Smithsonian National Museum of Natural History

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Smithsonian Botanical Symposium
May 18, 2018
National Museum of
   Natural History and
the U.S. Botanic Garden
Washington, DC



Presented by the Smithsonian's National Museum of Natural History Department of Botany in collaboration with the United States Botanic Garden:

"Plants in the Past: Fossils and the Future"

Present-day plant diversity is remarkably rich and varied. It fully occupies those of us working in the United States National Herbarium and the United States Botanic Garden. Nonetheless, it is well known that the vast majority of plant species to have ever lived are now extinct. Knowledge of the past is key to understanding the origins of present-day plant diversity and to illuminating the fundamental evolutionary processes that generate it.

The 16th Smithsonian Botanical Symposium, hosted by the Department of Botany and the United States Botanic Garden, will explore plants in the past, from their early origins to the more recent rise of the angiosperms. Speakers will address current trends and the future of paleobotanical research. The Symposium coincides with the development of the Natural History Museum’s Deep Time exhibit, a major overhaul of the National Fossil Hall, which is scheduled to open to the public in June 2019.

NOTE: Unlike previous years, the Symposium presentations will take place in the Warner Bros. Theater in Smithsonian's National Museum of American History.


Grewiopsis saportiana

Fossil specimen of Grewiopsis saportana Lesquereux from the Hell Creek Formation. (image courtesy of the Smithsonian’s Department of Paleobiology Collections)

Speaker Abstracts

The enigmatic “Mesozoic seed ferns”
Sir Peter Crane, Oak Spring Garden Foundation, U.S.A.

A dominant trend in paleobotany over the last several decades has been the dramatic expansion of a critically evaluated angiosperm fossil record and increased appreciation of its relevance for understanding major patterns in angiosperm evolution. The picture that has emerged is rich with new insights, and has revealed a pattern that is broadly consistent with evidence from the molecular phylogenetics of living plants. However, much more problematic have been attempts to understand the origin of angiosperms and convincing resolution of this question has eluded both molecular phylogenetic and paleobotanical approaches. Progress has seemingly ground to a halt indicating that what is needed are new sources of data. Central to many discussions of angiosperm origins have been two groups of so-called, “Mesozoic” seed ferns - the Caytoniales and corystosperms (Umkomasiales). New material, mainly discovered and collected on field expeditions over the past decade from the Early Cretaceous of Mongolia and adjacent areas of China, is providing new information on both groups. These new data, derived from exceptionally well-preserved lignified mesofossils and high quality impressions, as well as specimens permineralized in chert, help to clarify previous misunderstandings and are revealing surprising architectural commonalities among the ovulate reproductive structures of several groups of living and fossil seed plants. These discoveries raise interesting questions and suggest new perspectives that are likely to have important implications for understanding seed plant evolution, including the origin of angiosperms.

Sir Peter Crane FRS is President of the Oak Spring Garden Foundation in Virginia <>, an estate of Rachel Lambert Mellon that includes an exquisite garden as well as an exceptional library focused on the history of plant science, plant exploration, and the development of gardens and landscape design. He is known internationally for his work on the diversity of plant life - its origin, fossil history, current status, conservation and use. Crane was elected to the Royal Society - the UK academy of sciences in 1998 and was knighted in the UK for services to horticulture and conservation in 2004. He is a Fellow of the American Academy of Arts and Sciences, Foreign Associate of the US National Academy of Sciences, a Foreign Member of the Royal Swedish Academy of Sciences, and a Member of the German Academy Leopoldina. He is the recipient of several honorary degrees from universities in the UK and US, including honorary doctorates of science from the University of Connecticut and Sewanee: The University of the South, in the US, and Cambridge University in the UK. He received the International Prize for Biology in December 2014.

Biotic seed dispersal, growth architecture, and the evolution of conifer cone diversity
Andrew Leslie, Brown University, U.S.A.

