Parsi-Pour P, Kilbourne B M
Institut für Biologie, Humboldt-Universität zu Berlin, Philippstraße 13, 10115 Berlin, Germany.
Museum für Naturkunde Berlin, Leibniz Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115 Berlin, Germany.
Integr Org Biol. 2020 Jan 8;2(1):obz032. doi: 10.1093/iob/obz032. eCollection 2020.
Locomotor habits in mammals are strongly tied to limb bones' lengths, diameters, and proportions. By comparison, fewer studies have examined how limb bone cross-sectional traits relate to locomotor habit. Here, we tested whether climbing, digging, and swimming locomotor habits reflect biomechanically meaningful differences in three cross-sectional traits rendered dimensionless- cross-sectional area (CSA), second moments of area (SMA), and section modulus (MOD)-using femora, tibiae, and fibulae of 28 species of mustelid. CSA and SMA represent resistance to axial compression and bending, respectively, whereas MOD represents structural strength. Given the need to counteract buoyancy in aquatic environments and soil's high density, we predicted that natatorial and fossorial mustelids have higher values of cross-sectional traits. For all three traits, we found that natatorial mustelids have the highest values, followed by fossorial mustelids, with both of these groups significantly differing from scansorial mustelids. However, phylogenetic relatedness strongly influences diversity in cross-sectional morphology, as locomotor habit strongly correlates with phylogeny. Testing whether hind limb bone cross-sectional traits have evolved adaptively, we fit Ornstein-Uhlenbeck (OU) and Brownian motion (BM) models of trait diversification to cross-sectional traits. The cross-sectional traits of the femur, tibia, and fibula appear to have, respectively, diversified under a multi-rate BM model, a single rate BM model, and a multi-optima OU model. In light of recent studies on mustelid body size and elongation, our findings suggest that the mustelid body plan-and perhaps that of other mammals-is likely the sum of a suite of traits evolving under different models of trait diversification.
哺乳动物的运动习性与四肢骨骼的长度、直径和比例密切相关。相比之下，研究四肢骨骼横截面特征与运动习性之间关系的研究较少。在这里，我们测试了攀爬、挖掘和游泳等运动习性是否反映了28种鼬科动物的股骨、胫骨和腓骨在三个无量纲横截面特征——横截面面积（CSA）、面积二次矩（SMA）和截面模量（MOD）——上具有生物力学意义的差异。CSA和SMA分别代表对轴向压缩和弯曲的抵抗力，而MOD代表结构强度。鉴于需要抵消水生环境中的浮力以及土壤的高密度，我们预测水生和穴居鼬科动物的横截面特征值会更高。对于所有这三个特征，我们发现水生鼬科动物的值最高，其次是穴居鼬科动物，这两组与树栖鼬科动物均有显著差异。然而，系统发育相关性强烈影响横截面形态的多样性，因为运动习性与系统发育密切相关。为了测试后肢骨骼横截面特征是否适应性进化，我们将特征多样化的奥恩斯坦-乌伦贝克（OU）模型和布朗运动（BM）模型应用于横截面特征。股骨、胫骨和腓骨的横截面特征似乎分别在多速率BM模型、单速率BM模型和多最优OU模型下发生了多样化。
