Population structure and larval dispersal in Caribbean coral reef fish

The dispersal scales of pelagic larvae in marine environments, including coral reefs, are central for understanding local population dynamics; and estimates of the spatial scales of larval dispersal are crucial for the design of sustainable marine reserves. My purpose was to use Caribbean coral reef fish species to define demographically significant, not necessarily evolutionarily significant population structure. This goal is easily misunderstood. The many insights gained from the use of genetic markers in phylogeographic analysis may have helped produce a focus in the literature on evolutionarily significant genetic differences, to the neglect of only demographically significant ones. Yet the latter are biologically significant since they define the extent to which populations may expect subsidies from other populations upstream and as such are crucial for conservation management. Chapter 1 is a review of the literature which suggests that microsatellite DNA is the molecular marker of choice for the analysis of genetic population structure in marine fish, when the focus is demographic time scales.In Chapters 2 and 3, I present and discuss the data constituting the first examples of genetic population structure using microsatellite markers for Caribbean reef fish and only the second example of any detection of genetic population structure for a fish species in the Caribbean. Population structure was detected for both French grunts (Haemulon flavolineatum) and bicolor damselfish (Stegastes partitus). This is also the first case of a clear stepping stone genetic structure, indicating a pattern of isolation by distance throughout the Caribbean basin for a reef fish species. Isolation by distance was detected for grunts at a Caribbean-wide scale and at smaller scales for bicolor damselfish. I was able to estimate that larval retention for French grunts is over 99% and that mean dispersal distance is between 150 and considerably less than 1800 kilometers for French grunts, and considerably less than 800 kilometers for bicolor damselfish. A third species, bluehead wrasse (Thalassoma bifasciatum), with longer pelagic larval duration than either grunts or damselfish, shows no explicit spatial pattern. (Abstract shortened by UMI.