Limited genetic connectivity of Pavona gigantea in the Mexican Pacific

Abstract

Coral reefs are the most complex and diverse of aquatic ecosystems. Their vulnerability and deterioration in the face of anthropogenic disturbance require the adoption of conservation and restoration efforts to maintain their resilience, for which connectivity is of paramount importance. Dispersal of meroplanktonic larval stages drives the levels of connectivity among coral populations and is influenced by the local current regime, the synchronization of spawning events, and the capacity of larvae to reach recruitment sites. This research aims to quantify the levels of connectivity among Pavona gigantea populations in the Mexican Pacific, using two mitochondrial genes and a nuclear gene. Mitochondrial genes were insufficiently variable to test geographical heterogeneity, whereas the more variable (h ≥ 0.86) nuclear rDNA indicated significant geographic differentiation (ΦST = 0.159, P < 0.001) among five locations along the Mexican Pacific, but no evidence of isolation by distance. Gene flow was limited among most sampled locales, and the largest estimate suggested moderate and unidirectional gene flow from Huatulco Bays to La Paz Bay and Marietas Islands. We found partial agreement between the patterns of connectivity among localities and the general pattern of superficial oceanographic circulation of the region, particularly in reference with the expected influence of the northward flowing West Mexican Current. These results suggest a limited demographic connectivity among Pavona gigantea populations along the Mexican Pacific, mediated by passive larval transport, and highlight the difficulty of predicting connectivity patterns on the basis of highly variable oceanographic regimes and reproductive events. The limited connectivity is of consequence for the viability and vulnerability of local populations and should be considered in the management and conservation strategies in the region.