Evolutionary rescue is determined by differential selection on demographic rates and density dependence

Abstract

Accelerated rates of climate change are expected to either lead to populations adapting and persisting, or suffering extinction. Traditionally ecological models make extinction predictions based on how environmental change alters the intrinsic growth rate (r). However, these often ignore potential for evolutionary rescue, or to avoid extinction via adaptive evolution. Moreover, the environment may impose selective pressure on specific demographic rates (birth and death) rather than directly on r (the difference between the birth and death rates). Therefore, when we consider the potential for evolutionary rescue, populations with the same r can have different abilities to persist amidst environmental change. We can’t adequately understand evolutionary rescue without accounting for demography, and interactions between density dependence and environmental change. Using stochastic birth-death population models, we found evolutionary rescue more likely when environmental change alters birth rather than the death rate. Furthermore, species that evolve via density dependent selection are less vulnerable to extinction than species that undergo selection independent of population density. Resolving the key demographic factors affected by environmental change can lead to an understanding of how populations evolve to avoid extinction. By incorporating these considerations into our models we can better predict how species will respond to climate change.