (Thoracobombus) pensylvanicus (DeGeer)13022 Colletini3 Colletes 33 Colletes thysanelle Mitchell 33 Epeolini Epeolus 3 Epeolus glabratus Cresson 1 Epeolus pus illus Cresson 2 Triepeolus 9 Triepeolus lunatus (Say) 7 Triepeolus rufithorax Graenicher 2 Eucerini163 Melissodes 16 Melissodes communis Cresson 16 Svastra 27 Svastra aegis (LaBerge) 226 Svastra petulca (Cresson) 1 Halictini3437 Agapostemon 13718 Agapostemon splendens (Lepeletier) 13718 Halictus 3278648 Halictus (Odontalictus) poeyi Lepeletier 3278648 Lasioglossum 2210 Lasioglossum (Dialictus) nymphale (Smith) 1 Lasioglossum (Dialictus) pectorale (Smith) 1 Lasioglossum (Dialictus) puteulanum Gibbs 1 Sphecodes 2 Sphecodes heraclei Robertson 2 Megachilini230 Coelioxys 12 Megachile 22959 Megachile (Acentron) albitarsis Cresson 433 Megachile (Litomegachile) brevis Say 2 Megachile (Litomegachile) mendica Cresson 16 Megachile (Argyropile) parallela Smith 1 Megachile (Leptorachis) petulans Cresson 2 Megachile (Sayapis) policaris Sa y 1 Megachile (Litomegachile) texana Cresson 4 NomadiniNomada 1 Nomada fervida Smith 1 Nomiinae1 Dieunomia 11 Dieunomia heteropoda (Say) 11 Xylocopini121 Xylocopa 121 6 Xylocopa (Schonnherria) micans Lepeletier435 Xylocopa (Xylocopoides) virginica (Linnaeus)51 Abbreviations refer to Observed (Obs.) and Collected & Identif ied (Coll.) bees. For some bee tribes, the identified bee species in t he last Obs. column are only a subset of the observed bees in that tribe. Bees in bold were those include d in the statistical analysis .

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37 Figure 2-1. Map of University of Florida Plant Science Research and Extension Unit near Citra, Florida. The four sites are labeled and separated by >1000 m. Permi ssion courtesy of Daniel L. Colvin. 1 1 4 3 2 1 2 3 4

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38 Figure 2-2. Plot spacing at the wildflower sites. 15m 22m 68m 10m 75m 3m

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39 Figure 2-3. Layout of plot s within: A) Site 1, B) Site 2, C) Site 3, D) Site 4. Note direction no rth. Abbreviations marking wildflower mixes in plots are as fo llows: AB = Annual Basic, AD = Annual Diverse, Combo = Combination of Annual and Perennial mixes, PB = Perenni al Basic, PD = Perennial Diverse. C ontrol is the control plot in which no seeds were sown. N PD Combo PB AD AB Control N AD Combo Control PD AB PB N Combo PB AD PD AB Control N AD PD PB AB Combo Control A B D C

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40 Figure 2-4. Grouped Aster-Like pollen at 400x magnification under a light microscope. Examples: A) Coreopsis lanceolata B) Coreopsis leavenworthii, C) Rudbeckia hirta Figure 2-5. Gaillardia pulchella pollen at 400x magnification under a light microscope. A B C

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41 Figure 2-6. Helianthus angustifolius pollen at 400x magnif ication under a light microscope. Figure 2-7. Chamaecrista fasciculata pollen at 400x under a light microscope.

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42 Figure 2-8. Monarda punctata pollen at 400x under a light microscope. Figure 2-9. Example frame locations (in grey ) for a vegetation survey. The large square outlined in black is a single plot. T he frames are 1 m PVC rectangles placed randomly in one of ten areas within the plot.

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43 CHAPTER 3 RESULTS Overall Bee Attraction to Na tive Florida Wildflow ers In order to determine the nativ e Florida wildflower species most attractive to bees, I analyzed bee attraction to the six dominant blooming species (those species that had the longest overlapping bloom throughout the study) as well as bee attraction to groups of wildflowers blooming in three different time periods. Regarding the latter, the attraction of bees to seasonally dominant flowers is important to know when attempting to provide year-round floral resources for bees. Principle Overlapping Flowers Six of the wildflower species planted attracted lar ge numbers of bees and bloomed from the first week of June through mid-October. These six spec ies were Chamaecrista fasciculata Coreopsis basalis Coreopsis lanceolata Coreopsis leavenworthii Gaillardia pulchella and Rudbeckia hirta These were the only wildflowers to bloom for an extended period of time as well as cons istently attract bees. For this study, I analyzed the number of bee visits/100 blooms/minute for the time period when all six species had overlapping bloom periods. Some of the wildflowers were significantly more attractive to bees than were others ( F =8, df=5, 524, P <0.01). Of the six main wildflower species, bees visited G. pulchella significantly more than all of the other species with the exception of C. lanceolata (Figure 3-1A). During morning hours, C. lanceolata and G. pulchella were visited by significantly more bees than were C. fasciculata and C. leavenworthii ( F =3, df=5, 265, P <0.01; Figure 3-1B). In the afternoon, bees visited G. pulchella significantly more than any other wildflo wer except C. basalis (F =10, df=5, 251, P <0.01; Figure 3-1C).

