Abstract

Effective design of marine reserves for use in fisheries management and conservation requires a clear understanding of patterns of larval transport and sink-source dynamics between populations, as well as a clear understanding of population demography. Mitochondrial and nuclear markers were analyzed to investigate potential mechanisms impacting connectivity among and the demographic history of subpopulations of a commercially important species in the Gulf of California, the leopard grouper (Mycteroperca rosacea). Demographic history and connectivity analyses included a coalescent analysis, estimating neutrality indices, estimating global and pairwise F'(ST), Phi(ST), or G''(ST), and a priori methodologies to identify genetically distinct units and barriers to dispersal. Average, long-term connectivity between geographic regions in the Gulf was also estimated. Divergence of mitochondrial lineages of leopard grouper dated to the late Pleistocene, with deep-water islands serving as demographically stable populations that may have acted as sources for new populations during periods of climate variability. Additionally, we observed genetically distinct units of leopard grouper in the Gulf, particularly between peninsular and mainland sites, as well as asymmetrical migration between the northern and central Gulf. Observed patterns of genetic differentiation are likely attributed to complex asymmetrical oceanographic currents and local larval retention. Based on our genetic findings and current fishing pressure in certain regions, we recommend implementing small, upstream no-take zones in the areas east of Isla Angel de la Guarda, around Isla San Lorenzo and Isla San Esteban, and north of Isla Tiburon, that would enhance connectivity among subpopulations, preserve sites with high genetic diversity, and benefit fisheries downstream of these sites.