Understanding connectivity at various spatial and temporal scales can aid in reef management. Here we report on the dispersal dynamics and demographic history of a coral reef invertebrate with high dispersal potential (up to 49 days larval duration in culture): the brittle star Ophiothrix suensonii. Mitochondrial COI sequences from 266 individuals collected from 10 locations throughout the Florida reef tract and Caribbean showed high overall connectivity (ΦST = 0.05). However, pairwise comparisons revealed three significantly differentiated regions: Florida, Honduras, and the remaining Caribbean, with Honduras showing substantially higher differentiation. A Bayesian analysis of migration was concordant with the AMOVA showing the lowest migration between Honduras and the remaining Caribbean. In contrast, migration rates between Honduras and Florida, and the Caribbean and Florida were considerably higher (19 and 45 times respectively). Despite long-range dispersal of O. suensonii throughout the wider Caribbean, the Honduras population appears isolated, and the persistent eddy current over the Meso-American Barrier Reef could be a major factor contributing to larval retention in this region. The phylogeographic pattern among haplotypes indicated a population expansion (confirmed by mismatch distribution) and coalescence analysis estimated that the expansion commenced approximately 300,000 years ago. A derived lineage dominated by Florida and virtually all Honduran haplotypes supports a colonization of Honduras from Florida. The large number of private haplotypes in Honduras and similar levels of molecular diversity for Honduras and Florida, suggest that Honduras has been genetically isolated for an extended period of time, likely predating the region wide population expansion. Finally, three widely distributed haplotypes formed a highly divergent lineage; the genetic distance between this lineage and the remaining haplotypes was comparable to other echinoderm congeners, suggesting cryptic speciation. The genetic isolation detected in Honduras, possibly due to local current patterns, highlights the need for independent management of reefs in this region.
Available at: http://works.bepress.com/mahmood-shivji/50/