Data from: Incongruence of mitochondrial and nuclear gene trees in the carabid beetles Ohomopterus

We studied the molecular phylogeny of the carabid subgenus Ohomopterus (genus Carabus) using two mtDNA regions (16SrRNA and ND5) and three nuclear DNA regions (wingless, phosphoenolpyruvate carboxykinase, and an anonymous locus). We revisited the previously reported incongruence between the distribution of mtDNA markers and morphologically defined species (Su et al., 1996, J. Mol. Evol., 43:662-671) which they attributed to "type switching", a concerted change in many morphological characters that results in the repeated evolution of a particular morphological type. Our mtDNA gene tree obtained from 44 individuals representing all 15 currently recognized species of Ohomopterus revealed that haplotypes isolated from individuals of a single "species" were frequently separated into distant clades, confirming the previous report. The three nuclear markers generally conformed better with the morphologically defined species. The phylogenetic signal in mtDNA and nuclear DNA data differed strongly and these two partitions were significantly incongruent with each other according to Farris et al.'s (1994) ILD test, although the three nuclear partitions were not homogeneous either. Our results did not support the type switching hypothesis which was proposed to fit the morphological data to the mitochondrial gene tree: incongruence of the mtDNA tree with other nuclear markers indicates that the mtDNA-based tree does not reflect species history any better than the morphological data. Incongruence of gene trees in Ohomopterus may have been promoted by the complex processes of geographic isolation and hybridization in the Japanese Archipelago that led to occasional gene flow and recombination between separated entities. It is intriguing that reticulate patterns occurred in this group, as species of Ohomopterus exhibit extremely divergent genitalic structures that represent a highly efficient reproductive isolation mechanism.

本研究针对步甲科步甲属（Carabus）下的虎步甲亚属（Ohomopterus）开展分子系统发育分析，选取2个线粒体DNA（mtDNA）区域（16SrRNA与ND5）以及3个核DNA区域（无翅基因（wingless）、磷酸烯醇式丙酮酸羧激酶（phosphoenolpyruvate carboxykinase）与1个匿名基因座（anonymous locus））作为分子标记。我们重新审视了此前报道的线粒体DNA标记分布与形态学定义物种间的不一致性（Su等，1996，《分子进化杂志》，43卷：662-671），该研究将这一现象归因于“性状转换（type switching）”——即多个形态性状发生协同改变，进而反复演化出某一特定形态类型。本研究基于覆盖虎步甲亚属当前全部15个已确认物种的44个个体构建线粒体DNA基因树，结果显示，单个“物种”个体所携带的单倍型常被归入相距甚远的不同演化支，这一结果验证了此前的研究报道。相较于线粒体DNA标记，3个核DNA标记的聚类结果与形态学定义的物种更为契合。线粒体DNA与核DNA数据所携带的系统发育信号存在显著差异，依据Farris等（1994）提出的不一致长度差异检验（ILD test），这两类数据分区间存在显著的不一致性；同时3个核DNA数据分区本身也并非完全同质。本研究结果不支持此前为使形态学数据契合线粒体DNA基因树而提出的性状转换假说：线粒体DNA基因树与其他核DNA标记间的不一致性表明，基于线粒体DNA构建的系统树并不比形态学数据更能反映物种演化历史。虎步甲亚属内基因树间的不一致性，可能由日本列岛复杂的地理隔离与杂交过程所驱动——这类过程使得分隔的类群间偶尔发生基因流与重组。值得注意的是，该类群中存在网状演化模式，而虎步甲亚属的物种展现出高度分化的生殖器官结构，这类结构本应是极为高效的生殖隔离机制。