Cycads are ancient seed plants that evolved approximately 300 million years ago. Because of their antiquity, novelty and association with dinosaurs, cycads have long fascinated the general public. Some of the species of the largest genus of cycads, Zamia, (commonly known as "coontie" or "bay rush") form a natural group restricted to the West Indies and Florida. These populations have been treated as comprising as few as one to as many as nine different species. The proposed research seeks to simultaneously investigate patterns of genetic variation in the Caribbean populations of Zamia throughout their range using microsatellite (repetitive) DNA markers, as well as test species boundaries using DNA sequences of genes from the nuclear genome that occur as a single copy or a low number of copies. The simultaneous analyses of different DNA data sets across organisms that inhabit the ?gray zone? between population and species will offer an opportunity to test the convergence of genetics and evolutionary history.
The Caribbean Islands form a biodiversity hotspot with global conservation priority. These studies will contribute to outline conservation strategies for Caribbean cycads, which are all endangered species. Six students from a university with the largest proportion of Hispanic undergraduates in the USA will gain research opportunities though this project. The research brings together a multi-institutional research team with complementary strengths and a proven collaborative history.
The Caribbean Basin is considered one of the five "hottest" of global biodiversity hotspots, despite a reduction to 11.3% of its original vegetation. In a relatively small area (ca. 229–550 km2), the islands support a native flora of ~12 000 species, of which ~8000 are found no where else. As critical an area of biodiversity as the Caribbean region is, research on the population genetics of its plants has not received a lot of activity. Our reasearch project focused on one of these uniquely Caribbean plant groups, the Zamia pumila L. complex that is currently considered to encompass either a single variable species or as many as nine distinct species. The group also appears to be the earliest branch in tree of life of the genis Zamia, found from Florida in the U.S. south to Bolivia. Zamia the most diverse of American cycads, an ancient group of seed plants. To explore the evolutionary history of this group of cycads which we know is of common ancestry, we developed two different libraries of genetic markers from the genome of the group: 32 microsatellite DNA markers, and 10 single copy genes. Our goals were to resolve genetic relationships within Caribbean Zamia using these markers, and test our theories about the evolution of the group. Simultaneous analyses of two different DNA data sets across organisms that inhabit the gray zone between population and species provides an unprecedented opportunity to test the in a recognized, and primarily island-based biodiversity hotspot. To this end, 3347 leaf samples for DNA extraction were collected from 135 populations across the entire range of the endangered Caribbean Zamia group. Our analyses present a picture of genetic variation across the entire Caribbean basin that is largely in accord with the geological history of the constituent islands. The current range of the genus represents the outcome of multiple radiations out of Cuba. Patterns within islands are diverse, a product of island size and topographic complexity. In some cases, multiple entries are inferred; while in Florida, we suggest that population structure has been influenced by native people before the European colonization. Traditional use of leaflet size and appearance to discriminate species in the group is shown to be unreliable. In addition to the scientific outcomes discussed above, we 1) presented two workshops on cycad biology to high school teachers of the Miami-Dade metropolitan area; 2) provided undergraduate research opportunities to minority group student populations; 3) trained a graduate student belonging to a minority group; 4) trained one postdoctoral fellow; 5) disseminated results in research journals, professional meetings, talks targeting the general public and popular articles published in the magazines of the two most important botanic gardens of Miami; 6) collected plant material for botanic gardens. Our data and resulting publications will have an impact on conservation strategies for a group of charismatic plants that have a complex history thoughout the Caribbean region.
