The evolution of ageing in cooperative breeders

Abstract

Cooperatively breeding animals live longer than their solitary counterparts. The traditional explanation for this is that cooperative breeding evolves more readily in long-lived species.Here, we reverse this argument and show that long lifespans are an evolutionary consequence of cooperative breeding. Natural selection favours a delayed onset of senescence in cooperative breeders, relative to solitary breeders, because cooperative breeders have a delayed age of first reproduction due to reproductive queueing. Especially long lifespans evolve in cooperative breeders with age-dependent reproductive queueing. Finally, we show that lower genetic relatedness among group members leads to the evolution of longer lifespans. This is because selection against higher mortality is weaker when mortality reduces competition between relatives. Our results link the evolutionary theory of ageing with kin selection theory, demonstrating that the evolution of ageing in cooperative breeders is driven by the timing of reproduction and kin structure within breeding territories. Results

Demographic responses of oceanic island birds to local and regional ecological disruptions revealed by whole‐genome sequencing

“…Mauritius Grey White-eyes (Gill, 1973;Hansen et al, 2002) that may delay first reproduction and overall increase generation time (Kreider et al, 2022). However, we note that the results from PSMC analyses did not change substantially after varying both mutation rate and generation time, suggesting that our results are also robust, to some extent, to variations in these parameters.…”

“…Second, we assumed similar generation times for the three species, while these have different social structures and population densities, that may influence this parameter. For example, cooperative breeding has been reported in Reunion and Mauritius Grey White‐eyes (Gill, 1973; Hansen et al., 2002) that may delay first reproduction and overall increase generation time (Kreider et al., 2022). However, we note that the results from PSMC analyses did not change substantially after varying both mutation rate and generation time, suggesting that our results are also robust, to some extent, to variations in these parameters.…”

Inclusive fitness forces of selection in an age-structured population

“…For example, previous work has found mixed evidence for extended lifespan in cooperative breeders 66 – 68 , and some evidence for differences in rates of senescence between cooperative and non-cooperative breeders 69 . Previous theory suggests that it is longer life and overlapping generations that initially favour cooperation 32 , but also that a delayed age of first reproduction as a result of queuing for reproduction might be a self-reinforcing mechanism for extended lifespan in cooperative breeders 70 . However, multiple other facets of the demography of cooperative breeding systems, including the process of group formation 71 , differences in phenotype between subordinates and dominants resulting in differential age-specific mortality and reproduction 72 , and the structure of dominance hierarchies 73 all have the potential to play a role in determining lifespan and rates of senescence.…”

Demographic responses of oceanic island birds to local and regional ecological disruptions revealed by whole-genome sequencing

“…Second, we assumed similar generation times for the three species, while these have different social structure and population densities, that may influence this parameter. For example, cooperative breeding has been reported in Reunion and Mauritius Grey White-eyes (Gill 1973; Hansen, Olesen, and Jones 2002) that may delay first reproduction and overall increase generation time (Kreider et al 2022). However, we note that the results from PSMC analyses did not change substantially after varying both mutation rate and generation time, suggesting that our results are also robust, to some extent, to variations in these parameters.…”