abstract

Within the discipline of conservation biology, genetics has been a useful tool to assess and manage threatened species. Genetic diversity is associated with fitness, population size and persistence, and the number of inbred individuals. Reduced genetic variation in a species can decrease fecundity, the ability to evolve and endure environmental change, and may eventually lead to extinction. The West Indian manatee is a threatened species with small, slowly reproducing populations. Comprehensive genetic studies could greatly benefit the management and conservation of the species.

The West Indian manatee is composed of the Florida (Trichechus manatus latirostris) and Antillean manatee (T. m. manatus) subspecies. In this study, the Antillean manatee is represented by the Belize and Puerto Rico populations. Previous Florida manatee molecular studies detected high migration rates, low genetic diversity, and only one maternally inherited mitochondrial DNA haplotype, A01. The A01 haplotype was additionally identified in the Puerto Rico population along with two others, A02 and B01. The three Puerto Rico haplotypes exhibited strong geographical division, which indicates a low female migration rate.

In this study, mitochondrial and microsatellite markers were used to determine the relatedness and genetic diversity of the Florida, Belize, and Puerto Rico manatees and investigate the geographical genetic organization of the Belize and Puerto Rico populations. Mitochondrial control region haplotypes from each study site were identified using the program SEQUENCHER 4.5. The genotypes of 96 Florida, 133 Belize, and 111 Puerto Rico manatees were investigated at 18, 15, and 16 microsatellite loci, respectively. To distinguish the ancestral populations of extant manatees, a Bayesian phylogenetic analysis was performed using STRUCTURE 2.2. Neighbor-joining trees illustrated genetic distances among individuals and populations.

Considerable diversity was identified among the Florida, Belize and Puerto Rico manatees. In the Belize and Puerto Rico populations, a relationship was observed between genotypes and geographic locations, suggesting geographically limited breeding and the potential for distinct populations. Conservation of these populations could maintain and potentially improve the existing genetic diversity. Furthermore, the identification and protection of source populations could lead to larger populations and increased expatriation of individuals. The results from this study will facilitate future management and recovery efforts for the West Indian manatee.

acknowledgements

This work was funded by the University of Florida Aquatic Animal Health Program and the United States Geological Survey, Sirenia Project.