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Title: Comparative patterns of genetic variation among populations of the Zamia pumila L. complex across three islands of the Greater Antilles

Author
item Meerow, Alan
item FRANCISCO-ORTEGA, JAVIER - Florida International University
item COLONJE, MICHAEL - Montgomery Botanical Center
item JIMENEZ, FRANCISCO - National Botanical Garden
item VELOZ, ALBERTO - National Botanical Garden
item STEVENSON, DENNIS - New York Botanical Garden
item GRIFFITH, PATRICK - Montgomery Botanical Center

Submitted to: International Botanical Congress
Publication Type: Abstract Only
Publication Acceptance Date: 4/13/2011
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Caribbean coonties are a distinctive group of American cycads (an ancient group of non-flowering seed plants) that are popular landscape plants. They are found in the West Indies and southeastern U. S. (Florida), and are considered to encompass either a single or as many as nine distinct species. We are extensively sampling populations of the group throughout its range and genotyping them with both microsatellite DNA markers and sequences of single copy genes. Here, we present our analysis of sixteen microsatellite DNA markers across three of the larger islands of the Greater Antilles: Dominican Republic, Jamaica and Puerto Rico. Of the three islands, Puerto Rico has the greatest morphological diversity; three species have been recognized as occurring there by some accounts. Across 16 SSR loci that could be amplified across all three islands, Puerto Rico has the highest genetic diversity. While Zamia populations from both the Dominican Republic and Jamaica have similar gene diversities (lower than Puerto Rico), only a single unique allele characterizes the Dominican Republic populations. Some populations in Jamaica show indications of genetic erosion, congruent with evidence of poaching and small population size. Populations in the Dominican Republic are the least different from each other, which we attribute to high levels of gene flow among the populations. Genetic distance resolves all of the Jamaican populations nested within Z. erosa from Puerto Rico, which may suggest human inter-island movement of plants, since these two islands have never been connected by land. Results of this project will be interpreted within the context of the complex environmental history of the region. We anticipate that an understanding of the genetic structure of the populations of this complex will help to delineate future conservation strategies, and serve as a model for population level studies of other rare Caribbean plants.

Technical Abstract: The Zamia pumila L. complex (Cycadales: Zamiaceae) is a distinctive, monophyletic, diploid (2n =16) assemblage of populations restricted to the West Indies and southeastern U. S. (Florida) that is currently considered to encompass either a single polymorphic, or nine distinct species. We are extensively sampling populations of the group throughout its range and genotyping them with both microsatellite DNA (simple sequence repeat, SSR) and sequences of single copy nuclear genes. To our knowledge, this will be the first systematic study of tropical plants contrasting sequence-based phylogeographic with SSR population genetic analyses. Here, we present our analysis of sixteen SSR loci across three of the larger islands of the Greater Antilles: Dominican Republic, Jamaica and Puerto Rico. Of the three islands, Puerto Rico has the greatest morphological diversity; three species have been recognized as occurring there by some accounts. Across 16 SSR loci that could be amplified across all three islands, Puerto Rico has the highest allelic diversity in terms of expected heterozygosity and mean number of alleles per locus. While Zamia populations from both the Dominican Republic and Jamaica have similar gene diversities, only a single private allele characterizes the Dominican Republic populations. Some populations in Jamaica show indications of genetic erosion, congruent with evidence of poaching and small population size. Mean pairwise Fst between populations is lowest in the Dominican Republic, which we attribute to high levels of gene flow among the populations. In Puerto Rico, while Dest values among three populations each of Z. portoricensis and Z. pumila are 0.026 and 0.037, respectively, the mean among four populations of Z. erosa = 0.186, a 6-8 fold higher level of inter-populational differentiation. Genetic distance resolves all of the Jamaican populations nested within Z. erosa from Puerto Rico, which may suggest Pre-colombian human inter-Island movement of plants, since these two islands have never been connected by land, and Zamia has limited long-distance dispersal capability. Results of this project will be interpreted within the context of the complex environmental history of the region. We anticipate that an understanding of the genetic structure of the populations of this complex will help to delineate future conservation strategies, and serve as a model for population level studies of other rare Caribbean plant taxa.