The diversification of anatomical structures with functional importance during the branching process of a clade is a widely studied phenomenon in evolutionary biology. In recent years, there is a growing interest in the study of the inner ear, a structure associated with hearing, locomotion, and indirectly, with body size. These studies have been particularly important in primates. The platyrrhine radiation is an ideal system in which to study inner ear diversification because it is one of the major groups of living primates and an example of an adaptive radiation related to body size and ecological characteristics. In this work, we used micro-tomography, 3D geometric morphometrics, and phylogenetic comparative methods to explore the pattern of shape variation in the inner ear of platyrrhines and to assess whether this variation is related to size, locomotion, and vocalization. Our main results suggest that (1) diversification of inner ear morphology was achieved early in the radiation, particularly for the shape of the semicircular canals and the relative size of the cochlea; (2) inner ear shape diversification is generally not associated with changes in vocalization features or locomotion behaviors; and (3) conversely, body size is a strong predictor of inner ear shape. This last result contrasts with recent studies indicating that allometry has weak effects on platyrrhine cranial diversification and suggests complex factors driving inner ear diversification in the clade.

中文翻译：

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桔梗灵长类动物内耳的异速生长、功能和形状多样化

在进化枝的分支过程中具有功能重要性的解剖结构的多样化是进化生物学中广泛研究的现象。近年来，人们对内耳的研究越来越感兴趣，内耳是一种与听力、运动相关的结构，并间接与体型相关。这些研究在灵长类动物中尤为重要。桔梗辐射是研究内耳多样化的理想系统，因为它是活灵长类动物的主要群体之一，也是与体型和生态特征相关的适应性辐射的一个例子。在这项工作中，我们使用显微断层扫描、3D 几何形态测量学和系统发育比较方法来探索桔梗内耳形状变异的模式，并评估这种变异是否与大小有关，运动和发声。我们的主要结果表明（1）在辐射早期实现了内耳形态的多样化，特别是在半规管的形状和耳蜗的相对大小方面；(2) 内耳形状多样化通常与发声特征或运动行为的变化无关；(3) 相反，体型是内耳形状的有力预测因素。最后一个结果与最近的研究形成对比，表明异速生长对 platyrrhine 颅骨多样化的影响较弱，并表明驱动进化枝中内耳多样化的复杂因素。特别是对于半规管的形状和耳蜗的相对大小；(2) 内耳形状多样化通常与发声特征或运动行为的变化无关；(3) 相反，体型是内耳形状的有力预测因素。最后一个结果与最近的研究形成对比，表明异速生长对 platyrrhine 颅骨多样化的影响较弱，并表明驱动进化枝中内耳多样化的复杂因素。特别是对于半规管的形状和耳蜗的相对大小；(2) 内耳形状多样化通常与发声特征或运动行为的变化无关；(3) 相反，体型是内耳形状的有力预测因素。最后一个结果与最近的研究形成对比，表明异速生长对 platyrrhine 颅骨多样化的影响较弱，并表明驱动进化枝中内耳多样化的复杂因素。