Relatedness predicts multiple measures of investment in cooperative nest construction in sociable weavers
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Although communal goods are often critical to society, they are simultaneously susceptible to exploitation and are evolutionarily stable only if mechanisms exist to curtail exploitation. Mechanisms such as punishment and kin selection have been offered as general explanations for how communal resources can be maintained. Evidence for these mechanisms comes largely from humans and social insects, leaving their generality in question. To assess how communal resources are maintained, we observed cooperative nest construction in sociable weavers (Philetairus socius). The communal nest of sociable weavers provides thermal benefits for all individuals but requires continual maintenance. We observed cooperative nest construction and also recorded basic morphological characteristics. We also collected blood samples, performed next-generation sequencing, and isolated 2358 variable single nucleotide polymorphisms (SNPs) to estimate relatedness. We find that relatedness predicts investment in cooperative nest construction, while no other morphological characters significantly explain cooperative output. We argue that indirect benefits are a critical fitness component for maintaining the cooperative behavior that maintains the communal good.
KeywordsSociable weavers Kin selection Inclusive fitness Tragedy of the commons Cooperation
We would like to thank the Bader family for hosting us on the Wiese property in Namibia and allowing us to collect this data. We thank Neil Thomson and Gudrun Middendorff for the assistance in the field. We thank the individuals at the Cornell Institute for Genomic Diversity for assisting with the data collection and analysis. We would also like to thank Elizabeth Cooper for the suggestions and guidance when analyzing the SNP data. This manuscript was improved by comments from J. David Van Dyken and two anonymous referees. This work was funded by a National Science Foundation grant to GML (#121500), a University of Miami College of Arts and Sciences Summer Fellowship awarded to GML, and the Robert E. Maytag Endowment.
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