Saproxylophagous beetles usually are considered ecosystem engineers (EEs) by providing microhabitats for a great variety of organisms in tree hollows. However, there is still little clarity on the contribution of EEs to hollow-dwelling biodiversity since environmental conditions can exert control over the ecological function of EEs. We hypothesized that saproxylophages act as ecosystem engineers with community effects that are mediated by environmental forces over different spatiotemporal scales. Structural Equation Models (SEMs) were used to test this hypothesis against alternative hypotheses explaining the community structure of vertebrates and invertebrates occupying hollows in South American temperate forests. SEMs provided evidence for the interactive effects of saproxylophages and landscape-scale variables on invertebrates (fungivores, non-beetle predators, parasitoids, and detritivores) while predatory beetles were additively affected by saproxylophages. The abundance and richness of fungivores were positively affected by the richness of saproxylophages in landscapes with low cover of forests, while the abundance of saproxylophages affected positively the abundance of both parasitoids and non-beetle predators when secondary forests covered >30% of landscapes. The abundance and richness of vertebrates and invertebrates was also affected by habitat variables over different spatial scales. The small-sized saproxylophages played a more important role as EEs when compared to large-sized species while the most frequent species had effects comparable to those of the saproxylophagous assemblage. Our results suggest that the richness/abundance of EEs and landscape properties have compensatory and synergistic effects that lead to landscape-scale thresholds, thus providing insights into ecological conditions needed to conserve hollow-dwelling organisms.

中文翻译：

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了解栖息地条件如何调节生态系统工程师对树空生物的影响

腐木甲虫通常被认为是生态系统工程师（EE），为树洞中的多种生物提供微栖息地。然而，由于环境条件可以控制EEs的生态功能，因此EEs对空心生物多样性的贡献仍不清楚。我们假设腐木噬菌体充当生态系统工程师，具有由不同时空尺度的环境力量介导的群落效应。结构方程模型（SEM）被用来检验这一假设与解释南美温带森林中空洞的脊椎动物和无脊椎动物群落结构的替代假设。SEM 提供了腐木噬菌体和景观尺度变量对无脊椎动物（食真菌动物、非甲虫捕食者、寄生蜂和食腐动物）相互作用的证据，而掠食性甲虫则受到腐木噬菌体的附加影响。在森林覆盖率低的景观中，食真菌动物的丰度和丰富度受到腐木噬菌体丰富度的积极影响，而当次生林覆盖> 30%的景观时，腐木噬菌体的丰度对寄生蜂和非甲虫捕食者的丰度产生积极影响。脊椎动物和无脊椎动物的丰度和丰富度也受到不同空间尺度上栖息地变量的影响。与大型物种相比，小型腐木噬菌体作为 EE 发挥着更重要的作用，而最常见的物种具有与腐木噬菌体组合相当的效果。我们的结果表明，EE 的丰富性/丰度和景观特性具有补偿和协同效应，导致景观规模阈值，从而提供对保护中空生物所需的生态条件的见解。