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Smithsonian Botanical Symposium
20 May 2016
National Museum of
   Natural History and
the U.S. Botanic Garden
Washington, DC


Smithsonian Botanical Symposium 2016 — Presented by the Smithsonian's National Museum of Natural History Department of Botany in collaboration with the United States Botanic Garden with support from the Cuatrecasas Family Foundation:

"Bats, Bees, Birds, Butterflies and Bouquets: New Research in Pollination Biology"

The act of pollination, transferring pollen from one flower to another, remains one of the most ecologically important interactions between plant and animal. It allows plants to produce seed and reproduce, and it provides pollen, nectar and other rewards to the animals that visit the flowers. Pollination is a keystone function of most terrestrial ecosystems, and an estimated 87 percent of flowering plants depend on animal pollination. Plant-pollinator interactions have led to the evolutionary diversification of major groups of both plants and animals. A diverse plate of foods for humans is a result of pollination as well: one out of every three bites of food we eat is the result of an animal pollinating a plant. Yet recent evidence shows that pollinator abundance and diversity is on the decline. What does the threat to the health of pollinators hold for the future of native plant populations and agriculture? Will plant and pollinator populations adapt to a changing climate, invasive species, and habitat loss?

The 13th Smithsonian Botanical Symposium, hosted by the Department of Botany and the United States Botanic Garden, will highlight current research in pollination biology, from plant physiology and ecology to evolution and animal behavior. New approaches to the study of plant-animal interactions may provide promise to safeguard biodiversity both here in the U.S. and around the world. The invited speakers will cover a wide range of approaches to illustrate the challenges in plant-pollinator relationships in a rapidly changing world.


ruby-throated hummingbird

Archilochus colubris (ruby-throated hummingbird) visits Campsis radicans (=Bignonia radicans, trumpet vine). From J.J. Audubon, The Birds of America: from Drawings Made in the United States and Their Territories, 1840-1844.

Speaker Abstracts


Patterns in pollen and plant specialization among native bees in eastern North America
Sam Droege, USGS Patuxent Wildlife Research Center, U.S.A.

The long co-evolution of flowering plants and their insect pollinators has created an abundance of strategies on both sides of the plant/insect equation. Many insects are visitors to flowers and their role as floral visitor from the plant perspective varies from outright thievery to obligate pollinator. Of those insect visitors, native bees are almost entirely unique in that they purposefully gather pollen and nectar to provision nests for their young. The 800 species of native bees east of the Mississippi River in North America have greatly compartmentalized their plant interactions. About 20 to 25 percent are highly specialized, using pollen from at times only one species or genus of plant. Other species are less restrictive in the pollen they use, but still may largely focus on gathering pollen from a single plant family and have only a brief, six-eight week period of flight activity. A smaller number of species, but often the most dominant in terms of individuals present, visit a wide range of plant families, often are social or colonial in life history strategy (but never to the extent that the introduced honeybee has taken social living) and are active throughout the flowering season. Specialized structures in both plants and their bee counterparts are abundant and will be illustrated in this talk along with illuminating broadscale geographic patterns in bee specialization, brief mention of conservation implications for both plants and bees, and presentation of a number of examples of specialized bee/plant pairings.

Sam Droege spent his childhood in the local woods and fields, received an undergraduate degree at the University of Maryland - College Park, and a Master’s at the State University of New York - Syracuse. Most of his career has been spent at the USGS Patuxent Wildlife Research Center. He has coordinated the North American Breeding Bird Survey Program, developed the North American Amphibian Monitoring Program, the Bioblitz, Cricket Crawl, and FrogwatchUSA programs and worked on the design and evaluation of monitoring programs. Currently he is developing an inventory and monitoring program for native bees, online identification guides for North American bees at, and reviving the North American Bird Phenology Program.

Shifting baselines and changing partners: Ecological and evolutionary responses to climate change in alpine bumble bees and their host plants
Candace Galen, University of Missouri, U.S.A.

