| 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. |
