Burbrink F T, Lawson R, Slowinski J B
Museum of Natural Science and Department of Biology, Louisiana State University, Baton Rouge 70803, USA.
Evolution. 2000 Dec;54(6):2107-18. doi: 10.1554/0014-3820(2000)054[2107:MDPOTP]2.0.CO;2.
Subspecies have been considered artificial subdivisions of species, pattern classes, or incipient species. However, with more data and modern phylogenetic techniques, some subspecies may be found to represent true species. Mitochondrial DNA analysis of the polytypic snake, Elaphe obsoleta, yields well-supported clades that do not conform to any of the currently accepted subspecies. Complete nucleotide sequences of the cytochrome b gene and the mitochondrial control region produced robust maximum-parsimony and maximum-likelihood trees that do not differ statistically. Both trees were significantly shorter than a most parsimonious tree in which each subspecies was constrained to be monophyletic. Thus, the subspecies of E. obsoleta do not represent distinct genetic lineages. Instead, the evidence points to three well-supported mitochondrial DNA clades confined to particular geographic areas in the eastern United States. This research underscores the potential problems of recognizing subspecies based on one or a few characters.
亚种曾被视为物种、模式类群或初始物种的人为划分。然而，随着更多数据和现代系统发育技术的出现，一些亚种可能会被发现代表真正的物种。对多型蛇——北美鼠蛇（Elaphe obsoleta）进行的线粒体DNA分析产生了得到充分支持的分支，这些分支与目前任何已被接受的亚种都不相符。细胞色素b基因和线粒体控制区的完整核苷酸序列产生了稳健的最大简约树和最大似然树，二者在统计学上没有差异。这两棵树都明显短于一棵最简约树，在该最简约树中每个亚种都被限定为单系的。因此，北美鼠蛇的亚种并不代表不同的遗传谱系。相反，证据指向三个得到充分支持的线粒体DNA分支，它们局限于美国东部的特定地理区域。这项研究强调了基于一个或几个特征来识别亚种的潜在问题。
