How density dependence, genetic erosion and the extinction vortex impact evolutionary rescue

Area of Science:

• Ecology
• Evolutionary Biology
• Conservation Biology

Background:

• Severe environmental change necessitates adaptation for population survival, a process known as evolutionary rescue.
• Existing models often simplify population dynamics, neglecting density dependence and genetic diversity erosion, which are critical in real-world conservation scenarios.

Purpose of the Study:

• To investigate the combined effects of density-dependent growth and genetic diversity loss on populations undergoing adaptation to environmental change.
• To assess how these factors influence the probability of evolutionary rescue and extinction.

Main Methods:

• Utilized stochastic, individual-based simulations to model population dynamics.
• Incorporated density-dependent population growth and erosion of genetic diversity over time.

Main Results:

• Density dependence significantly decreased the probability of evolutionary rescue and increased extinction risk, particularly in large, initially well-adapted populations.
• Populations experiencing extinction rapidly declined, entering an extinction vortex characterized by increased drift, genetic diversity loss, and maladaptive allele fixation.
• Evolutionary rescue led to a loss of genetic diversity, exacerbated by density dependence.

Conclusions:

• Density-dependent growth and genetic diversity erosion are critical factors that can undermine evolutionary rescue potential.
• Conservation strategies must account for these factors to accurately predict population fates and mitigate extinction risks.
• Understanding these dynamics is crucial for effective management of populations facing environmental change.