Diversidade de presas e predadores (Insecta) em mesohabitats de córregos de Cerrado

ABSTRACT Tropical streams feature high variety of habitats and environmental gradients, which reflect on the greater richness of aquatic insects. In this way, we evaluate if the diversity of aquatic insects of prey and predator categories is influenced by the type of substrates or by longitudinal portions in Cerrado streams. Our hypothesis is that prey and predator diversity will be determined by the type of substrate, assuming that the substrate serves as a source for foraging and / or refuge. In addition, the folhiço substrate will present greater abundance and richness due to the availability of shelter and food provided by this type of substrate. There will be differences in prey and predator composition among substrates, since some species have associations with the substrate type. The portions of the stream will have no effect on the diversity of prey and predator, since in streams of up to third order does not present considerable changes in physical characteristics. The study was carried out in nascent (1st order), intermediate (2nd) and estuary (3rd), in two streams, during dry and rainy periods. Five subsamples of sand, gravel, rocks or boulders were collected, backwaters, rapids and roots (substrate). The substrate influenced all prey and predator responses (abundance, richness and composition), but the environment (longitudinal portions) did not influence the abundance and predator composition. The influence of substrates on the diversity of prey and predators evidences the importance of riparian vegetation as a source of allochthonous material in bedside streams.

【摘要】热带溪流拥有丰富多样的生境类型与环境梯度，这与水生昆虫的高物种丰富度密切相关。本研究以塞拉多（Cerrado）流域溪流为研究对象，探讨水生昆虫中猎物类群与捕食者类群的多样性是否受底质类型或溪流纵向区段的影响。我们提出如下假说：底质可作为觅食与庇护场所的来源，因此猎物类与捕食者类昆虫的多样性将由底质类型决定。此外，叶状底质因可提供庇护与食物资源，将拥有更高的个体丰度与物种丰富度。不同底质间的猎物类与捕食者类昆虫群落组成存在差异，因部分物种与特定底质类型存在关联。而溪流纵向区段对该类昆虫的多样性无显著影响，因为三级及以下的溪流物理特征无明显变化。本研究于旱季与雨季期间，在两条溪流的源头（1级溪流）、中段（2级溪流）及河口段（3级溪流）开展采样。共采集砂、砾石、岩石/巨砾、静水区、急流区与根系共6类底质的5份子样本。结果显示，底质类型对猎物类与捕食者类昆虫的所有响应指标（个体丰度、物种丰富度与群落组成）均存在显著影响，但环境因子（纵向区段）对其个体丰度与捕食者类群的群落组成无显著影响。底质对猎物类与捕食者类昆虫多样性的影响，印证了河岸植被作为近岸溪流外源物质来源的重要性。