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University of Exeter (2020)

The evolution of cooperation in an arid-zone bird : bet-hedging, plasticity and constraints

Capilla-Lasheras, P

Titre : The evolution of cooperation in an arid-zone bird : bet-hedging, plasticity and constraints

Auteur : Capilla-Lasheras, P

Université de soutenance : University of Exeter

Grade : Doctor of Philosophy (PhD) 2020

Résumé partiel
The evolution of cooperation represents a long-standing puzzle in evolutionary biology. From insects to mammals, this behaviour has evolved multiple times in separate lineages. Even though inclusive fitness theory provides a solid theoretical framework to understand the evolution of cooperation, there are still many research challenges in the evolutionary study of cooperation. First, most of the evidence for the effects of cooperation on the reproductive success of beneficiaries in vertebrate societies is based on correlational studies, which can be confounded by several environmental factors. Second, there are recent theoretical formulations to explain the evolution of cooperation that have not been empirically tested yet but could shed new light on the selective pressures that facilitate the evolution of cooperation. Third, we still have a poor understanding of the sources of among individual variation in cooperative behaviours. In particular, few studies have investigated whether the level of cooperation expressed by individuals is heritable and, therefore, could respond to natural selection. In this thesis, I combine nine years of life-history and behavioural information with field experiments and genomics to investigate (i) the routes for non-breeding individuals to acquire indirect fitness benefits and (ii) the sources of among-individual variation in cooperation in white-browed sparrow-weavers (Plocepasser mahali), an arid-zone cooperative breeder. After a general introduction to the subject of cooperative breeding, in Chapter 2 I test a novel hypothesis for the evolution of cooperation, the ‘altruistic bet-hedging’ hypothesis. There, I show that non-breeding helpers reduce variation in the reproductive success of breeders without affecting their arithmetic mean reproductive success. Furthermore, I show that this reproductive variance compression appears to arise because helpers specifically reduce unpredictable rainfall-induced variation in reproductive success, just as hypothesised by global comparative studies of the evolution of cooperative breeding in birds. Then, I investigate alternative routes through which helpers may gain indirect fitness benefits.

Présentation

Page publiée le 10 décembre 2020