Castro Alberto A, Garland Theodore
Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, California, 92521.
J Morphol. 2018 Jun;279(6):766-779. doi: 10.1002/jmor.20809. Epub 2018 Mar 13.
We have used selective breeding with house mice to study coadaptation of morphology and physiology with the evolution of high daily levels of voluntary exercise. Here, we compared hindlimb bones and muscle masses from the 11th generation of four replicate High Runner (HR) lines of house mice bred for high levels of voluntary wheel running with four non-selected control (C) lines. Mass, length, diameter, and depth of the femur, tibia-fibula, and metatarsal bones, as well as masses of gastrocnemius and quadriceps muscles, were compared by analysis of covariance with body mass or body length as the covariate. Mice from HR lines had relatively wider distal femora and deeper proximal tibiae, suggesting larger knee surface areas, and larger femoral heads. Sex differences in bone dimensions were also evident, with males having thicker and shorter hindlimb bones when compared with females. Several interactions between sex, linetype, and/or body mass were observed, and analyses split by sex revealed several cases of sex-specific responses to selection. A subset of the HR mice in two of the four HR lines expressed the mini-muscle phenotype, characterized mainly by an ∼50% reduction in hindlimb muscle mass, caused by a Mendelian recessive mutation, and known to have been under positive selection in the HR lines. Mini-muscle individuals had elongated distal elements, lighter and thinner hindlimb bones, altered 3rd trochanter muscle insertion positions, and thicker tibia-fibula distal widths. Finally, several differences in levels of directional or fluctuating asymmetry in bone dimensions were observed between HR and C, mini- and normal-muscled mice, and the sexes. This study demonstrates that skeletal dimensions and muscle masses can evolve rapidly in response to directional selection on locomotor behavior.
我们利用家鼠进行选择性育种，以研究形态学和生理学与高水平日常自愿运动进化之间的协同适应。在此，我们比较了为高水平自愿转轮跑步而培育的四代重复的高跑步者（HR）品系家鼠第11代的后肢骨骼和肌肉质量，以及四个未选择的对照（C）品系。通过以体重或体长作为协变量的协方差分析，比较了股骨、胫腓骨和跖骨的质量、长度、直径和深度，以及腓肠肌和股四头肌的质量。HR品系的小鼠股骨远端相对更宽，胫骨近端更深，表明膝关节表面积更大，股骨头也更大。骨骼尺寸的性别差异也很明显，与雌性相比，雄性的后肢骨骼更粗更短。观察到性别、品系类型和/或体重之间的几种相互作用，按性别进行的分析揭示了几种对选择的性别特异性反应情况。四个HR品系中的两个品系的一部分HR小鼠表现出小肌肉表型，其主要特征是后肢肌肉质量减少约50%，这是由孟德尔隐性突变引起的，并且已知在HR品系中受到正选择。小肌肉个体的远端骨骼拉长，后肢骨骼更轻更细，第三转子肌肉插入位置改变，胫腓骨远端宽度更厚。最后，在HR和C品系、小肌肉和正常肌肉小鼠以及性别之间，观察到骨骼尺寸在定向或波动不对称水平上的几个差异。这项研究表明，骨骼尺寸和肌肉质量可以响应于对运动行为的定向选择而迅速进化。
