Majer Marija, Agnarsson Ingi, Svenning Jens-Christian, Bilde Trine
Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000, Aarhus-C, Denmark,
Naturwissenschaften. 2013 Nov;100(11):1031-40. doi: 10.1007/s00114-013-1106-6. Epub 2013 Nov 1.
Latitude, rainfall, and productivity have been shown to influence social organisation and level of sociality in arthropods on large geographic scales. Social spiders form permanent group-living societies where they cooperate in brood care, web maintenance, and foraging. Sociality has evolved independently in a number of unrelated spider genera and may reflect convergent evolutionary responses to common environmental drivers. The genus Anelosimus contains a third of approximately 25 described permanently social spider species, eight to nine species that all occur in the Americas. To test for environmental correlates of sociality in Anelosimus across the Americas, we used logistic regression to detect effects of annual rainfall, productivity, and precipitation seasonality on the relative likelihood of occurrence of social and non-social Anelosimus spiders. Our analyses show that social species tend to occur at higher annual rainfall and productivity than non-social species, supporting the hypothesised effects of these environmental variables on the geographical distribution of social species. We did not find support for the hypothesis that permanently social species occur in areas with low precipitation seasonality. High annual precipitation and, to less extent, high productivity favour the occurrence of permanently group-living Anelosimus spiders relative to subsocial and solitary species. These results are partially consistent with previous findings for the Old World spider genus Stegodyphus, where a link between high habitat productivity and sociality was also found. Unlike Anelosimus, however, Stegodyphus typically occur in dry habitats negating a general importance of high precipitation for sociality. Sociality in spiders thus seems to be strongly linked to productivity, probably reflecting the need for relatively high availability of large prey to sustain social colonies.
在大地理尺度上，纬度、降雨量和生产力已被证明会影响节肢动物的社会组织和社会性水平。群居蜘蛛形成永久性的群体生活社会，它们在育幼、蛛网维护和觅食方面进行合作。社会性在一些不相关的蜘蛛属中独立进化，可能反映了对共同环境驱动因素的趋同进化反应。在约25种已描述的永久性群居蜘蛛物种中，近三分之一属于Anelosimus属，有八九种都分布在美洲。为了测试美洲Anelosimus属蜘蛛社会性的环境相关因素，我们使用逻辑回归来检测年降雨量、生产力和降水季节性对群居和非群居Anelosimus蜘蛛相对出现可能性的影响。我们的分析表明，群居物种往往比非群居物种出现在年降雨量和生产力更高的地方，这支持了这些环境变量对群居物种地理分布的假设影响。我们没有找到证据支持永久性群居物种出现在降水季节性低的地区这一假设。相对于亚社会性和独居物种，高年降水量以及在较小程度上的高生产力有利于永久性群体生活的Anelosimus蜘蛛的出现。这些结果与之前对旧世界蜘蛛Stegodyphus属的研究结果部分一致，在该属中也发现了高栖息地生产力与社会性之间的联系。然而，与Anelosimus不同的是，Stegodyphus通常出现在干燥栖息地，这否定了高降水量对社会性具有普遍重要性的观点。因此，蜘蛛的社会性似乎与生产力密切相关，这可能反映了维持社会群体需要相对高可用性的大型猎物。
