Description:

Alan W. Meerow, PhD,
Agricultural Research Service,

Phylogeny and conservation genetics of the Caribbean Zamia clade: an integrated systematic approach with SSRs and single copy nuclear genes,

Abstract:
The Zamia pumila L. complex (Cycadales: Zamiaceae) is a monophyletic, diploid (2n = 16) and distinctive assemblage of cycad populations restricted to the West Indies and southeastern U. S. that has been treated as comprising one to nine species. It appears to represent the first branch in the Zamia tree of life. Over the past five years, my collaborators and I have been simultaneously investigating patterns of microsatellite DNA (31 loci) and sequence variation across ten single copy nuclear genes in the complex. The simultaneous analyses of microsatellite DNA and sequence-based data sets across the same organisms – particularly of a group that appears to inhabit the gray zone between population and species – offers an unprecedented and multi-dimensional opportunity to test the convergence of genetics and phylogenetics, and contribute further to our understanding of speciation. Here, I present the results of our analyses across the entire distribution of the clade, comprising 124 populations, and a total of 3522 samples. Florida and the islands of the Caribbean present varying scenarios of population structure, migration and divergence in Zamia, each of which will be discussed in turn. We hypothesize that Cuban populations have been the ultimate source of all populations elsewhere in the Caribbean, with perhaps as many as three radiations, with subsequent regional patterns of panmixis, speciation, and isolation. We anticipate that a resolute picture of the phylogeographic history of the clade will result from the analyses that allows us to pinpoint the origins of the clade, as well as assess areas of greatest conservation concern.