University of Washington, Seattle, WA, United States of America.
University of Texas at Austin, Austin, TX, United States of America.
PeerJ. 2023 Jan 25;11:e14800. doi: 10.7717/peerj.14800. eCollection 2023.
Body size is often hypothesized to facilitate or constrain morphological diversity in the cranial, appendicular, and axial skeletons. However, how overall body shape scales with body size (, body shape allometry) and whether these scaling patterns differ between ecological groups remains poorly investigated. Here, we test whether and how the relationships between body shape, body size, and limb lengths differ among species with different locomotor specializations, and describe the underlying morphological components that contribute to body shape evolution among squirrel (Sciuridae) ecotypes. We quantified the body size and shape of 87 squirrel species from osteological specimens held at museum collections. Using phylogenetic comparative methods, we first found that body shape and its underlying morphological components scale allometrically with body size, but these allometric patterns differ among squirrel ecotypes: chipmunks and gliding squirrels exhibited more elongate bodies with increasing body sizes whereas ground squirrels exhibited more robust bodies with increasing body size. Second, we found that only ground squirrels exhibit a relationship between forelimb length and body shape, where more elongate species exhibit relatively shorter forelimbs. Third, we found that the relative length of the ribs and elongation or shortening of the thoracic region contributes the most to body shape evolution across squirrels. Overall, our work contributes to the growing understanding of mammalian body shape evolution and how it is influenced by body size and locomotor ecology, in this case from robust subterranean to gracile gliding squirrels.
体型通常被假设为促进或限制颅面、附肢和轴骨骼的形态多样性。然而，整体身体形状如何随体型缩放（即身体形状的异速生长），以及这些缩放模式是否在生态群之间存在差异，仍未得到充分研究。在这里，我们检验了具有不同运动特化的物种之间，体型、身体形状和肢体长度之间的关系是否以及如何不同，并描述了导致松鼠（Sciuridae）生态型之间身体形状进化的基础形态成分。我们从博物馆收藏的骨骼标本中量化了 87 种松鼠物种的体型和形状。使用系统发育比较方法，我们首先发现身体形状及其基础形态成分与体型呈异速生长关系，但这些异速生长模式在松鼠生态型之间存在差异：花栗鼠和滑翔松鼠的体型随体型的增加而变得更加细长，而地松鼠的体型随体型的增加而变得更加粗壮。其次，我们发现只有地松鼠表现出前肢长度与体型之间的关系，即体型较长的物种相对具有较短的前肢。第三，我们发现肋骨的相对长度和胸部区域的伸长或缩短对松鼠的身体形状进化贡献最大。总的来说，我们的工作有助于深入了解哺乳动物身体形状的进化以及体型和运动生态学如何影响它，在这种情况下，从强壮的地下到灵巧的滑翔松鼠。
