Shelley McMahon - Herbarium Director

Shelley McMahon, Herbarium Director and Associate Research Professor in the School of Plant Sciences, studies large-scale phylogenetic analysis and plant systematics. She has studied the Amorpheae, a group of c. 240 New World arid/semi-arid species of papilionoid legumes, which includes Dalea, Marina, Psorothamnus, and Amorpha. Her interests include the evolution of variation in floral morphology among lineages, as well as developmental morphology. She also works on phylogenetic methodology, including techniques for large-scale phylogenetics and assembling the Tree of Life with multi-locus molecular data. She teaches "Plant Systematics" for undergraduate and graduate students and "Practical Computing for the Biosciences" for graduate students.

You can e-mail her at

George Ferguson - Senior Curatorial Specialist

George Ferguson, collections manager at ARIZ since 2013, is in the Department of Ecology and Evolutionary Biology and was Laboratory Coordinator for the introductory biology and genetics classes previously. His interest in botany began as an undergraduate at Duke. A native Texan, he chose graduate programs at Texas A&M and UTEP, studying phylogenetics of Mexican Sceloporus lizards for his thesis where the field work did not ignore the plants, and he began cataloging botanical specimens. He has taught biology classes at El Paso Community College and worked summers as ranger-naturalist in the national parks-- Carlsbad Caverns, and Grand Canyon’s North and South Rims. His focus in the floras and faunas of the Chihuahuan and Sonoran Desert regions, and Sierra Madre has led him on a number of expeditions revolving around the reissue of Gentry’s Rio Mayo Plants, in which he authored the Pinaceae (UA Press 1998), and coauthored the conifers section in The Trees of Sonora, Mexico (Oxford U. Press 2001). He continues field work on conifers, and has participated in field surveys with explorations to sky islands in Sonora. He coauthored “Biogeography and Diversity of Pines in the Madrean Archipelago” and “Preliminary Flora of the Sierra Bacadéhuachi, Sonora, Mexico” both in USDA Rocky Mountain Research Station Proceedings RMRS-P-67 (2013), and “Preliminary Flora of Sierra Los Buenos Aires, Sonora, Mexico” in The Plant Press (Arizona Native Plant Society 2018). He authored final reports to the U.S. Forest Service and U.S. Fish and Wildlife Service (2014, 2017) on Graptopetalum bartramii Habitat Assessment and Inventory.

You can e-mail him at

Mima Falk

Mima is a plant ecologist who worked for 30 years for various Federal agencies in California and Arizona. She is retired and joined the herbarium staff in 2014. Working in the herbarium is a gift because it allows her to continue learning about plants and interacting with the public. When not at work, she enjoys reading, designing and making stained glass windows, gardening and cooking. Mostly retired from ARIZ, she continues to manage our Rare Plant program.

Betsy Arnold - Curator Mycological Herbarium

Betsy is a mycologist with expertise in fungal ecology and evolution. email address: Also see webpages for Gilbertson Mycological Herbarium and Arnold Lab:

Associated Researchers and Taxonomic Specialists

Mike Bauer: Grasses

David Bertelsen ( Plants of southeastern Arizona

Susan Davis Carnahan( Plant Atlas Project of Arizona, Flora of the Guaymas region

Richard Felger (1934-2020): Sonoran Desert and Southwest borderlands, ethnobotany, and new aridland crops; biosketch and publications, Celebration of Life, Tucson, AZ

George Ferguson ( Conifers

Edward Gilbert ( Biodiversity informatics and SEINET

Stephen Hale ( Plants of Sonora

Gene Hall ( Sonoran Desert Arthropods and Plants

Ries Lindley ( Sphaeralcea, Acmispon, mosses

Kathryn Mauz: Arizona flora, historic botany

Anthony Mendoza ( Plants of Colombia,
Plant Atlas of Arizona

Ana Lilia Reina ( Plants of Sonora

Iris Rodden ( Southern Arizona Floristics

Greg Starr ( Agaves

Tom Van Devender ( / Director of Biodiversity Programs at, Madrean Discovery Expeditions

Jim Verrier ( An Annotated Flora of the Santa Catalina Mountains