Blackburn Daniel G
Department of Biology, Electron Microscopy Center, Trinity College, Hartford, Connecticut.
J Exp Zool B Mol Dev Evol. 2015 Sep;324(6):473-86. doi: 10.1002/jez.b.22625. Epub 2015 May 13.
Viviparity in squamate reptiles is widely recognized as having evolved convergently from oviparity more than 100 times. However, questions persist as to whether reversals from viviparity back to oviparity have ever occurred. Based on a theoretical model, a recent paper (Pyron and Burbrink, 2014) has proposed that viviparity is ancestral for squamates and that viviparity-oviparity reversals have far outnumbered origins of viviparity in reproductive history. Close examination of this analysis reveals features that cast doubt on its plausibility, notably the requirement of repeated, sequential transformations back and forth between these reproductive modes, as well as numerous, uncounted evolutionary transformations that have produced inaccurate estimates of parsimony. Evidence derived from studies of anatomy, physiology, and developmental biology strongly supports the inference that oviparity is ancestral for squamates and has given rise to viviparity on numerous occasions. Biological data provide important insights into the likelihood of evolutionary transformations, and deserve to be incorporated fully into future analyses of the evolution of reproductive modes.
有鳞目爬行动物的胎生现象被广泛认为是从卵生现象趋同进化而来的，这种情况发生了100多次。然而，关于是否曾出现过从胎生逆转回卵生的情况，仍然存在疑问。基于一个理论模型，最近的一篇论文（派伦和布尔布林克，2014年）提出，胎生是有鳞目动物的祖先特征，并且在生殖历史中，从胎生到卵生的逆转次数远远超过了胎生现象的起源次数。仔细研究这一分析会发现一些令人质疑其合理性的特征，特别是在这些生殖模式之间需要反复、连续地来回转变，以及存在大量未计算在内的进化转变，这些转变导致了简约性估计不准确。来自解剖学、生理学和发育生物学研究的证据有力地支持了这样的推断：卵生是有鳞目动物的祖先特征，并且在许多情况下卵生进化出了胎生现象。生物学数据为进化转变的可能性提供了重要见解，理应充分纳入未来对生殖模式进化的分析中。
