Body shape variation should play a central role in determining the feeding ability of a fish species. We tested whether variations in feeding resource use of sympatric and closely related fish species could be explained by differences in ecologically relevant metrics, such as body morphology, trophic apparatus or combinations thereof. Fish were sampled at 14 sampling sites from Pelotas River and tributaries, Upper Uruguay, Brazil. The stomach contents of five species of Characidae (Astyanax and Bryconamericus) were analysed by the volumetric method. A geometric morphometric approach was used together with internal morphological traits to predict their patterns of prey use. Significant differences in body depth, snout and caudal peduncle lengths were found. Concomitant pronounced variations were verified to occur among species in structures related to digestion and absorption. Increased numbers of cusps, more pyloric caeca and higher intestinal coefficient values were observed in species that consumed greater proportions of plants. The opposite trends occurred in species that consumed greater proportions of insects. Mixed linear models indicated that the characin species differed significantly in the use of algae, aquatic insects, terrestrial insects, plant remains/seeds and detritus. Dietary differences reflected in low trophic niche overlap. Partial least squares regression results indicated strong correlations between morphological divergences and the corresponding variations in species diet. These outcomes combined confirm that the morphological traits that best enables the exploration of certain resource were an important factor in the resource‐related divergence and were the underlying reasons for these species' respective feeding modes.

中文翻译：

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与新热带河流域共生的小型查拉金鱼物种的资源分配相关的形态特征

体形变化在决定鱼类的摄食能力中应发挥中心作用。我们测试了同养和紧密相关鱼类的饲料资源使用变化是否可以通过生态相关指标（例如人体形态，营养设备或其组合）的差异来解释。鱼从巴西的上乌拉圭佩洛塔斯河和支流的14个采样点采样。五种Characidae（Astyanax和Bryconamericus）的胃内容）通过体积法进行分析。几何形态计量学方法与内部形态特征一起用于预测猎物使用的模式。发现在身体深度，鼻子和尾柄长度上有显着差异。证实伴随消化和吸收的结构中物种之间发生了明显的变化。在消耗更多植物的物种中，观察到了更多的尖齿数量，更多的幽门盲肠和更高的肠道系数值。相反的趋势发生在消耗更多昆虫的物种中。混合线性模型表明，characin物种在使用藻类，水生昆虫，陆生昆虫，植物残骸/种子和碎屑方面有显着差异。饮食差异反映在低营养位的重叠上。偏最小二乘回归结果表明形态差异与物种饮食的相应变化之间有很强的相关性。这些结果相结合，证明最能使某些资源的勘探成为可能的形态特征是与资源有关的差异的重要因素，并且是这些物种各自觅食方式的根本原因。