Do Developmental Constraints and High Integration Limit the Evolution of the Marsupial Oral Apparatus?
Do Developmental Constraints and High Integration Limit the Evolution of the Marsupial Oral Apparatus?
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DOI：
10.1093/icb/icw039
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发表时间：
2016-09
影响因子：
2.6
通讯作者：
Sánchez-Villagra MR
中科院分区：
文献类型：
--
作者：
Goswami A;Randau M;Polly PD;Weisbecker V;Bennett CV;Hautier L;Sánchez-Villagra MR
发展制约对进化的幅度和方向有重要的影响，许多研究表明，这些影响表现在宏观进化尺度上。表型整合，或性状之间的强相互作用，已被类似地援引为形态变异的主要影响，许多研究表明，性状整合通过个体发育而变化，在许多情况下随着年龄的增长而减少。在这里，我们统一这些观点的哺乳动物头骨的个体发育的案例研究，重点是有袋动物和胎盘之间的比较。有袋类动物出生时处于一种非常晚期的状态，在大多数情况下，需要使用前肢爬到育儿袋，并且在所有情况下，都需要长时间的连续哺乳，在此期间，它们的大部分发育发生。以前的工作表明，有袋类动物是不太不同的成人颅骨形式比胎盘，特别是在口腔器，并在前肢个体发育和成人形态，可能是由于这两个系统的功能选择压力在出生后早期的发展。使用表型轨迹分析，以量化产前和出生后早期的颅骨个体发育在10种兽目哺乳动物，我们表明，这种模式的有限的变化也很明显，在有袋类动物的口腔器的发展，相对于胎盘，但不是在头骨更普遍。结合观察，有袋类动物显示极高的集成的口腔器在出生后的个体发育早期，而其他颅区显示类似的整合水平，观察胎盘，我们认为，高集成可能复合的影响的功能限制连续哺乳，最终限制个体发育和成人的差距有袋类口腔器在整个进化历史。
Developmental constraints can have significant influence on the magnitude and direction of evolutionary change, and many studies have demonstrated that these effects are manifested on macroevolutionary scales. Phenotypic integration, or the strong interactions among traits, has been similarly invoked as a major influence on morphological variation, and many studies have demonstrated that trait integration changes through ontogeny, in many cases decreasing with age. Here, we unify these perspectives in a case study of the ontogeny of the mammalian cranium, focusing on a comparison between marsupials and placentals. Marsupials are born at an extremely altricial state, requiring, in most cases, the use of the forelimbs to climb to the pouch, and, in all cases, an extended period of continuous suckling, during which most of their development occurs. Previous work has shown that marsupials are less disparate in adult cranial form than are placentals, particularly in the oral apparatus, and in forelimb ontogeny and adult morphology, presumably due to functional selection pressures on these two systems during early postnatal development. Using phenotypic trajectory analysis to quantify prenatal and early postnatal cranial ontogeny in 10 species of therian mammals, we demonstrate that this pattern of limited variation is also apparent in the development of the oral apparatus of marsupials, relative to placentals, but not in the skull more generally. Combined with the observation that marsupials show extremely high integration of the oral apparatus in early postnatal ontogeny, while other cranial regions show similar levels of integration to that observed in placentals, we suggest that high integration may compound the effects of the functional constraints for continuous suckling to ultimately limit the ontogenetic and adult disparity of the marsupial oral apparatus throughout their evolutionary history.