"Ecological inheritance promotes the coexistence of environmental helpers and defectors"Prigent, IrisThe maintenance of adaptive polymorphism in social behaviour relies on negative frequency-dependent selection whereby rare genetic types are favoured over common ones. While such selection is well understood for social interactions occurring directly between individuals, many interactions occur indirectly through the environment, such as through the exploitation of a resource or the release of toxins. Additionally, these environmental modifications can be transmitted to downstream relatives owing to ecological inheritance, thereby associating genes to the environment they modify. Using mathematical modelling, we investigate in a patch-structured population the emergence and maintenance of polymorphism in a trait that improves the local patch environment, which can then be transmitted to future generations. We find that ecological inheritance promotes the coexistence of two types: one that invests into the environment at a personal cost (‘environmental helpers’); and one that only enjoys environmental benefits (‘environmental defectors'). Ecological inheritance boosts the advantages of helping when rare as rare helpers preferentially transmit intergenerational benefits to downstream relatives, but also the advantages of defecting when rare since rare defectors reap the environmental benefits accumulated from multiple generations of helpers. Owing to random genetic fluctuations within patches (i.e. local drift), this polymorphism leads to genetic and environmental heterogeneity among patches that is exacerbated by isolation-by-distance where clusters of high and low quality patches persist over long periods of time. More broadly, our results indicate that environmentally-mediated social interactions can play an important role in promoting long term behavioural and environmental variation, thereby driving inequalities between individuals. |
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