Aquatic macrophytes increase habitat complexity and influence the structure of fish communities. We investigated relations between macrophyte stand complexity and functional alpha and beta diversity of fish. We sampled fish and plants in 30 macrophyte stands with differences in density and diversity in the Paraná River floodplain. The functional alpha diversity, measured as functional richness index (FRic), was calculated for each macrophyte stand. The functional beta diversity was examined using pairwise Jaccard dissimilarity as well as its turnover and nestedness components. We also partitioned functional beta diversity into contributions of single sites to overall beta diversity (LCBD) aiming to assess its relationship to macrophyte stand characteristics. We then used beta regressions and generalized dissimilarity modeling (GDM) to examine diversity patterns. As we expected, the greatest FRic occurred in stands with intermediate macrophyte density and high macrophyte diversity. The functional beta diversity responded mainly to the variation in macrophyte density, but the turnover component increased slowly at the beginning of the gradient (low density) and, after a certain point, it started to increase more rapidly. The stands that contributed the most to the functional beta diversity (higher LCBD values) were those with low and high FRic and, consequently, with lower and higher macrophyte density, as well as lowest macrophyte diversity. Our findings highlight the role of macrophytes as environmental filters that select the traits in fish communities, and the variation in fish traits is probably a result of factors such as food availability, shelter from predators and physical space for locomotion.

中文翻译：

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大型植物群复杂性解释了热带河流泛滥平原鱼类的功能性 α 和 β 多样性

水生大型植物会增加栖息地的复杂性并影响鱼类群落的结构。我们调查了大型植物群落复杂性与鱼类功能性 alpha 和 beta 多样性之间的关系。我们在巴拉那河漫滩中密度和多样性不同的 30 个大型植物林中对鱼类和植物进行了采样。计算每个大型植物林分的功能性 alpha 多样性，以功能丰富度指数 (FRic) 衡量。使用成对的 Jaccard 相异性及其周转率和嵌套性分量来检查功能性 beta 多样性。我们还将功能β多样性划分为单个站点对整体β多样性（LCBD）的贡献，旨在评估其与大型植物林分特征的关系。然后，我们使用 beta 回归和广义相异建模 (GDM) 来检查多样性模式。正如我们预期的那样，最大的 FRic 出现在具有中等大型植物密度和高大型植物多样性的林分中。功能性β多样性主要对大型植物密度的变化做出反应，但周转分量在梯度开始时（低密度）缓慢增加，在某一点之后，它开始更快地增加。对功能性β多样性贡献最大的林分（较高的 LCBD 值）是那些具有低和高 FRic 的林分，因此，具有越来越低和越来越高的大型植物密度以及最低的大型植物多样性。我们的研究结果强调了大型植物作为环境过滤器的作用，可以选择鱼类群落中的特征，