Bumble bees (Bombus) are a key pollinator guild in North America with multiple species in decline. Globally, bumble bees are moving upward in altitude, suggesting alpine regions represent potential thermal refugia from climate change in lower, southern regions of their range. Yet our research over four decades in the Rocky Mountains indicates that as warming continues, these high altitude refugia are themselves likely to be imperiled. In central Colorado (USA), encroachment of woody vegetation near timberline (tundra greening) and reduced flowering of tundra plant communities near the krummholz ecotone has led to landscape scale declines in historically preferred resources for bumble bee foragers. Only in small habitat patches near alpine summits are bees shielded from these negative effects of warming. Over a 500 m altitudinal gradient on Pennsylvania Mountain (CO), past bumble bee host species flower for only 33% of the time span observed in the 1970s. Advancement of flowering phenology with warming is especially pronounced in historically late season host plants, leading to increased flowering overlap among species, causing temporal mismatches between bumble bee colony production and resource availability, and favoring generalized foraging in two long-term resident bumble bee species. Results from pollination experiments suggest that a positive feedback loop links generalized foraging in bumble bees to foreign pollen contamination and impaired seed set of alpine host plants. Using herbarium specimens to reconstruct past trajectories of pollination quality we can test this idea, addressing broad scale impacts of global warming on pollination services.

Candace Galen is a Professor of Biological Sciences at the University of Missouri. Since the mid-1970s she has conducted field studies of pollination mutualisms in the Colorado Rocky Mountains. Her research has revealed tradeoffs between attracting pollinators and defending against floral antagonists; demonstrated evolutionary responses of floral traits to pollinator-mediated selection; and documented rapid evolution of foraging traits in bumble bee pollinators under climate change. The alpine regions where Galen works provide thermal refugia for myriad heat-sensitive species including iconic Rocky Mountain bristlecone pine, yellow-bellied marmots and American pikas, along with two rare bumble bee species, Bombus balteatus and B. sylvicola. Galen’s work with land trusts, county agencies, and conservation non-profit groups has led to the establishment of the Pennsylvania Mountain Natural Area, protecting hundreds of acres of alpine habitat in the central Colorado Rocky Mountains from future development. In Missouri, Galen has developed science outreach programs partnering MU graduate students and undergraduates with elementary school students to address scientific research topics of their choosing. For these efforts, she was selected as Scientist of the Year by the Columbia, MO Public School District and received an excellence in teaching award from the University of Missouri.

The evolutionary ecology of ultraviolet floral pigmentation at micro- and macroevolutionary scales
Matthew Koski, University of Virginia, U.S.A.

The tremendous diversity in flower color has fascinated biologists for decades. Because pollinators are visually perceptive of ultraviolet (UV) color, flower color patterns in the UV spectrum have particularly sparked interest in pollination biologists. A common UV ‘bullseye’ floral phenotype has long been held to function as a nectar guide for pollinators, increasing pollination efficiency. I experimentally test how variation in floral UV pigmentation phenotype affects pollinator behavior using phenotypic manipulation, and then address whether pollinators may contribute to UV floral variation in nature using the common plant, Argentina anserina (Rosaceae). Pollinators preferentially visit flowers with a distinct UV bullseye pattern, however UV pattern variation does not affect their alighting, or foraging behavior. There is pronounced variation in the size of the UV bullseye in nature, and geographically shifting pollinator preference can contribute to patterns of floral variation across space. While UV pigmentation patterns are variable within species, they also differ substantially among taxa, potentially owing to pollinator-mediated trait divergence. I test whether pollinators may drive phenotypic variation among taxa in the Potentilleae (Rosaceae) tribe using a biogeographically-informed sister taxon analysis. Interestingly, species that co-occur have more similar UV pigmentation phenotypes than those that grow in spatially distinct regions, suggesting a lack of reproductive character displacement for UV pigmentation. Instead, I present data that suggest how selection via abiotic factors (in conjunction with pollinators) may drive variation in UV floral pattern.

Matthew Koski received his Ph.D. from the University of Pittsburgh in 2015 working with Tia-Lynn Ashman on flower color evolution in Potentilla and the evolution of plant sexual systems in Fragaria. He is a postdoctoral research associate with Laura Galloway at the University of Virginia evaluating mating system evolution in Campanula.


Putting milkweeds in context: The evolution and function of pollen aggregation in Apocynaceae
Tatyana Livshultz, Drexel University, U.S.A.

