Two nearly complete mitogenomes of wheat stem borers, Cephus pygmeus (L.) and Cephus sareptanus Dovnar-Zapolskij (Hymenoptera: Cephidae): an unusual elongation of rrnS gene

The complete mitochondrial genome and novel gene arrangement in Nesodiprion zhejiangensis Zhou & Xiao (Hymenoptera: Diprionidae)

The complete mitochondrial genome (mitogenome) of the sawfly, Nesodiprion zhejiangensis Zhou & Xiao, was sequenced, assembled, and deposited in GenBank (Accession Number: OM501121). The 15,660 bp N. zhejiangensis mitogenome encodes for 2 ribosomal RNAs (rrnL and rrnS), 22 transfer RNAs (tRNAs), 13 protein-coding genes (PCGs), and an AT-rich region of 450 bp in length. The nucleotide composition is biased toward adenine and thymine (A + T = 81.8%). Each PCG is initiated by an ATN codon, except for cox2, which starts with a TTG. Of 13 PCGs, 9 have a TAA termination codon, while the remainder terminate with a TAG or a single T. All tRNAs have the classic cloverleaf structure, except for the dihydrouridine (DHU) arm of tRNA^val, which forms a simple loop. There are 49 helices belonging to 6 domains in rrnL and 30 helices belonging to 4 domains in rrnS. In comparison to the ancestral architecture, N. zhejiangensis has the most rearranged mitogenome in Symphyta, in which rearrangement events of local inversion and transposition are identified in three gene clusters. Specifically, the main hotspot of gene rearrangement occurred between rrnS and trnY, and rearranged from rrnS-(AT-rich region)-I-Q-M-nd2-W-C-Y to rrnS-Q-W-C-nd2-I-M-(AT-rich region)-Y, involving a local inversion event of a large gene cluster and transposition events of some tRNAs. Transposition of trnA and trnR (rearranged from A-R to R-A) was observed at the nd3-nd5 gene junction while shuffling of trnP and trnT (rearranged from T-P to P-T) occurred at the nd4l-nd6 gene junction. While illegitimate inter-mtDNA recombination might explain the opposite orientations of transcription between rrnS and trnY, transposition events of tRNA in some gene blocks can be accounted for by the tandem duplication/random loss (TDRL) model. Our phylogenetic analysis suggests that N. zhejiangensis is closely related to congeneric species N. biremis and N. japonicus, which together form a sister lineage with the European pine sawfly, Neodiprion sertifer.

Characterization of the complete mitochondrial genome sequence of Smerinthus caecus (Lepidoptera: Sphingidae)

In this study, we sequenced and analyzed the complete mitogenome of Smerinthus caecus Ménétriés, 1857. The mitogenome of S. caecus is a circular structure, and 15,363 bp long in size and encodes 13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and a control region (CR). An extremely high AT bias of 79.2% was found in the nucleotide composition of mitogenome. Most of the PCGs used ATN as the start codon and TAA or TAG as the stop codon, which is similar to most other insect mitogenomes, except cox1, which starts with CGA. The phylogeny of Smerinthinae was reconstructed using a maximum-likelihood method, a total of 33 mitogenomes were sampled for phylogenetic analyses. The subfamily Langiinae was selected as outgroup. The results confirmed the position of S. caecus in the Smerinthinae, in which Smerinthus caecus was placed as the sister taxon to Smerinthus planus, then to Laothoe amurensis.

Characterization of the Complete Mitochondrial Genome of Eight Diurnal Hawkmoths (Lepidoptera: Sphingidae): New Insights into the Origin and Evolution of Diurnalism in Sphingids

