Local adaptation when competition depends on phenotypic similarity.

Area of Science:

• Evolutionary biology
• Population genetics
• Ecological genetics

Background:

• Local adaptation is shaped by population size, gene flow, and selection.
• Existing models often assume uniform density-dependent survival, neglecting unequal competition among individuals.
• Frequency-dependent competition, where similar phenotypes compete more intensely, is common in nature but its evolutionary consequences are not fully understood.

Purpose of the Study:

• To investigate how frequency-dependent competition modifies the interplay between population size, gene flow, and local adaptation.
• To integrate migration-selection dynamics with frequency-dependent competition within a quantitative genetic framework.

Main Methods:

• Development of a coupled demographic-quantitative genetic model.
• Simulation of two populations connected by dispersal.
• Inclusion of local stabilizing selection and frequency-dependent competition.

Main Results:

• Frequency-dependent competition slightly enhances local adaptation and significantly increases within-patch genetic variance.
• It reduces the negative impact of migration on population size, despite increased genetic load.
• The magnitude of these effects is contingent on divergent selection strength, heritability, and life-cycle timing.

Conclusions:

• Frequency-dependent competition alters density-dependent interactions between migrants and residents, influencing adaptation.
• Competition can modify the effects of gene flow and divergent selection on local adaptation and carrying capacity.
• This highlights the importance of incorporating realistic competition dynamics into evolutionary models.