Evolution of Personality: Developmental Constraints on Behavioral Flexibility

Abstract

Recent studies suggest that personalities—in which the expression of behavior is highly consistent within individuals—are ubiquitous among animals; however, the evolution of personalities remains poorly understood (Dall et al. 2004, Bell 2007, Bergmüller and Taborsky 2010). Context-independent expression of behavior combined with fitness costs of behavioral inflexibility suggest that constraints on behavioral flexibility are important in shaping the evolution of personalities (Sih et al. 2004a, b; Duckworth 2006), yet we lack a framework for understanding the origin and occurrence of such constraints. Current models for the evolution of personality traits assume that inflexibility of behavior is a product of natural selection; however, intrinsic constraints on behavioral flexibility may explain the origin of behavioral inflexibility without the need to invoke natural selection. Here, I present a framework for investigating the evolution of personality traits that draws on concepts in the field of developmental evolution and explicitly considers constraints to behavioral flexibility. I argue that intrinsic limitations to behavioral flexibility due to time, energetic, or functional constraints can lead to individual specialization, which in turn results in natural selection for correlated suites of behaviors and life-history traits. Further, I suggest that studies of avian behavior are uniquely positioned to provide novel insights into the evolution and development of animal personalities.