Kelly E M, Marcot J D, Selwood L, Sears K E
School of Integrative Biology, University of Illinois, Urbana, IL61801, USA.
Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
Integr Org Biol. 2019 Feb 8;1(1):oby013. doi: 10.1093/iob/oby013. eCollection 2019.
The morphological interdependence of traits, or their integration, is commonly thought to influence their evolution. As such, study of morphological integration and the factors responsible for its generation form an important branch of the field of morphological evolution. However, most research to date on post-cranial morphological integration has focused on adult patterns of integration. This study investigates patterns of correlation (i.e., morphological integration) among skeletal elements of the fore- and hind limbs of developing marsupial and placental mammals. The goals of this study are to establish how patterns of limb integration vary over development in marsupials and placentals, and identify factors that are likely responsible for their generation. Our results indicate that although the overall pattern of correlation among limb elements is consistent with adult integration throughout mammalian development, correlations vary at the level of the individual element and stage. As a result, the relative integration among fore- and hind limb elements varies dynamically between stages during development in both marsupial and placental mammals. Therefore, adult integration studies of the limbs may not be indicative of developmental integration. Results are also consistent with integration during early limb development being more heavily influenced by genetic and developmental factors, and later by function. Additionally, results are generally consistent with a constraint on marsupial forelimb evolution caused by the functional requirements of the crawl to the teat that operates by limiting morphological variation before and at the time of birth, and not after.
性状的形态学相互依存关系，即它们的整合，通常被认为会影响其进化。因此，对形态整合及其产生因素的研究构成了形态进化领域的一个重要分支。然而，迄今为止，大多数关于颅后形态整合的研究都集中在成年个体的整合模式上。本研究调查了有袋类和胎盘类哺乳动物发育过程中前肢和后肢骨骼元素之间的相关性模式（即形态整合）。本研究的目的是确定有袋类和胎盘类动物肢体整合模式在发育过程中是如何变化的，并找出可能导致这些变化的因素。我们的结果表明，尽管在整个哺乳动物发育过程中，肢体元素之间的总体相关性模式与成年个体的整合情况一致，但在个体元素和发育阶段层面上，相关性存在差异。因此，在有袋类和胎盘类哺乳动物的发育过程中，前肢和后肢元素之间的相对整合在不同阶段动态变化。所以，对肢体的成年个体整合研究可能无法反映发育过程中的整合情况。研究结果还表明，肢体早期发育过程中的整合受遗传和发育因素影响更大，后期则受功能影响更大。此外，研究结果总体上与一种观点一致，即有袋类动物前肢进化受到爬向乳头功能需求的限制，这种限制在出生前及出生时通过限制形态变异起作用，而不是在出生后。
