Establishment in a new habitat by polygenic adaptation

Area of Science:

• Evolutionary biology
• Population genetics
• Ecology

Background:

• Colonization of new habitats by maladapted populations requires rapid adaptation for survival, a process termed evolutionary rescue.
• Log fitness in a novel environment is modeled as a polygenic trait, crucial for understanding population establishment.

Purpose of the Study:

• To investigate the probability of successful colonization by analyzing the evolution of growth rate under the infinitesimal model.
• To determine how population parameters, migration rates, and genetic variation influence evolutionary rescue.

Main Methods:

• Utilized the infinitesimal model to track the evolution of log fitness as a polygenic trait.
• Employed deterministic and diffusion approximations to model population dynamics and trait evolution.
• Analyzed the impact of genetic variance, mean fitness, and migration rates on establishment probability.

Main Results:

• Establishment probability is contingent on the mean and genetic variance of the trait in the source population.
• Low initial mean fitness significantly reduces colonization success, with founder's fitness and offspring adaptation being key factors.
• Migration rates influence establishment: rare migration speeds up expected time, while high rates can trap populations in a 'sink' state, hindering adaptation.

Conclusions:

• Evolutionary rescue is a complex process influenced by genetic architecture, population parameters, and migration dynamics.
• A threshold migration rate exists, above which gene flow impedes adaptation, increasing establishment time.
• The study provides a framework for predicting colonization success and understanding adaptation in novel environments.