Parent-offspring conflict and the evolution of dispersal distance.

Parent-offspring conflict emerges in many different contexts, but a rarely emphasized perspective is that of space as a resource that is allocated or acquired through dispersal. Early theoretical work has shown that there are different optima in rates of dispersal between parents and offspring. Here we examine this principle when space is explicitly modeled and dispersal is achieved through a dispersal kernel. We find a consistent pattern that selection favors longer dispersal distances under maternal control of dispersal (e.g., maternal tissue surrounding a seed) compared with scenarios where offspring themselves control dispersal (as in many animals). Intriguingly, offspring control leads to better resource utilization (higher habitat occupancy) in equilibrium scenarios than does maternal control. In contrast, in species that expand their ranges, maternal control of dispersal initially leads to faster range expansion. If there is evolutionary potential for dispersal kernels to change at the leading edge of a population, this difference vanishes quickly during an invasion because offspring-controlled dispersal evolves faster and catches up with scenarios involving maternal control. There is thus less conflict in nonequilibrium scenarios. In invasive scenarios with an evolving kernel shape, disruptive selection against intermediate distances can make the kernel not only fat-tailed but also bimodal.