Global environmental change is challenging the adaptive capacity of ecological communities. Communities exposed to severe anthropogenic stress may experience loss and turnover of different facets of biodiversity through dynamic patterns of selection and drift. However, populations may recover from stress via evolutionary rescue if they are large, possess substantial genetic variation, and are connected by migration. In this talk, I will synthesize evidence for evolutionary rescue in populations and (meta)communities and draw out the implications for evolutionary conservation biology.
Communities can resist extirpation caused by the degradation of their environment or expand their range to degraded environments through three kinds of processes. First, the harsh environment can trigger plastic changes eliciting the tolerance of some of the organisms via, for example, the activation or expression of stressor-relevant physiological pathways. Second, the sorting of stress-tolerant species already present in the metacommunity can occur in the short term, in a fashion akin to the sorting of standing genetic variation in an asexual population by natural selection. Third, dispersal (gene flow) may bring resistant phenotypes that contribute to the rescue of extinction-prone species. The compositional characteristics and functional properties of the new community may differ from their original state and result in changes in diversity, distribution, and abundance, and measures of ecosystem functioning within and across the rescued metacommunity.
I will draw upon evidence from multiple experiments to show that community rescue is more likely in diverse communities with high overall abundance that have previously experienced sublethal levels of the same stress. Prior exposure to sublethal levels of stress can occur through time when an environment is gradually degraded or through space when communities are dispersed across a heterogeneous landscape that contains conditions ranging from benign to those lethal to the initial community. I will also show that dispersal is a particularly important process governing the probability of community rescue. Manipulating migration experimentally reveals how it contributes to evolutionary rescue by maintaining local and regional diversity, allows gene flow, and enables species to shift their ranges to track habitable sites across the landscape through time.
Insights from a general theory of evolutionary rescue, applicable to both populations and communities, can be identified to guide conservation action in environments experiencing complex patterns of disturbance, selection, and restoration in a range of social and economic contexts, ecosystems, and land uses (e.g. cities, agroecosystems, and protected areas).
