Abstract:

Objective: Nematus is the first established genus in the Nematinae (Tenthredinidae), and its morphological classification is very complicated and difficult. This study aims to determine the taxonomic status of the questionable species within the genus. Method: Two species of Nematus were collected from Salix paraplesia var. subintegra in the courtyard of Forestry and Grassland Bureau of the Xizang Autonomous Region and Salix matsudana in Zhalantun, Hulunbeier, Inner Mongolia, respectively. Traditional morphological classification methods were used to identify the species. The mitochondrial genome of the two species were re-sequenced using Illumina Hiseq 4,000 platform by following the standard protocols. The assembled and annotated mitochondrial genomes were analyzed based on alignment and secondary structure. Result: The two species were identified as N. trochanteratus (Malaise, 1931) and N. hequensis Xiao, 1990. The mitochondrial genomes of N. trochanteratus and N. hequensis were 16337 bp and 16126 bp long, respectively. The comparison between the two showed that the consistency was as high as 98.02%, with 17 gene sequences completely identical, and the other 20 gene sequences showing only minor differences. There were differences in 8 base sites of six tRNAs between the two species, four sites in 12S rRNA, and seven sites in 16S rRNA. Among the 13 protein coding genes, COI, ND2 and ND4L had the largest genetic distance (K2P) of 0.011, and ATP8 had the Minimum genetic distance of 0. Conclusion: Based on the morphological and mitochondrial genome difference analyses of the two species, it has been confirmed that they are synonymous. According to the International Code of Animal Nomenclature, N. hequensis is identified as the secondary synonym of N. trochanteratus.

Key words: Nematus, morphology, mitochondrial genome, taxonomy, synonym