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44 Spring Time Period The spring sampling time during which the b loom period fo r most flowers overlapped occurred from the second week of May through the first week of June. This was the only time during which the clovers ( Trifolium incarnatum and T. repens ) bloomed. Additional bl ooming plants included C. basalis C. lanceolata C. tinctoria G. pulchella and R. hirta Bees visited G. pulchella significantly more than all other plants except T. repens (F =4, df=6, 89, P <0.01; Figure 3-2A). During morning hours, G. pulchella had the highest bee visitation rates, but its rates were not significantly different from those of C. lanceolata C. tinctoria or R. hirta (F =3, df=6, 37, P =0.02; Figure 3-2B). In the afternoon, G. pulchella and T. repens were visited by significantly more bees than were the other wildflowers ( F =2, df=6, 43, P =0.05; Figure 3-2C). Late Summer/Early Fall Time Period The late summer/early fall period time peri od lasted from the end of July through mid-October and is when the Dotted Horsemint ( Monarda punctata ) produced its main bloom. C. fasciculata C. leavenworthii G. pulchella and R. hirta also were blooming during this period. Overall, bees visited G. pulche lla significantly more than any flower except R. hirta (F =16, df=4, 326, P <0.01; Figure 3-3A). Duri ng AM hours, the flowers were visited equally by bees with the exception of M. punctata which was visited significantly less by bees than were any other wildflower species ( F =13, df=4, 167, P <0.01; Figure 3-3B). During the afternoon, G. pulchella was visited by bees significantly more than were the other wildflower species ( F =8, df=4, 152, P <0.01; Figure 3-3C).

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45 Late Fall Time Period The late fall time period lasted from ear ly October through early November and was when the Narrow-leaved Sunflower ( Helianthus ang ustifolius) bloomed. C. fasciculata C. leavenworthii G. pulchella, M. punctata, and R. hirta were in bloom as well. G. pulchella H. angustifolius and R. hirta were visited most by bees, though not more so statistically than C. fasciculata ( F =9, df=5, 142, P <0.01; Figure 3-4A). Bees did not prefer any wildflower species over another one duri ng the am hours ( F =2, df=4, 62, P =0.18). During the afternoon, bees preferred to visit G. pulchella H. angustifolius and R. hirta significantly more than the other test wildflowers ( F =8, df=4, 72, P <0.01; Figure 3-4B). Wildflower Visita tion by Bee Tribe Apini (Apidae) In Florida, the Apini tribe consists of only one species, Apis m ellifera Linnaeus or the Western honey bee. Honey bees visited some wildflower species more than others throughout the entire sampling season, t hough no clear patterns were observed ( F =26, df=6, 643, P <0.01; Figure 3-5A). Spring time period Although I occasionally saw honey bees at my sites th roughout the year, they only visited the sites enough to analyze flower visi tation rates for the sp ring sampling period. Honey bee s did not visit the wildflower sites enough in summer/fall to analyze those time periods. During spring, honey bees visited C. lanceolata significantly more so than the other flower species ( F =533, df=2, 69, P <0.01, Figure 3-5B). This pattern remained true statistically during t he morning sampling period ( F =387, df=2, 30, P <0.01, Figure 35C).

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46 Augochlorini (Halictidae) Augochlorini is the tribe that contains the green sweat bees. In Florida, it is composed of the genera Augochlora Augochloropsis and Augochlorella While these bees are common, I did not see them in suffici ent numbers at any time of the year to run seasonal analyses, so only an overall test (all wildflowers over all time periods) could be performed. The overall analysis did indicate b ee visitation preferenc e for some of the flowers though the pattern was hard to interpret due to the amount of absence data ( F =594, df=4, 643, P <0.01; Figure 3-6). That said, A ugochlorini bees were recorded from the fol lowing plant species: C. fasciculata C. lanceolata C. leavenworthii and G. pulchella Bombini (Apidae) In Florida, the Bombini tribe consists of six different bumble bee species. Of these six spec ies, approximately 99% of all bumble bee sightings at my research sites were either Bombus impatiens Cresson or B. pensylvanicus (DeGeer). Bombus fraternus (Smith), B. griseocollis (DeGeer) and B. bimaculatus (Cresson) accounted for the remainder of the bumble bee sightings. B. variabilis Cresson, the sixth and very uncommon bumble bee parasite species, was never seen. Bumble bees were rarely present on my research plots in the spring an d the late fall, but they were present in large numbers during the overlapping bloom period of the principle six wildflowers, and in the late summer/early fall bloom period. Principle overlapping flowers For the principle six flower species, bum ble bees exhibited a very clear preference ( F =21, df=3, 423, P <0.01). C. fa sciculata was visited by bumble bees more than were the other flowers overall (Fi gure 3-7A) and during AM hours ( F =9, df=2, 220, P <0.01;

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47 Figure 3-7B). In the afte rnoon, bumble bees visited C. fasciculata and G. pulchella similarly to one another but significantly more so than the other flowers ( F =1494, df=2, 195, P <0.01; Figure 3-7C). Late summer/early fall time period During late summer/ea rly fall, C. fasciculata was the wildflower most visited by bumble bees ( F =10072, df=2, 276, P <0.01, Figure 3-7D). During AM hours, bumble bees visited C. fasciculata significantly more than t he other wildflower species ( F =1617, df=2, 145, P <0.01, Figure 3-7E). In the afternoon, C. fasciculata G. pulchella and M. punctata were visited more by bumble bees than were the other flowers ( F =8114, df=2, 124, P <0.01, Figure 3-7F). Eucerini (Apidae) The Eucerini or long-horned bees are a common group in Florida. The species caught most regularly on my plots were Melissodes communis Cresson and Svastra aegis (LaBerge). Infrequently found in the spring on my plots, there was insufficient data to perform an analysis for the principle six or the late su mmer/early fall bloom periods. Late fall time period The long-horned bees were very co mmon in the late fall during the H. angustifolius bloom. In the overall test, H. angustifolius was visited most ( F =11, df=2, 106, P <0.01; Figure 3-8A). In the morni ng the long-horned bees visited H. angustifolius significantly more as well ( F =245, df=1, 50, P <0.01; Figure 3-8B). The long-horned bees did not demonstrate a flower visitation preferenc e during the afternoon observation period ( F =2, df=2, 50, P =0.12).