Pollination is an inefficient process. On average, less than 1% of exported pollen grains are deposited on conspecific stigmas. Pollen transfer is an order of magnitude more efficient (ca. 25% on average) in species with pollen packaged into pollinia, yet pollinia have evolved in only two families, Orchidaceae and Apocynaceae, indicating strong fitness costs under most ecological conditions. I develop the hypothesis that pollinia and elevated pollen transfer efficiency are adaptations to conditions of strong mate-finding Allee effects and high levels of interspecific competition for pollination, allowing plants to continue outbreeding, but at the cost of drastic reduction in the number of mates. Apocynaceae, with ca. 5000 species, have a diversity of floral morphologies and degrees of pollen aggregation, including monads, tetrads, and pollinia, making them an ideal lineage to investigate the evolution of pollen aggregation and its adaptive value using the comparative method. By placing both direct measures of pollen transfer efficiency and a correlated trait (pollen-to-ovule ratios) in a phylogenetic context, I show that pollinia evolved in an ancestral flower that already had functionally aggregated and highly efficient pollen transfer. However, power analysis indicates that the sample size is not yet adequate to detect if Apocynaceae with pollinia (milkweeds) have significantly more efficient pollen transfer than those without. Comparative climate niche analysis links the origin of pollinia to ecological conditions generated by the aridification of Africa during the Cenozoic, consistent with the hypothesis that ecological adversity has selected for the evolution of efficiency.

Tatyana Livshultz is assistant professor in the Department of Biodiversity, Earth and Environmental Sciences (BEES) of Drexel University and assistant curator and chair of the Botany Department at the Academy of Natural Sciences. She received her B.A. in Biology from the University of Chicago in 1995 and her Ph.D. in Plant Sciences from Cornell University in 2003, working with Melissa Luckow. Before starting at the Academy in 2008, she did post-doctoral research with David Middleton at the Arnold Arboretum and Harvard University Herbaria and taught at the University of Nebraska Omaha. She decided to work on Apocynaceae for her Ph.D. because they have cool flowers, and she hasn’t regretted that decision since. Her current research interests include the macroevolution of plant traits mediating plant-insect interactions including functional floral morphology and secondary metabolism, phylogenomics, and digitization of herbarium collections.


Bats, birds, and bellflowers: The evolution of specialized pollination systems in the Neotropics
Nathan Muchhala, University of Missouri - St. Louis, U.S.A.

Animal pollination is thought to have played a central role in angiosperm diversification, especially in the tropics, where over 98% of plants are animal-pollinated. Research in my lab combines experiments and theory to explore the ecology and evolution of plant-pollinator interactions, with a focus on bat pollination in the Neotropics. In this talk I begin by discussing research on an unusual species of nectar bat which can launch its tongue 1.5 times its body length, an extension more than double that of other bats and longer than any other mammal. Unique adaptations allow it to store its tongue in its rib cage. Experiments suggest that this bat is involved in a coevolutionary race with the long-tubed flowers; tongue elongation allows bats to reach more nectar, while flower elongation maximizes pollen transfer. In the second part of the talk, I present evidence for two cases of character displacement in response to competition for pollination. The first involves overdispersion in flower morphology: co-occurring Burmeistera were found to place their pollen in different regions of bats heads’, thus maximizing conspecific pollen transfer despite sharing bats as pollinators. The second involves overdispersion in flower color: co-occurring Iochroma were found to differ significantly in color, as perceived by their primary pollinators (hummingbirds and bees), relative to random expectations. I end the talk with a brief overview of other ongoing projects in the lab. Together, this research shows some of the ways that coevolution and competition have shaped the highly specialized pollination systems found in the tropics.

Nathan Muchhala is an Assistant Professor at the University of Missouri - St. Louis. His first experience in tropical biology came after college, when he spent a year in Ecuador with a Fulbright Fellowship studying bat pollination in cloud forests. He has been returning to the tropics ever since, through his Ph.D. with the University of Miami and postdoctoral positions with the University of Toronto and University of Nebraska-Lincoln, and has published 30 papers on this research, including studies of plant-plant competition for pollinators, a bat-flower coevolution, nectar bat foraging behavior, evolutionary tradeoffs, and descriptions of new species of nectar bats and plants. Current members of his lab at UMSL hail from and work in Bolivia, Colombia, Peru, and Ecuador, and study both the plant and animal perspectives of bat pollination systems.


Floral scent: The dark matter of plant-pollinator interactions
Robert Raguso, Cornell University, U.S.A.

