Densmore Llewellyn D, Wright John W, Brown Wesley M
Laboratory of Molecular Systematics, Museum of Zoology, and Department of Biology, University of Michigan, Ann Arbor, MI, 48109-1079.
Section of Herpetology, Natural History Museum of Los Angeles County, Los Angeles, CA, 90007.
Evolution. 1989 Aug;43(5):943-957. doi: 10.1111/j.1558-5646.1989.tb02541.x.
Restriction-endonuclease analyses of mitochondrial DNAs from all six color-pattern classes (A-F) of the parthenogenetic lizard Cnemidophorus tesselatus yield estimates of nucleotide divergence that are extremely low (π = 0.06%). In digests of 75 C. tesselatus mtDNAs with 20 different restriction enzymes, only four cleavage-site differences were noted, three of which were found only in pattern class F. The near-identity of these mitochondrial DNAs with those from C. tigris marmoratus shows unequivocally that C. t. marmoratus was the species to which the maternal parent(s) of all C. tesselatus belonged. Mitochondrial-DNA analyses of another unisexual species, C. neomexicanus, led to the same conclusion. Mitochondrial DNAs from 96 individuals of these three species were extensively analyzed for cleavage-site differences; only 13 were found. The low interspecific sequence diversity found within C. neomexicanus and the C. tesselatus complex suggests a recent origin for both. Based on diversity data for mitochondrial DNA and allozymes, we estimate that a minimum of two hybridizations were required to produce all diploid C. tesselatus (C-F), followed by at least two more to generate the triploids (A and B). These data and those presented in the two accompanying papers indicate that events leading to parthenogenesis in Cnemidophorus are rare and strengthen the hypothesis that interspecific hybridization is a necessary, causal event in its establishment.
对孤雌生殖的棋盘斑鞭尾蜥（Cnemidophorus tesselatus）所有六种体色类型（A - F）的线粒体DNA进行限制性内切酶分析，得出的核苷酸分歧估计值极低（π = 0.06%）。在用20种不同的限制性酶消化75个棋盘斑鞭尾蜥的线粒体DNA时，仅发现了四个切割位点差异，其中三个仅在F型中发现。这些线粒体DNA与虎斑鞭尾蜥（C. tigris marmoratus）的线粒体DNA几乎完全相同，明确表明所有棋盘斑鞭尾蜥的母本都属于虎斑鞭尾蜥这个物种。对另一个单性物种新墨西哥鞭尾蜥（C. neomexicanus）的线粒体DNA分析也得出了相同的结论。对这三个物种的96个个体的线粒体DNA进行了广泛的切割位点差异分析；仅发现了13个差异。在新墨西哥鞭尾蜥和棋盘斑鞭尾蜥复合体中发现的种间序列多样性较低，表明两者的起源都很新。根据线粒体DNA和同工酶的多样性数据，我们估计至少需要两次杂交才能产生所有的二倍体棋盘斑鞭尾蜥（C - F），随后至少还需要两次杂交才能产生三倍体（A和B）。这些数据以及随附的两篇论文中呈现的数据表明，导致鞭尾蜥孤雌生殖的事件很少见，并强化了种间杂交是其建立过程中必要的因果事件这一假设。
