Who We Are

Our departmental mission: We serve as conservation leaders, by studying and advocating for native plants, communicating their value, and convening people in support of them.



Stephanie Calloway

Conservation Technician

photo of Stephanie CallowayStephanie works with conservation staff at the Garden on various projects focusing on insect-plant interactions, rare plants, and restoration. Stephanie has a B.S in Entomology from the University of California, Davis. She has diverse work experience, ranging from working with tardigrades to mangrove gastropods, but most of her work has focused on California plants. Stephanie is currently interested in documenting plant-pollinator interactions within our project systems. She has worked in several regions across California, including the Sierra Nevada, Channel Islands, and Mojave Desert for nearly a decade.

Sean Carson

Rare Plant Technician

photo of Sean CarsonAs the Rare Plant Technician, Sean works to conserve California's rare and endangered flora. His work includes surveying and documentation of rare plants as well as seed collection for long term conservation, research, and restoration. Sean received his B.A. in Environmental Studies at California State University, San Bernardino. Sean has many years of field experience working in restoration ecology, where he worked in the San Bernardino National Forest before moving to the Channel Islands and eventually to the California Central Coast.

Susana Delgadillo

Herbarium Curatorial Assistant

photo of Susana DelgadilloSusana works at the Garden’s Clifton Smith Herbarium as an herbarium curatorial assistant. Her duties consist of developing and maintaining the Garden’s herbarium collection, as well as digitally imaging the collection to upload onto a public online database. Susana received her B.A in Environmental Studies from the University of California, Santa Barbara, where she was a restoration assistant at the university’s North Campus Open Space restoration project. Susana also spent three years as an assistant at the university’s library where she managed records and kept inventory of varied print collections. Her interests include curating natural history collections to make them more readily accessible to a diverse global community.

Matt Guilliams, Ph.D.

Ken and Shirley Tucker Plant Systematist

Curator of the Clifton Smith Herbarium

Photo of Matt Guilliams, Ph.D.

Matt is a plant systematist and curator of the Garden's Clifton Smith Herbarium. As a botanist/plant systematist, his overall focus is the study of the flora of California, which includes floristics, biodiversity description, inferring evolutionary patterns, and conservation genetics of rare plants. Matt earned his B.S. and M.S. in Evolutionary Biology at San Diego State University and his Ph.D. in Integrative Biology from U.C. Berkeley. He has been working as a botanist in the state since 1998.

Denise Knapp, Ph.D.

Director of Conservation and Research

photo of Denise Knapp Ph.D.Denise oversees the Conservation program at the Garden, including all biodiversity, rare plant, restoration, and outreach/advocacy work, and conducts ecological research. Denise has a Ph.D. in Ecology from the University of California, Santa Barbara and an M.A. degree in Geography from the University of California, Los Angeles. She has worked on vegetation, fire ecology, invasive species, habitat restoration, and rare plant projects; her current focus is plant-insect interactions. She has worked as a plant ecologist in California (particularly the Channel Islands) for nearly two decades, including the consulting, University, and nonprofit worlds.

Kristen Lehman, Ph.D.

Conservation Geneticist and Lab Manager

Photo of Kristen Lehman, Ph.D.Kristen oversees the conservation genetics lab at the Garden. She integrates field studies, molecular tools and histological techniques to document biodiversity and understand the interplay of ecological and evolutionary effects on plants of conservation concern. After receiving a M.S. at San Diego State University, Kristen earned her Ph.D. in Botany at Rancho Santa Ana Botanic Garden and worked at the Smithsonian Museum of Natural History in the plant DNA barcoding lab. She has worked with California native plants since 2006.

Rikke Reese Naesborg, Ph.D.

Tucker Lichenologist and Curator of the Lichen Herbarium

Photo of Rikke Naesborg, Ph.D.Rikke is the Garden lichenologist and curator of the Garden’s lichen herbarium. She is interested in investigating lichen community composition and ecology in order to identify why different lichen species are distributed differently across the landscapes. Another major interest is conservation of lichens; a complicated task that is only possible by expanding knowledge of lichen distribution and ecology. Rikke received her B.S. and M.S. at University of Southern Denmark and went on to earn a Ph.D. in systematic botany from Uppsala University in Sweden. She has lived in California since 2011.

