Social queuing in animal societies: a dynamic model of reproductive skew

Previously developed models of reproductive skew have overlooked one of the main reasons why subordinates might remain in a group despite restricted o pportunities to breed: the possibility of social queuing; i.e, acquiring do minant status in the future. Here, we present a dynamic ESS model of skew i n animal societies that incorporates both immediate and future fitness cons equences of the decisions taken by group members? based on their probabilit y of surviving from one season to the next (when post-breeding survival pro babilities drop to zero, our analysis reduces to the model produced by Reev e and Ratnieks in 1993, which considered only a single breeding season). Th is allows us to compare the delayed benefits of philopatry and the immediat e opportunities for independent breeding. We show that delayed benefits gre atly reduce the need for dominants to offer reproductive concessions to ret ain subordinates peacefully in the group. Moreover, this effect is strong e nough that differences in survival have a much greater impact on the group structure than differences in other parameters, such as relatedness. When t he possibility of acceding to dominant status is taken into account, groups where the dominant completely monopolizes reproduction can be stable, even if they consist of unrelated individuals, and even if subordinates have a reasonably high probability of winning a fight for dominance. Finally, we s how that stable groups are possible even if association leads to a decrease in current productivity. Subordinates may still stand to gain from group m embership under these circumstances, as acquiring breeding positions by que uing may be more efficient than the attempt to establish a new territory. A t the same time, the dominant may be unable to exclude unwelcome subordinat es, may enjoy increased survival when they are present, or may gain indirec t benefits from allowing relatives to stay and queue for dominance. We conc lude that reproductive skew in animal groups, ranging from eusocial insect colonies to mating aggregations (leks), will be strongly influenced by the future prospects of group members.