Trait-specific indirect effects underlie variation in the response of spiders to cannibalistic social partners

Organisms may respond in different ways to the risk posed by conspecifics, but the cause of such variation remains elusive. Here, we use a half-sib/full-sib design to evaluate the contribution of (indirect) genetic or environmental effects to the behavioral response of the cannibalistic wolf spider Lycosa fasciiventris (Dufour, 1835) towards conspecific cues. Spiders showed variation in relative occupancy time, activity, and velocity on patches with or without conspecific cues, but direct genetic variance was only found for occupancy time. These three traits were correlated and could be lumped in a principal component: spiders spending more time in patches with conspecific cues moved less and at a lower rate in those areas. Genetic and/or environmental components of carapace width and weight loss in the social partner were significantly correlated with the principal component of focal individuals. Variation in these traits may reflect the quality and/or quantity of cues produced by social partners, hence focal individuals were likely behaving along a continuum of strategies in response to the risk posed by social partners. Therefore, environmental and genetic trait variation in the social partners may be key to maintain trait diversity in focal individuals, even in the absence of direct genetic variation.