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48 Halictini (Halictidae) The Halictini tribe contained the most commonly found bee on my research plots, the primitively eusocial Halictus poeyi Lepeletier. Agapostemon splendens (Lepeletier), a solitary green sweat bee, is also a member of this tribe and was seen frequently. Principle overlapping flowers In the overall test for the principle si x wildflo wer species, Halictini visited G. pulchella significantly more than all the other wildflowers except C. basalis and C. lanceolata (F =15, df=5, 423, P <0.01; Figure 3-9A). In the morning sampling period, only C. fasciculata was not visited significantly by Halictini ( F =8, df=5, 220, P <0.01; Figure 39B). During the afternoon sampling periods, G. pulchella was visited significantly more than were the other flower s pecies with the exception of C. basalis (F =13, df=5, 195, P <0.01; Figure 3-9C). Spring time period In the overall test in the spring, Halictini visit ed G. pulchella the most numerically, though its visitation rate was not signi ficantly different from those of C. basalis, C. lanceolata or R. hirta (F =4, df=5, 69, P <0.01; Figure 3-9D). Sim ilarly, in the morning, C. lanceolata and G. pulchella were visited significantly more than all but C. basalis and R. hirta (F =5, df=5, 30, P <0.01; Figure 3-9E). In the afternoon, Halictini visited C. basalis C. lanceolata G. pulchella and T. repens significantly more than the other wildflower species (F =4, df=5, 30, P =0.01; Figure 3-9F). Late summer/early fall time period In the over all test for the late summer/early fall, Halictini visited G. pulchella the most, though not significantly more so than R. hirta ( F =35, df=4, 276, P <0.01; Figure 39G). In the morning, C. leavenworthii G. pulchella and R. hirta were significantly more

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49 visited than the ot her wildflowers ( F =22, df=4, 145, P <0.01; Figure 3-9H). In the afternoon, G. pulchella, C. leavenworthii, and R. hirta were visited by Halictini more than was M. punctata ( F =4, df=4, 124, P <0.01; Figure 3-9I). Late fall time period In the late fall overall test, G. pulchella H. angustifolius and R. hirta were visited signific antly more than C. leavenworthii (F =4, df=3, 106, P =0.02; Figure 3-9J). In the morning and afternoon tests, bee visitation across all wildflower species was similar ( F =2, df=3, 50, P =0.22; F =2, df=3, 50, P =0.17). Megachilini (Megachilidae) The Megachilini are a tribe of leafcutter bees. The majority of the leafcutter bees caught and identified were Megachile albitar sis Cresson and M. mendica Cresson, although smaller numbers of other native specie s also were identified. It should be noted that the leafcutter bees used my sites for not only nectar and pollen, but also were observed cutting pieces of petals off G. pulchella for their nests. The leafcutter bees were not common in the spring, but were all other times of the year. Principle overlapping plants For the principle six wildflowers, leafcutters vi sited G. pulchella most ( F =5, df=5, 423, P <0.01; Figure 3-10A). In the morning, C. fasciculata was visited significantly less than were the other flowers ( F =3, df=5, 220, P =0.03; Figure 3-10B). The analysis of afternoon flower visitation by leafcutter bees in the afternoon could not be performed due to insufficient data. Late summer/early fall time period In the late summer/ea rly fall overall test, G. pulchella was most visited, though not significantly more so than C. leavenworthii ( F =6, df=3, 276, P <0.01; Figure 3-10C). Bee

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50 visitation of flowers in the morning and afte rnoon did not vary significantly (morning: F =2, df=3, 145, P =0.21; afternoon: F =2, df=2, 124, P =0.10). Late fall time period The overall and morning tests were not significant ( F =1, df=3, 106, P =0.42; F =0, df=3, 50, P =0.99), but the afterno on test for late fall was. In the late fall afternoons leafcutter bees visited G. pulchella and H. angustifolius significantly more than they visited the other wildflower species ( F =1555, df=1, 50, P <0.01; Figure 3-10D). Xylocopini (Apidae) The Xylocopini tribe in Florida consists of only two species of carpenter bees: Xylocopa micans Lepeletier and X. virginica (Linnaeus). The majority of the carpenter bees I saw on my research plots were X. micans I rarely saw carpenter bees on my plots in the spring and late fall, which probably was due to when the flowers they preferred in my sites bloomed. Principle overlapping flowers For the principle six wildflower species, carpenter bees visited C. fasciculata signific antly more than all other wildflowers ( F =958, df=2, 423, P <0.01; Figure 3-11A), a trend that held true during morning observations ( F =2962, df=1, 220, P <0.01; Figure 311B). Carpenter bee visitation rates of flower did not vary among wildflower species in the afternoon ( F =0, df=1, 195, P =0.98). Late summer/early fall time period In the late summer/ea rly fall overall test, C. fasciculata and M. punctata were the most significantly attractive wildflowers to carpenter bees ( F =16466, df=1, 276, P <0.01; Figure 3-11C). In the morn ing carpenter bees visited C. fasciculata more than any other flower (F = df=4, 145, P <0.01; Figure 3-11D). The af ternoon analysis could not be

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51 performed due to low bee flower visitation ra tes during the afternoon observations. Bee tribe attraction by season and time of day (Table 3-1) and bee tribe by plant species (Table 3-2) are summarized. Pollen Washes Pollen Wash Means Only bees visibly carrying pollen were colle c ted, so the number of pollen grains on each bee was high. Furthermore, the amount of pollen carried by a bee varied by bee species and plant species (Table 3-3). Pollen Wash Percentage Likelihood The pollen wash percentage likelihood data indicate the likelihood t hat a bee collected from a particular wildflower species actually has pollen from that wildflower species on it. This is probably a better indica tor of given bees pollen collection habits because some plants naturally produce less pol len than others. Fo r example, oak (a wind pollinated plant) produces la rge amounts of pollen, which bees will collect actively. Many legumes, such as C. fasciculata do not produce much pollen as they are pollinated exclusively by insects. As such, they rely on insects to carry their pollen from flower to flower. In general, bees captured on a particular wildflower species had a high likelihood of carrying pollen from that species (Table 3-4). Pollen on Bumble Bees Bumble bees carrying pollen were caught only on C. fasciculata Surprisingly, most of the pollen they carried was not from Chamaecrista, but was from unknown sources (Table 3-5). Additionally the bumble bees captured from Chamaecrista did not always carry Chamaecrista pollen, and a quarter of the time had aster pollen on them despite only rare sightings of bumble bees on aster flowers (Table 3-6).

