Description of mitochondrial genomes and phylogenetic analysis of Megophthalminae (Hemiptera: Cicadellidae).

To elucidate phylogenetic relationships within the leafhopper's subfamily Megophthalminae (Hemiptera: Cicadellidae), mitogenomes of 12 species of the subfamily were sequenced and assembled. These were added to the mitogenomes of the eight other species that are currently available. Mitogenome size ranged from 15,193 bp in Onukigallia onukii (Matsumura, 1912) to 15,986 bp in Multinervis guangxiensis (Li and Li, 2013), they all contained 37 genes, and gene order was similar to that in other leafhoppers. Nucleotide composition analysis showed that the AT content was higher than that of GC, and the protein-coding genes usually ended with A/T at the 3rd codon position. The Ka/Ks ratio showed that the CYTB gene has the slowest evolutionary rate, while ND4 is the gene with the fastest evolutionary rate. Relative synonymous codon usage analysis revealed the most frequently used codon was UUA (L), followed by CGA (R), and the least frequently used codon was CCG (P). Parity plot and neutrality plot analyses showed that the codon usage bias of mitochondrial genes was influenced by natural selection and mutation pressure. However, natural selection plays a major role, while the effect of mutation pressure was small. Effective number of codons values were 40.15-49.17, which represented relatively low codon bias. Phylogenetic analyses based on three datasets (AA, 13PCG, 13PCG_2rRNA) using two methods (maximum likelihood and Bayesian inference). In the obtained topology, the Megophthalminae species were clustered into a monophyletic group. In conclusion, our results clarify structural modules of the mitochondrial genes and confirm the monophyly of Megophthalminae within Cicadellidae.