Evolution of delayed dispersal and subsequent emergence of helping, with implications for cooperative breeding

Abstract

Cooperative breeding occurs when individuals help raise the offspring of others. It is widely accepted that help displayed by cooperative breeders emerged only after individuals' tendency to delay dispersal had become established. We use this idea as a basis for two inclusivefitness models: one for the evolution of delayed dispersal, and a second for the subsequent emergence of helpful behaviour exhibited by non-breeding individuals. We focus on a territorial species in a saturated environment, and allow territories to be inherited by non-breeding individuals who have delayed dispersal. Our first model predicts that increased survivorship and increased fecundity both provide an incentive to non-breeding individuals to delay dispersal, and stay near their natal territory for some period of time. Predictions from the first model can be well understood by ignoring complications arising from competition among relatives. Our second model shows that effects on relatives play a primary role in the advantage of helping. In addition, the second model predicts that increased survivorship and fecundity promote the emergence of help. Together, our models lead us to conclude that the emergence of cooperative-breeding systems is made easier by life-history features associated with high survivorship and fecundity. We discuss the implications of our conclusions for life-history-based hypotheses of cooperative breeding and social evolution.

The evolution of cooperative breeding by direct and indirect fitness effects

“…The likelihood of filling an empty breeding position is implemented as a lottery weighted by the age of the candidates, with older individuals having a higher probability, regardless of relatedness levels. This contrasts with previous models assuming that dispersers join the queue for inheritance at the end ( 13 , 77 , 78 ) and conforms with empirical observations ( 79 , 80 ). Age was chosen as a proxy for RHP since it enables individuals to assess their competitiveness, a simplification allowing for the evolution of a simple rule to adjust helping and dispersal strategies to the likelihood of becoming a breeder.…”

Ageing and sociality: why, when and how does sociality change ageing patterns?

“…Yet, correlations do not reveal causality, and in fact, a mathematical model has shown that increased survivorship, i.e. low extrinsic mortality, and/or a high fecundity, a priori select for the evolution of helping and sociality ( [53], see also [54] and, for the evolution of delayed dispersal, [55]). Thus, reinforcing feedback processes may lead to increasing lifespan and fecundity with increasing sociality, which again results in larger colony size (figure 1).…”

Rapid changes in seed dispersal traits may modify plant responses to global change

“…From an evolutionary perspective, changes in animal dispersal have been addressed in the context of delayed dispersal in the evolution of cooperative breeding (Wild and Korb 2017), evolution of density-dependent dispersal with range expansion (Fronhofer et al 2017), the single gene pleiotropic effect on local dispersal (Edelsparre et al 2014), morphological changes and specialization for limited resources (e.g. Darwin’s Finches) (Grant and Grant 2006) and the quantitative genetic variation underlying local dispersal and the rate of exploration of novel environments (Korsten et al 2013).…”