Longevity Hinders Evolutionary Rescue through Slower Growth but Not Necessarily Slower Adaptation

AbstractEvolutionary rescue is the process by which populations experiencing severe environmental change avoid extinction through adaptation. Applying theory to natural populations and conservation targets requires investigating the effects of several life history traits, including longevity. Theory demonstrates that longevity can inhibit rescue through slower phenotypic adaptation when selection acts once per lifetime, leaving open questions about longevity's effects when individuals face multiple rounds of selection. We developed a model integrating evolutionary rescue with concepts from life history theory, particularly the trade-off where increasing longevity produces slower population growth rates. Our model varies longevity by modifying the balance of survival and reproduction, with selection acting on survival, allowing for adaptation within cohorts. We used this model to study life history strategies with different longevities responding to sudden environmental change. Simulations demonstrated that higher longevity resulted in more time at low density and increased extinction. With perfect trait heritability, rates of adaptation were nearly identical across longevities. But at lower heritabilities, repeated selection under longevity decoupled mean population phenotypes and genotypes, producing a transient phase of rapid phenotypic change. Our results demonstrate that longevity impedes rescue by slowing population growth but does not always slow rates of adaptation.