Direct and Indirect Genetic Methods Reveal Patterns of Larval Connectivity in Space and Time

Marine metapopulations consist of separate local populations connected by larval dispersal. Understanding marine metapopulation dynamics is critical to inform fisheries management, guide marine reserve design, and establish effective conservation efforts. Because larval dispersal patterns characterize metapopulations, we examined the genetic structure of multiple cohorts of a common coral-reef fish over 5 years. We used neutral genetic markers (10 microsatellite loci) to identify dispersal patterns in bicolor damselfish (Pomacentridae: Stegastes partitus). We genotyped tissue samples collected from 3647 fish (1601 adults and 2046 recruits) collected from 5 sites surrounding the Exuma Sound, Bahamas, from 2004 through 2008. Bayesian parentage analysis indentified several parent-offspring pairs and directly documented self-recruitment at 3 of the 5 sites. Principal coordinates analysis revealed that recruits from each site clustered in the same multivariate space as the adults from the same site, and did not cluster with individuals from other sites. This indirect evidence indicated that self-recruitment likely occurred at all sites. Nevertheless, measures of genetic differentiation (e.g., F_ST, G_ST) and results from assignment methods suggested high levels of gene flow among populations over longer time periods. Additionally, we compared heterozygosity and relatedness among adult and recruits, which indicated spatially and temporally independent sweepstakes recruitment events. Our findings suggest that connectivity among subpopulations explained metapopulation structure on evolutionary time scales. However, because we found evidence of self-recruitment and locally independent sweepstakes events over multiple years, local larval production is probably important to structuring metapopulations on ecological time scales.