The complete mitochondrial genome of the woodwasp Euxiphydria potanini (Hymenoptera, Xiphydrioidea) and phylogenetic implications for symphytans

The long-necked woodwasp superfamily Xiphydrioidea belongs to the suborder Symphyta (Hymenoptera). Here we newly characterize the complete mitochondrial genome of the South Korean Euxiphydria potanini (Xiphydriidae) using next-generation sequencing: 16,500 bp long with 84.27% A + T content and 37 typical mitochondrial genes including those encoding 13 PCGs, 2 rRNAs, 22 tRNAs, and one A + T rich region. We compare the patterns of symphytan mitochondrial gene arrangement with those of an ancestral insect form and found some synapomorphic rearrangements in phylogenetic context. We use a variety of nucleotide and amino acid sequence alignments (thirteen mtPCGs and/or eight nDNAs) alongside step-by-step exclusions of long-branched taxa to elucidate the phylogenetic position of Xiphydrioidea and phylogenetic relationships among the seven symphytan superfamilies, except for Anaxyeloidea of which no mtgenome was available. The monophyly of symphytan superfamilies (with weak support for Pamphilioidea), sister-group relationship of Xiphydrioidea and Cephoidea, and Symphyta being paraphyletic to Apocrita, etc. are consistently supported by maximum likelihood and Bayesian inference trees. We also discuss the problematic phylogenetic positions of Orussoidea and Siricoidea and propose a hypothetical scenario of morphological character transition during hymenopteran evolution based on morphological key characteristics, such as the cenchrus and the wasp-waist.