Evolution of schooling propensity in the guppy drives changes in anti-predator behavior that are linked to neuroanatomy

Abstract

AbstractOne of the most spectacular displays of social behavior is the synchronized movements that many animal groups perform to travel, forage and escape from predators. However, the mechanistic basis of the evolution of such collective behaviors, as well as their fitness effects, remains empirically untested. Here, we study anti-predator behavior in guppies experimentally selected for divergence in polarization, an important behavioral aspect of coordinated movement. We find that groups from artificially selected lines remain more polarized than control groups in the presence of a threat. Neuroanatomical measurements show these behavioral differences are linked to changes in brain regions previously suggested as important regulators of perception, fear and attention, and motor response. We use further analyses of behavior and visual capabilities to show that differences in anti-predator behavior are not attributable to changes in visual perception, but likely to more efficient transfer of social information in polarization-selected fish. Our findings highlight that brain morphology may play a fundamental role in the evolution of coordinated movement and anti-predator behavior.