Complete Mitochondrial Genome of the Free-Living Earwig, Challia fletcheri (Dermaptera: Pygidicranidae) and Phylogeny of Polyneoptera

Abstract

The insect order Dermaptera, belonging to Polyneoptera, includes ∼2,000 extant species, but no dermapteran mitochondrial genome has been sequenced. We sequenced the complete mitochondrial genome of the free-living earwig, Challia fletcheri, compared its genomic features to other available mitochondrial sequences from polyneopterous insects. In addition, the Dermaptera, together with the other known polyneopteran mitochondrial genome sequences (protein coding, ribosomal RNA, and transfer RNA genes), were employed to understand the phylogeny of Polyneoptera, one of the least resolved insect phylogenies, with emphasis on the placement of Dermaptera. The complete mitochondrial genome of C. fletcheri presents the following several unusual features: the longest size in insects is 20,456 bp; it harbors the largest tandem repeat units (TRU) among insects; it displays T- and G-skewness on the major strand and A- and C-skewness on the minor strand, which is a reversal of the general pattern found in most insect mitochondrial genomes, and it possesses a unique gene arrangement characterized by a series of gene translocations and/or inversions. The reversal pattern of skewness is explained in terms of inversion of replication origin. All phylogenetic analyses consistently placed Dermaptera as the sister to Plecoptera, leaving them as the most basal lineage of Polyneoptera or sister to Ephemeroptera, and placed Odonata consistently as the most basal lineage of the Pterygota.

Molecular phylogeny of Polyneoptera (Insecta) inferred from expanded mitogenomic data

“…Some authors agreed on the relative primitive position of the Plecoptera2222367, while the sister relationship between Plecoptera and Dermaptera has been suggested by recent molecular studies1526. In the PhyloBayes tree from the data set of PCGDegenRNA (Fig.…”

“…C. fletcheri ) is available in GenBank. This mitogenome displayed unusual features of strand-bias, and a unique gene arrangement26. With the inclusion of three newly sequenced Dermaptera mitogenome sequences, the long branch of C. fletcheri is shortened, and the whole Dermaptera consistently appears as the earliest divergent lineage of Polyneoptera.…”

“…Additional hypotheses of embiopteran affinities to other insect lineages had also been suggested2. Besides the uncertain placement of Embioptera, a universal consensus on the positions of Zoraptera, Plecoptera, Dermaptera, and Mantophasmatodea remains elusive152223242526. For example, no less than ten hypotheses on the phylogenetic placement of Zoraptera have been proposed2127.…”

Progress, pitfalls and parallel universes: a history of insect phylogenetics

“…Many ancient nodes that are accepted and corroborated by other data are recovered from mitochondrial data [274,277 -281], and many relationships among polyneopterans are shared between nuclear and mitochondrial analyses [190]. For example, using mtDNA genomes, Wan et al [281] found many of the nodes that Misof et al [50] recovered from transcriptomes (box 4) and some of these nodes (figure 5: P,Q,R) have only rarely been seen before. Mitochondrial data consistently recover Mantophasmatodea with Phasmatodea [273,281].…”

The mitochondrial genome of the winter stonefly Apteroperla tikumana (Plecoptera, Capniidae)

“…This mitogenome was used to generate a phylogram with the following complete mitogenomes of closely related insects: M. arizonensis (KP642637.1), P. princeps (NC 006133.1), Acroneuria hainana (NC 026104.1), Dinocras cephalotes (NC 022843.1), Kamimuria wangi (NC 024033.1), Tamolanica tamolana (NC 007702.1), Ruspolia dubia (NC 009876.1), Sclerophasma paresisense (NC 007701.1), Entoria okinawaensis (NC 014694.1), Blattella bisignata (NC 018549.1), Reticulitermes santonensis (NC 009499.1), and Challia fletcheri (NC 018538.1) (Cameron & Whiting, 2007;Cameron et al, 2006;Chen, 2013;Elbrecht & Leese, 2015;Elbrecht et al, 2013;Huang et al, 2015;Kômoto et al, 2011;Qian et al, 2014;Wan et al, 2012;Zhou et al, 2007). Multiple sequence alignments were performed using ClustalW (Larkin et al, 2007).…”