Section 2 of 2. Rare plants occur in nearly every type of habitat in California and are an important part of the state’s ecosystems, pollinator communities, and overall biodiversity. While great progress has been made in our understanding of rare plant taxonomy and ecology, many unanswered questions remain. Join us in this session to learn more about the fascinating rare plants that call California home.
SESSION CHAIRS Aaron E. Sims1, Margie Mulligan2
1California Native Plant Society, Sacramento, CA, United States. 2San Diego Natural History Museum, San Diego, CA, United States
Aaron E. Sims
California Native Plant Society
Aaron is responsible for directing and managing the status review process for additions and changes to the CNPS Rare Plant Inventory (RPI) and the California Natural Diversity Database (CNDDB), updating and maintaining the RPI, and developing and overseeing rare plant research and field projects throughout the state. He received a degree in Ecology and Systematic Biology with an emphasis in Botany from Cal Poly, San Luis Obispo, where he also assisted with David Keil’s Field Botany course for five consecutive years. Aaron has 19 years of professional botany experience, with prior work in environmental consulting and as an ecologist for the San Luis Obispo Coast District of California State Parks, where he performed rare plant and vegetation surveys, prescribed fire management, and GIS specialties. In his free time, he enjoys being a dad, baking, dancing, and spending time outside snowboarding, kayaking, botanizing, and photographing wildflowers.
Margie Mulligan
San Diego Natural History Museum
Margie Mulligan, M.S., has 29 years of experience in botany, including 20 years dedicated to the flora of San Diego County. Her focus on floristics and endangered species in the region has led to extensive research and monitoring efforts across southern California. She has led and collaborated on field studies, long-term monitoring programs, and made voucher collections that contribute to regional conservation and management initiatives.
6.1 Island Endemism, Land Management Decisions, and the Plants that Cling on (Malacothrix, Asteraceae)
Annie Ayers1,2, Dr. Matt Guilliams1, Dr. Kristen Hasenstab-Lehman1, Dr. Heather Schneider1, John Knapp3
1Santa Barbara Botanic Garden, Santa Barbara, CA, United States. 2California Native Plant Society Channel Islands Chapter, Santa Barbara, CA, United States. 3Catalina Island Conservancy, Santa Catalina Island, CA, United States
Description The California Channel Islands exhibit a complex history of land-use change. This includes the displacement of Indigenous peoples (Chumash/Tongva) and the cessation of traditional lifeways as well as extensive impacts from a protracted ranching period (late 18th century to 2014), which introduced invasive grazers. Following the recent removal of invasive ungulates, many island plant communities are recovering, yet others remain challenged by persistent invasive species and habitat degradation. Within these recovering systems, the Malacothrix foliosa species complex, which comprises six island endemics, serves as a model system for conservation challenges. We discuss the conservation actions and concerns for four key taxa within this group: M. indecora, M. squalida, M. junakii, and M. foliosa ssp. polycephala. These annual vascular plants highlight three critical conservation issues: (1) habitat degradation from historical and ongoing invasive species, (2) direct conflicts with other conservation priorities, notably seabird nesting on restricted, critical habitat, and (3) the looming ecological risk of hybridization leading to a loss of genetic distinctiveness and potential displacement of single-island endemics. As a model system at the intersection of land management and rare plant recovery, the Malacothrix foliosa complex is used in this talk to evaluate how recent management actions and survey results inform the persistence of rare, island-endemic annuals.
Presenter Bios
Annie Ayers
Santa Barbara Botanic Garden
Annie cut her teeth on California botany studying at Cal Poly San Luis Obispo, where she fell in love with Herbaria. After communing in the Hoover Herbarium and spending stints in other collections, Annie now spends her time in the herbarium of the Santa Barbara Botanic Garden as the Collections Manager.