Flowers are not merely objects of aesthetic beauty; they serve as engines of biological diversity, lynchpins of ecological stability and fonts of human ecosystem services from agriculture and floriculture to cosmetics. Botanists have long been dazzled by the visual aspects of floral display (color, shape and pattern). In contrast, the chemical aspects of floral function, from the scents that guide pollinator attraction and learning to the composition of the nectars, resins and oils that reward their visits, somehow remain peripheral to the central bodies of ecological and evolutionary theory concerning pollination. However, recent technological and conceptual advances have made it easier to analyze and manipulate floral chemistry, particularly floral scent, and a growing body of evidence points to more central roles for scent in mediating floral isolation, constancy, gene flow and defense. I will highlight several recent manipulative studies, in which visual signals were tracked and controlled, to illustrate the unexpected roles played by scent in otherwise well-studied model systems. Floral scent provides critical mechanisms that explain conditional reproductive isolation among sympatric Ipomopsis aggregata and I. tenuituba, balance floral defense and pollinator-mediated selection on floral form in Polemonium viscosum, and dictate the network structure of floral visitors to generalized pollinator hubs such as Cirsium arvense and Achillea millefolium. In addition, I will explore our current knowledge of geographic variation in floral scent -the potential for local scent dialects - in the context of the Geographic Mosaic Theory of Coevolution, with reference to an ongoing study on the genus Oenothera

Robert Raguso grew to appreciate chemically mediated insect-plant interactions during his undergraduate research on butterflies at Yale University. He studied the genetics, physiology and ecology of floral volatiles for his doctoral research at the University of Michigan and insect olfaction and behavior for his postdoctoral work in the Center for Insect Science at the University of Arizona. He currently serves as chair of the Department of Neurobiology and Behavior at Cornell University. His research interests include multi-modal communication and signal evolution, the role of “private channels” in obligate mutualism and the impact of geographic mosaics of coevolution on variation in chemical phenotypes.


Whose bees are these? The pollen taxonomy of bee nests and its story in recent decades
David W. Roubik, Smithsonian Tropical Research Institute, Panama

We need to know more about why the populations of our bees go up and down, and a good deal more about what makes those bees in the first place. Making a pollen reference collection to a particular flora is both time-consuming and rewarding. For bee ecology, there is no greater source of detailed information. We have characterized honey origins from its pollen content, and pollen in orchid bee and solitary bee nests - without barcoding - but with replicated work. Our studies can, in contrast to all but a very small number of places that have established molecular reference libraries to the local flora, usually identify pollen grains to species. Armed with this insight, we can begin to picture the consumer’s dilemma (for a bee) and plant community efforts to obtain pollination service and reproduce.

An early question that motivated our building of two reference pollen libraries, one for Panama and one for the Yucatán Peninsula of Mexico, was the escape and explosive range extension of African honeybees in the Neotropics. What do they eat, and which plants are primarily responsible for sustaining them? By quantifying their pollen taken to hives, and also pollen ingredients of their honey, we saw striking evidence that many primary forest resources of the invasive honeybees are trees, and often not pollinated by bees, but yielding huge surpluses of nectar and pollen for “cleanup” organisms, such as social bees and their colonies. Much of their food was “leftovers”, from nocturnal flowers designed to feed and attract larger animals, like bats or moths. We documented the decline of native bee resource use when displaced by the invasive honeybee, but saw rapid ‘resource partitioning’, as local bees escaped food competition with the invader. We also witnessed subsequent growth of tree populations pollinated by the honeybees, and a boom in native bee resources that were offered via honeybee pollination services. Some solitary bees, on the other hand, did not respond to the Africanized bee invasion, but maintained their broad relationship with flowering plants that sustain them, in remarkably flexible fashion, and in the face of long-term climate changes and hurricanes. Our primary conclusion is that the wide diversity in native vegetation, particularly in the tropics (and also in the Washington, DC area), insures that flower visitors can adjust to and survive the tests of floral resource availability and other challenges.

David W. Roubik is a Smithsonian tropical biologist who has worked at the Smithsonian Tropical Research Institute (STRI) in Panama since 1979. His Googlebooks, NatHist films and Research Gate timelines are beginning to catch up with him. His field work covers much of the tropical world and his efforts include detailed studies on pollination ecology of native plants and food crops, the evolution, ecology, behavior and taxonomy of bees, island biogeography, and long-term monitoring and biology of pollinators, especially the orchid bees and Africanized honeybees. His studies of pollen taxonomy have been a collaboration with J. E. Moreno, at STRI in Panama, and with R. Villanueva at ECOSUR, Mexico.