Conifer cones are some of the most recognizable and well-known botanical structures, and their evolution has long fascinated botanists. The fossil record has proven essential in understanding the origins of modern conifer cones from fertile shoot systems in Paleozoic ancestors, and cones remain a promising system in which to incorporate paleobotanical data into macroevolutionary studies. In particular, advances in comparative methods using dated phylogenetic trees may provide answers to persistent problems in conifer cone evolution, such as the origin of simplified and fleshy seed cone morphologies like the “berries” of yews. I use a combination of fossil data, ancestral state reconstructions, and models of character evolution to illustrate how the appearance of specialized animal seed dispersal strategies over the late Mesozoic and Cenozoic played a large role in the evolution of modern conifer cone diversity, although the exact morphological adaptations that clades exhibit depends on their branching architecture. For example, the simplified fleshy cones found in some Cupressaceae and most Podocarpaceae evolved from small woody cones characteristic of conifers with highly ramified distal twigs bearing imbricated scale leaves. In contrast, conifer clades with large diameter branches bearing large cones never evolve fleshy tissues for biotic dispersal, but instead produce large dry seeds that animals pluck out of the cones. Because conifers combine rich living diversity with an extensive fossil record, they represent an ideal group in which to apply a variety of phylogenetic and comparative methods to deep-time evolutionary studies.

Andrew Leslie is an Assistant Professor at Brown University who studies the evolution of plant reproductive morphology. After graduating from the University of Pennsylvania, he received his Ph.D. at the University of Chicago and then conducted postdoctoral work at Yale University. His work focuses on integrating phylogenetic analysis, data from the fossil record, and insights from ecology and functional morphology in order to understand the drivers of morphological diversification in plant reproductive structures. Most of Leslie’s work has focused on conifers, a group with considerable living diversity, diverse reproductive morphologies, an extensive fossil record stretching back more than 300 million years, and a well-resolved phylogeny. His research also includes field and specimen-based paleobotany, including ongoing projects in the Jurassic of Argentina, the Cretaceous of Mongolia, and the Miocene of New Caledonia.


The different roles of fossils for time-calibrating phylogenies
Susana Magallón, Universidad Nacional Autónoma de México, Mexico

Time-calibrated phylogenies provide direct information about the age of clades, and represent the starting point of studies on morphological evolution, biogeographic history, and the dynamics of the process of diversification. It is clearly recognized that independent temporal calibrations are determinant to molecular clock analyses - far more relevant that the amount of molecular data, and clock method. Fossils have been used in varied ways and to different degrees in different clock methods. A few studies have entirely omitted the paleobotanical record, drawing their calibrations from phylogenetically distant nodes or absolute substitution rates. Other studies are entirely based on fossil evidence, including estimating a confidence interval around the age of selected nodes, and a model that simultaneously estimates ages, diversification and preservation parameters. Relaxed molecular clocks combine molecular data with fossil information applied in different ways, to estimate divergence times and other parameters. Most conventionally, fossils are used to calibrate selected internal nodes, but are not included in the phylogeny, nor do they play a role in generating it. Tip-dating methods rely on total evidence data to simultaneously estimate phylogenetic relationships and divergence times among extant and fossil taxa. A recently developed, highly parametric method integrates extant and fossil taxa as part of the same diversification process under a common phylogeny-generating model, including estimation of the role of fossils as extinct terminals, or as ancestors of prevailing phylogenetic branches. These different roles of fossils in time-calibration methods will be exemplified with published and ongoing studies estimating angiosperm age.

Susana Magallón studied biology during her BSc at the Universidad Nacional Autónoma de México in Mexico City, and specialized in botany and paleontology during her M.Sc. at the same University. During her Ph.D., she acquired training in quantitative paleobiology at the Department of Geophysical Sciences of the University of Chicago, combined with structural botany and phylogenetics at the Field Museum of Natural History, under the guidance of Professor Peter R. Crane. She practiced molecular systematics and parametric phylogenetics during her postdoctoral appointment working with Michael J. Sanderson at the University of California, Davis. She obtained a position as senior research scientist at the Department of Botany of the Institute of Biology of the Universidad Nacional Autónoma de México in 2001, where she is now a Professor. Her research is guided by questions of plant macroevolution in a phylogenetic context, in particular on evolution of floral structure, diversification dynamics of major plant clades, and mechanisms driving high species richness in hiperdiverse Neotropical plant groups. To develop this research, she combines molecular and morphological data of living and extinct species, and uses methods of comparative macroevoultionary phylogenetics. Magallón is an Editor of International Journal of Plant Sciences, and of New Phytologists. She is currently the President of the Society of Systematic Biologists.

Laying the foundations for automated pollen analysis
Surangi Punyasena, University Of Illinois at Urbana-Champaign, U.S.A.

