Roe deer on ice: Selection despite limited effective population size through the Pleistocene.

Roe deer (Capreolus spp.) are a little odd. They are one of only a few placental mammals-and the only genus among even-toed ungulates-capable of putting embryonic development "on ice", also known as embryonic diapause (Figure 1). It would seem such an unusual trait is probably the product of natural selection, but a big question is, how does selection for important traits, such as diapause, interact with the historical demography of a species? In a 'From the Cover' article in this issue of Molecular Ecology, de Jong et al. (2020) demonstrate that selection is acting on genes associated with reproductive biology in roe deer, despite heightened genetic drift due to reduced effective population size through the Pleistocene.