Surface-active arthropods have limited dispersal abilities and their abundances are responsive to changes in the environment. Their sensitivity allows for the identification of aspects of environmental variation that are responsible for changes in community assemblages of these arthropods. Limited dispersal abilities allow for changes in the populations of surface-active arthropods to be linked reliably to changes in their local environment. In this study, we tested the hypothesis that seasonal variation in resource availability drives assemblages of three groups of surface-active arthropods (ants, beetles and spiders). Ten study sites were selected, where sampling was carried out continually during the wet, austral summer season (December 2018–February 2019) and then repeated at the same sites in the dry winter season (June 2019–August 2019) in a mesic savannah of Mpumalanga province, South Africa. Pitfall trapping was used to sample the surface-active arthropods. We found 89 morphospecies of ants, 48% of which were members of the Myrmicinae, while 32% of the 163 morphospecies of beetles were the Scarabaeidae. There were 262 morphospecies of spiders, of these, 22% were from the Salticidae. We found similar abundance and species richness of ants between seasons but significantly greater abundance and species richness of beetles and spiders in summer than in winter. These results show that the impact of seasonal variation in resource availability differs among arthropod taxa. However, the species compositions of all three taxa were significantly different between summer and winter. These results can be explained by the ‘niche differentiation hypothesis’ coupled with the ‘resource-ratio hypothesis’. Additionally, these results highlight the role that temporal and dietary niche differentiation play in driving the assemblage composition of surface-active arthropods in a mesic savannah.

中文翻译：

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南非大草原表面活性节肢动物物种组成季节变化的初步模式

表面活性节肢动物的传播能力有限，它们的丰度对环境的变化有反应。它们的敏感性允许识别导致这些节肢动物群落组合变化的环境变化方面。有限的传播能力使得表面活性节肢动物种群的变化能够可靠地与其当地环境的变化联系起来。在这项研究中，我们检验了资源可用性的季节性变化驱动三组表面活性节肢动物（蚂蚁、甲虫和蜘蛛）组合的假设。选择了十个研究地点，在潮湿期间连续进行采样，南夏季（2018 年 12 月至 2019 年 2 月），然后在干燥的冬季（2019 年 6 月至 2019 年 8 月）在南非姆普马兰加省的大草原的相同地点重复。陷阱捕获用于对表面活性节肢动物进行采样。我们发现蚂蚁的 89 种形态种，其中 48% 是 Myrmicinae 的成员，而甲虫的 163 种形态种中有 32% 是金龟子科。蜘蛛有 262 种形态，其中 22% 来自盐蛛科。我们发现不同季节蚂蚁的丰度和物种丰富度相似，但夏季甲虫和蜘蛛的丰度和物种丰富度明显高于冬季。这些结果表明，季节性变化对资源可用性的影响在节肢动物类群中有所不同。然而，夏季和冬季所有三个分类群的物种组成均存在显着差异。这些结果可以用“利基分化假说”和“资源比率假说”来解释。此外，这些结果突出了时间和饮食生态位分化在驱动中生草原中表面活性节肢动物的组合组成中所起的作用。