Abstract Selective pressures favor morphologies that are adapted to distinct ecologies, resulting in trait partitioning among ecomorphotypes. However, the effects of these selective pressures vary across taxa, especially because morphology is also influenced by factors such as phylogeny, body size, and functional trade-offs. In this study, we examine how these factors impact functional diversification in mammals. It has been proposed that trait partitioning among mammalian ecomorphotypes is less pronounced at small body sizes due to biomechanical, energetic, and environmental factors that favor a “generalist” body plan, whereas larger taxa exhibit more substantial functional adaptations. We title this the Divergence Hypothesis (DH) because it predicts greater morphological divergence among ecomorphotypes at larger body sizes. We test DH by using phylogenetic comparative methods to examine the postcranial skeletons of 129 species of taxonomically diverse, small-to-medium-sized (<15 kg) mammals, which we categorize as either “tree-dwellers” or “ground-dwellers.” In some analyses, the morphologies of ground-dwellers and tree-dwellers suggest greater between-group differentiation at larger sizes, providing some evidence for DH. However, this trend is neither particularly strong nor supported by all analyses. Instead, a more pronounced pattern emerges that is distinct from the predictions of DH: within-group phenotypic disparity increases with body size in both ground-dwellers and tree-dwellers, driven by morphological outliers among “medium”-sized mammals. Thus, evolutionary increases in body size are more closely linked to increases in within-locomotor-group disparity than to increases in between-group disparity. We discuss biomechanical and ecological factors that may drive these evolutionary patterns, and we emphasize the significant evolutionary influences of ecology and body size on phenotypic diversity.

中文翻译：

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小型哺乳动物颅后的功能多样性与基质偏好和体型有关

摘要 选择压力有利于适应不同生态的形态，导致生态形态类型之间的性状划分。然而，这些选择压力的影响因分类群而异，特别是因为形态还受到系统发育、体型和功能权衡等因素的影响。在这项研究中，我们研究了这些因素如何影响哺乳动物的功能多样化。有人提出，由于生物力学、精力充沛和环境因素有利于“通才”的身体计划，哺乳动物生态形态类型之间的特征划分在小体型时不太明显，而较大的类群表现出更实质性的功能适应性。我们将其命名为发散假说 (DH)，因为它预测了较大体型的生态形态类型之间存在更大的形态差异。我们通过使用系统发育比较方法来测试 DH，以检查 129 种分类多样的中小型（<15 公斤）哺乳动物的颅后骨骼，我们将它们归类为“树栖动物”或“地栖动物”。 ” 在一些分析中，地栖动物和树栖动物的形态表明，较大体型的群体间差异更大，为 DH 提供了一些证据。然而，这种趋势并不是特别强烈，也没有得到所有分析的支持。相反，出现了一种与 DH 预测不同的更明显的模式：在“中等”大小的哺乳动物中，由形态异常值驱动的地栖动物和树栖动物的群内表型差异随着体型的增加而增加。因此，体型的进化增加与组内运动差异的增加比与组间差异的增加更密切相关。我们讨论了可能驱动这些进化模式的生物力学和生态因素，并强调了生态和体型对表型多样性的显着进化影响。