Sexual selection: when to expect trade-offs

Area of Science:

• Evolutionary Biology
• Behavioral Ecology

Background:

• Interspecific trade-offs in sexually selected traits are empirically mixed.
• Resource allocation patterns among species may explain these mixed findings.

Purpose of the Study:

• To investigate how resource distribution affects the evolution of trade-offs between song and plumage in sexually selected traits.
• To evaluate existing empirical data in light of simulation results.

Main Methods:

• Simulations modeling resource allocation under normal and negative binomial distributions.
• Analysis of three published studies quantifying song and plumage elaboration.

Main Results:

• Normal resource distribution simulations revealed significant negative correlations between song and plumage (r = -0.54).
• Negative binomial distribution simulations typically yielded positive correlations (r = 0.11).
• Re-analysis of published data suggested trade-offs are probable but require further assumption evaluation.

Conclusions:

• Resource distribution is a critical factor influencing the direction and strength of interspecific trade-offs in sexually selected traits.
• Current empirical data are insufficient to generalize the prevalence of these trade-offs.