Lee Taehwan, Hong Hyeon Chol, Kim Jae Jin, O Foighil Diarmaid
Museum of Zoology and Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109-1079, USA.
Mol Phylogenet Evol. 2007 May;43(2):386-97. doi: 10.1016/j.ympev.2007.02.018. Epub 2007 Feb 25.
We investigated the population genetic structure and phylogenetic relationships of four morphospecies of Semisulcospira sampled from multiple South Korean drainages. One, S. extensa, displayed modest levels of genetic diversity and formed a species-specific clade for both mitochondrial (mt) and nuclear markers. In contrast, the other three, S. coreana, S. gottschei, and S. libertina, were polyphyletic for both mt and nuclear markers. They formed, together with other nominal congeners (S. forticosta, S. multicincta, S. nodiperda, and S. tegulata), a taxonomically heterogeneous species complex containing population-level admixtures of genotypes from numerically predominant modal clades in addition to rare, phylogenetically divergent, mt and nuclear genotypes. The modal mt haplotypes exhibited far more geographic than taxonomic congruence and typically co-clustered into drainage-specific tip clades, irrespective of nominal taxonomic status. The evolutionary origins of the observed non-extensa phylogenetic heterogeneity are unclear at present although the available data do not support paralogous mt marker phenomena or the presence of cryptic species. We cannot distinguish among retention of ancestral polymorphisms or recticulate evolutionary origins as explanatory mechanisms and it may require the genetic characterization of Semisulcospira lineages throughout much of their collective east Asian range to address this issue. Based on the available data, we consider it best to view all of our non-extensa Korean study taxa as a single polymorphic species complex of the type species S. libertina. There is considerable evidence that similarly complex genetic structuring, at least for mt, may be typical of many other freshwater cerithioidean snail taxa. In light of our Semisulcospira results, we suggest that meaningful molecular phylogenetic characterization of freshwater cerithioidean lineages may require the use of both mt and nuclear markers together with population level sampling of all nominal taxa within regional drainages.
我们研究了从韩国多个排水系统采集的四种拟沼螺形态种的种群遗传结构和系统发育关系。其中一种，即宽身拟沼螺（Semisulcospira extensa），显示出适度的遗传多样性水平，并且在线粒体（mt）和核标记方面均形成了一个物种特异性分支。相比之下，其他三种，即韩国拟沼螺（S. coreana）、戈氏拟沼螺（S. gottschei）和放逸拟沼螺（S. libertina），在线粒体和核标记方面均为多系的。它们与其他名义上的同属物种（强壮拟沼螺（S. forticosta）、多带拟沼螺（S. multicincta）、结节拟沼螺（S. nodiperda）和瘤拟沼螺（S. tegulata））一起，形成了一个分类学上异质的物种复合体，除了稀有、系统发育上有差异的线粒体和核基因型外，还包含来自数量上占优势的模式分支的基因型的种群水平混合。模式线粒体单倍型表现出的地理一致性远多于分类学一致性，并且通常共同聚类成特定排水系统的末端分支，而不考虑名义分类地位。尽管现有数据不支持线粒体标记的旁系同源现象或隐存物种的存在，但目前尚不清楚观察到的非宽身拟沼螺系统发育异质性的进化起源。我们无法区分祖先多态性的保留或网状进化起源作为解释机制，可能需要对拟沼螺谱系在其整个东亚分布范围内的大部分地区进行遗传特征分析来解决这个问题。基于现有数据，我们认为最好将我们所有的非宽身拟沼螺韩国研究分类单元视为以放逸拟沼螺为模式种的单一多态物种复合体。有相当多的证据表明，至少对于线粒体而言，类似的复杂遗传结构可能是许多其他淡水蟹守螺类蜗牛分类单元的典型特征。鉴于我们对拟沼螺的研究结果，我们建议对淡水蟹守螺类谱系进行有意义的分子系统发育特征分析可能需要同时使用线粒体和核标记，并对区域排水系统内的所有名义分类单元进行种群水平采样。