In this study, the mitochondrial genomes of 22 species from three subfamilies in the Sphingidae were sequenced, assembled, and annotated. Eight diurnal hawkmoths were included, of which six were newly sequenced (Hemaris radians, Macroglossum bombylans, M. fritzei, M. pyrrhosticta, Neogurelca himachala, and Sataspes xylocoparis) and two were previously published (Cephonodes hylas and Macroglossum stellatarum). The mitochondrial genomes of these eight diurnal hawkmoths were comparatively analyzed in terms of sequence length, nucleotide composition, relative synonymous codon usage, non-synonymous/synonymous substitution ratio, gene spacing, and repeat sequences. The mitogenomes of the eight species, ranging in length from 15,201 to 15,461 bp, encode the complete set of 37 genes usually found in animal mitogenomes. The base composition of the mitochondrial genomes showed A+T bias. The most commonly used codons were UUA (Leu), AUU (Ile), UUU (Phe), AUA (Met), and AAU (Asn), whereas GCG (Ala) and CCG (Pro) were rarely used. A phylogenetic tree of Sphingidae was constructed based on both maximum likelihood and Bayesian methods. We verified the monophyly of the four current subfamilies of Sphingidae, all of which had high support. In addition, we performed divergence time estimation and ancestral character reconstruction analyses. Diurnal behavior in hawkmoths originated 29.19 million years ago (Mya). It may have been influenced by the combination of herbaceous flourishing, which occurred 26-28 Mya, the uplift of the Tibetan Plateau, and the large-scale evolution of bats in the Oligocene to Pre-Miocene. Moreover, diurnalism in hawkmoths had multiple independent origins in Sphingidae.

The first complete mitochondrial genome of the hawkmoth Marumba saishiuana (Lepidoptera: Sphingidae) and insights into its phylogenetic position

In this study, we sequenced and analyzed the complete mitogenome of Marumba saishiuana Okamoto, 1924. The complete mitogenome sequence of M. saishiuana is circular, 15,662 bp in size and encodes 13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and a control region (CR). Nucleotide composition is highly biased toward A + T nucleotides (81.2%). Most of 13 PCGs initiate with the standard start codon of ATN, except cox1, which starts with CGA. Phylogenetic analyses were performed using nucleotide sequences. A total of 32 Smerinthinae species were selected. The topology based on mitogenome showed that M. saishiuana, M. gaschkewitschii, and M. sperchius formed a clade, and this indicated that M. saishiuana was a member of genus Marumba. Polyptychus trilineatus was the most closely related to genus Marumba on the phylogenetic tree reconstructed by mitogenomes.

Phylogenetic relationship and characterization of the complete mitochondrial genome sequence of Smerinthus planus (Lepidoptera: Sphingidae)

In this study, the complete mitochondrial genome of Smerinthus planus Walker, 1856 was sequenced and analyzed. This mitochondrial genome is circular, 15,375 bp long, and includes 37 typical metazoan mitochondrial genes (13 protein-coding genes (PCGs), two ribosomal RNA genes, and 22 transfer RNA genes) and an A + T-rich region. Nucleotide composition is highly biased toward A + T nucleotides (80.1%). All 13 PCGs initiate with the standard start codon of ATN and terminate with the typical stop codon TAA/TAG. Phylogenetic analyses were performed using amino acids of 13 PCGs which shows that S. planus is closely related to Barbourion lemaii.

Sequencing and analysis of the complete mitochondrial genome of Laothoe amurensis sinica (Lepidoptera: Sphingidae) from China and its phylogenetic analysis

The complete mitochondrial genome (mitogenome) of Laothoe amurensis sinica (Rothschild & Jordan, 1903) was sequenced. The L. amurensis sinica mitogenome is circular, double-stranded, with length of 15,341 bp. Gene content, gene order and orientation are all typical of Sphingidae. Nucleotide composition is highly biased toward A + T nucleotides (79.2%). Most of 13 protein-coding genes (PCGs) initiate with the standard start codon of ATN and terminate with the typical stop codon TAA/TAG or incomplete T. Phylogenetic analyses based on the maximum-likelihood (ML) on the W-IQ-Tree web server showed that L. amurensis sinica have a close relationship to the lineage formed by Clanis bilineata and Leucophlebia lineata.

The complete mitochondrial genome sequence of the hawkmoth, Ambulyx tobii (Lepidoptera: Sphingidae) and phylogenetic analysis

In this study, we sequenced and analyzed the complete mitochondrial genome of Ambulyx tobii to compare mitochondrial genome structures and reconstruct phylogenetic relationships. The complete mitochondrial genome sequence of A. tobii is circular, 15,343 bp in size and encodes 13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and a control region (CR). Nucleotide composition is highly biased toward A + T nucleotides (81.2%). Most PCGs initiate with the standard start codon of ATN and terminate with the typical stop codon TAA/TAG. Phylogenetic analyses were performed using both 13 PCGs and whole mitochondrial genomes showed that A. tobii is closely related to A. substrigilis.

