How dispersal influences parent-offspring conflict over investment

Models that investigate family conflicts over parental investment have generally ignored population structure above the level of the family. Here, we extend conventional models to assess the impact of spatial population structure and limited dispersal on the intensity and resolution of parent-offspring conflict. Although one might naively predict that limited dispersal should reduce parent-offspring conflict, due to increased local relatedness, we show that this is not necessarily the case. Parent-offspring conflict may actually become more intense when dispersal is limited because local competition among related young can reduce the cost of any decline in maternal productivity, favoring greater selfishness on the part of the offspring. We also investigate the impact of limited dispersal on the resolution of parent-offspring conflict when the young can solicit extra resources by means of costly begging. Our model predicts that begging will be more intense when dispersal is limited but that the impact of dispersal on size then depends on the effect of parental supply on offspring demand. When greater supply leads to reduced demand, we find that parental investment should be higher in more viscous populations. By contrast, when greater supply leads to greater demand, parental investment should be lower in more viscous populations.