Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record
Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record
复制标题
DOI：
10.3374/014.053.0101
复制
发表时间：
2012-04-01
影响因子：
1.3
通讯作者：
Behlke, Adam Rr.
中科院分区：
文献类型：
--
作者：
Gauthier, Jacques A.;Kearney, Maureen;Behlke, Adam Rr.
我们收集了一个精心挑选的192个物种的数据集--51个灭绝物种和191个现存物种--以及分布在610个表型特征中的976个拟态，以研究鳞目动物(包括蛇和两栖动物)的系统发育。这些数据使我们能够推断出一棵树，与之前的形态分析得出的树非常相似，但对一些关键分支有更好的支持。还有一些新的元素，其中一些与关于蜥蜴进化的传统观点截然不同(例如，马赛龙和多齿龙位于硬舌动物的茎上，而不是树冠的一部分，分别与变齿类和苔藓类有关)。身体修长、四肢缩小、像蛇一样的化石蜥蜴--最著名的是双肢蜥蜴、两栖动物和蛇--一直是并将继续是有鳞动物形态系统发育中特征冲突的主要来源。食肉蜥蜴(尤其是蛇、马赛龙和变形目蜥蜴)已被证明紧随其后。基因数据可能不会受到与化石有关的适应性趋同的潜在影响，因此有望解决这些冲突。尽管最近的基因系统发育看起来是这样的，但它们也与任何基于表型的系统发育有着根本的不同，特别是发生在中生代后半段的最古老的树冠鳞片分化。我们的研究依赖于传统准备的标本以及高分辨率的计算机断层扫描，这为我们提供了前所未有的访问鳞状颅骨解剖的途径。这与茎化石的包含一起，提供了一个无与伦比的表型样本，使我们能够更充分地探索鳞状生命树的分子和形态拓扑之间的极端不一致。尽管有这个广泛的新数据库，但我们无法找到形态上的支持，以支持最近的分子研究提出的鳞片类中深度分歧的主要重排。相反，我们的数据有力地支持了大多数先前形态研究提出的相同的基本拓扑--Iguania-Skeroglossa基本分裂，Gekota和Autarchoglossa之间的姐妹群关系，以及Anguimforma和Scincomoga之间的分歧-并证明了这些分子拓扑所需的形态同源性的极端程度。
We assembled a dataset of 192 carefully selected species-51 extinct and 191 extant-and 976 apomorphies distributed among 610 phenotypic characters to investigate the phylogeny of Squamata ("lizards," including snakes and amphisbaenians). These data enabled us to infer a tree much like those derived from previous morphological analyses, but with better support for some key clades. There are also several novel elements, some of which pose striking departures from traditional ideas about lizard evolution (e.g., that mosasaurs and polyglyphanodontians are on the scleroglossan stem, rather than parts of the crown, and related to varanoids and teiids, respectively). Long-bodied, limb-reduced, "snake-like" fossorial lizards-most notably dibamids, amphisbaenians and snakes-have been and continue to be the chief source of character conflict in squamate morphological phylogenetics. Carnivorous lizards (especially snakes, mosasaurs and varanoids) have proven a close second. Genetic data, presumably less burdened by the potential for adaptive convergence related to fossoriality, were expected to resolve these conflicts. Although recent gene phylogenies seem to do so, they also differ radically from any phylogeny based-on the phenotype, especially for the most ancient crown squamate divergences that occured during the latter half of the Mesozoic. Our study relied on traditionally prepared specimens as well as high-resolution computed tomography scans that afforded unprecendented access to the cranial anatomy of Squamata. This, along with the inclusion of stem fossils, provided an unparalleled sample of the phenotype enabling us to more fully explore the extreme incongruences between molecular and morphological topologies for the squamate tree of life. Despite this extensive new database, we were unable to find morphological support for the major rearrangement of the deep divergences in Squamata proposed by recent molecular studies. Instead, our data strongly support the same fundamental topology suggested by most previous morphological studies-an Iguania-Scleroglossa basal split, a sister-group relationship between Gekkota and Autarchoglossa, and the divergence between Anguimorpha and Scincomorpha-and documents the extreme degree of morphological homoplasy required by those molecular topologies.