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52 Pollen on Halictus poeyi Halictus poeyi in comparison to bumble bees, were caught only rarely on C. fasciculata and instead usually were caught on Coreopsis spp., R. hirta and G. pulchella Most of the pollen carried by H. poeyi was from the Asteraceae flowers, with a few unknown pollen grains and no C hamaecrista pollen grains (Table 3-7). A third of the bees caught on nonGaillardia Asteraceae plants had Gaillardia pollen on them, and almost three quarters of the bees caught on Gaillardia had other Asteraceae pollen on them as well (Table 3-8). It should be further noted that in the field, H. poeyi frequently were observed flying from Gaillardia to Coreopsis and back again.

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53 Table 3-1. Bee visitation of the tested wildflower species Time Period Tribe Main Six Spring Late Summer to Early Fall Late Fall Overall Apini NA C. lanceolata NA NA NA Augochlorini NA NA NA NA C. fasciculata, C. lanceolata, C. leavenworthii, G. pulchella Bombini C. fasciculata, G. pulchella NA C. fasciculata, M. punctata, G. pulchella NA NA Eucerini NA NA NA H. angustifolius NA Halictini C. basalis, C. lanceolata, C. leavenworthii, G. pulchella, R. hirta C. basalis, C. lanceolata, G. pulchella, T. repens C. leavenworthii, G. pulchella, R. hirta G. pulchella, H. angustifolius, R. hirta NA Megachilini C. basalis, C. lanceolata, C. leavenworthii, G. pulchella, R. hirta NA G. pulchella G. pulchella, H. angustifolius NA Xylocopini C. fasciculata NA C. fasciculata, M. punctata NA NA Flower species listed are those significantly attractive to that tribe of bees Superscripts next to species names mean the following: = significance differences were present in the overall test, = significant differences were present in the morning test, = significant differences were pr esent in the afternoon test. NA means data were not available.

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54 Table 3-2. Bee tribe visitation by plant species Apini Augochlorini Bombini Eucerini Halictini Megachilini Xylocopini C. fasciculata X X X C. basalis X X C. lanceolata X X X X C. leavenworthii X X X G. pulchella X X X X H. angustifolius X X X M. punctata X X R. hirta X X T. repens X X indicates significant visitation in at least one time period. Table 3-3. Pollen wash data Plant from which bees were captured Pollen found on the bee Aster Gaillardia Chamaecrista Helianthus Aster 175752381(29) 4024164(49) 186470(31) 1554684428(4) Gaillardia 84086(29) 8647094(49) 100(31) 98438818(4) Chamaecrista 0(29) 0(49) 14798744(31) 0(4) Monarda 0(29) 0(49) 6655(31) 0(4) Helianthus 0(29) 31(49) 0(31) 6000049339(4) Unknown 77538(29) 45973(49) 14286245147(31) 1250510(4) Data are the mean standard er ror (n) of the estimated num ber of pollen grains found on an individual bee captured on a given wildflower species. Table 3-4. Pollen wash percentage likelihoods Plant from which the bees were captured Pollen found on the bee Aster Gaillardia Chamaecrista Helianthus Aster 100%(29) 73%(49) 22%(31) 75%(4) Gaillardia 34%(29) 95%(49) 9%(31) 75%(4) Chamaecrista 0%(29) 0%(4 9) 87%(31) 0%(4) Monarda 0%(29) 0%(49) 3%(31) 0%(4) Helianthus 0%(29) 4%(4 9) 0%(31) 75%(4) Unknown 41%(29) 32%(4 9) 100%(31) 75%(4) Data are mean percent like lihood standard error (n).

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55 Table 3-5. Bumble bee pollen wash means Plant from which the bees were captured Pollen found on the bee Chamaecrista Aster 1793(23) Gaillardia 54(23) Chamaecrista 14538(23) Unknown 168070(23) Data are the mean standard er ror (n) of the estimated num ber of pollen grains found on an individual bumble bee ( Bombus spp.) captured on Chamaecrista fasciculata Table 3-6. Bumble bee polle n wash percentage likelihoods Plant from which the bees were captured Pollen found on the bee Chamaecrista Aster 26%(23) Gaillardia 4%(23) Chamaecrista 91%(23) Unknown 100%(23) Data are mean percent like lihood standard error (n). Table 3-7. Halictus poeyi pollen wash means Plant from which the bees were captured Pollen found on the bee Aster Gaillardia Chamaecrista Aster 19170(26) 3344(37) 8281(2) Gaillardia 625(26) 4797(37) 625(2) Chamaecrista 0(26) 0(37) 0(2) Helianthus 0(26) 42(37) 0(2) Unknown 168(26) 135(37) 937(2) Data are the mean standard er ror (n) of the estimated num ber of pollen grains found on an individual Halictus poeyi captured on a given wildflower species. Table 3-8. Halictus poeyi pollen wash percentage likelihoods Plant from which the bees were captured Pollen found on the bee Aster Gaillardia Chamaecrista Aster 100%(26) 73%(37)50%(2) Gaillardia 35%(26) 95%(37) 50%(2) Chamaecrista 0%( 26) 0%(37) 0%(2) Helianthus 0%(26) 5%(37) 0%(2) Unknown 38%(26) 24%(37) 100%(2) Data are mean percent likelihood standard error (n).

