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。蛇极其简化的身体结构提供了很少的解剖学特征来区分它们，在许多情况下，两个或两个以上的物种独立地发展了相同的解剖学特征。因此，过去对解剖特征的依赖在关于蛇的关系方面提供了很少的可靠信息。为了纠正这一点，有人建议从八个最大的假定的高级蛇群的代表中获得两个线粒体基因的DNA序列，并且为了比较的目的，从两个原始蛇群中获得。DNA序列比对这些研究提供了两个巨大的优势解剖比较。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存在于确定关系中。另一个是，与许多解剖变化的情况不同，几乎不可能在两个不同的物种中独立发生相同的序列变化；因此，与那些由于家谱遗传的功能收敛。对高级蛇类之间的遗传关系有一个准确的认识，这是理解一系列特征发展的方式所必需的。例如，确切地知道无毒和有毒的蛇是如何联系在一起的，将解决目前围绕着毒液腺的发育和释放毒液的解剖成分的一些争议。这些知识也将为未来研究这里没有研究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.