Iterative evolution of increased behavioral variation characterizes the transition to sociality in spiders and proves advantageous

The evolution of group living is regarded as a major evolutionary transition and is commonly met with correlated shifts in ancillary characters. We tested for associations between social tendency and a myriad of abiotic variables and behavioral traits (e.g., boldness, activity level) in a clade of spiders that exhibit highly variable social structures.We found that social species tended to exhibit reduced aggressiveness towards prey, increased fearfulness towards predators, reduced activity levels, and occurred in warm, wet habitats with low wind velocities. Within-species variation in aggressiveness and boldness were greater in social species. We then assessed the functional consequences of within-species trait variation on reconstituted colonies of four species (A. eximius, A. rupununi, A. guacamayos, A. oritoyacu). We used colonies consisting of known ratios of docile versus aggressive individuals and group foraging success as a measure of colony performance.We found that groups comp...