Microsatellite loci reveal sex-dependent responses to inbreeding and outbreeding in red deer calves

Mean d(2) is a recently devised microsatellite-based measure that is hypoth esised to allow the detection of inbreeding depression and heterosis in fre e-living population Two studies that have investigated the measure have dem onstrated an association between mean d(2) and traits related to fitness. H ere we present an association between mean d(2) and an important component of fitness, first-year overwinter survival, in a population of red deer on the Isle of Rum, Scotland. The association between survival and mean d(2) d iffered between males and females. As predicted, outbred female calves (hig h mean d(2)) survived better than those that were inbred (low mean d(2)). H owever, the association was in the opposite direction in male calves. We su ggest that this difference is due to different early growth strategies betw een the sexes. The association between mean d(2) and survival was not significantly influe nced by any single locus. Decomposition of mean d(2) into a recent inbreedi ng component and an outbreeding component showed that it was the degree of outbreeding that influenced survival in males and both the degree of outbre eding and recent inbreeding that influenced in females. Our analyses sugges t that mean d(2) is an easy-to-calculate measure of inbreeding and degree o f outbreeding that can reveal interesting interactions between genetics and ecology.