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56 Figure 3-1. Bee visitation (LS-mean num ber of bees/100 blooms/minute) on the principle six wildflower species, i.e ., those with the longest overlapping bloom period. LS-Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. T he graphs are A) overall bee visitation; B) bee visitation during AM hours; C) and bee visitation during PM hours c b,c a,b b b a A B a,b a b,c a a,b,c c Based on 3767 observations of bees Based on 2554 observations of bees

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57 Figure 3-1. Continued C b a b b a,b c Based on 1213 observations of bees

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58 Figure 3-2. Bee visitation (LS-mean number of bees/100 blooms/minute) on the spring blooming flowers. LS-Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. T he graphs are A) overall bee visitation; B) bee visitation during AM hours; C) and bee visitation during PM hours A b,c b b,c a c d a,b B b a,b a,b a a,b c b Based on 1319 observations of bees Based on 861 observations of bees

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59 Figure 3-2. Continued C b b b,c a c d a Based on 458 observations of bees

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60 Figure 3-3. Bee visitation (LS-mean number of bees/100 blooms/minute) on the late summer/early fall blooming flowers. LS -Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) overall bee visitation; B) bee visitation during AM hours; C) and bee visitation during PM hours A a,b d a b,c c B a a a b a Based on 1663 observations of bees Based on 1093 observations of bees

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61 Figure 3-3. Continued C c b a c b Based on 570 observations of bees

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62 Figure 3-4. Bee visitation (LS-mean number of bees/100 blooms/minute) on the late fall blooming flowers. LS-Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) overall bee visitation; B) bee visitation during PM hours. A a,b c a a b a,b B d b a a c a Based on 284 observations of bees Based on 157 observations of bees

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63 Figure 3-5. Apini visitation (LS-mean num ber of bees/100 blooms/minute). LS-Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) over all bee visitation; B) overall Spring bee visitation; C) Spring bee visitation during AM hours A b b b f d b aea,b a,b c B dc g f e a b Based on 85 observations of Apini bees Based on 12 observations of Apini bees

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64 Figure 3-5. Continued d c g f e a b C Based on 6 observations of Apini bees

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65 Figure 3-6. Augochlorini overall flower visitation (LS-mean number of bees/100 blooms/minute). LS-Means with the sa me letter are not different at P 0.05. Plus/minus bars are standard errors. a c a a e a f g a db Based on 14 observations of Augochlorini bees

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66 Figure 3-7. Bombini visitation (LS-mean num ber of bees/100 blooms/minute). LS-Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) Princi ple six overlapping flowers overall bee visitation; B) Principle six overl apping flowers bee visitation by AM; C) Principle six overlapping flowers bee vi sitation by PM; D) Late summer/early fall overall bee visitation; E) Late summe r/early fall overall bee visitation by AM; F) Late summer/early fall overall bee visitation by PM A c b e c d a B b b e c d a Based on 694 observations of Bombini bees Based on 592 observations of Bombini bees

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67 Figure 3-7. Continued C c a e b d a D d b c e a Based on 102 observations of Bombini bees Based on 596 observations of Bombini bees

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68 Figure 3-7. Continued E d b c e a F b a a c a Based on 93 observations of Bombini bees Based on 503 observations of Bombini bees

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69 Figure 3-8. Eucerini visitation (LS-mean number of bees/100 blooms/minute) on late fall blooms. LS-Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) overall bee visitation; B) bee visitation by AM. A c a b d B c a b d Based on 97 observations of Eucerini bees Based on 41 observations of Eucerini bees

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70 Figure 3-9. Halictini visitation (LS-mean number of bees/100 blooms/minute). LS-Means with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) principl e six flowers overall bee visitation; B) principle six flowers bee visitation by AM; C) principle six flowers bee visitation by PM; D) Spring blooming flow ers overall bee visitation; E) Spring blooming flowers bee visitation by AM ; F) Spring blooming flowers bee visitation by PM; G) Lat e summer/early fall bloom ing flowers overall bee visitation; H) Late summer/early fall bl ooming flowers bee visitation by AM; I) Late summer/early fall blooming flower s bee visitation by PM; J) Late fall blooming flowers overall bee visitation A b a b a,b a,b c B a a a a a b Based on 2617 observations of Halictini bees Based on 1674 observations of Halictini bees

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71 Figure 3-9. Continued C b a b b a,b c D a,b a,b c a a,b,c d b,c Based on 943 observations of Halictini bees Based on 1252 observations of Halictini bees

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72 Figure 3-9. Continued E a,b a b,c a a,b d c F a a b a b c a Based on 824 observations of Halictini bees Based on 428 observations of Halictini bees

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73 Figure 3-9. Continued G a,b c a b c H a b a a b Based on 748 observations of Halictini bees Based on 388 observations of Halictini bees

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74 Figure 3-9. Continued I a b a a a,b J a a a b Based on 360 observations of Halictini bees Based on 141 observations of Halictini bees

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75 Figure 3-10. Megachilini visitation (LS -mean number of bees/100 blooms/minute). LSMeans with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) principl e six flowers overall bee visitation; B) principle six flowers bee visitation by AM; C) late summer/early fall blooming flowers overall bee visitation; D) late fall blooming flowers bee visitation by PM A b a b b a,b c B a a a a a b Based on 149 observations of Megachilini bees Based on 63 observations of Megachilini bees

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76 Figure 3-10. Continued C b d a a,b c D b a a c Based on 112 observations of Megachilini bees Based on 22 observations of Megachilini bees

