Vitamin D status is heritable and under environment‐dependent selection in the wild

Vitamin D has a well‐established role in skeletal health and is increasingly linked to chronic disease and mortality in humans and companion animals. Despite the clear significance of vitamin D for health and obvious implications for fitness under natural conditions, no longitudinal study has tested whether the circulating concentration of vitamin D is under natural selection in the wild. Here, we show that concentrations of dietary‐derived vitamin D(2) and endogenously produced vitamin D(3) metabolites are heritable and largely polygenic in a wild population of Soay sheep (Ovis aries). Vitamin D(2) status was positively associated with female adult survival, and vitamin D(3) status predicted female fecundity in particular, good environment years when sheep density and competition for resources was low. Our study provides evidence that vitamin D status has the potential to respond to selection, and also provides new insights into how vitamin D metabolism is associated with fitness in the wild.