School of Integrative Biology, University of Illinois, Urbana, IL, USA.
J Evol Biol. 2013 Jul;26(7):1536-48. doi: 10.1111/jeb.12160. Epub 2013 May 16.
Morphological integration has the potential to link morphological variation within populations with morphological evolution among species. This study begins to investigate this link by comparing integration among shoulder girdle elements (e.g. scapular blade, glenoid, coracoid, etc.) during the origin and evolution of therian mammals, and within modern bat, opossum and mouse populations. In this study, correlations among skeletal elements and patterns of allometry are used as proxies for integration. Results suggest that shoulder girdle elements tended to vary and evolve independently during the origin of mammals and subsequent radiation of placentals, consistent with the elements' distinct developmental and evolutionary origins. This finding suggests that skeletal element correlations, and therefore integration, can be conserved over large taxonomic and temporal scales. However, marsupials display a different pattern in which shoulder girdle elements tend to be more integrated, with the exception of the coracoid. This finding is consistent with a shift in the pattern of skeletal element integration coincident with the appearance of the marsupial mode of reproduction. This finding provides further evidence that development can play a significant role in the establishment of patterns of skeletal element correlation and that patterns of skeletal element correlation can themselves evolve when faced with sufficient selective pressures.
形态整合有可能将群体内部的形态变化与物种之间的形态进化联系起来。本研究通过比较有袋目动物、蝙蝠和老鼠现代种群中肩带元素（如肩胛骨叶片、关节盂、喙突等）起源和进化过程中的整合情况，开始研究这种联系。在本研究中，骨骼元素之间的相关性和异速生长模式被用作整合的代理。结果表明，在哺乳动物起源和随后胎盘类动物辐射进化过程中，肩带元素往往独立变化和进化，这与这些元素独特的发育和进化起源一致。这一发现表明，骨骼元素的相关性，因此整合，可以在大的分类和时间尺度上得到保留。然而，有袋目动物的情况则不同，肩带元素之间的相关性更高，除了喙突。这一发现与骨骼元素整合模式的转变是一致的，这种转变与有袋类动物生殖方式的出现相吻合。这一发现进一步证明，发育可以在骨骼元素相关性模式的建立中发挥重要作用，并且当面临足够的选择压力时，骨骼元素相关性模式本身也可以进化。
