Resource partitioning is a stabilising mechanism known to maintain species diversity in a variety of environments. Assemblages of stream shrimp species are structured by habitat features and predation. Therefore, segregation along habitat dimensions could facilitate coexistence among species in shrimp assemblages even when segregation is a result of predation pressure by fish species. These ecological interactions take place on a background modulated by biogeographic features, such as connectivity among drainages. However, these generalisations are mainly based on studies undertaken in temperate regions. We investigated whether abundances of rainforest shrimp species are related to habitat dimensions, and whether habitat–abundance relationships might be mediated through fish‐assemblage structure and the effect of drainages on connectivity. We detected effects of habitat variation on densities of shrimp species, but the magnitudes of the effects were larger for some species than others. Fish‐assemblage composition also affected shrimp densities. Two of the three species of shrimp showed some degree of habitat specialisation, but only along current‐velocity, depth, and pH gradients. Habitat segregation among species occurred along the current‐velocity and pH gradients. Relationships between density and environmental gradients differed between catchments for only one species and only along the pH gradient. Our findings provide evidence that rainforest‐stream shrimp species respond differently to environmental gradients and this could facilitate coexistence among species. However, interactions with fish seem to have a stronger effect on species densities, and consequently species segregation, than direct effects of the environmental gradients, resulting in apparent competition for these resources.

中文翻译：

---

亚马逊雨林溪流系统中淡水虾物种的栖息地隔离

资源划分是一种已知的稳定机制，可以在各种环境中保持物种多样性。溪流虾种类的组合由栖息地特征和捕食性构成。因此，即使隔离是鱼类捕食压力的结果，沿栖息地维度的隔离也可以促进虾群中物种之间的共存。这些生态相互作用发生在受生物地理特征调节的背景下，例如排水系统之间的连通性。然而，这些概括主要基于在温带地区进行的研究。我们调查了热带雨林虾物种的丰度是否与栖息地维度有关，以及栖息地-丰度关系是否可能通过鱼类组合结构和排水对连通性的影响来调节。我们检测到栖息地变化对虾物种密度的影响，但某些物种的影响程度大于其他物种。鱼群的组成也影响虾的密度。三种虾中的两种表现出一定程度的栖息地专业化，但仅沿水流速度、深度和 pH 梯度。物种之间的栖息地隔离沿着水流速度和 pH 梯度发生。密度和环境梯度之间的关系在流域之间只有一种物种并且仅沿着 pH 梯度不同。我们的研究结果提供证据表明，雨林溪流虾物种对环境梯度的反应不同，这可以促进物种之间的共存。然而，与鱼类的相互作用似乎对物种密度有更大的影响，