Abstract:
【Aim】 Endoclita davidi is the primary host of the entomogenous fungus Ophiocordyceps xuefengensis. In order to identify the host species in different developmental stages and its caterpillar infected by the Cordyceps fungi, the gene sequence of mtDNA cytochrome oxidase subunit I (COI) of E. davidi was analyzed for DNA barcoding. 【Methods】 The partial fragments (about 658 bp) of the mtDNA COI gene were amplified from 21 samples of tissues of adults (thoracic legs, pectorals, wing base), egg, larva (thoracic legs), pupa (body wall), caterpillar fungus (thoracic legs, body wall) of E. davidi by PCR, and the obtained COI gene fragments were sequenced and aligned. The intra-and inter-species genetic distances were calculated with MEGA version 6.0 software using the Kimura 2-parameter model. The phylogenetic trees were constructed among the closely-related species with neighbor-joining (NJ) and maximum parsimony (MP) methods. 【Results】 The identification results based on the phylogenetic tree were consistent with those based on the morphological analysis of the 20 samples, which were all verified to be originated from the same host species. The bootstrap values of the original divergence among different haplotypes within the same species were over 99%. The average inter-species genetic distance between  E. davidi and other six hepialid species was 19.39 times as high as the average intra-species genetic distance of the 20 samples of E. davidi (10.47% vs 0.54%). There was no overlap between intra-and inter-species genetic distances. 【Conclusion】 The results indicate that DNA barcoding based on the partial sequence of mtDNA COI gene provides rapid and accurate identification of E. davidi. The technology has important significance for molecular phylogenetic studies of Hepialidae.

Key words: Endoclita davidi; DNA barcoding, mtDNA COI gene, species identification, molecular phylogeny