Curth Stefan, Fischer Martin S, Kupczik Kornelius
Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbertstr. 1, D-07743 Jena, Germany; Max Planck Weizmann Center for Integrative Archaeology and Anthropology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103 Leipzig, Germany.
Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbertstr. 1, D-07743 Jena, Germany.
Zoology (Jena). 2017 Dec;125:1-9. doi: 10.1016/j.zool.2017.06.002. Epub 2017 Aug 18.
The skull shape variation in domestic dogs exceeds that of grey wolves by far. The artificial selection of dogs has even led to breeds with mismatching upper and lower jaws and maloccluded teeth. For that reason, it has been advocated that their skulls (including the teeth) can be divided into more or less independent modules on the basis of genetics, development or function. In this study, we investigated whether the large diversity of dog skulls and the frequent occurrence of orofacial disproportions can be explained by a lower integration strength between the modules of the skull and by deviations in their covariation pattern when compared to wolves. For that purpose, we employed geometric morphometric methods on the basis of 99 3D-landmarks representing the cranium (subdivided into rostrum and braincase), the mandible (subdivided into ramus and corpus), and the upper and lower tooth rows. These were taken from CT images of 196 dog and wolf skulls. First, we calculated the shape disparity of the mandible and the cranium in dogs and wolves. Then we tested whether the integration strength (measured by RV coefficient) and the covariation pattern (as analysed by partial least squares analysis) of the modules subordinate to the cranium and the mandible can explain differing disparity results. We show, contrary to our expectations, that the higher skull shape diversity in dogs is not explained by less integrated skull modules. Also, the pattern of their covariation in the dog skull can be traced back to similar patterns in the wolf. This shows that existing differences between wolves and dogs are at the utmost a matter of degree and not absolute.
家犬颅骨形状的变异程度远超过灰狼。对犬类的人工选择甚至导致了一些品种出现上下颌不匹配和牙齿咬合不正的情况。因此，有人主张基于遗传学、发育学或功能，可将它们的颅骨（包括牙齿）大致划分为相对独立的模块。在本研究中，我们探究了与狼相比，犬类颅骨的巨大多样性以及口面部比例失调的频繁发生，是否可以用颅骨模块之间较低的整合强度以及它们协变模式的偏差来解释。为此，我们运用几何形态测量方法，基于99个三维地标点进行分析，这些地标点分别代表颅骨（细分为吻部和脑壳）、下颌骨（细分为下颌支和下颌体）以及上下齿列。这些地标点取自196个犬类和狼类颅骨的CT图像。首先，我们计算了犬类和狼类下颌骨与颅骨的形状差异。然后，我们测试了从属于颅骨和下颌骨的模块的整合强度（通过RV系数衡量）和协变模式（通过偏最小二乘法分析）是否能够解释不同的差异结果。与我们的预期相反，我们发现犬类较高的颅骨形状多样性并非由整合程度较低的颅骨模块所致。此外，犬类颅骨的协变模式可以追溯到狼类的相似模式。这表明狼和犬之间现有的差异至多只是程度问题，而非绝对差异。
