Measuring inbreeding depression in the wild: the old ways are the best

Measuring inbreeding depression in normally outbreeding natural populations is an uphill task, because it requires inbreeding coefficients that are calculated from pedigrees. Instead of calculating inbreeding coefficients directly, several studies have reported the use of microsatellite-derived metrics, such as heterozygosity, to infer relative inbreeding among individuals. In two new papers, Slate et al. and Balloux et al. show that these molecular metrics are often only weakly correlated with inbreeding coefficients, and that correlations between heterozygosity and fitness require a new interpretation.