Data from: Rain, predators, and spider sociality: a manipulative experiment

Group-living organisms offer a unique perspective on how environmental gradients influence geographic distributions, as not only the properties of individuals, but also those of their groups interact with the environment to determine a species range. In turn, the ranges of group-living organisms should provide insights on the conditions that favor group versus solitary living. Here we show that rain intensity and predation by ants, factors postulated to exclude subsocial Anelosimus spiders from the lowland tropical rainforest, are greater in this habitat than at higher elevations. We further show that experimentally excluding these factors increases the survival of subsocial Anelosimus colonies when transplanted to the lowland rainforest, but not at their native higher elevation range. While providing a rare experimental test of the simultaneous importance of abiotic and biotic gradients on species range limits, these results provide direct evidence that adverse environmental factors may prevent solitary living and require group living in certain environments.

群居生物为解析环境梯度如何影响地理分布提供了独特视角——不仅个体自身的性状，其所在群体的特征也会与环境相互作用，共同决定物种的分布范围。反过来，群居生物的分布范围也能为判断哪些环境条件更利于群居而非独居生活提供理论参考。本研究表明，降雨强度与蚂蚁捕食压力这两个被假设为会将亚社会阿内蛛属（Anelosimus）蜘蛛排除出低地热带雨林的因素，在该生境中的强度均高于高海拔生境。我们还通过实验证实，当将亚社会阿内蛛属蜘蛛的蛛群移植到低地热带雨林时，移除上述两类因素可显著提升其存活率，但在其原生的高海拔分布范围内则无此效果。本研究既为非生物与生物梯度对物种分布范围限制的协同重要性提供了罕见的实验验证，也直接证明了在特定环境中，不利的环境因素会阻碍独居生存，进而促使生物选择群居策略。