Is evolution in response to extreme events good for population persistence?

Climate change is predicted to increase the severity of environmental perturbations, including storms and droughts, which act as strong selective agents. These extreme events are often of finite duration (pulse disturbances). Hence, while evolution during an extreme event may be adaptive, the resulting phenotypic changes may become maladaptive when the event ends. Using individual-based models and analytic approximations that fuse quantitative genetics and demography, we explore how heritability and phenotypic variance affect population size and extinction risk in finite populations under an extreme event of fixed duration. Since more evolution leads to greater maladaptation and slower population recovery following an extreme event, slowing population recovery, greater heritability can increase extinction risk when the extreme event is short, as in random environments with low autocorrelation. Alternatively, when an extreme event is sufficiently long, heritability often helps a population persist, as under a press perturbation. We also find that when events are severe, the buffering effect of phenotypic variance can outweigh the increased load it causes. Our results highlight the importance of the length and severity of a disturbance when assessing the role of evolution on population recovery; the rapid adaptive evolution observed during extreme events may be bad for persistence.

Population Dynamics

This chapter considers population dynamics where the population changes over time, owing to environmental noise, fishing, or both. It first derives the population growth rate with various analytic and numeric approximations. Next, the chapter develops a full numerical solution to the McKendrick–von Foerster equations and uses it to create stylized recovery plans. Last, the chapter describes how a fish stock responds to fluctuations in the recruitment. From there, the chapter develops a general understanding of how a fish stock responds to idealized perturbations: a press perturbation and a continuously varying perturbation. It then makes general expectations of the responses to perturbations in general, citing three rules: lag, averaging, and nonmetabolic scaling of population growth rate.