Genetic patterns of Zamia in Florida are consistent with ancient human influence and recent near extirpation

Authors: GRIFFITH, PATRICK - Montgomery Botanical Center; MEEROW, ALAN - Retired ARS Employee; CALONJE, MICHAEL - Montgomery Botanical Center; GONZALEZ, ELIZA - Montgomery Botanical Center; Nakamura, Kyoko; FRANCISCO-ORTEGA, JAVIER - Florida International University

Submitted to: International Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2022
Publication Date: 3/4/2022
Citation: Griffith, P., Meerow, A.W., Calonje, M., Gonzalez, E., Nakamura, K., Francisco-Ortega, J. 2022. Genetic patterns of Zamia in Florida are consistent with ancient human influence and recent near extirpation. International Journal of Plant Sciences. 183(3):169-185. https://doi.org /10.1086/717657.
DOI: https://doi.org/10.1086/717657

Interpretive Summary: Zamia is a genus consisting of 70 species of cycads in the Zamiaceae family. These plants are native to tropical and subtropical areas of America. Many Zamia species are listed in the IUCN Red List of Threatened Species as either endangered or critically endangered. We studied the genetic patterns of Zamia integrifolia, the only cycad native to the continental United States, presently found only in Florida. Due to its high ecological and horticultural importance, the extraction of Z. integrifolia is known to have occurred since 1952 by the Native Americans. Such a history of mass extraction readily explained the current dwindling numbers of Zamia plants from their local habitats once known to occur in abundance. We assessed the spatial and temporal genetic variations of 25 populations of Z. integrifolia in Florida using 26 simple sequence repeats (SSR) molecular markers. The study highlighted the genetic diversity loss and correlated results based on morphology and geography of occurrence in peninsular Florida that are consistent with the history of commercial exploitation of Z. integrifolia. Our results have important implications highlighting a global pattern of impacts of anthropogenic disturbance on the native endemic plant populations and propose management strategies to efficiently conserve them.

Technical Abstract: The only cycad native to the continental United States, Zamia integrifolia, is a taxonomically controversial species with a long history of use by people culminating in near extirpation 100 yr ago. We sought to illuminate the geographic and morphological variation in these plants, to inform the conservation of this threatened species, and to investigate hypotheses about human-mediated dispersal using molecular genetic data. We genotyped 25 populations from the Florida peninsula with 26 microsatellite loci and analyzed the data with neighbor-joining and multivariate analysis of genetic distance, Bayesian clustering, and network analyses. Patterns of genetic diversity are congruent with patterns of morphology and geography. Populations from northeast Florida that correspond to Z. integrifolia var. umbrosa are genetically distinct and cohesive. Overall, the genetic diversity of Florida’s Zamia is reduced relative to that of closely related populations in the Caribbean, consistent with the history of commercial exploitation and the recent geological history of the Florida peninsula. We offer specific management recommendations based on these data. We recognize only two varieties of the species in Florida: var. integrifolia and var.umbrosa. Patterns of genetic and geographic diversity are closely consistent with interaction networks of Woodland period (1000 BC to 1000 AD) Native Peoples and are not consistent with natural dispersal dynamics. This suggests that human-mediated dispersal played a role in the current distribution and diversity of the species.