Economies of scale shape energetics of solitary and group living spiders and their webs

Metabolic scaling, whereby larger individuals use less energy per unit mass than smaller ones, may apply to the combined metabolic rate of group-living organisms as group size increases. Spiders that form groups in high disturbance environments can serve to test the hypothesis that economies of scale benefit social groups. Using solitary and group-living spiders, we tested the hypothesis that spiders exhibit negative allometry between body or colony mass and the standing mass of their webs and whether, and how, such a relationship may contribute to group-living benefits in a cooperative spider. Given the diverse architecture of spider webs—orb, tangle, and sheet-and-tangle, and associated differences in silk content, we first assessed how standing web mass scales with spider mass as a function of web architecture and whether investment in silk differs among web types. As group-living spiders are predominantly found in clades that build the presumably costlier sheet-and-tangle webs...代谢缩放（metabolic scaling）指体型更大的个体单位质量能量消耗低于体型更小的个体，这一规律或可推广至群体规模扩大时群居生物的总代谢率。在高扰动环境中营群居生活的蜘蛛，可用于验证“规模经济有益于社会群体”这一假说。研究团队以独居及群居蜘蛛为实验材料，验证了两项科学命题：其一，蜘蛛的个体体重或群体总重量与其静置蛛网质量之间存在负异速生长（negative allometry）关系；其二，该关系是否以及如何为协作型蜘蛛带来群居优势。鉴于蛛网结构具有多样性（包括圆网、乱网以及sheet-and-tangle网（sheet-and-tangle web）），且不同结构蛛网的蛛丝含量存在差异，研究团队首先评估了以蛛网结构为调节因子时，静置蛛网质量随蜘蛛体重的缩放规律，以及不同蛛网类型的蛛丝投入是否存在差异。由于群居蜘蛛主要集中于构建据推测成本更高的sheet-and-tangle网的演化支系中……