The complete mitochondrial genome sequence of the hawkmoth, Dahira obliquifascia (Lepidoptera: Sphingidae) and phylogenetic analysis

In this study, we sequenced and analyzed the complete mitogenome Dahira obliquifascia to compare mitogenomic structures and reconstruct phylogenetic relationships. The complete mitogenome sequence of D. obliquifascia is circular, 15,939 bp in size and encodes 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNA), 22 transfer RNA genes (tRNA) and a control region (CR). Nucleotide composition is highly biased toward A + T nucleotides (80.3%). All 13 protein-coding genes (PCGs) initiate with the standard start codon of ATN and terminate with the typical stop codon TAA/TAG. Phylogenetic analyses were performed using 13 protein coding genes (PCGs) showed that D. obliquifascia is closely related to Theretra oldenlandiae.

Complete mitochondrial genome of a parasitoid, Trichogramma chilonis (Hymenoptera: Chalcidoidea: Trichogrammatidae) and phylogenetic analysis

Trichogramma chilonis is a kind of ovoid parasitic wasp, which has important application value in the biological control of pests. In this study, we sequenced and analyzed the complete mitogenome T. chilonis to compare mitogenomic structures and reconstruct phylogenetic relationships. The complete mitogenome sequence of T. chilonis is circular, 16,176 bp in size and encodes 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNA), 22 transfer RNA genes (tRNA), and a control region (CR). Nucleotide composition is highly biased toward A + T nucleotides (85.2%). All 13 protein-coding genes (PCGs) initiate with the standard start codon of ATN and terminate with the typical stop codon TAA/TAG. Phylogenetic analyses were performed using amino acids of 13 PCGs showed that T. chilonis is closely related to Trichogramma ostriniae.

Complete mitochondrial genome sequence for the Thrips hawaiiensis (Thysanoptera: Thripidae)

Thrips hawaiiensis (Morgan) (Thysanoptera: Thripidae) is a common Thysanoptera insect widely distributed in Asia and the Pacific, it damages various plants. In this study the complete mitochondrial genome of T. hawaiiensis was sequenced and characterized by using next-generation sequencing technique. The total length of the complete genome is 15,357 bp and A + T content of 77.8% (GeneBank accession No. MW582621). The T. hawaiiensis mitochondrial genome consists of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, 22 transfer RNA genes (tRNAs) and 2 non-coding control regions (Dloop region). According to previous studies, only a few complete mitochondrial genomes from Order Thysanoptera have been reported. Thus, T. hawaiiensis complete mitochondrial genome sequence reported will provide molecular information for mitochondrial genome research on Thysanoptera.

Mitochondrial Phylogenomics of Tenthredinidae (Hymenoptera: Tenthredinoidea) Supports the Monophyly of Megabelesesinae as a Subfamily

Tenthredinidae represents one of the external feeders of the most diverse superfamily, Tenthredinoidea, with diverse host plant utilization. In this study, four complete mitochondrial genomes (mitogenomes), those of Cladiucha punctata, Cladiucha magnoliae, Megabeleses magnoliae, and Megabeleses liriodendrovorax, are newly sequenced and comparatively analyzed with previously reported tenthredinid mitogenomes. The close investigation of mitogenomes and the phylogeny of Tenthredinidae leads us to the following conclusions: The subfamilial relationships and phylogenetic placements within Tenthredinidae are mostly found to be similar to the previously suggested phylogenies. However, the present phylogeny supports the monophyly of Megabelesesinae as a subfamily, with the sister-group placement of Cladiucha and Megabeleses outside of Allantinae. The occurrence of the same type of tRNA rearrangements (MQI and ANS1ERF) in the mitogenomes of Megabelesesinae species and the presence of apomorphic morphological characters also provide robust evidence for this new subfamily. The divergence and diversification times of the subfamilies appear to be directly related to colonization of the flowering plants following the Early Cretaceous. The origin time and diversification patterns of Megabelesesinae were also well matched with the divergence times of their host plants from Magnoliaceae.

