First mitogenome of subfamily Langiinae (Lepidoptera: Sphingidae) with its phylogenetic implications

To date, a relatively complete classification of Sphingidae (Lepidoptera) has been generated, but the phylogeny of the family remains need to be fully resolved. Some phylogenetic relationships within Sphingidae still remains uncertain, especially the taxonomic status of the subfamily Langiinae and its sole included genus and species, Langia zenzeroides. To begin to address this problem, we generated nine new complete mitochondrial genomes, including that of Langia, and together with that of Theretra oldenlandiae from our previous study and 25 other Sphingidae mitogenomes downloaded from GenBank, analyzed the phylogenetic relationships of Sphingidae and investigated the mitogenomic differences among members of the Langiinae, Sphinginae, Smerinthinae and Macroglossinae. The mitogenomes of Sphingidae varied from 14995 bp to 15669 bp in length. The gene order of all newly sequenced mitogenomes was identical, containing 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes and the A + T-rich region. Nucleotide composition was A + T biased, and all the protein-coding genes exhibited a positive AT-skew, which was reflected in the nucleotide composition, codon, and amino acid usage. The A + T-rich region was comprised of nonrepetitive sequences, which contained regulatory elements related to the control of replication and transcription. We analyzed concatenated gene sequences, with third codon positions of protein coding genes and rRNAs excluded, using Maximum Likelihood and Bayesian Inference techniques. All four currently recognized subfamilies were recovered as monophyletic but in contrast to the most recent studies, our preferred tree placed Langiinae as the first subfamily to diverge within Sphingidae rather as sister to Smerinthinae + Sphinginae. Our results also support the removal of the genus Barbourion from the smerinthine tribe Ambulycini to an unresolved position in "Smerinthinae incertae sedis".