Molecular Phylogenetics of Colubroid Snakes (Colubroidea)

确定各种高级蛇之间的遗传关系是一个最困难和最具挑战性的问题。蛇的身体结构大大简化，几乎没有可以用来区分它们的解剖特征，在许多情况下，两个或更多的物种独立地形成了相同的一组解剖特征。因此，过去对解剖学特征的依赖在提供有关蛇的关系的可靠信息方面提供的信息很少。为了纠正这一点，建议从八个最大的高级蛇类推定群体的代表中获得两个线粒体基因的DNA序列，并为了比较的目的，从两个原始蛇类群体中获得。在这些研究中，DNA序列比较比解剖学比较有两个巨大的优势。其中之一是，解剖复杂性的降低并没有反映在DNA水平上；DNA序列复杂性的全部范围都存在，用于确定关系。另一种是，与许多解剖变化的情况不同，相同的序列变化几乎不可能在两个不同的物种中独立发生；因此，功能上的趋同于那些由于谱系遗传而产生的变化。对高级蛇之间的遗传关系的准确了解是理解一系列特征发展的方式所必需的。例如，准确地了解无毒和毒蛇是如何相关的，将解决目前围绕毒腺发育和输送毒液的解剖成分的一些争议。这些知识还将为未来研究这里没有讨论的蛇群之间的关系提供基础。

Determining genetic relationships among the various kinds of advanced snakes is a most difficult and challenging problem. The greatly simplified body plan of snakes offers few anatomical characters that can be used to distinguish among them, and in many cases two or more species have developed the same sets of anatomical characteristics independently. The past reliance on anatomical characteristics has, therefore, provided little in the way of reliable information about snake relationships. To rectify this, it is proposed that the DNA sequences of two mitochondrial genes be obtained from representatives of the eight largest presumptive groups of advanced snakes and, for comparative purposes, from two primitive snake groups. DNA sequence comparisons offer two huge advantages over anatomical comparisons for these studies. One is that the reduction in anatomical complexity is not reflected at the DNA level; the full range of DNA sequence complexity is present for use in determining relationships. The other is that, unlike the case with many anatomical changes, there is almost no possibility that the same sequence changes will occur independently in two different species; thus, with functional convergences from those due to genealogical inheritance. An accurate knowledge of the genetic relationships among advanced snakes is required for understanding the ways in which suites of characteristics develop. For example, knowing exactly how non-poisonous and poisonous snakes are related will resolve some of the controversies that presently surround the development of venom glands and the anatomical components for delivering venom. This knowledge will also provide the foundation for future studies of relationships among snake groups not examined here.