Microhabitat predicts species differences in exploratory behavior in Lake Malawi cichlids

Abstract

Encountering and adaptively responding to unfamiliar or novel stimuli is a fundamental challenge facing animals and is linked to fitness. Behavioral responses to novel stimuli, or exploratory behavior, can differ strongly between closely related species; however, the ecological and evolutionary factors underlying these differences are not well understood, in part because most comparative investigations have focused on only two species. In this study, we investigate exploratory behavior across 23 species in a previously untested vertebrate system, Lake Malawi cichlid fishes, which comprises hundreds of phenotypically diverse species that have diverged in the past one million years. We investigate behavioral variation across species, across microhabitats, and across environmental contexts. We find strong species differences in behavior that are associated with microhabitat, demonstrate that intermediate microhabitats are associated with higher levels of exploratory behavior, show that patterns of behavioral covariation across contexts are characteristic of modular complex traits, and contrast Malawi cichlid data with behavioral data from selectively bred high-and low-exploratory zebrafish. Taken together, our results tie ecology to species differences in behavior, and highlight Lake Malawi cichlids as a powerful system for understanding the evolution, ecology, and biology of natural behavioral variation.