Despite the considerable scientific interest in the variability and patterns of integration in the dog skull, how these patterns impact or are driven by function remains largely unexplored. Since the mandible is directly involved in mastication, it can be expected to be directly related to the development of the adductor and abductor muscles. Here, we explore whether variation in the architecture and size of the masticatory muscles is associated with the variation in mandibular shape in dogs. We obtained muscle data from the dissection of 48 dogs from different breeds and morphotypes to explore the architecture of the muscles and used 3D geometric morphometric approaches to quantify the shape of the mandible. Covariations between the masticatory muscles and mandibular shape were explored using two-block partial least square analyses (2B-PLS). Our results show there is a strong covariation between mandibular shape and masticatory muscles mass (rPLS from 0.70 to 0.74 for the first axis representing more than 90% of the total covariance) and physiological cross-sectional area (rPLS from 0.64 to 0.73 for the first axis representing more than 80% of the total covariance), irrespective of whether size is taken into account or not. These results suggest muscle size and thus attachment area requirements for individual muscles are likely drivers of mandibular shape. Moreover, mandible shape is likely to be a good predictor of muscle force. Finally, it appears that domestication of dogs has not resulted in a disuse phenotype characterized by a decoupling between form and function.

中文翻译：

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家犬的下颌形咀嚼肌结构如何变形？

尽管对狗头骨整合的变异性和模式有相当大的科学兴趣，但这些模式如何影响功能或由功能驱动的方式仍大有待探索。由于下颌骨直接参与咀嚼，因此可以预期它与内收肌和外展肌的发育直接相关。在这里，我们探索咀嚼肌的结构和大小的变化是否与狗的下颌形状的变化有关。我们从解剖不同品种和形态的48条狗中获得了肌肉数据，以探索肌肉的结构，并使用3D几何形态计量学方法来量化下颌骨的形状。使用两块偏最小二乘分析（2B-PLS）探索咀嚼肌和下颌形状之间的协变。我们的结果表明，下颌形状与咀嚼肌质量之间存在很强的协变（第一轴的rPLS从0.70到0.74，占总协方差的90％以上）和生理截面积（第一轴的rPLS从0.64到0.73）轴代表总协方差的80％以上），无论是否考虑尺寸。这些结果表明肌肉大小，因此单个肌肉的附着面积要求可能是下颌形状的驱动因素。此外，下颌的形状很可能是肌肉力量的良好预测指标。最后，看来狗的驯化没有导致以形式和功能之间的脱钩为特征的废用表型。不考虑尺寸大小，第一轴代表大于90％的总协方差的74％）和生理横截面积（第一轴代表大于80％的rPLS占总协方差的80％）或不。这些结果表明肌肉大小，因此单个肌肉的附着面积要求可能是下颌形状的驱动因素。此外，下颌的形状很可能是肌肉力量的良好预测指标。最后，看来狗的驯化没有导致以形式和功能之间的脱钩为特征的废用表型。第一轴表示74％，代表总协方差的90％以上；生理横截面积（第一轴的rPLS从0.64到0.73，代表总协方差的80％以上），无论是否考虑尺寸或不。这些结果表明肌肉大小，因此单个肌肉的附着面积要求可能是下颌形状的驱动因素。此外，下颌的形状很可能是肌肉力量的良好预测指标。最后，看来狗的驯化没有导致以形式和功能之间的脱钩为特征的废用表型。不论是否考虑尺寸。这些结果表明肌肉大小，因此单个肌肉的附着面积要求可能是下颌形状的驱动因素。此外，下颌的形状很可能是肌肉力量的良好预测指标。最后，看来狗的驯化没有导致以形式和功能之间的脱钩为特征的废用表型。不论是否考虑尺寸。这些结果表明肌肉大小，因此单个肌肉的附着面积要求可能是下颌形状的驱动因素。此外，下颌的形状很可能是肌肉力量的良好预测指标。最后，看来狗的驯化没有导致以形式和功能之间的脱钩为特征的废用表型。