Effects of deforestation on headwater stream fish assemblages in the Upper Xingu River Basin, Southeastern Amazonia

ABSTRACT The expansion of the Amazonian agricultural frontier represents the most extensive land cover change in the world, detrimentally affecting stream ecosystems which collectively harbor the greatest diversity of freshwater fish on the planet. Our goal was to test the hypotheses that deforestation affects the abundance, richness, and taxonomic structure of headwater stream fish assemblages in the Upper Xingu River Basin, in Southeastern Amazonia. Standardized sampling surveys in replicated first order streams demonstrated that deforestation strongly influences fish assemblage structure. Deforested stream reaches had twice the fish abundance than reference stream reaches in primary forests. These differences in assemblage structure were largely driven by increases in the abundance of a handful of species, as no influence of deforestation on species richness was observed. Stream canopy cover was the strongest predictor of assemblage structure, possibly by a combination of direct and indirect effects on the provision of forest detritus, food resources, channel morphology, and micro-climate regulation. Given the dynamic nature of change in land cover and use in the region, this article is an important contribution to the understanding of the effects of deforestation on Amazonian stream fish, and their conservation.

摘要 亚马逊农业前沿的扩张是全球规模最大的土地覆被变化事件，正持续损害着栖息着全球最丰富淡水鱼类物种多样性的溪流生态系统。本研究旨在验证下述假说：森林砍伐会影响亚马逊东南部上欣古河流域源头溪流鱼类群落的丰度、物种丰富度及分类学结构。对多组重复布设的一级溪流开展标准化采样调查后证实，森林砍伐对鱼类群落结构具有显著影响。经森林砍伐的溪流河段的鱼类丰度是原生林对照溪流河段的两倍。群落结构的上述差异主要由少数物种的丰度提升所驱动，研究未观测到森林砍伐对物种丰富度存在影响。溪流冠层覆盖度是群落结构的最强预测因子，其可能通过对森林枯落物供给、食物资源供应、河道形态维持及微气候调节的直接与间接协同作用实现调控效应。鉴于该区域土地覆被与利用变化的动态特性，本研究对于深化认知森林砍伐对亚马逊溪流鱼类的影响及其保护工作具有重要价值。