Data from: 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 composed of a mixture of docile and aggressive individuals outperformed monotypic groups: (1) mixed groups were more effective at subduing medium and large sized prey, and (2) mixed groups collectively gained more mass during shared feeding events. Our results suggest that the iterative evolution of depressed aggressiveness and increased within-species behavioral variation in social spiders is advantageous, and could be an adaptation to group living that is analogous to the formation of morphological castes within the social insects群居生活（group living）的演化被视为一项关键的演化过渡事件，通常伴随附属性状（ancillary characters）的协同改变。我们以一类社会结构（social structures）高度多样的蜘蛛演化支（clade）为研究对象，检验了其社会倾向（social tendency）与诸多非生物变量（abiotic variables）、行为性状（behavioral traits，如勇敢性、活动水平）之间的关联。研究发现，群居蜘蛛物种通常表现出对猎物的攻击性（aggressiveness towards prey）降低、对捕食者的畏惧性（fearfulness towards predators）增强、活动水平下降，且多栖息于温暖湿润、风速较低的生境。群居物种内部，攻击性与勇敢性的种内变异程度更高。随后，我们针对四个物种（A. eximius、A. rupununi、A. guacamayos、A. oritoyacu）的重构群体（reconstituted colonies），评估了种内性状变异的功能效应。我们构建了已知温顺个体与攻击性个体比例的实验群体，并以群体觅食成功率（group foraging success）作为群体表现的衡量指标。结果显示，由温顺与攻击性个体混合组成的群体表现优于单型群体（monotypic groups）：其一，混合群体在制服中、大型猎物时效率更高；其二，共享取食事件中，混合群体的总增重更多。本研究结果表明，群居蜘蛛中攻击性降低与种内行为变异提升的迭代演化具有适应性优势，这类群适应群居生活的机制可类比于社会性昆虫的形态级型（morphological castes）分化。