Despite of a substantial effort, the phylogeny of Lepidoptera still has unstable taxa and unresolved relationships particularly form Apoditrysia to Ditrysia (e.g. phylogenetic position and familial relationships of Gelechioidea, the monophylies of Tineoidea and Zygaenoidea and so on). We performed phylogenetic analysis using ~13,000-bp length of mitogenome sequences form 50 species (with seven species in two superfamilies form this study) representing 13 superfamilies to improve the lepidopteran phylogeny from Apoditrysia to Ditrysia. A close relationship of Gelechioidea to Obtectomera than to apoditrysian taxa was noteworthy, although the nodal support is very weak (ML, 23%; BI, BPP = 0.94). Monophyly of Zygaenoidea without Epipyropidae (Epipomponia nawai) was also noteworthy in spite of weak nodal support (ML, 64%; BI, 1.0). Scrutinized analysis is currently underway.

In this study, we tested the effect of a range of insect orders including Trichoptera as outgroups for lepidopteran phylogeny. Phylogenetic analyses performed with four different partitioning schemes using the maximum-likelihood method provided four different topologies (T1-T4) and topological test most supported T1 topology. When the means of first principle component for nucleotide frequency between A/T and G/C of PCGs was considered Trichoptera, Diptera, Coleoptera, and Orthoptera tended to result in T1 topology more frequently in the given ingroup taxa and outgroups tested. This result contradicts to the general view that the sister taxon might be the best outgroup. The T1 topology was largely consistent with a recent large molecular dataset-based lepidopteran phylogeney, presenting the relationships ((((((((((Noctuoidea + Geometroidea) + (Bombycoidea + Lasiocampoidea)) + Drepanoidea) + Mimallonoidea) + Pyraloidea) + Gelechioidea) + Papilionoidea) + Tortricoidea) + (Gracillaroidea + Yponomeutoidea)) + Hepialoidea).

The sister relationship between Trichoptera and Lepidoptera has often been supported in a diverse study, but mitochondrial genomes (mitogenomes) based lepidopteran phylogenetic studies have never utilized Trichoptera as outgroup mainly due to unavailability. Therefore, the effect of alternatives that were previously used (e.g., Diptera, Hymenoptera, and Orthoptera) or Trichoptera as outgroups on the lepidopteran phylogeny remained unknown. In this study, we sequenced three complete mitogenomes of Trichoptera belonging to two suborders and characterized the genomic features of Trichoptera and tested the outgroup effect for lepidopteran phylogeny. The 15,208 ~ 15,285-bp long caddisfly mitogenomes harbor gene content typical of the animal mitogenomes. The orientation and gene order of the three species belonging to the suborder Integripalpia was identical to that of the most common type that has been hypothesized as ancestral for insects, but Cheumatopsyche brevilineata belonging to another suborder Annulipalpia has rearranged QIM, all encoded in forward direction between the A+T-rich region and ND2, instead of the ancestral IQM, with Q inverted. Further, the annulipalpian species had a typical start codon ATG, instead of CGA that are commonly found in other trichopteran species and majority of Lepidoptera. Phylogenetic analysis with different outgroups (Diptera, Hymenoptera, and Orthoptera, Coleoptera, and Trichoptera) and 115 lepidopteran mitogenomes has shown insensitivity either with Trichoptera, Diptera, or Coleoptera, but artificial grouping and lowered nodal support were found with Hymenoptera. The Trichoptera-based consensus topology were: (((((((Bombycoidea + Noctuoidea) + Pyraloidea) + Papilionoidea) + Cossoidea) + Tortricoidea) + Yponomeutoidea) + Hepialoidea).