Abstract
The additive genetic variance (V(A)) of fitness quantifies the expected response to selection; lifetime breeding success (LBS) is an effective metric of fitness in animal populations. However, data on LBS are relatively rare for wild populations of long-lived species, while time-limited metrics such as annual survival or fertility are more readily available. The magnitude of V(A) for these time-limited metrics, and the degree to which they are genetically correlated with LBS, remains unclear in most cases. Here we estimated the V(A) and heritability (h(2)) of LBS and four time-limited fitness metrics in wild female baboons in Kenya. The most highly heritable metrics were LBS (h(2)=0.25) and annual survival (h(2)=0.23). Notably, all the V(A) for LBS was attributable to survival to first successful reproduction. Furthermore, all fitness metrics examined were highly genetically correlated with each other, supporting the potential use of time-limited metrics where LBS data are limited. Our analyses predicted faster phenotypic evolution than we observed, raising the possibility that environmental effects have masked responses to selection ("cryptic evolution") or that social effects inflate estimated V(A). Together, our findings reveal a substantial genetic contribution to variation in survival, and in turn, to fitness and contemporary evolution in a long-lived animal.