Variation in behavioral traits across a broad latitudinal gradient in a livebearing fish

Variation in animal behavior can have important consequences for ecological processes like mate choice, resource competition and invasive potential. Characterizing behavioral variation across major environmental gradients can therefore provide insight into key ecological dynamics that govern the distribution and evolution of biodiversity. This study examined variation in a suite of social and non-social behaviors across 17 populations of eastern mosquitofish ( Gambusia holbrooki ) spanning a broad latitudinal gradient. Multiple axes of behavior varied significantly across the latitudinal cline, though not always in the predicted direction. Three primary axes of behavioral variation emerged putatively representing activity (movement), boldness (risk-taking), and sociability, respectively. There was no latitudinal variation for the activity axis, but fish from low latitudes were bolder and more social. Sex and/or body size affected behavior along all axes. These patterns demonstrate that broad scale geographic variation in the environment influences divergence in behavior, which could impact ecological and evolutionary processes. Although all of the results are consistent to some degree with small scale studies in other systems, I discuss how the patterns observed in this study highlight the importance of correctly interpreting the ecological context of ex situ laboratory studies.