6.2 Conservation Genomics of Crocanthemum greenei: Effects of Land Management on the Genetic Structure and Diversity of a Channel Islands Endemic
Dr. Sandra M. Namoff1, Dr. Kristen Hasenstab-Lehman2
1ECORP Consulting, Rocklin, CA, United States. 2Santa Barbara Botanic Garden, Santa Barbara, CA, United States
Description The California Channel Islands have had a varied ecological history. From the mid-19th century until the late 20th century, habitats were managed with a human-centric focus to the detriment of rare taxa. Crocanthemum greenei is a Channel Islands endemic shrub that has experienced significant demographic decline well into the 1980s, when it was only known from a few dozen occurrences. Since the species’ listing in the late 1990s, populations have rebounded, and several dozen occurrences have been documented and are being monitored on Santa Cruz, Santa Rosa, and Santa Catalina Islands. In this study, population genomic data are used to evaluate the genetic consequences of historical management practices. Single-nucleotide polymorphism datasets were used to understand genetic differentiation, variation, and potential hybridization. Results show that occurrences on the northern Channel Islands form one genetic cluster that is moderately differentiated from a genetic cluster represented by occurrences on Santa Catalina Island. Genetic divergence among islands, as evidenced by pairwise FST values, is lower than expected and could indicate gene flow among the islands. The data shows evidence of recent hybridization between C. greenei and C. scoparium on Santa Catalina Island. The inbreeding coefficient for Santa Cruz Island is low to moderate, indicating that reproduction is slightly higher than expected between close relatives on that island. Increased inbreeding is an expected outcome in populations that have experienced high grazing pressure from nonnative mammals and encroachment from invasive plants. Management efforts that promote gene flow among occurrences are recommended, especially on Santa Cruz Island.
Presenter Bios
Dr. Sandra M. Namoff
ECORP Consulting
Sandra Namoff is a professional botanist working as a biological consultant in northern California. She has also taught numerous botany workshops for the California Native Plant Society and other organizations. After completing her undergraduate degree in Biology at Florida International University, she worked at Fairchild Tropical Botanic Garden as a research assistant for their Palm Biology Program. She then moved out west to study Calystegia at California Botanic Garden/Claremont Graduate University. During her Ph.D. work she traveled around California and became enamored with the flora. Her research interests include conservation genetics, systematics and floristics.
6.3 A Line in the Sand: Floristics and Rare Plant Conservation Along the California-Nevada Border
Peri Lee Pipkin
New Mexico BioPark Society, Albuquerque, NM, United States
Description California and Nevada share multiple floristic regions along their roughly 610 mile shared border, including the California Floristic Province’s north high Sierra Nevada, the Mojave Desert, and the Great Basin floristic provinces. While the geopolitical border separating them does not represent a biogeographical or natural physical boundary between the two states, it has serious implications for the conservation of rare plants and sensitive ecological communities. Several rare and endangered plant species span the divide, and conservation policy and law in Nevada is severely limited in comparison to California’s more robust protections for biodiversity. Over the past several decades, floristic documentation has been driven by just a few hardworking botanists, but recent botanical discoveries and state records underscore the need for further floristic work in the region. The documentation of botanical diversity is not only critical in understanding plant biogeography as a whole, but contributes to greater conservation efforts in the region. This talk will briefly explore recent floristic records along the border in both California and Nevada, dethroned California endemics, pressing rare plant conservation issues in the region, and the future of interstate floristic endeavors and collaborations.
Presenter Bios
Peri Lee Pipkin
New Mexico BioPark Society
Peri Lee completed her graduate work at the California Botanic Garden in Claremont, where she wrote a flora of the Silver Peak Range in Esmeralda County, Nevada, and researched rare plants facing conservation crises along the California-Nevada border. Prior to her graduate studies she spent close to a decade working as a botanist, horticulturalist, and field biologist across the western US from Palm Springs to Alaska. Despite this broad geographical range, she always considers California her botanical home. Most recently she has worked as the rare plant program manager and International Union for Conservation of Nature species survival specialist for plants at the New Mexico BioPark Society in Albuquerque, NM.
