中国具有专性雄性生殖方式类群——蚬属的系统分类与生殖特征研究

The taxonomy of the genus Corbicula, a commercially improtant and widespread invasive group, has not been accurately resolved. Comprehensive systematic analysis combining mitochondrial and nuclear gene markers is thought to be the most effective method to deal with this problem, due to their ploymorphic shells and divertified and peculiar reproduction characteristics of genus Corbicula, especially the hermaphroditism and androgenesis which resulting in the mismatch of mitochondrial/nuclear genome in progeny. China is one of the native areas for genus Corbicula, but the taxa status of genus Corbicula still needs to be further proved integrating the modern systematic methods, and the androgenesis reproductive mode of genus Corbicula has also not been reproted in China. In the proposed study, the taxonomy of genus Corbicula form China and their main reproductive characteristics, especially for the androgenesis reproductive mode will be studied. Firstly, the systematic relationships of genus Corbicula will be analyzide by the comprehensive systematic analysis combining the DNA barcode of mitochondrial COI gene and nuclear 28S rDNA gene. Then the taxonomy of genus Corbicula will be established based on the results of systematic analysis taken together with those deduced from morphology methods (traditional morphological parameters and geometry). Secondly, the main reproductive characteristics of Corbicula species will be evaluated through analyzing the sexual mechanisms, position of broods, flagellate number, ploids, and reduction or not of sperm. Finally, an accurate and effective identification method for genus Corbicula will be provided. The results of the proposed study will be helpful for resolving the taxonomy of genus Corbicula globally and evaluating and managing the diversity of Corbicula in China.

作为重要的经济类群和广泛的入侵类群，蚬属的分类尚未准确厘定。形态的高度可塑性和生殖特征的复杂多样性，尤其是专性雄性生殖易造成的子代细胞质与细胞核基因组错配，使得联合采用基于线粒体和细胞核基因条形码的系统分类方法被认为是厘定蚬属分类的最有效方法。中国作为原产地之一，其蚬属依据形态的分类体系仍需结合分子系统学方法进一步核实，且其蚬属的雄性生殖特征亦尚未见报道。本项目拟在联合采用基于线粒体COI与细胞核28S rDNA基因条形码对我国蚬属进行系统分类的基础上，结合形态特征确定我国蚬属的种类，并分别从性别机制、幼蚬孵育方式、精子鞭毛数量、精子倍性、精子是否减数等方面确定蚬属各种类的主要生殖特征，最终提出一套实用的鉴别方法，从而为全球蚬属分类的厘定及我国蚬的多样性评价与管理提供基础。

通过构建基于线粒体 COⅠ 基因序列的系统进化树，再结合性腺组织学、鳃组织学、精子形态、体细胞/精子 DNA 含量分析，初步确定中国蚬属由三个类群或谱系组成，且三个谱系蚬的空间分布具有显著的区域偏好。除长江口群体外，长江流域蚬群体的遗传多样性呈现出沿长江由西到东逐渐升高趋势。盐度可能是影响长江流域蚬属贝类遗传分化的主要环境因子。长江流域蚬呈现由河口群体的二倍体、雌雄异体、精子单鞭毛到中游群体的二倍体与三倍体共存、三性异体、精子单鞭毛或双鞭毛再到上游群体的三倍体与四倍体共存、雌雄同体、精子双鞭毛的分布特征，且双鞭毛精子与体细胞 DNA 含量一致，而单鞭毛精子的 DNA 含量则为体细胞一半。研究表明，中国蚬属种类应该低于文献报道中基于形态特征所提到的 7 种，但因所研究的蚬的谱系与其形态、性别、倍性及生殖特征之间均没有显著对应关系，使得我们无法确定其具体种数，只能确定为蚬属复合种 Corbicula species complex。中国蚬存在雄核生殖现象，但雄核生殖的细胞学过程还有待于进一步分析。