Palynological data are derived from the expert identification of fossil pollen and spore specimens. Although the microscopes for observing palynological specimens have dramatically improved over the last century, our methods for comparison and classification are still largely visual and qualitative. Automated, machine-based pollen analysis holds the potential to transform the discipline. Automation would increase data throughput, producing more pollen counts per expert per unit of time, and improve data quality, by increasing the taxonomic resolution of identifications and by calculating explicit estimates of identification uncertainty for the first time.
I present three examples of research problems that we have successfully addressed using a generalized workflow for automated classification: automation of pollen counts from species-rich airborne pollen samples from a Neotropical lowland forest; reconstruction of the extinction history of a North American spruce; and an investigation of the biogeography and diversification history of a pantropical legume clade. These diverse classification problems were solved using modified convolutional neural networks (CNNs), trained on image libraries created using optical superresolution microscopy and automated slide scanners.
The diversity of these problems demonstrate the generalizability and transferability of these machine learning methods to other visual classification problems. CNNs represent a powerful new group of computer vision algorithms. However, the efficacy of these automated approaches is limited by the training data available in any given analysis. The future of these automated analyses will largely rely on the development of expansive specimen image databases incorporating well-curated image data, derived from well-curated specimens.

Surangi Punyasena is an Associate Professor and Associate Head of Plant Biology at the University of Illinois, Urbana-Champaign. She is also an affiliate of the Program in Ecology, Evolution and Conservation Biology, the Illinois Informatics Institute, and the Departments of Geology and Geography. She completed her B.A. at Yale University and her S.M. and Ph.D. in Evolutionary Biology at the University in Chicago. Her research uses the Neogene plant microfossil record (primarily pollen) to reconstruct the ecological and evolutionary dynamics of Neotropical plant communities.


Late Cretaceous floras from northern South America and the evolution of Neotropical rainforests
Mónica Ramírez-Carvalho, Smithsonian Tropical Research Institute, Panama

Tropical South America has the highest plant diversity of any region in the world today. The origin and causal mechanisms that underlie this diversity remain an open question in evolutionary biology. Fossil floras from northern South America provide direct evidence of the timing of origin and diversification of Neotropical biomes, as well as their response to global perturbations in the geological past. Among these fossil floras are the Late Paleocene Cerrejón and Bogotá Floras, dating back to 58-60 million years ago, and considered to be the earliest known examples of Neotropical rainforests based on their paleoclimate, family-level taxonomic composition and comparable paleoecology with living rainforests. Even though these fossil floras have given a baseline for understanding the evolution of Neotropical rainforests throughout the Cenozoic, little is known about what kind of ecosystems and floristic associations existed in the Neotropics before this time. Using the pollen and leaf fossil record, we describe the floristic composition of Late Cretaceous forests in northern South America and evaluate the impact of the End-Cretaceous mass extinction on these early tropical forests.
The continuous pollen record across the K/Pg boundary indicates drastic plant extinction at the end of the Cretaceous that is also reflected in Late Cretaceous and Late Paleocene leaf assemblages. Fossil leaves collected in four Late Cretaceous sites show that many extant tropical plant families such as Lauraceae, Arecaceae, Araceae, existed in the Late Cretaceous floras, these forests lacked the family-level composition typical of Late Paleocene and living Neotropical rainforests. Similarly, diverse and highly specific plant-insect associations seen in fossil leaf damage in the Late Cretaceous floras are replaced with distinct leaf damage traces in the Late Paleocene assemblages, indicating an ecological turnover. Plant extinction at the K/Pg boundary and the differences observed between the Late Cretaceous and Late Paleocene floras from northern South America indicate that the End-Cretaceous mass extinction could have enabled the evolution of Neotropical rainforests as we know them today.

Mónica Carvalho is an Earl S. Tupper Post-doctoral Fellow at the Smithsonian Tropical Research Institute in Panama. She has a M.S. in Geosciences from The Pennsylvania State University and a Ph.D. in Plant Biology from Cornell University. Her work combines research on living plants and the plant fossil record as a means to understand the evolution of terrestrial ecosystems. Carvalho has described various fossil plants from the Cretaceous, Paleocene and Eocene of South America, and is currently working on evolution of tropical rainforests and their response to past extinction and global warming events.


