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.

群居生物为探究环境梯度如何调控地理分布提供了独特视角——不仅物种个体的性状，其群体的特征亦会与环境相互作用，共同决定物种的分布范围。反之，群居生物的分布范围亦可助力揭示哪些环境条件更有利于群居而非独居生存。本研究发现，降雨强度与蚂蚁捕食这两个被假说认为会将亚社会性阿内蛛（Anelosimus）排除出低地热带雨林的因素，在该生境中的强度显著高于高海拔区域。我们进一步证实，通过实验移除这两类因素后，移植至低地雨林的亚社会性阿内蛛巢群存活率显著提升，但在其原生的高海拔分布区域则无此效应。本研究不仅罕见地通过实验验证了非生物与生物环境梯度对物种分布范围边界的共同调控作用，还直接提供了证据表明：不利的环境因素可能会阻碍独居生存，进而迫使某些环境中的生物选择群居生活。