Department of Genetics, Evolution & Environment, University College London, London, UK.
J Evol Biol. 2013 Jun;26(6):1294-306. doi: 10.1111/jeb.12127. Epub 2013 Mar 27.
Heterochronic changes in the rate or timing of development underpin many evolutionary transformations. In particular, the onset and rate of bone development have been the focus of many studies across large clades. In contrast, the termination of bone growth, as estimated by suture closure, has been studied far less frequently, although a few recent studies have shown this to represent a variable, although poorly understood, aspect of developmental evolution. Here, we examine suture closure patterns across 25 species of carnivoran mammals, ranging from social-insectivores to hypercarnivores, to assess variation in suture closure across taxa, identify heterochronic shifts in a phylogenetic framework and elucidate the relationship between suture closure timing and ecology. Our results show that heterochronic shifts in suture closure are widespread across Carnivora, with several shifts identified for most major clades. Carnivorans differ from patterns identified for other mammalian clades in showing high variability of palatal suture closure, no correlation between size and level of suture closure, and little phylogenetic signal outside of musteloids. Results further suggest a strong influence of feeding ecology on suture closure pattern. Most of the species with high numbers of heterochronic shifts, such as the walrus and the aardwolf, feed on invertebrates, and these taxa also showed high frequency of closure of the mandibular symphysis, a state that is relatively rare among mammals. Overall, caniforms displayed more heterochronic shifts than feliforms, suggesting that evolutionary changes in suture closure may reflect the lower diversity of cranial morphology in feliforms.
发育速率或时间的异时性变化是许多进化转变的基础。特别是，骨骼发育的开始和速度一直是许多大型类群研究的焦点。相比之下，骨骼生长的终止（通过缝合线闭合来估计）研究得要少得多，尽管最近的一些研究表明这是发育进化中一个具有变化但理解较差的方面。在这里，我们检查了 25 种食肉哺乳动物的缝合线闭合模式，范围从社会性食虫动物到超肉食动物，以评估分类群之间缝合线闭合的变化，在系统发育框架中识别异时性转变，并阐明缝合线闭合时间与生态学之间的关系。我们的研究结果表明，缝合线闭合的异时性转变在食肉目中广泛存在，大多数主要类群都有几个转变。食肉目与其他哺乳动物类群的模式不同，表现出腭骨缝合线闭合的高度可变性，大小与缝合线闭合水平之间没有相关性，在外形亚目中几乎没有系统发育信号。结果进一步表明，摄食生态对缝合线闭合模式有强烈影响。大多数具有大量异时性转变的物种，如海象和土狼，以无脊椎动物为食，这些类群的下颌联合闭合频率也很高，而这种状态在哺乳动物中相对较少见。总体而言，犬形目比猫形目显示出更多的异时性转变，这表明缝合线闭合的进化变化可能反映了猫形目颅形态多样性较低。
