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Mammalian limb morphology: the role of the crawl in determining marsupial limb integration, development, and evolution

机译:哺乳动物肢体形态学:爬行在确定有袋动物肢体整合,发育和进化中的作用

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摘要

Marsupials and eutherians, though closely related sister taxa, differ greatly in the variety of morphologies found within their groups. This inequality has largely been argued to be due to the reproductive differences. The crawl most marsupial neonates complete after birth has constrained the evolution of the forelimb and the group as a whole. However, the hind limb, which does not participate in the crawl, may have “escaped” the crawl’s constraint. This strong selective pressure to develop the forelimb early has also led to a decrease in integration (i.e. covariance) between the serially homologous elements of the limb. While limb integration has been well studied in adults, there exists study quantifying developmental integration in any system, which is unfortunate as it is important to examine integration across contexts (genetic, developmental, functional) in order to understand the evolution of morphologies. The purpose of this study is to determine both if marsupials are more likely to adapt their hind limbs than their forelimbs as well as to determine developmental patterns of limb integration to better understand the role of the crawl in marsupial evolution. To determine whether or not marsupials are more likely to adapt their hind limbs, length and width measurements were taken from the skeletal elements of the girdles, stylopod, zeugopod, and autopod from 196 therian taxa (82 marsupials, 114 eutherians). This data were then incorporated into principal component analyses and correlation matrices compared with the species’ functional group. Marsupials were found to be less likely to specialize their forelimbs than eutherians and while also more likely to specialize their hind limbs than forelimbs, still less likely to specialize their hind limbs than eutherians. In order to determine developmental integration, embryos at different but comparable stages were cleared and stained to visualize bone and cartilage growth from three marsupials (Monodelphis domestica, Sminthopsis macroura, Trichosurus vulpecula) and one eutherian (M. musculus). A reflex scope was used to place four points on the stylopod, zeugopod, and autopod and these points were used to determine gross length and width for each element. A combination of correlation and covariance matrices, Mantel’s test, and Mann-Whitney U tests were used to determine the integration patterns, both within and between the limbs, for each embryonic stage. Integration patterns significantly differed between stages and for marsupials, between limb integration decreased over time. Overall this study found that the hind limb of marsupials has been constrained by the crawl and that developmental integration changes between stages, suggesting a post-birth period of limb flexibility in both marsupials and eutherians.
机译:有袋动物和有真人的动物虽然有着密切的姊妹分类,但是在他们的群体中发现的形态却有很大的不同。人们普遍认为这种不平等是由于生殖差异造成的。大多数有袋类新生婴儿出生后完成的爬行活动限制了前肢和整个群体的进化。但是,不参与爬网的后肢可能“逃脱了”爬网的约束。这种早期发育的强大选择性压力还导致肢体的系列同源元件之间的整合(即协方差)降低。尽管成年人的肢体整合已经得到了很好的研究,但已有研究量化了任何系统中的发育整合,这是不幸的,因为重要的是检查跨上下文(遗传,发育,功能)的整合以了解形态的演变。这项研究的目的是确定有袋动物是否比前肢更容易适应其后肢,并确定四肢整合的发展模式以更好地了解爬行在有袋动物进化中的作用。为了确定有袋动物是否更有可能适应其后肢,从196个泰安生物分类群(82个有袋动物,114个以太人)中的腰带,针足类,类足动物和独脚架的骨骼元素中进行了长度和宽度测量。然后将该数据与主要物种的功能组进行比较,并纳入主成分分析和相关矩阵中。人们发现有袋动物的前肢专业性不如欧洲人,而后肢的专业性也比前肢高,而后肢的专业性却不如欧洲人。为了确定发育整合,清除并染色处于不同但可比较阶段的胚胎,以可视化来自三只有袋动物(家蝇(Monodelphis domestica),Sminthopsis macroura,Trichosurus vulpecula)和一只以太鱼(M. musculus)的骨骼和软骨生长。反射镜用于将四个点放置在节肢动物,类足动物和自足类动物上,这些点用于确定每个元素的总长度和宽度。相关和协方差矩阵,Mantel检验和Mann-Whitney U检验相结合,用于确定每个胚胎阶段肢体内部和肢体之间的整合模式。不同阶段和有袋动物的整合模式差异显着,肢体整合随着时间的推移而下降。总体而言,该研究发现有袋动物的后肢受到爬行的约束,并且发育整合在各个阶段之间发生变化,这表明有袋动物和以太坊人的肢体柔韧性在出生后。

著录项

  • 作者

    Kelly Elizabeth M.;

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  • 年度 2011
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  • 原文格式 PDF
  • 正文语种 {"code":"en","name":"English","id":9}
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