Handicap principle implies emergence of dimorphic mating displays

TL;DR

This paper presents a mathematical model based on the handicap principle that explains the emergence of dimorphic (bimodal) ornament sizes in animal species, highlighting how costly signals ensure honest communication of individual quality.

Contribution

It introduces a formal mathematical framework demonstrating that the handicap principle can produce bimodal ornament size distributions, a phenomenon observed across many species.

Findings

Bimodal ornament size distributions can arise from handicap principle dynamics.

Costly ornaments serve as honest signals of individual quality.

The model explains diverse species' ornament dimorphism through evolutionary stability.

Abstract

Species spanning the animal kingdom have evolved extravagant and costly ornaments to attract mating partners. Zahavi's handicap principle offers an elegant explanation for this: ornaments signal individual quality, and must be costly to ensure honest signalling, making mate selection more efficient. Here we incorporate the assumptions of the handicap principle into a mathematical model and show that they are sufficient to explain the heretofore puzzling observation of bimodally distributed ornament sizes in a variety of species.