Plant paleobiology in the digital era: How X-ray microCT is helping to shed light on the history of plants
Selena Y. Smith, University of Michigan, U.S.A.

Fossils provide critical data for understanding broad patterns of biodiversity, biogeography, ecology, and evolution over geological time scales. Challenges remain in various areas of interpreting the fossil record, including difficulties presented by variable preservation, accessibility to specimens, and accurately interpreting morphology in order to place fossils in the Tree of Life. A tool with much potential to help overcome some of these challenges is the use of 3D imaging via synchrotron-based or industrial X-ray micro-computed tomography (microCT). MicroCT is non-destructive, rapid, and provides 2D and 3D morphoanatomical data, making it ideal for fossils. In addition, digital data provide a lasting record of specimen morphology, preserving information in case of compromised integrity and enabling virtual sharing and examination of material. MicroCT facilitates acquisition of comparative morphological data from extant taxa. Using either fossil or modern datasets, virtual dissections and the creation of virtual fossils from these 3D datasets can be used generate hypotheses of expected morphologies from either extant or extinct taxa to aid in correctly placing fossils in a taxonomic and phylogenetic framework. Examples of the usefulness of microCT include understanding biodiversity in the Cretaceous-Paleogene Deccan Intertrappean Beds of India and helping to place fossils in a phylogenetic context in studies of specific groups like the Arecales (palms) and Zingiberales (gingers, bananas, and relatives). MicroCT is proving to be an invaluable tool for paleobotanical studies, enhancing our ability to study natural history collections and build comparative datasets that will ultimately help to elucidate broader patterns of plant diversity and evolution.

Selena Y. Smith uses the fossil record of plants to better understand past environments and plant evolution, with a particular interest in Cretaceous and Paleogene floras, the importance of morphology, and taxonomy. Her research has largely focused on monocot flowering plants (such as gingers, bananas, palms, and sedges) but she holds an interest in (and occasionally also works on) other plant groups such as ferns and conifers. She has had a long interest in plants and fossils, leading her to earn a Ph.D. from the University of Alberta in 2007. As a Royal Society postdoctoral researcher in the UK, Smith started using synchrotron-based and industrial microCT methods to unlock more information from the plant fossils themselves, and this is now a core technique in much of her research today. She has been at University of Michigan as an Assistant Professor since 2014.


Ecophysiology of extinct plants
Jonathan Wilson, Haverford College, U.S.A.

Plants are unique among multicellular organisms because much of their physiology is biophysical, rather than behavioral, and the anatomy that defines these biophysical capabilities is preserved in the fossil record. However, many extinct plants lack close living relatives or morphological analogues for fossilized anatomical features, limiting the ability of experimental methods to provide a perspective on extinct plant growth, development, and function. Mathematical models, when applied to fossilized plant organs—particularly leaves and stems—can provide quantitative insight into the physiology and ecology of plants that have been extinct for hundreds of millions of years. Within the Euramerican Carboniferous tropical forests, key plants from seed and non-seed plant lineages occupied physiological niches that were later explored by flowering plants, suggesting an early history of complex physiological behavior and environmental response. Furthermore, understanding the physiological properties of Carboniferous plants permits paleoenvironmental proxies, including geochemical proxies for carbon dioxide concetration, to be refined. Comparing the physiology of extinct plants with strategies that are currently employed by living plants sheds light on ecophysiological trajectories in plant evolutionary history and the history of plant-environment coevolution.

Jonathan Wilson is a paleobotanist interested in the evolution of plant form and function. He is Associate Professor of Biology and Environmental Studies at Haverford College, an undergraduate liberal-arts college near Philadelphia, where he also directs the interdisciplinary Environmental Studies Program. His research applies methods from biophysics and geobiology to paleobotanical problems, focused on quantitative approaches to the evolution of terrestrial ecosystems in the Paleozoic Era. Wilson received his undergraduate degree in Computer Science and Earth and Planetary Science from Johns Hopkins, completed his Ph.D. at Harvard University in Earth and Planetary Sciences in 2009, and was a postdoc at Caltech before arriving at Haverford. He has conducted fieldwork in Australia, Namibia, Puerto Rico, Trinidad and Tobago, and across the continental United States.


