Evolution of sociality in spiders leads to depleted genomic diversity at both population and species level

Across several animal taxa, the evolution of sociality involves a suite of characteristics, a ‘social syndrome’, that includes cooperative breeding, reproductive skew, primary female biased sex-ratio, and the transition from outcrossing to inbreeding mating system, factors that are expected to reduce effective population size (Ne). This social syndrome may be favoured by short-term benefits but come with long-term costs, because the reduction in Ne amplifies loss of genetic diversity by genetic drift, ultimately restricting the potential of populations to respond to environmental change. To investigate the consequences of this social life form on genetic diversity, we used a comparative RAD-sequencing approach to estimate genome-wide diversity in spider species that differ in level of sociality, reproductive skew, and mating system. We analysed multiple populations of three independent sister-species pairs of social inbreeding and subsocial outcrossing Stegodyphus spiders, and a subsoci...