Genetic diversity loss associated to high mortality and environmental stress during the recruitment stage of a coral reef fish

We investigated the short-term impact of environmental-induced stress on survival and neutral genetic diversity of recently settled juveniles of a damselfish, Dascyllus aruanus, using spatiotemporal caging experiments in various natural environmental conditions in Moorea (French Polynesia). Juveniles' mortality was followed at five study sites and overall four experiments, mortality rates ranged from 0 to 45%. Mortality rate and average daily water temperature were positively correlated (P = 0.018). Juveniles' mortality rate and allelic richness estimated from ten microsatellite loci were negatively correlated (P = 0.046). Together, an overdominance of heterozygotes was observed within hostile environments. These results suggest that an allelic richness loss may be expected as a direct consequence of unfavorable environmental conditions. Thus, a worrisome scenario on demographic and genetic consequences may be expected from habitat degradation in the context of global change and human pressure increases