Density-dependent selection on mate search and evolution of Allee effects

Area of Science:

• Ecology
• Evolutionary Biology
• Population Dynamics

Background:

• Allee effects, where population growth rate decreases at low densities, are often driven by difficulties in mate finding.
• The evolution of mate search strategies can influence the strength and prevalence of Allee effects.
• Population density regimes may shape adaptive responses in mate search, with potential consequences for population persistence.

Purpose of the Study:

• To investigate how mating systems and fitness trade-offs interact with population density to drive the evolution of mate search rates.
• To explore how Allee effects respond to the evolution of mate search under varying density conditions.
• To determine if adaptations to high-density populations can be reversed at low densities.

Main Methods:

• Development of an individual-based, eco-genetic model to simulate the evolution of mate search rates.
• Incorporation of finite mate search rates as a trigger for Allee effects.
• Analysis of population adaptation across different population density regimes, considering trade-offs between search, survival, and fecundity.

Main Results:

• Density-dependent selection was observed in most scenarios, leading to evolved search rates that reduce Allee thresholds in low-density populations.
• Fecundity costs associated with mate search were a key factor in this density-dependent adaptation.
• Optimizing selection for the lowest Allee threshold depended on specific trade-offs (search vs. survival) and mating systems (monogamy).

Conclusions:

• Mate search evolution is crucial for understanding Allee effects, with density, mating systems, and fitness trade-offs playing significant roles.
• Evolved mate search strategies do not always minimize the population density threshold for persistence.
• The findings offer insights into why Allee effects are prevalent in rare species and highlight the complexity of evolutionary responses to density variation.