WHAT DETERMINES FITNESS WHEN DISPERSAL IS LIMITED?

Simple evolutionary models typically assume a homogeneous environment in which all individuals have equal access to resources. However, when dispersal is limited this assumption is unlikely to correspond to reality. Instead, the offspring of relatively fecund parents can be expected to find that resources are scarce because of competition from their relatively large number of siblings. We show that these factors lead to selection for decreased variation in the number of offspring produced. We investigate the relationship between fitness and variation in fertility for a variety of different circumstances. Our results indicate that, in some cases, selection for reduced variation in fertility can be very substantial.