Speaker
Description
Evolutionary rescue occurs when one or more populations are declining in abundance and occupancy, and are facing extinction because of environmental change, but adaptation by natural selection occurs sufficiently rapidly to boost mean fitness and abundance, permitting persistence in the changed environments. Understanding when rescue occurs, and when it does not, is pertinent not just to applied questions, such as species persistence in the face of anthropogenic environmental change, and the evolution of resistance to antibiotics and pesticides, but also to a range of classical evolutionary problems. This includes understanding the evolutionary stability of species’ geographical range limits, and broad issues of niche conservatism and adaptive radiations in paleobiology. A concern with temporal variability has been a longstanding focus of research in evolutionary biology, and some classic results suggest that temporal variation in the environment in general hampers adaptive evolution. Temporal variation can arise in selection (e.g., via position of an adaptive optimum, or the width of fitness curves) as well as demographic components of fitness not directly under selection, as well as other factors such as dispersal rates and density dependence. We will touch on all of these. We present theoretical explorations on how temporal variation can be a two-edged sword, sometimes indeed making rescue less likely, but in some circumstances actually enhancing the likelihood of evolutionary rescue and thus population persistence. There is also an intriguing ‘inflationary effect’ of temporal variation on population size that can influence the supply of genetic variation needed to permit rescue. All these recent theoretical insights are ripe for empirical investigation.