Weisrock D W, Kozak K H, Larson A
Department of Biology, Box 1137, Washington University, Saint Louis, MO 63130, USA.
Mol Ecol. 2005 Apr;14(5):1457-72. doi: 10.1111/j.1365-294X.2005.02524.x.
Plethodon shermani comprises a series of geographically disjunct populations occupying high-elevation mountain isolates. These populations hybridize at their borders with salamanders of the Plethodon glutinosus species complex, and past range expansions inferred from Pleistocene climatic cycles may have increased the possible genetic interactions between P. shermani and species of the P. glutinosus complex. Because mitochondrial DNA haplotypes often show introgression across species borders, we survey mtDNA variation for evidence of past and ongoing genetic interactions between P. shermani, its close relative Plethodon cheoah, and species of the P. glutinosus complex. Ongoing hybridization with the P. glutinosus-complex species Plethodon teyahalee is accompanied by extensive mitochondrial introgression in some Unicoi populations of P. shermani, but it has little genetic impact on P. shermani populations outside hybrid zones at three other isolates (Tusquitee, Wayah Bald, Standing Indian). Some Unicoi populations of P. shermani exhibit mtDNA evidence of past hybridization with diverse lineages from P. aureolus and P. glutinosus. The Tusquitee isolate of P. shermani is also characterized by mtDNA haplotypes most closely related to Plethodon aureolus and P. glutinosus, presumably introduced by past genetic contact with these species or with introgressed populations of Unicoi P. shermani. The mtDNA variation in sampled populations of the Wayah Bald and Standing Indian isolates of P. shermani appears largely unaffected by ongoing hybridization. Principal components analyses of allozymic data indicate that P. shermani isolates collectively form a genetically homogeneous unit clearly demarcated from species with which they have had current or past genetic interactions. Rapid mtDNA introgression associated with transient contacts between P. shermani and other species permits a fine-level resolution of evolutionary lineages not evident from allozymic data.
谢氏脊口螈由一系列地理上隔离的种群组成，这些种群占据着高海拔山区孤立地带。这些种群在其边界处与黏体脊口螈物种复合体的蝾螈杂交，从更新世气候周期推断出的过去的范围扩张可能增加了谢氏脊口螈与黏体脊口螈复合体物种之间可能的基因相互作用。由于线粒体DNA单倍型常常显示出跨物种边界的基因渗入，我们调查线粒体DNA变异，以寻找谢氏脊口螈、其近亲乔阿脊口螈以及黏体脊口螈复合体物种之间过去和正在进行的基因相互作用的证据。谢氏脊口螈与黏体脊口螈复合体物种泰亚哈莱脊口螈正在进行的杂交，伴随着谢氏脊口螈一些尤尼科伊种群中广泛的线粒体基因渗入，但对其他三个孤立地带（塔斯基蒂、瓦亚山、印第安站）杂交区以外的谢氏脊口螈种群几乎没有基因影响。谢氏脊口螈的一些尤尼科伊种群显示出过去与金色脊口螈和黏体脊口螈不同谱系杂交的线粒体DNA证据。谢氏脊口螈的塔斯基蒂孤立地带的特征还在于其线粒体单倍型与金色脊口螈和黏体脊口螈关系最为密切，推测是过去与这些物种或与尤尼科伊谢氏脊口螈的渗入种群发生基因接触所致。谢氏脊口螈瓦亚山和印第安站孤立地带抽样种群中的线粒体DNA变异似乎在很大程度上未受正在进行的杂交影响。对等位酶数据的主成分分析表明，谢氏脊口螈各孤立地带共同构成一个基因同质单元，与它们目前或过去有基因相互作用的物种有明显区分。与谢氏脊口螈和其他物种短暂接触相关的快速线粒体基因渗入，使得从等位酶数据中不明显的进化谱系能够得到精细分辨率。
