Genetic Patterns of Zamia in Florida Are Consistent with Ancient Human Influence and Recent Near Extirpation

Abstract

Premise of research. 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.Methodology. We genotyped 25 populations from the Florida peninsula with 26 microsatellite (simple sequence repeat) loci and analyzed the data with neighbor-joining and multivariate analysis of genetic distance, Bayesian clustering, and network analyses.Pivotal results. 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.Conclusions. 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.