Exploring the mechanisms underlying a heterozygosity-fitness correlation for canine size in the Antarctic fur seal Arctocephalus gazella

Although heterozygosity-fitness correlations (HFCs) are widely reported in the literature, most studies use too few markers to allow the proximate mechanisms to be convincingly resolved. Two competing hypotheses have been proposed: the general effects hypothesis, in which marker heterozygosity correlates with genome-wide heterozygosity and hence the inbreeding coefficient f, and the local effects hypothesis, in which one or more of the markers by chance exhibit associative overdominance. To explore the relative contributions of general and local effects in a free-ranging marine mammal population, we revisited a strong HFC found using nine microsatellite loci for canine tooth size in 84 male Antarctic fur seals Arctocephalus gazella (Hoffman et al. 2010). Increasing the number of markers to 76, we find that heterozygosity is uncorrelated across markers, indicating that inbred individuals are rare or absent. Similarly, while the HFC based on overall heterozygosity is lost, stochastic ...