Casey Richart, Ph.D.

Invertebrate Biodiversity Postdoctoral Scholar

Casey Richart, Ph.D.Casey's research foci include species delimitation, biodiversity data management, and the conservation of short-range endemic organisms. He is broadly trained as a naturalist, but his research primarily focuses on terrestrial gastropods, millipedes, and harvestmen arachnids. Casey received his Ph.D. in the Evolutionary Biology Program at San Diego State University jointly with University of California, Riverside. Casey’s position at the garden is to document the terrestrial invertebrates from San Clemente Island. This research has already resulted in documenting many new species for the island, and likely many new species to science. This systematic faunal survey aims to lay the groundwork for important future research including developing baselines upon which to evaluate future trends and ecological restoration, and to attain a better understanding of the biogeographical scenarios that led to the unique fauna of the California Channel Islands.

Heather Schneider, Ph.D.

Rare Plant Biologist

Schneider, Heather, Ph.D.Heather oversees the rare plant conservation program, which includes conducting research, implementing conservation and recovery actions, managing the conservation seed bank, and providing outreach and education opportunities focused on California’s rare plants. Heather’s research interests and experience in plant ecology, seed banks, conservation, invasive plants and evolutionary biology. She earned a PhD in botany and plant sciences from the University of California, Riverside, worked as an ecologist for the US Geological Survey, and was a postdoctoral scholar at the University of California, Santa Barbara before joining the Garden. Heather has been working to understand and protect the California flora since 2005.

Adam Searcy

Invertebrate Technician

Adam Searcy portraitAdam works with Dr. Casey Richart, Invertebrate Biodiversity Postdoctoral Scholar, on our invertebrate survey of San Clemente Island. He assists with sorting, identification, and curation of arthropod specimens collected over the 2019 field season. He earned his B.S. in Ecology and Evolutionary Biology from the University of California, Santa Cruz. Adam has field experience collecting and identifying California insects, and California native plants, and has worked extensively on research projects involving California’s avifauna. He is interested in developing a greater understanding of the invertebrate fauna of the Channel Islands and mainland California.

Emily Thomas

Laboratory Technician

Emily ThomasEmily is a lab technician in the Conservation Genetics lab where she performs DNA isolation, quantitation, and PCR along with helping to curate the Garden’s tissue bank. She earned her B.S. in Environmental Studies from the University of California Santa Barbara, and her work experience has primarily revolved around ecological restoration. She participated in active restoration projects on UCSB’s campus as an undergraduate, and she has contributed to research that will inform future restoration of fuel breaks in Los Padres National Forest. Emily is particularly interested in the causes of diversification of plants in southern California, and she is excited to be a part of the Garden’s efforts to study and protect the native flora.



Research Associates

Sherwin Carlquist, Ph.D.

Research Associate

photo of Sherwin Carlquist by Don MatsumotoDr. Carlquist is Professor Emeritus at Claremont Graduate School and Pomona College, and has been a research Botanist at SBBG since 1993. He was named a John Simon Guggenheim Fellow in 1973 and holds awards from such prestigious institutions as the Smithsonian Institution and the California Academy of Sciences. His?extensive list of publications?centers on studies of island botanical life, but also includes monographs on plant anatomy, structure, and evolution.

Kristina M. Gill, Ph.D.

Research Associate

photo of Kristina Gill, Ph.D.Kristina M. Gill is an archaeobotanist and archaeologist working primarily in island and coastal areas of central and southern California. She completed her PhD in anthropology at the University of California Santa Barbara in 2015. Her research focuses on ancient plant use, subsistence, and settlement patterns among the Island Chumash/Tongva and their ancestors, who inhabited the islands off the coast of southern Alta California for more than 13,000 years. She combines historical ecological data from archaeological sites and Traditional Ecological Knowledge to inform modern land management and restoration practices, especially in the face of climate change.

Barbara Holzman, Ph.D.