6.4 Assessing the Genetic Diversity and Conservation Status of Disjunct Populations of Spiranthes infernalis (Ash Meadows Ladies’ Tresses, Orchidaceae) in the Great Basin
Allison A. Autry
California Botanic Garden, Claremont, CA, United States. Claremont Graduate University, Claremont, CA, United States
Description Spiranthes infernalis (Ash Meadows Ladies’ Tresses) is a rare perennial terrestrial orchid that was first described in the late 1980s and was thought to be endemic to Ash Meadows National Wildlife Refuge in Nye County, Nevada. A new population was discovered in 2020, 200 miles northeast in Railroad Valley, Nevada, and a third population in Owens Valley, Inyo County, California is also suspected to belong to the species. Like many groundwater-dependent species, S. infernalis is threatened by hydrological extraction and alteration due to agriculture, mining, geothermal development, and industrial scale solar facilities. However, despite its rarity and the high degree of threat, this orchid has yet to be thoroughly studied. The primary aim of this research is to investigate the patterns of population genetic diversity across the range of the species, while also evaluating its conservation needs, such as mechanisms for legal protection and the development of ex situ conservation methods. All three globally known populations of S. infernalis were surveyed and sampled for population genetic analysis in 2024 and 2025. I will present the preliminary results from an analysis of ddRADseq data produced from these samples, as well as an overview of the conservation status of S. infernalis. The findings of this research will contribute to a growing body of study on threatened desert species in groundwater dependent habitats, and it will improve the understanding of highly disjunct specialist species and associated patterns of genetic diversity.
Presenter Bios
Allison A. Autry
California Botanic Garden
Allison Autry is a PhD Candidate at the California Botanic Garden in Claremont, California who specializes in rare orchid conservation and genetics research. Prior to her time at CalBG, she earned a Bachelor's in plant science and environmental science from the University of Delaware and worked as a research assistant at Longwood Gardens. Presently, she is conducting fieldwork in Ash Meadows Nevada, Railroad Valley Nevada, and eastern California in support of her dissertation on rare and disjunct orchids in the American West.
6.5 Baja Rare: Binational Collaboration for the Conservation of Borderland Rare Plants
Dr. Mariana Delgado1,2, Dr. Sula Vanderplank3, Dr. Jon Rebman4
1Ecotono Sustentable A.C., Tijuana, Baja California, Mexico. 2Universidad AutĂłnoma de Baja California, Ensenada, Baja California, Mexico. 3Conserva Loreto, Loreto, Baja California Sur, Mexico. 4San Diego Natural History Museum, San Diego, CA, United States
Description Rare plants do not recognize political boundaries. Since 2018, the San Diego Zoo Wildlife Alliance’s Baja Rare project has collaborated with botanists from both Baja California and California to assess the status of 60 rare plant species with binational distributions. The project aims to determine whether historical populations persist amid ongoing development, improve distribution maps, estimate population sizes, collect and bank seeds, and identify the most pressing threats, with the goal of guiding effective conservation and protection strategies for rare plants across the borderlands.
Beyond field research, Baja Rare places strong emphasis on community engagement, partnering with non-governmental organizations, government agencies, and academic institutions in Baja California to raise awareness and involve local communities in rare plant documentation. Over the past eight years, the project has documented dozens of new rare plant populations, rediscovered long-unseen species, and witnessed the disappearance of others. In the process, surveys have led to the discovery of two species new to science near Tijuana, while many remote areas of Baja California remain to be explored. Together, these efforts highlight both the urgency and promise of binational collaboration in safeguarding the unique rare flora of the California–Baja California borderlands.
Presenter Bios
Dr. Mariana Delgado
Ecotono Sustentable A.C.
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The mission of the California Native Plant Society is to protect California’s native plants and their natural habitats, today and into the future, through science, education, stewardship, gardening, and advocacy.
DateThursday, February 5