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77 Figure 3-11. Xylocopini visitation (LS-m ean number of bees/100 blooms/minute). LSMeans with the same letter are not different at P 0.05. Plus/minus bars are standard errors. The graphs are A) principl e six flowers overall bee visitation; B) principle six flowers bee visitation by AM; C) late summer/early fall blooming flowers overall bee visitation; D) late summer/early fall blooming flowers bee visitation by AM A c b e b d a B c f e b d a Based on 121 observations of Xylocopini bees Based on 110 observations of Xylocopini bees

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78 Figure 3-11. Continued C b a c c a D a e d c b Based on 112 observations of Xylocopini bees Based on 104 observations of Xylocopini bees

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79 CHAPTER 4 DISCUSSION Benefits of Wildflower Mixes Multiple inv estigators have shown that one of the best methods of attracting and improving populations of nativ e pollinators on agricultural field margins is with sown wildflowers and bee forage plants (Bckman & Ti ainen 2002; Meek et al. 2002; Pywell et al. 2005; Pywell et al. 2006; Carvell et al 2007; Potts et al. 2009). However, not all wildflower species likely attract pollinators equally nor can one expect them to work well in all situations. For example, a wildflower s pecies that attracts pollinators well in parts of Arizona would not do the same in Florida intuitively. To understand the attraction of native bee pollinators to Florida wildflowers, I developed a study to te st the following two hypotheses: (1) different wildflower species w ould be attractive to different bee groups and (2) bee attraction to Florida wildflower spec ies would vary throughout the year. Both hypotheses were supported by my research. The data presented herein support work by other investigators who have shown outside of Florida that different groups of bees, such as honey bees and bumble bees, preferentially visit different wildflower spec ies (Patien et al. 1993; Carvell et al. 2006; Tuell et al. 2008; Frankie et al. 2009). Previous investigators also have shown that time of year can be a factor in pollinator pr eference (Bckman & Tiainen 2002; Carreck & Williams 2002). Native Bee Use of Wildflower Species Data are available on bee communities of Florida (Graenicher 1930; Pascarella et al. 1999; Deyrup et al. 2002; Hall & A scher 2010) and bee-plant as sociations (Graenicher 1930; Mitchell 19 60; Balduf 1962; Mitchell 1962; Hardin et al. 1972;

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80 Buchmann & Nabhan 1996; Deyrup et al. 2002; Pascarella 2008). Though the data are survey, rather than comparative data, they coincide with my results in most cases. These known associations from the lit erature are summarized in Table 4-1. For example Svastra aegis a long horned bee, is known to be an oligolege on Asteraceae (a composite family), with a strong preference to Helianthus species (Hurd et al. 1980). My data suggested that even am ong Asteraceae members, which Eucerini were seen visiting in my study, the bees in this tribe preferred to visit H. angustifolius Halictus poeyi also is known to frequent Asteraceae (Deyrup et al. 2002; Pascarella 2008). My data demonstrate that H. poeyi prefers Asteraceae flowers, especially G. pulchella which they preferred over ot her Asteraceae species during multiple time periods. Similarly, bumble bees are listed as polyl ectic with strong preferences towards Lamiaceae (mint family), Fabaceae (legume fa mily) and Asteraceae (Pascarella 2008). Otherwise, they are known to visit a large variety of plant s (Deyrup et al. 2002). In my results, bumble bees preferred C. fasciculata (Fabaceae) most, followed by G. pulchella (Asteraceae), then M. punctata (Lamiaceae). In a few cases, my data were in consistent with lit erature reports. Xylocopa micans the carpenter bee, is known to be polylectic and visits a large variety of flowers (Balduf 1962; Hardin et al. 1972; Deyrup et al. 2002; Pascarella 2008). My data suggest a preference for only one or two flowers (C. fasciculata and M. punctata ). Asteraceae flowers were seldom visited by X. micans despite the reported carpenter bee use of multiple Asteraceae species (Deyrup et al. 2002; Pascarella 2008). However, it should be noted that only the flower species growing in my plots were compared in their

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81 visitation by bees. It is entirely possible, ev en likely, that flower s outside of my plots were more attractive than the ones in my plot s. This is especially likely in the case of Apis mellifera, which were notably rarely seen in t he plots, despite several apiaries located within 1000 meters of all of my site s. The notable lack of several bee groups at specific times of the year (such as bumble bees in the spring) leads me to believe that either none of the wildflowers in those time periods were attractive to those bee groups or that there were other, fa r more attractive, wildflower s blooming somewhere in the vicinity. This is one of the main reasons why I think any future studies should include a far larger number of wildflower species. I believe that surveys of bee communities and their floral hosts are a vital first step in the conservation of bees and pollination services. Contro lled comparison tests of bee flower species use should follow general surve ys. They reveal new levels of interactions between bees and flowers, and narrow our search for good bee forage plants to plants that the bees actually prefer to use. Developing a Florida Wildflower Mi x That Is Used By Native Bees One goal of this research was to reco mmend wildflowe r species that can be used to support native bee populations throughout a co mplete season. Based on the results, a seed mixture of Chamaecrista fasciculata, Coreopsis basalis Coreopsis lanceolata, Coreopsis leavenworthii, Gaillardia pulchella Helianthus angustifolius Monarda punctata Rudbeckia hirta Trifolium incarnatum and Trifolium repens would provide forage for the greatest number and diversity of bees for the longest period of time. Of the twenty wildflower species tested in this project, only these ten plus Coreopsis tinctoria either bloomed in sufficient number s or attracted enough bees to be used in the statistical tests. This does not mean that the flowers which failed to bloom