Program and Schedule

Friday, May 18
Morning Session
NMAH Warner Bros. Theater
9:00 a.m. Registration (Constitution Avenue lobby, National Museum of American History)
9:30 a.m. Opening Remarks, Kirk Johnson, Sant Director, National Museum of Natural History, 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

10:00 a.m. Sir Peter Crane, Oak Spring Garden Foundation, “The enigmatic ‘Mesozoic seed ferns’”

10:45 a.m. Coffee break, Jazz Café

11:15 a.m. Andrew Leslie, Brown University, “Biotic seed dispersal, growth architecture, and the evolution of conifer cone diversity”
12:00 p.m. Jonathan Wilson, Haverford College, “Ecophysiology of extinct plants”

12:45 p.m. Lunch break - on your own

Afternoon Session
NMAH Warner Bros. Theater
2:00 p.m. Surangi Punyasena, University of Illinois at Urbana-Champaign, “Laying the foundations for automated pollen analysis”
2:45 p.m. Selena Y. Smith, University of Michigan, “Plant paleobiology in the digital era: How X-ray microCT is helping to shed light on the history of plants”

3:30 p.m. Coffee break, Jazz Café

4:00 p.m. Mónica Ramírez-Carvalho, Smithsonian Tropical Research Institute, “Late Cretaceous floras from northern South America and the evolution of Neotropical rainforests”
4:45 p.m. Susana Magallón, Universidad Nacional Autónoma de México, “The different roles of fossils for time-calibrating phylogenies”

Evening Events
The United States Botanic Garden Conservatory
6:30 p.m. 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 the 16th Smithsonian Botanical Symposium, "Plants in the Past: Fossils and the Future", which will be held May 18, 2018 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 2018.
  • Abstract selections will be made by 20 April 2018. 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 paleobotany 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 18th 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.


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 American History is located on the National Mall at 1300 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.

For maps, directions, and additional information, visit the NMAH or USBG websites.


Metrorail, Washington's subway system, and Metrobus link the city with nearby communities in Maryland and Virginia. The closest subway stations to the National Museum of Natural History are Federal Triangle and Smithsonian (both on the Blue, Orange, and Silver lines). The closest subway station to the United States Botanic Garden is Federal Center SW (also on the Blue, Orange, and Silver lines). For a Metrorail map and more information, visit the Metro website.

Washington is served by three major airports: Reagan National (DCA), which is most convenient for domestic travelers; Dulles International (IAD); and Baltimore/Washington International (BWI). DCA is served directly by Metrorail. IAD and BWI can both be accessed via public transportation, but are not directly served by Metrorail.

Parking is not available at the museum. There are several private parking garages in the vicinity.


There are many options in the Washington area. In general, prices decrease with distance from the National Mall (city center). However, it is important to factor in the cost and time required to travel between a particular option and the conference venues on the National Mall. It is recommended that you prioritize options within walking distance to a Metrorail stop or the conference venues.

For hotels, the popular online booking sites for travelers should provide you with a range of possibilities. As always, reading reviews can be helpful. Please keep in mind that Washington is a popular tourist destination; for the greatest number of options and best prices, book early. Please note that there is not an official conference hotel.

SBS 2018 - Optional Behind-the-Scenes Tour

A behind-the-scenes tour of the Joseph F. Cullman 3rd Library of Natural History
National Museum of Natural History, 10th St. and Constitution Ave. NW, Washington DC, 20560
Hosted by Smithsonian Libraries

Come see rare paleobotanical books in the Smithsonian Libraries' Joseph F. Cullman 3rd Library of Natural History. The Cullman Library will have on display a wide selection of publications that highlight fossil plants, from Boccone's Recherches (1674), through the editions of Scheuchzer's Herbarium diluvianum (1709, 1723), to Brongniart's works in the 19th century, and more.

To sign up, please send an email message to indicating which tour you would like to attend. First come, first serve. A waiting list will be made to accommodate demand. RSVP by Monday, May 14.

  • Thursday, May 17 at 3:00 - 4:00 pm
  • Thursday, May 17 at 4:00 - 5:00 pm
  • Friday May 18 at 5:30 - 6:30 pm

Capacity for each tour is 20 people.

For more information on the Cullman Library collections, go to and click on the pdf at the bottom of the page.

Please note: The Cullman Library is a high-security facility; you will be on video camera. No food or drink is allowed in the library. Photography is allowed, but no flash.

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