Genetic variation of the Caribbean sea fan coral, Gorgonia ventalina, correlates with survival of a fungal epizootic

Theory predicts that genetic variation within individuals may confer a variety of fitness benefits, including resistance to infectious disease. However, evidence for such heterozygosity-fitness correlations is taxonomically patchy and frequently based on experimentally manipulated populations with unnaturally low genetic diversity. Here, I survey natural populations of the Caribbean sea fan coral, Gorgonia ventalina, immediately following an epizootic of the fungal parasite, Aspergillus sydowii. Corals that survived in the face of high disease prevalence and attendant mortality had higher levels of heterozygosity compared to individuals from low-disease localities. In contrast to survivors of the epizootic, corals that recruited to highly impacted populations after the peak of disease tended to have lower levels of heterozygosity. Together, these results suggest that, in this host-parasite system, genetic variation within individuals confers resistance to disease and that populations heavily impacted by disease may be more susceptible to subsequent outbreaks due to reduced heterozygosity of newly recruited hosts.