The evolution of cooperative breeding in birds: kinship, dispersal and life history

Abstract

The evolution of cooperation among animals has posed a major problem for evolutionary biologists, and despite decades of research into avian cooperative breeding systems, many questions about the evolution of their societies remain unresolved. A review of the kin structure of avian societies shows that a large majority live in kin-based groups. This is consistent with the proposed evolutionary routes to cooperative breeding via delayed dispersal leading to family formation, or limited dispersal leading to kin neighbourhoods. Hypotheses proposed to explain the evolution of cooperative breeding systems have focused on the role of population viscosity, induced by ecological/demographic constraints or benefits of philopatry, in generating this kin structure. However, comparative analyses have failed to generate robust predictions about the nature of those constraints, nor differentiated between the viscosity of social and non-social populations, except at a coarse level. I consider deficiencies in our understanding of how avian dispersal strategies differ between social and nonsocial species, and suggest that research has focused too narrowly on population viscosity and that a broader perspective that encompasses life history and demographic processes may provide fresh insights into the evolution of avian societies.

Unmatedness Promotes the Evolution of Helping More in Diplodiploids than in Haplodiploids

“…While population density and structure are important parts of the suite of ecological constraints that underlie the evolution of helping (Emlen 1982;Hatchwell 2009), their impact on resource levels and chances of obtaining a territory or a nest site have been studied more than their effects on possible mating failures. Studies of unmatedness in haplodiploids have mainly concentrated on demonstrating whether mated females shift their offspring sex ratio as a response to the presence of unmated females, as suggested by Godfray (1990).…”

Life histories and the evolution of cooperative breeding in mammals

“…Recent comparative studies of vertebrates using phylogenetic reconstruction have shown that the evolution of cooperative breeding systems has been confined to socially monogamous species where most recruits to breeding groups have the same father and coefficients of relatedness are high [5,6]. However, cooperative breeding systems have not evolved in all groups of mammals characterized by monogamous mating systems, suggesting that other factors may constrain the evolution of cooperative breeding [7,8].…”

“…The evolution of cooperative breeding might, alternatively, be restricted to lineages where breeding history allows non-breeding helpers to make a substantial contribution to the reproductive output of breeders [8,13], for example, in species with relatively high fecundity. Previous studies in mammals have shown that females of cooperative breeders commonly have larger litters and shorter inter-birth intervals than non-cooperative social species [14 -17].…”

Predation risk drives social complexity in cooperative breeders

“…The lack of relatedness between larger subordinates and dominants reduces the opportunity for selective benefits of assisting kin, which differs sharply from the situation proposed for many other cooperative breeders (cf. 8,37,38). This finding suggests that other mechanisms are in place to explain helping behavior by larger subordinates (33,39).…”