Shaffer H Bradley, McKnight Mark L
Section of Evolution and Ecology, and Center For Population Biology, University of California, Davis, California, 95616.
Evolution. 1996 Feb;50(1):417-433. doi: 10.1111/j.1558-5646.1996.tb04503.x.
We present a phylogenetic analysis of the Ambystoma tigrinum complex, based on approximately 840 base pairs of mitochondrial-DNA sequence from the rapidly evolving D-loop and an adjacent intron. Our samples include populations of the continentally distributed species, A. tigrinum, plus all described species of Mexican ambystomatids. Sequence divergence is low, ranging from 0-8.5%, and most phylogenetic groupings are weakly supported statistically. We identified eight reasonably well-defined clades from the United States and Mexico, with the geographically isolated A. californiense from California as the probable sister group to the remaining taxa. Our sequence data are not capable of resolving the relationships among these clades, although the pattern of transitional-site evolution suggests that these eight lineages diverged during a period of rapid cladogenesis. We roughly calibrate a molecular clock and identify a few lineages that significantly deviate from the slow, baseline rate of 0.5-0.75% per million years. Our data also suggest that species boundaries for several U.S. and Mexican species need to be altered and that the concept of a continentally distributed, polytypic tiger salamander is not valid.
我们基于来自快速进化的D环和一个相邻内含子的约840个碱基对的线粒体DNA序列，对虎纹钝口螈复合体进行了系统发育分析。我们的样本包括大陆分布物种虎纹钝口螈的种群，以及所有已描述的墨西哥钝口螈物种。序列差异较低，范围为0 - 8.5%，并且大多数系统发育分组在统计学上的支持较弱。我们从美国和墨西哥确定了八个定义较为明确的分支，来自加利福尼亚的地理隔离物种加州钝口螈可能是其余分类群的姐妹群。尽管转换位点进化模式表明这八个谱系在快速分支形成期分化，但我们的序列数据无法解析这些分支之间的关系。我们大致校准了分子钟，并确定了一些显著偏离每百万年0.5 - 0.75%的缓慢基线速率的谱系。我们的数据还表明，几个美国和墨西哥物种的物种界限需要改变，并且大陆分布的多型虎螈这一概念是无效的。