Program and Schedule

Friday, May 20
Morning Session
NMNH Baird Auditorium
9:00 a.m. Registration and coffee, Evans Gallery (enter through Constitution Avenue lobby)
9:30 a.m. Opening Remarks, Maureen Kearney, Associate Director for Science, Smithsonian Institution, and Laurence J. Dorr, Chair of Botany, Smithsonian Institution. Presentation of the José Cuatrecasas Medal for Excellence in Tropical Botany, Kenneth J. Wurdack, Department of Botany, Smithsonian Institution.
Session Moderator: Seán Brady, Department of Entomology, Smithsonian Institution
10:00 a.m. Sam Droege, USGS Patuxent Wildlife Research Center, “Patterns in pollen and plant specialization among native bees in eastern North America”
10:45 a.m. Coffee Break, Executive Conference Room
11:15 a.m. David W. Roubik, Smithsonian Tropical Research Institute, “Whose bees are these? The pollen taxonomy of bee nests and its story in recent decades”
12:00 p.m. Tatyana Livshultz, Drexel University, “Putting milkweeds in context: The evolution and function of pollen aggregation in Apocynaceae”
12:45 p.m. Lunch break - on your own

Afternoon Session
NMNH Baird Auditorium
Session Moderator: Laurence J. Dorr, Department of Botany, Smithsonian Institution
2:00 p.m. Robert Raguso, Cornell University, “Floral scent: The dark matter of plant-pollinator interactions”
2:45 p.m. Matthew Koski, University of Virginia, “The evolutionary ecology of ultraviolet floral pigmentation at micro- and macroevolutionary scales”
3:30 p.m. Coffee Break, Executive Conference Room
4:00 p.m. Nathan Muchhala, University of Missouri-St. Louis, “Bats, birds, and bellflowers: The evolution of specialized pollination systems in the Neotropics”
4:45 p.m. Candace Galen, University of Missouri, “Shifting baselines and changing partners: Ecological and evolutionary responses to climate change in alpine bumble bees and their host plants”

Evening Events
The United States Botanic Garden
6:30 p.m. Closing reception and poster session, United States Botanic Garden, Washington, DC.


CALL FOR POSTERS The National Museum of Natural History and the U.S. Botanic Garden have begun accepting abstracts for poster presentations for the 14th Smithsonian Botanical Symposium, "Bats, Bees, Birds, Butterflies and Bouquets: New Research in Pollination Biology", which will be held May 20, 2016 in Washington, DC. Space is limited and will be accepted based upon the quality of the abstract and the order received.


  • Abstracts must be submitted electronically to before 13 April 2016.
  • Abstract selections will be made by 20 April 2016. Notifications will be sent by email only.

INSTRUCTIONS FOR PREPARING ABSTRACTS Abstract submissions should include the following:

  • Topic must be related to the study of pollination biology and contain original research.
  • Author(s) name(s) including affiliation(s) and email address(es).
  • List the title in upper and lower case. Titles are limited to 150 characters.
  • Abstracts may not exceed 1,500 characters (approx. 200 words), including spaces.
After you submit your abstract, you will receive a confirmation email. If you do not receive an email, your abstract has not been received. Registration is mandatory to be included in the program.



  • Posters will be displayed on May 20th at the U.S. Botanic Garden during the closing reception.


  • Posters should be no larger than 30" x 40" (portrait orientation)
  • Presenting authors are requested to attend the poster session (6:00 pm - 8:00 pm) to take advantage of opportunities to discuss their work with symposium participants.

What will be provided:

  • Easels, foam board and binder clips for each accepted presenter.
  • We will NOT provide you with a table, computers, monitors or other electronic equipment and cannot guarantee access to electricity for your presentation should it be required.


Cuatrecasas Family Foundation
National Museum of Natural History
   Department of Botany
   Office of the Associate Director for Science
United States Botanic Garden

Visitor Information


The National Museum of Natural History is located on the National Mall at the intersection of 10th St and Constitution Ave NW in Washington, DC 20560.

The United States Botanic Garden is also located on the National Mall, at 100 Maryland Ave SW in Washington, DC 20001.

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