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82 are of no use to bee pollinators. Several species did not bloom because they are perennials that begin to bloom only during the second year. For wildflower plantings allowed to grow more than one season, these might in fact be ideal flowers to use to attract bee pollinators. However, I was unable to test this assumption. Furthermore, some of the wildflower spec ies that did not bloom exhibited lower germination rates or failed to germinate al together. In many of these cases, the germination rate of the seeds was known to be low beforehand; however the cost of the seeds was high, thus prohibiting my ability to compensate for the lower germination rate by simply planting more seeds. For example, only two Solidago fistulosa Miller (Pinebarren Goldenrod) bloomed at all and then fo r only a few weeks in late fall. Despite this, one of these plants attracted an eighth tr ibe of bees that I di d not mention in the results section: Colletini. Th ree of these bees from the genus Colletes were seen on the goldenrod. In natural settings, goldenrod specie s are often an important late fall floral source. It is also a perennial, and individual s that did not bloom this year may have been overlooked. The wildflower species that I list above were visited by significant numbers of bees during at least one time period, but also bloo med well the first year they were planted. For these reasons I recommend them not onl y as good bee forage plants, but also as plants that are easy to grow, hardy and produce a large number of blooms. I can also recommend them in places besid es Florida. Most of the plants used in this study are found outside of Flori da (with the possible exception of Coreopsis leavenworthii which was until recently consi dered entirely endemic to Florida). Asclepias tuberosa Linnaeus, C. lanceolata C. tinctoria G. pulchella M. punctata R. hirta T.

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83 repens and T. incarnatum are all found from Florida to C anada to California. Most of the rest of the plants are co mmon throughout the eastern Un ited States (USDA, NRCS 2011). Similarly, all of the bee tribes, and even individual bee species are widespread throughout the United States. For these r easons my study may have applicability beyond Florida. Study Limitations Along with low seed germination rates for some tested wildflower species, there were several other limitations to this project. First, the study lasted only one field season. Bee communities have been shown to change drastically from year to year (Kremen et al. 2004). As such, a number of new species may have been found in the wildflower plots had it run a second season. However, a bloom period of one year is indic ative of what might o ccur if these wildflowers are sown on an agricultural field margin. In this case, only annual wildflowers could be planted beside a field that will be used only for one season or planted in its place during the fallow year. Another limitation of the study is that mo st bee identification occurred in the field and was accomplished by the sight identification of bees. Some bees such as the bumble bees, carpenter bees and honey bees are large, common and easily sight identified. With minor training, a field technician could sight identify these three species. Other groups of bees, notably many Euceri ni and Augochlorini, require a microscope and dichotomous key to identify to genus or a taxonomic level of greater resolution. To account for variability between field technici ans, I recognized bee tribe as the best level of resolution I could use in my study. Reference specimens were captured and identified, thus allowing me to co rroborate the sight identifications.

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84 Further Investigations While conducting my experiments, I recogni zed a number of additional studies that could be conducted. One would be a compar ison between two of the main methods used to compare bee visitation rates: the v egetation survey method and the standard area method. Both the vegetation survey method and standard area method provide valuable inf ormation. Both provide a measur e of bloom density. The vegetation survey method provides a bloom density based on bloom availability in a mixed wildflower planting while in the standard area method, wildflower s pecies are planted in uniform areas, individually by species with a goal of standardizing the number of blooms available per unit area. Determining bloom dens ity is important for estimating bee use of flowers. For example, if flower A is very abundant and frequently visited by bees, and flower B is equally abundant but not visit ed by bees, flower A can be assumed to be more attractive to bees. If flower A is very abundant and frequently visited by bees but flower B is not abundant, then flower Bs apparent unattractiveness to bees could be due to its rarity or a true lack of preferenc e by the bees for it. Bloom density estimates allow for standardization of the average bee use of flowers. The vegetation survey method is what I us ed in this study. In this method, bloom density is estimated from repeated vegetat ion surveys. The vegetation survey accurately measures the resulting flower mosaic in a plot r egardless of the seed composition of the original common seed mi xture. However, sampling personnel must be able to identify visiting bees and the target pl ants for this survey method to be useful. Furthermore, an observer can overlook plant species that do not germinate in large numbers or favor larger plants that may out shade smaller ones ( C. fasciculata for

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85 example shaded out many of t he other species in the annu al mix plots until it was thinned). The standard area method, on the other hand, does not mimic agricultural field margin conditions. In a standard area experim ent, plant species are planted separately in individual, standard sized plots. When eac h plant is labeled accurately, the observer does not need to be able to identify each plant since the plant is labeled. Raw data received from this type of survey do not need to be standardized with vegetation survey data, but can be used as is. Since the surv ey typically is conducted using a smaller numbers of plants, the plants need to be in peak blooming conditions to increase study accuracy. My attempt to conduct this type of survey, per my or iginal proposal, was unsuccessful due to the poor performance of t he plants at the study sites. Ideally, the study sites should have been located in we ll-maintained gardens and established to mimic ornamental gardens rather than agricultu ral field margins. This would have made possible higher plant survival rates, a more standardized number of blooms, and greater numbers and quality of blooms. Viewed in tota l, vegetation surveys (like those used in the current study) are best used for agricultural field margin studies while standard area surveys are more suited to address garden vegetation plantings. As a future investigation, a comparison of data on bee flower preference collected using both of these methods would highlight the pros and cons of both methods and may indicate the effects of plant density and distributi on on bee visitation (Cresswell 1997). Further questions were raised as a result of the implementation of this study. First, what is the best way to sample bee prefer ence for flowering plants? Pan traps, which commonly are used to sample for smaller bee species (Roulston et al. 2007), could not