Research Associate

photo of Barbara Holzman, Ph.D.Dr. Holzman studies vegetation dynamics. Her California research foci have included Point Reyes conifer regeneration, Farallon Islands vegetation change and plant invasions, blue oak woodland regeneration, and conservation of Ione endemic plants. She co-founded the Environmental Studies program at San Francisco State University, where she was a professor of Geography until her retirement in 2016. She received her PhD from U.C. Berkeley.

Steve Junak

Research Associate, SBBG Botanist Emeritus

photo of Steve Junak

Steve retired from his longtime position as the Garden’s?Herbarium Curator in 2013. He is an active researcher and expert on the flora of the islands of California and Baja California.? Steve holds an M.A. in botany, has led field trips for more than 25 years, and has co-authored several books on the Channel Islands including?A Flora of San Nicolas Island?and?Flora of Santa Cruz Island.

Tom Mulroy, Ph.D.

Research Associate

Photo of Tom Mulroy, Ph.D.Tom is a botanist/plant ecologist with a long-held research interest in?Dudleya?and botany of Baja California, Mexico.? He joined the Botanic Garden following a career in environmental consulting based in the Santa Barbara area and has wide-ranging field experience in arid and semiarid environments in the southwestern United States and adjacent Mexico.? Tom earned his B.A. in Zoology from Pomona College, his M.S. in Biology from the University of Arizona, and his Ph.D. in Ecology and Evolutionary Biology from the University of California, Irvine.

Elizabeth Painter, Ph.D.

Research Associate

Photo of Elizabeth Painter, Ph.D.Dr. Elizabeth Painter holds an M.A. in botany and a Ph.D. in ecology from Colorado State University and is also a Research Associate at UC Berkeley. She is a range ecologist with strong interests in conservation, and is a contributor to the Jepson Manual and The Jepson Desert Manual. Beth is a recognized expert on the impacts of grazing on rare and endangered plant species in rangelands.

Shirley Tucker, Ph.D.

Research Associate

Photo of Shirley Tucker, Ph.D.When Shirley retired from Louisiana State University and began her relationship with the Botanic Garden in 1995, she brought her immense passion and knowledge of plants, as well as her extensive collection of lichens. She has published over 140 papers on floral morphology, plant systematics, and the lichens of California. Among her many notable achievements and awards, Shirley was president of both the Botanical Society of America and the American Society of Plant Taxonomists. Shirley received her Bachelor’s and Master’s degrees at the University of Minnesota, and her PhD from the University of California, Davis.

Greg Wahlert, Ph.D.

Research Associate

Photo of Greg Wahlert, Ph.D.Dr. Wahlert is the Tucker Curator of Biodiversity Collections and Botanical Research at the Cheadle Center for Biodiversity and Ecological Restoration at UCSB. His primary research interests are floristic studies in central California, phylogeny and diversification of the manzanitas (Arctostaphylos) and lupines (Lupinus), systematics of the Violet Family, and taxonomic revision of various plant groups from Madagascar, including Rinorea (Violaceae), Grewia (Malvaceae), and Polygala (Polygalaceae).

Cam Williams, Ph.D.

Research Associate

Photo of Cam Williams, Ph.D.Cam has been botanizing since 1996. He really likes epiphytes, lichens, community ecology, wood anatomy, tree architecture, forest structure, forest canopy ecology, and the dynamics of plant water use. He earned undergraduate and master’s degrees from Humboldt State University, and a PhD from the University of California, Berkeley. Cam is also a Research Associate in the Gotsch Lab at Franklin and Marshall College, studying the physiological ecology of epiphyte communities in the cloud forests of Monteverde, Costa Rica. He works extensively with the Garden’s lichenologist.

Dieter Wilken, Ph.D.

Research Associate

Photo of Dieter Wilken, Ph.D.Dieter retired as Director of Research and Conservation in 2013 after 20 years of service at the Garden. Before coming to the Garden, Dieter was a professor at Colorado State University, and manager of the Jepson Manual project at UC Berkeley (1990-1993). Dieter received his undergraduate degree in botany from California State University, Los Angeles, and his doctoral degree from the University of California, Santa Barbara. Currently, he works in the Garden herbarium assisting database and imaging efforts, completing taxonomic treatments for the Flora of North America, and continuing to serve as an emeritus member of the California Native Plant Society’s Rare Plant Committee.