Few studies have considered the effects of environmental variables at different spatial scales on Neotropical stream biodiversity. Furthermore, scale-related studies mostly include only one facet of biodiversity. To determine the contribution of local and landscape variables to the variation in the taxonomic, functional and phylogenetic α-diversity of stream fish assemblages, we sampled 85 streams in the Upper Parana River basin, Brazil. Local variables explained a substantial fraction of the variance in almost all biodiversity facets. Landscape variables (i.e., land-use and spatial variables) contributed little to the variation in the α-component of biodiversity. Our results thus highlight the importance of local features for maintaining stream fish biodiversity in agroecosystems. Probably, land-use were not significant because the study area was in a relatively homogeneous landscape severely impacted by anthropogenic activities. It is possible that insignificant effects of spatial structuring occurred because the ichthyofauna has already gone through a homogenization process and/or due to the spatial scale of our study. We suggest that even though local-scale restoration actions would influence biodiversity, we should not neglect landscape restoration because substantial improvements in the ecological integrity of streams are more likely to be accomplished with large-scale actions (e.g., re-establishment of the native riparian forest).

中文翻译：

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地方和景观变量对新热带农业生态系统中河流鱼类生物多样性的多个方面的重要性

很少有研究考虑不同空间尺度的环境变量对新热带河流生物多样性的影响。此外，与规模相关的研究大多只包括生物多样性的一个方面。为了确定局部和景观变量对河流鱼类组合的分类、功能和系统发育 α 多样性变化的贡献，我们对巴西巴拉那河流域上游的 85 条河流进行了采样。局部变量解释了几乎所有生物多样性方面的很大一部分差异。景观变量（即土地利用和空间变量）对生物多样性 α 分量的变化几乎没有贡献。因此，我们的结果强调了当地特征对于维持农业生态系统中河流鱼类生物多样性的重要性。大概，土地利用并不显着，因为研究区处于受人为活动严重影响的相对均质的景观中。空间结构的微不足道的影响可能是因为鱼群已经经历了同质化过程和/或由于我们研究的空间尺度。我们建议，即使局部规模的恢复行动会影响生物多样性，我们也不应该忽视景观恢复，因为溪流生态完整性的实质性改善更有可能通过大规模行动（例如，重建原生河岸森林）。空间结构的微不足道的影响可能是因为鱼群已经经历了同质化过程和/或由于我们研究的空间尺度。我们建议，即使局部规模的恢复行动会影响生物多样性，我们也不应该忽视景观恢复，因为溪流生态完整性的实质性改善更有可能通过大规模行动（例如，重建原生河岸森林）。空间结构的微不足道的影响可能是因为鱼群已经经历了同质化过程和/或由于我们研究的空间尺度。我们建议，即使局部规模的恢复行动会影响生物多样性，我们也不应该忽视景观恢复，因为溪流生态完整性的实质性改善更有可能通过大规模行动（例如，重建原生河岸森林）。