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86 be used in this study as they do not provide flower use information, especially when flowers occur in mixed plantings. Consequen tly, I had to use sweep netting and sight identification techniques to survey bees. Wh ile more labor intensive than pan trapping, netting has been proven to be approximately as e ffective (Roulston et al. 2007) or more effective at surveying bee communities t han pan trapping (Cane et al. 2000; Wilson et al. 2008). Another question resulting from this study dealt with temporal sampling techniques, i.e. what length of time is suffi cient to determine bees use of wildflowers, but short enough to avoid repeat sampling of bees? Coupled with sampling time, one must consider how many sites/plots/flower species can be surveyed accurately in a day and what manpower is needed to conduct the survey. The ten minute observation period used in this survey seemed to work well, but a comparison of different observation periods should be conducted in the future. Additional temporal sampling issues aros e. I found an interact ion between time of day and bees flower visitation. Bee plant use habits changed from morning to afternoon samplings (Table 3-1). It is well known that some bee begin foraging earlier in the morning than others (bumble bees, for example, are well known to be one of the first flower visitors). However, it was a surprise to find that most of the bees were more active on flowers in the morning than in the afternoon. It would be interesting to see if this holds true in other studies, especially ones taking place in different climates. In addition, data collection rarely began before 09: 00 and usually ended by 16:30. To that end, it is possible that bees foraging before 09:00 or after 16:30 were sampled inadequately. This is true especially in t he summer months when sunrise was occurred

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87 before 06:00. Future investigators coul d study bee species richness and diversity throughout an entire day. Future investigators also could conduc t studies that include more wildflower species. Only commercially available wildflow er species were used in my study. Future studies could include plant spec ies that are not commercially available. The seeds of many flowering plants can be hand-picked for an experiment. If such species are shown to be attractive to bees, then seed compani es may begin offering them commercially. Additionally, crop plants may serve as a good addition to any further comparison studies. Some wildflowers may compete in t heir attractiveness to crop plants, which goes against the purpose of pl anting wildflowers to increase crop production. This is one of the reasons why the bloom period of different species is so important. When choosing wildflower species for pollinators of a specific crop it is important to choose wildflowers that would bloom before and after, but not during, the crops bloom. This is another type of interaction that has yet to be adequately studied. Additionally, studies should be conducted in other areas and climates to address unique bee and wildflower communities. Such studies could include woody plants as well. Bushes that provide good bee forage would be ideal for hedgerows and home gardens. Furthermore, trees can provide more permanent bee forage, and often are responsible for winter and early spring nectar and pollen sources. Pe rennials often have energy stores and deep root systems that annuals do not have (Mauseth 2009). This allows them to bloom during droughts or ti mes of the year that annuals cannot. These investigations may be used to furt her the study of pollination ecology. It would be useful to better standardize methods used in pollination ecology and may lead

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88 to streamlined methods that take advantage of bee and plant biology. Knowing the pros and cons of research methods would allow for incoming researchers to better design their experiments in this quickly expanding field of study. More streamlined methods would also help to make studies with great er numbers of species and types of plants possible, leading to a greater enhancement of our knowledge of bee-plant interaction. Conclusion Further research into native bees and bee wi ldflower use will be useful to the long term conservation of native bees, native plants and the ecological services they provide. Understanding the links bet ween bees and plants allows us as scientists to predict and solve problems with pollination services that will occur as a result of habitat loss and fragmentation, agricultural intensificat ion and the globalization of bee pests and diseases (National Research Council of the National Academies 2007). As in any conservation effort, research alone is not enough. Extens ion and outreach efforts aimed at convincing growers and homeow ners that there is a problem and that they can help are key steps in the conservation of native bees and other pollinators. Ultimately native polli nators like the bees seen in my study help maintain a healthy ecosystem and ensure food security. Ou r understanding of native bees and their importance is causing the fields of pollinat ion ecology and pollinator conservation to blossom. New publications are beginning to bridge the gap between the science and its application (Kremen et al. 2007; Byrne & Fi tzpatrick 2009; Tallamy 2009; Grissell 2010; The Xerces Society 2011). It is my hope that the work I and others have done will help to preserve bees and the flowers that feed them for generations to come.

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89 Table 4-1. Bee-plant associations from literature Bee Genus Known Floral Associations Augochlorella Asclepias, Coreopsis, Chamaecrista, Eryngium, Helianthus, Monarda, Rudbeckia, Salvia, So lidago, Trifolium, Vernonia Augochloropsis Asclepias, Chamaecrist a, Coreopsis, Eryngium, Helianthus, Solidago, Trifolium Bombus Asclepias, Baptisia, C hamaecrista, Coreopsis, Eryngium, Gaillardia, Helianthus, Liatris, Monarda, Phlox, Rudbeckia, Solidago, Trifolium, Vernonia Melissodes Asclepias, Baptisia, Coreopsis, Helianthus, Monarda, Rudbeckia, Salvia, Solidago, Vernonia Svastra Gaillardia, Helianthus, Vernonia Agapostemon Chamaecreista, Coreopsis, Gaillardia, Helianthus, Monarda, Solidago, Vernonia Halictus Asclepias, Coreopsis, Eryngium, Helianthus, Liatris, Monarda, Rudbeckia, Solidago, Trifolium, Vernonia Lasioglossum Asclepias, Coreopsis, Er yngium, Helianthus, Liatris, Monarda, Rudbeckia, Salvia, Solidago, Trifolium, Vernonia Megachile Asclepias, Baptisia, Coreops is, Eryngium, Gaillardia, Helianthus, Liatris, Monarda, Rudbeckia, Salvia, Solidago, Trifolium, Vernonia Xylocopa Chamaecrista, Solidago, Vernonia

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99 BIOGRAPHICAL SKETCH Katharine Buckley gr aduated in 2011 with a ma sters degree in entomology from University of Florida. She received her bac helor of science in entomology from Purdue University in August of 2009. As an undergraduate she did research on Florida mosquito population dynamics as affected by te mperature, precipitation and hurricanes. She plans on pursuing a PhD in entomology, working on native pollinator conservation and biological control in grapes at Washington State University where she is currently enrolled.