Extensive trans‐species mitochondrial polymorphisms in the carabid beetles Carabus subgenus Ohomopterus caused by repeated introgressive hybridization
Extensive trans‐species mitochondrial polymorphisms in the carabid beetles Carabus subgenus Ohomopterus caused by repeated introgressive hybridization
复制标题
由重复渐渗杂交引起的步甲甲虫 Ohomopterus 亚属中广泛的跨物种线粒体多态性
作者：
T. Sota;R. Ishikawa;Masayuki Ujiie;F. Kusumoto;A. Vogler;A. Vogler
为了研究渐渗杂交对步甲谱系进化多样性的潜在重要性，我们研究了日本本州中部和东部的四种Ohomopterus亚属（属Carabus）的线粒体NADH脱氢酶亚基5（ND 5）基因序列（1083 bp）的种内和跨种多态性。在这4种中，C.岛生菌与其他三种菌有亲缘关系，并能与至少两种菌自然杂交。该物种具有两个单倍型的远程谱系。我们采用聚合酶链反应-限制性片段长度多态性技术对524份样本进行ND 5单倍型分类，并对143份样本进行测序。分析显示，每个物种的线粒体DNA同源性都是多系的，这代表了跨物种多态性的一个明显例子。最近从C. arrowianusnakamurai到C. insulicola和C. insulicola到C. esakii，是从这些物种之间的相同序列的频率和从它们的接触区杂交的直接证据推断出来的。这四个物种中的其他种内多态性可能是由于未检测到的渐渗杂交（例如C。insulicola到C. maiyasanus）或来自祖先多态性的随机谱系分类。这个甲虫组有一个生殖器锁和钥匙系统，具有物种特异性或亚种特异性生殖器形态，可能会成为杂交的障碍。然而，我们的研究结果表明，渐渗杂交已经发生多次，至少对线粒体，尽管差异和稳定性，形态特征，区分当地人群。因此，杂交和渐渗可能是同翅目进化多样化的关键过程。
To study the potential importance of introgressive hybridization to the evolutionary diversification of a carabid beetle lineage, we studied intraspecific and trans‐species polymorphisms in the mitochondrial NADH dehydrogenase subunit 5 (ND5) gene sequence (1083 bp) in four species of the subgenus Ohomopterus (genus Carabus) in central and eastern Honshu, Japan. Of the four species, C. insulicola is parapatric with the other three, and can hybridize naturally with at least two. This species possesses two haplotypes of remote lineages. We classified ND5 haplotypes using polymerase chain reaction–restriction fragment length polymorphism with TaqI endonuclease for 524 specimens, and sequenced 143 samples. Analysis revealed that each species was polyphyletic in its mitochondrial DNA phylogeny, representing a marked case of trans‐species polymorphism. Recent one‐way introgression of mitochondria from C. arrowianus nakamurai to C. insulicola, and from C. insulicola to C. esakii, was inferred from the frequency of identical sequences between these species and from direct evidence of hybridization in their contact zones. Other intraspecific polymorphisms in the four species may be due to undetected introgressive hybridization (e.g. C. insulicola to C. maiyasanus) or from stochastic lineage sorting of ancestral polymorphisms. This beetle group has a genital lock‐and‐key system, with species‐specific or subspecies‐specific genital morphology that may act as a barrier to hybridization. However, our results demonstrate that introgressive hybridization has occurred multiple times, at least for mitochondria, despite differences among, and stability within, morphological characters that distinguish local populations. Thus, hybridization and introgression could have been key processes in the evolutionary diversification of Ohomopterus.