Received 18 May 2020, accepted 9 September 2020

Complex environments often have diverse animal communities. The structural complexity of plants has been directly and indirectly responsible for the abundance and diversity of spiders, allowing the establishment of different types of webs and influencing prey availability. Piptadenia gonoacantha and Croton floribundus trees are native species of the Atlantic Forest and have trunks with different structural complexities. The structural characteristics of the former vary according to the stem diameter, while the latter has a relatively simple trunk. This variation makes these plant species a good natural model for natural experiments designed to study how the structural components of trunks can affect the arthropod community, especially spiders. For this purpose, we sampled 30 trees of each species to determine their structural complexity and the abundance and richness of associated spiders. We classified the trees by level of complexity based on the abundance of their structural categories. As expected, the structural complexity of tree trunks explained almost 50% of the variation in species richness and abundance of spiders. Spider diversity, evaluated by the Shannon-Wiever index, was higher in trunks of P. gonoacantha included in the groups of higher complexity. This pattern however, was not observed in relatively simpler trunks of C. floribundus. On the other hand, the species-area relationship pattern was not supported by our data as we observed a nonlinear relationship between trunk surfaces and species richness. Differences in spider richness in the trunks appeared to be caused mainly by their specific microhabitat demands, which differed between groups according to their complexity. For some spiders, the overall trunk structure may play an essential role in the establishment of individuals. For others, specific structures such as loose bark or branches may be essential variables.

2020年5月18日收到，2020年9月9日接受

复杂的环境通常具有多样化的动物群落。植物的结构复杂性直接或间接地导致了蜘蛛的丰富和多样性，从而允许建立不同类型的网并影响猎物的可利用性。Piptadenia gonoacantha和巴豆floribundus树木是大西洋森林的原生物种，树干具有不同的结构复杂性。前者的结构特征根据茎直径而变化，而后者具有相对简单的躯​​干。这种变化使这些植物物种成为自然实验的良好自然模型，旨在研究树干的结构成分如何影响节肢动物群落，尤其是蜘蛛。为此，我们对每种物种的30棵树进行了采样，以确定它们的结构复杂性以及相关蜘蛛的丰度和丰富度。我们根据树木的结构类别的丰富程度对树木进行分类。不出所料，树干的结构复杂性解释了蜘蛛物种丰富度和丰富度的近50％的变化。蜘蛛的多样性P. gonoacantha包括在较高复杂性的组中。然而，在相对简单的多角梭菌的树干中未观察到这种模式。另一方面，由于我们观察到树干表面与物种丰富度之间存在非线性关系，因此我们的数据不支持物种-区域关系模式。树干蜘蛛丰富度的差异似乎主要是由它们特定的微生境需求引起的，根据它们的复杂性，它们在群体之间也有所不同。对于某些蜘蛛，总体躯干结构可能在建立个体方面起着至关重要的作用。对于其他人，特定的结构（例如松散的树皮或树枝）可能是必不可少的变量。