我国及东南亚地区东方牙甲属的形态分类及系统发育关系研究

The members of the genus Pelthydrus are a group of small-sized aquatic beetles which belong to Coleoptera, Polyphaga，Hydrophilidae. At present, 63 species were recorded all over the world, mainly occurring in China and Southeast Asia. The genus Pelthydrus generally live in little streams with high quality, and usually hidden in the litter, or under stone, sand, so it is very difficult to be found. Furthermore, because of the similar morphological characters, the identification of Pelthydrus species usually depends on male genital characters; with collection intensity and density increased, the genitalia of some similar species showing a continuous change trend, resulting a difficult identification on the species level. So, the taxonomy of this genus has been progressed slowly in a long time. The classification of subgenus and species-group are only based on simple somatic characters, are also need to be revised.The genus Pelthydrus has never been systematically investigated in the past years, many new species await to be discovered. Here the genus Pelthydrus is selected as research object, a systematic investigations in China and Southeast Asia will be carried out. On the basis of comprehensive morphological observation, the known species will be revised, and many new taxa will be discovered and reported; the concatenated genes, i.e., 28S rRNA, H3, ITS, CO I, 16S rRNA and ND4, will be used to establish the phylogenetic relationships, to solve the taxonomic problems, such as the identification of difficult species and the revision of classification system. So the implementation of this project has important significance for us to understand the species diversity of the genus Pethydrus and helpful to the fast species identification.

东方牙甲属隶属于鞘翅目多食亚目的牙甲科，是一类小型的水生鞘翅目昆虫；目前，全球已经报告63种，主要分布在我国及东南亚地区。东方牙甲一般生活在水质清澈的小溪中，常隐藏于枯枝落叶下，或石头、沙子下面，故很难被人发现；而且，由于外形十分相似，该属昆虫主要依据雄性生殖器鉴定；随着采集强度与采集密度加大，一些近似种的生殖器出现连续变化趋势，物种鉴定十分困难；东方牙甲属的亚属及种团的划分，主要基于简单的形态特征，其分类地位均有待验证。本项目以东方牙甲属为研究对象，进行全面而系统的野外调查；在全面的形态学观察基础上，对已知种类重新修订，发现并报告新物种；通过28S rRNA，H3，ITS，COI，16S rRNA和ND4共六个基因，联合建立系统发育树，解决疑难物种鉴定等分类问题，修订东方牙甲属的分类体系。因此，本项目实施对于全面了解东方牙甲属多样性及其种类的快速鉴定具有重要意义。

东方牙甲属（Pelthydrus）是昆虫纲鞘翅目（Coleoptera）牙甲科（Hydrophilidae）下的一个重要类群，主要分布在我国南方多省及东南亚地区。该属昆虫一般生活在水质清澈，无污染的小溪中，可作为水质监测的指示物种。然而，东方牙甲属的两亚属间形态学差异较大，是否将该亚属提升到属级阶元引发争议；物种间差异极小，只有通过观察雄性外生殖器的形态来进行物种鉴定。本项目以东方牙甲属为研究对象，基于核基因H3和ITS2、线粒体基因CO1和16S片段对东方牙甲属开展分类及系统发育研究。. 本研究主要结论：本研究通过野外调查，在全面的形态学观察基础上，拍照得到国内该属24种昆虫的形态照片以及20个物种的尾器图片。发现了新物种瑞丽东方牙甲及邵氏东方牙甲，2个中国新记录种马德尔东方牙甲和满东方牙甲。.利用核基因H3和ITS2、线粒体基因CO1和16S，以及多基因联合数据矩阵建立系统发育树，经过观察分析，最终得出以下结论：1）系统发育分析结果与形态学分类结果基本吻合；2）东方牙甲属并不是单系，随着新物种鉴定的增多，两个亚属应该各自升级至属级阶元。3）部分种类种团重新归属。. 研究结合对现有分布资料的整理及分析，总结了本属区系组成的特点：（1）岛屿地区报告的物种常为该地区特有物种；（2）物种分布不连续，跨地域分布的情况常见；（3）东洋界明显占分布主导，区系组成成分单调。提出了印度西部—日本中部—印度尼西亚分布型。该属昆虫于我国分布的物种丰富，占总数37.5%；华南区占主导；单区型物种较多。