EVOLUTION OF SCAPULA SIZE AND SHAPE IN DIDELPHID MARSUPIALS (DIDELPHIMORPHIA: DIDELPHIDAE)
EVOLUTION OF SCAPULA SIZE AND SHAPE IN DIDELPHID MARSUPIALS (DIDELPHIMORPHIA: DIDELPHIDAE)
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DOI：
10.1111/j.1558-5646.2009.00720.x
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发表时间：
2009-09-01
期刊：
影响因子：
3.3
通讯作者：
Astua, Diego
中科院分区：
文献类型：
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作者：
Astua, Diego
新大陆Didelphidae科是有袋类动物的基本谱系，通常被认为在形态上是保守的，但包括水生、陆生、爬行和树栖物种。在这里，我使用几何形态计量学定量地估计了Didelphidae肩胛骨(56个物种的1076个标本)在大小和形状上的现有变异性，并将大小和形状差异与进化和生态距离进行了比较。我发现肩胛骨的形态有相当大的差异，其中大部分与物种之间的大小差异有关。这导致了较大物种不同运动习性之间的形态差异(由于机械负荷增加)，但大多数较小物种的肩胛骨形状相似。唯一的例外是水负鼠和短尾负鼠，对这些差异的功能解释尚不清楚。肩胛骨的大小和形状被绘制到32个选定分类群的分子系统发育图上，并使用平方变化的简约重建了祖先的大小和形状。结果表明，Didelphidae是由一个具有全面性肩胛骨的中小型祖先进化而来，与树栖物种略有相似，但与现在的大体树栖物种明显不同，这表明祖先Didelphidae是一种小型爬行动物，对树栖或陆地习性没有特别的适应，这些特化只在较大的身体支系中进化。
The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium- to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades.