Rodríguez-Robles J A, De Jesús-Escobar J M
Museum of Vertebrate Zoology, University of California, Berkeley, California 94720-3160, USA.
Mol Phylogenet Evol. 2000 Jan;14(1):35-50. doi: 10.1006/mpev.1999.0698.
Pituophis melanoleucus (gopher, bull, and pinesnakes) is among the most widely distributed polytypic species complexes in North America, with most authors recognizing from a single transcontinental species (the melanoleucus complex, composed of 15 subspecies) to four (monotypic and polytypic) species. We used mitochondrial gene sequences from the two middle American species, P. deppei and P. lineaticollis, and from 13 subspecies from most of the range of the melanoleucus complex to test various phylogenetic hypotheses for Pituophis. Maximum parsimony and maximum likelihood methods identified the same major clades within Pituophis and indicated that two segments of the melanoleucus complex, the lodingi-melanoleucus-mugitus eastern pinesnake clade and the affinis-annectens-bimaris-catenifer-deserticola- sayi-ruthveni-vertebr alis clade from central and western United States and northern Mexico, represent divergent, allopatric lineages with no known intergradation zone. We recognize each of these two groupings as a different species. Our data also indicate that some ruthveni are more closely related to sayi than to other ruthveni. Nonetheless, ruthveni is an allopatric taxon diagnosable from its closest relatives by a combination of morphometric characters, and because it is likely that at least some of these traits are independent and genetically inherited, we interpret this as evidence that ruthveni has attained the status of independent evolutionary lineage, despite the fact that it retains strong genetic affinities with sayi. The endemic Baja Californian gopher snakes (bimaris and vertebralis) are considered by some taxonomists as a different species, P. vertebralis, but we discovered that these serpents belong to two different clades and hence we do not agree with the recognition of P. vertebralis as presently defined. In summary, we believe that three distinct species are included in the melanoleucus complex, Pituophis melanoleucus (sensu stricto), P. catenifer, and P. ruthveni, and that their recognition better represents the evolutionary diversity within this species complex.
岩蟒（地鼠蛇、牛蛇和松树蛇）是北美分布最广的多型物种复合体之一，大多数作者认为它有从单一的跨大陆物种（由15个亚种组成的黑白带锦蛇复合体）到四个（单型和多型）物种不等。我们使用了来自中美洲的两个物种——德佩氏锦蛇和细纹锦蛇，以及来自黑白带锦蛇复合体大部分分布范围的13个亚种的线粒体基因序列，来检验关于岩蟒的各种系统发育假说。最大简约法和最大似然法在岩蟒中识别出了相同的主要分支，并表明黑白带锦蛇复合体的两个部分，即东部松树蛇分支的洛丁氏锦蛇 - 黑白带锦蛇 - 穆吉图斯锦蛇分支，以及来自美国中部和西部以及墨西哥北部的亲缘锦蛇 - 毗连锦蛇 - 双带锦蛇 - 链纹锦蛇 - 沙漠锦蛇 - 赛氏锦蛇 - 鲁思文锦蛇 - 椎纹锦蛇分支，代表了不同的异域谱系，没有已知的渐变带。我们将这两个分类群中的每一个都视为不同的物种。我们的数据还表明，一些鲁思文锦蛇与赛氏锦蛇的亲缘关系比与其他鲁思文锦蛇的亲缘关系更近。尽管如此，鲁思文锦蛇是一个异域分类单元，通过形态测量特征的组合可与它最亲近的亲属区分开来，而且由于这些特征中至少有一些可能是独立的且可遗传的，我们将此解释为鲁思文锦蛇已达到独立进化谱系地位的证据，尽管它与赛氏锦蛇仍保持着很强的遗传亲缘关系。一些分类学家认为特有的下加利福尼亚地鼠蛇（双带锦蛇和椎纹锦蛇）是一个不同的物种——椎纹锦蛇，但我们发现这些蛇属于两个不同的分支，因此我们不同意目前对椎纹锦蛇的认定。总之，我们认为黑白带锦蛇复合体包括三个不同的物种，即狭义的黑白带锦蛇、链纹锦蛇和鲁思文锦蛇，并且对它们的认定能更好地体现这个物种复合体中的进化多样性。
