江西新岗山森林昆虫种内遗传距离研究

DNA条形码目前广泛用于昆虫多样性研究。本研究采用DNA条形码（即线粒体细胞色素c氧化酶亚基I基因COI 5′端），通过比较所获分子分类操作单元（Molecular operational taxonomic units，MOTU）的种内遗传距离，探究DNA条形码在亚热带森林（位于我国江西省新岗山）不同昆虫类群中的物种鉴定和界定效用。数据分析中结合数据库比对信息，采用jMOTU、ABGD、bPTP、GMYC 这4种物种界定方法获得MOTU，从而开展种内遗传距离分析。本研究共挑选出479个昆虫样本，获得475条COI序列，经NCBI、BOLD在线数据库比对属于6个目，与形态初步划分一致；物种界定分析获得288个MOTU，其中鳞翅目最多，达85个，膜翅目、双翅目、半翅目、鞘翅目次之，分别为80、74、21和20个，直翅目最少，仅8个。膜翅目和双翅目的种内遗传距离均值及标准偏差较大（膜翅目：0.89%±0.87%；双翅目：0.73%±0.58%），鳞翅目的最小（0.28%±0.20%）。研究表明：不同昆虫类群的种内遗传距离虽然整体在一定范围，但仍然存在一定的差异，因此不能笼统地依靠遗传距离的距离阈值进行物种划分；现有数据库需要补充足够的昆虫物种信息，才能提升物种鉴定效率。本研究丰富了亚热带森林昆虫分子数据库，同时也为进一步探索基于分子分类学开展昆虫多样性研究提供了基础数据和参考。

Insect intraspecific genetic distance in a forest of Xingangshan, Jianxi Province

DNA barcoding has been widely used to study insect diversity. This study explored the utility of DNA barcoding in species identification and delimitation for multiple insect groups sampled from a subtropical forest (located at Xingangshan, Jiangxi Province). We compared their intraspecific genetic distance of the identified molecular operational taxonomic units (MOTUs), based on the universal DNA barcodes (i.e., the 5'' end of the mitochondrial Cytochrome c oxidase subunit I gene, COI). Combined with alignment information against public databases, four methods, jMOTU, ABGD, bPTP and GMYC were used for molecular species delimitation to infer the MOTUs, and the intraspecific genetic distances were then calculated. In this study, we totally selected 479 insect samples and obtained 475 COI sequences. We found that their preliminary identifications with NCBI and BOLD online databases were consistent with our preliminary morphological classifications, belonging to six orders. After species delimitation analyses, we finally gained a total of 288 MOTUs; Lepidoptera was the most abundant group (85/288), while there were 80, 74, 21, 20 and 8 MOTUs for Hymenoptera, Diptera, Hemiptera, Coleoptera and Orthoptera, respectively. The mean and standard deviation of intraspecific genetic distances were relatively high in Hymenoptera (0.89%, 0.87%) and Diptera (0.73%, 0.58%), while being the lowest in Lepidoptera (0.28%, 0.20%). Our results showed that although the intraspecific genetic distance of different insect groups was within a certain range, there were still some variations; therefore, species delimitation should not be generalized based on a single distance threshold of genetic distance. Our results additionally indicate that the existing database needs to be supplemented with sufficient insect species information to promote the efficiency of species identification. On the whole, our study enriches the molecular database of insects from a subtropical forest, and also provides basic data and references for further research on insect diversity based on DNA barcoding.