How to quantify (the response to) sexual selection on traits

Area of Science:

• Evolutionary biology
• Quantitative genetics
• Behavioral ecology

Background:

• Natural selection acts through fitness components like mating success, fecundity, and longevity.
• Sexual selection specifically focuses on traits influencing mating or fertilization success.
• Previous methods for quantifying sexual selection can be limited and prone to misestimation.

Purpose of the Study:

• To develop a novel path analysis model for quantifying the strength of sexual selection.
• To improve estimates of sexual selection by analyzing the causal chain from traits to fitness.
• To refine the definitions of the Bateman gradient and Jones index using partial regressions.

Main Methods:

• A single path analysis model was developed to quantify both trait-mediated mating success and its subsequent impact on fitness.
• The model controls for confounding variables like body size and condition.
• It can be applied to both phenotypic data and quantitative genetic parameters.

Main Results:

• The new model provides more accurate estimates of sexual selection strength compared to previous path-based approaches.
• Phenotypic and quantitative genetic approaches were developed to decompose selection differentials and evolutionary response, respectively.
• Application to dusky pipefish (Syngnathus floridae) and simulated data demonstrated the model's utility.

Conclusions:

• The proposed path analysis offers a statistically robust framework for estimating sexual selection.
• This method addresses limitations in prior approaches, reducing the risk of substantial misestimation.
• The refined Bateman gradient and Jones index provide a clearer understanding of sexual selection dynamics.