Elevated mortality of fish larvae on coral reefs drives the evolution of larval movement patterns

Coral reef fishes typically undergo a pelagic larval phase prior to recruitment to reef habitat. This is potentially risky, but likely to be important in connecting populations and avoiding local crowding. Predation pressures on larvae on and off the reef are likely to differ both in origin and intensity. In this study, we used individual-based models to explore in isolation the effect of elevated levels of larval mortality on the reef in 22 different landscapes. We allowed the movement of highly simplified larvae to evolve through selection and mutation events and tracked emerging strategies over 180 generations. The pressure of increased larval mortality on the reef affected overall population sizes and selected for higher levels of larval movement. However, the evolution of movement was constrained, and self-recruitment back to the reef of origin was prevalent, with levels rarely dropping below 50%. The evolved strategies were highly landscape specific, suggesting that movement in contiguous reefs is more readily evolved than at isolated reefs. Future development of this simulation approach will provide a valuable research tool for exploring important evolutionary, ecological, and management-based questions.