Genetic Diversity and Conservation of Pseudophoenix (Arecaceae) in Hispaniola

The Caribbean genus Pseudophoenix (Arecaceae) has its center of taxonomic diversity in Hispaniola (Haiti and the Dominican Republic). Three species (P. ekmanii, P. lediniana, and P. vinifera) are restricted to this island. In this thesis I investigated the population genetic diversity and structure of Pseudophoenix using ten microsatellite loci. Results showed homozygote excess and high inbreeding coefficients in all populations across all polymorphic loci. Overall, there was high differentiation among populations. Results from the Bayesian and Neighbor Joining cluster analyses identified groups that were consistence with currently accepted species delimitation. We included the only known population of an undescribed morph from the Dominican Republic that has been suggested to represent a new species. Results from the cluster analyses suggested that this putative species is closely related to P. sargentii from Turk and Caicos. Our study provided insights pertinent to the conservation genetics and management of this genus in Hispaniola.

Conservation implications of the reproductive biology of the endangered vine Ipomoea microdactyla Griseb. (Convolvulaceae)

A plant's reproductive biology exerts a significant influence on both population persistence within changing environments and successful establishment of new populations. However, the interaction between extrinsic (i.e. ecological) and intrinsic (i.e. genetic) factors also is an important driver of demographic performance for plant populations. It is light of this that I performed a multidisciplinary investigation of the breeding system, seed and seedling establishment dynamics, and population genetic structure of the endangered Caribbean vine Ipomoea microdactyla Griseb. (Convolvulaceae). The results from the breeding system study show individuals from Florida, USA and Andros Island, Bahamas to be self-incompatible. Plants from the two regions are cross-compatible but there is evidence for outbreeding depression in their progeny. Significant regional differences were found in floral traits and progeny traits that suggests incipient speciation for the Florida populations. The results from the seed and seedling establishment dynamics experiment demonstrate that the restoration of small populations in Florida via seed and seedling augmentation is a successful strategy. The demographic performance of the outplanted individuals was driven significantly by ecological factors (e.g. herbivory) rather than by genetic factors which emphasizes that the ecological context is very important for successful restoration attempts. The results from the population genetic study using an analysis of molecular variation (AMOVA) reveal significant differences in genetic variation among individuals from Florida, Andros, and Cuba. A Bayesian analysis of population genetic structuring coincided with the previous AMOVA results among the three regions. The Mantel test indicated significant 'isolation by distance' for these regional populations implying restricted gene flow over relatively short distances. Overall, the Florida populations had the lowest measures of genetic diversity which is most likely due to the effects of both colonization founder events and habitat fragmentation. The results of my study highlight the value of performing multidisciplinary studies in relation to species conservation as knowledge of both extrinsic and intrinsic factors can best guide decisions for species preservation.

Genetic Structure of the Florida Key Tree Cactus, Pilosocereus robinii, using Restriction Site associated DNA (RAD) markers

Rare plant conservation efforts must utilize current genetic methods to ensure the evolutionary potential of populations is preserved. One such effort involves the Key Tree Cactus, Pilosocereus robinii, which is an endangered columnar cactus native to the Florida Keys. The populations have precipitously declined over the past decade because of habitat loss and increasing soil salinity from rising sea levels and storm surge. Next-generation DNA sequencing was used to assess the genetic structure of the populations. Twenty individuals representative of both wild and extirpated cacti were chosen for Restriction Site Associated DNA (RAD) analysis. Samples processed using the HindIII and NotIII restriction enzymes produced 82,382,440 high quality reads used for genetic mapping, from which 5,265 Single Nucleotide Polymorphisms (SNPs) were discovered. The analysis revealed that the Keys’ populations are closely related with little population differentiation. In addition, the populations display evidence of inbreeding and low genetic diversity.