Guevara Jennifer, Avilés Leticia
Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
Ecology. 2007 Aug;88(8):2015-23. doi: 10.1890/06-0995.1.
Social and subsocial spiders of the genus Anelosimus exhibit an altitudinal pattern in their geographic distribution at tropical latitudes in the Americas. Social species, which capture prey cooperatively, occur primarily in the lowland rain forest and are absent from higher elevations, whereas subsocial species are common at higher elevations but absent from the lowland rain forest. Previous studies have suggested that differences in the size of potential insect prey along altitudinal gradients may explain this pattern as insects were found to be, on average, larger in lowland rain forests than at higher elevations. These studies, however, may have under-sampled the insect size composition of each habitat because only one sampling technique was used. Using a number of collection methods we sampled the insect size composition in the environments of social and subsocial spiders in this genus. We found that the average insect size in lowland rain forest habitats was indeed larger than at high-elevation cloud forests in eastern Ecuador. We also found that, even though the various techniques differed in the size of the insects they captured (visual searching and blacklighting yielding larger insects than beating, sweeping, or malaise trapping), they all caught, on average, larger insects in the lowlands. Overall, spider colonies in the lowlands caught larger prey than did spider colonies at higher elevations, paralleling differences in insect size distribution obtained by the various techniques in their respective environments.
美洲热带地区的阿内洛西姆斯属社会性蜘蛛和亚社会性蜘蛛在地理分布上呈现出一种海拔模式。社会性物种通过合作捕食猎物，主要分布在低地雨林，在较高海拔地区不存在；而亚社会性物种在较高海拔地区很常见，但在低地雨林中不存在。先前的研究表明，沿着海拔梯度潜在昆虫猎物大小的差异可能解释了这种模式，因为据发现，低地雨林中的昆虫平均比高海拔地区的昆虫更大。然而，这些研究可能对每个栖息地的昆虫大小组成抽样不足，因为只使用了一种抽样技术。我们使用多种收集方法，对该属社会性蜘蛛和亚社会性蜘蛛所处环境中的昆虫大小组成进行了抽样。我们发现，厄瓜多尔东部低地雨林栖息地的昆虫平均大小确实比高海拔云雾森林中的昆虫大。我们还发现，尽管各种技术捕获的昆虫大小不同（视觉搜索和黑光灯诱捕捕获的昆虫比拍打、扫网或马氏网诱捕的昆虫大），但它们在低地平均捕获的昆虫都更大。总体而言，低地的蜘蛛群落捕获的猎物比高海拔地区的蜘蛛群落更大，这与各种技术在其各自环境中获得的昆虫大小分布差异一致。