Complete mitochondrial genome sequence of Labriocimbex sinicus, a new genus and new species of Cimbicidae (Hymenoptera) from China

Labriocimbex sinicus Yan & Wei gen. et sp. nov. of Cimbicidae is described. The new genus is similar to Praia Andre and Trichiosoma Leach. A key to extant Holarctic genera of Cimbicinae is provided. To identify the phylogenetic placement of Cimbicidae, the mitochondrial genome of L. sinicus was annotated and characterized using high-throughput sequencing data. The complete mitochondrial genome of L. sinicus was obtained with a length of 15,405 bp (GenBank: MH136623; SRA: SRR8270383) and a typical set of 37 genes (22 tRNAs, 13 PCGs, and two rRNAs). The results demonstrated that all PCGs were initiated by ATN codon, and ended with TAA or T stop codons. The study reveals that all tRNA genes have a typical clover-leaf secondary structure, except for trnS1. Remarkably, the secondary structures of the rrnS and rrnL of L. sinicus were much different from those of Corynis lateralis. Phylogenetic analyses verified the monophyly and positions of the three Cimbicidae species within the superfamily Tenthredinoidea and demonstrated a relationship as (Tenthredinidae + Cimbicidae) + (Argidae + Pergidae) with strong nodal supports. Furthermore, we found that the generic relationships of Cimbicidae revealed by the phylogenetic analyses based on COI genes agree quite closely with the systematic arrangement of the genera based on the morphological characters. Phylogenetic tree based on two methods shows that L. sinicus is the sister group of Praia with high support values. We suggest that Labriocimbex belongs to the tribe Trichiosomini of Cimbicinae based on adult morphology and molecular data. Besides, we suggest to promote the subgenus Asitrichiosoma to be a valid genus.

Characterization of the mitochondrial genome of Analcellicampa xanthosoma gen. et sp. nov. (Hymenoptera: Tenthredinidae)

A new genus with a new species of the tribe Hoplocampini of Hoplocampinae was described from China: Analcellicampa xanthosoma Wei & Niu, gen. et sp. nov. Hoplocampa danfengensis G. Xiao 1994 was designated as the type species of the new genus. The characters of Analcellicampa danfengensis (G. Xiao) comb. nov. were briefly discussed. A key to the tribes and known genera of Hoplocampinae was provided. The nearly complete mitochondrial genome of A. xanthosoma was characterized as having a length of 15,512 bp and containing 37 genes (22 tRNAs, 13 protein-coding genes (PCGs), and 2 rRNAs). The gene order of this new specimen was the same as that in the inferred insect ancestral mitochondrial genome. All PCGs were initiated by ATN codons and ended with TAA or T stop codons. All tRNAs had a typical cloverleaf secondary structure, except for trnS1. Remarkably, the helices H991 of rrnS and H47 of rrnL were redundant, while helix H563 of rrnL was highly conserved. A phylogeny based on previously reported symphytan mitochondrial genomes showed that A. xanthosoma is a sister group to Monocellicampa pruni, with high support values. We suggest that A. xanthosoma and M. pruni belong to the tribe Hoplocampini of Hoplocampinae.

The first complete mitochondrial genome of marigold pest thrips, Neohydatothrips samayunkur (Sericothripinae) and comparative analysis

Complete mitogenomes from the order Thysanoptera are limited to representatives of the subfamily Thripinae. Therefore, in the present study, we sequenced the mitochondrial genome of Neohydatothrips samayunkur (15,295 bp), a member of subfamily Sericothripinae. The genome possesses the canonical 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and two ribosomal RNA genes (rRNAs) as well as two putative control regions (CRs). The majority strand was 77.42% A + T content, and 22.58% G + C with weakly positive AT skew (0.04) and negative GC skew (-0.03). The majority of PCGs start with ATN codons as observed in other insect mitochondrial genomes. The GCG codon (Alanine) was not used in N. samayunkur. Most tRNAs have the typical cloverleaf secondary structure, however the DHU stem and loop were absent in trnV and trnS1, while the TΨC loop was absent in trnR and trnT. The two putative control regions (CR1 and CR2) show 99% sequence similarity indicated a possible duplication, and shared 57 bp repeats were identified. N. samayunkur showed extensive gene rearrangements, with 11 PCGs, 22 tRNAs, and two rRNAs translocated when compared to the ancestral insect. The gene trnL2 was separated from the 'trnL2-cox2' gene block, which is a conserved, ancestral gene order found in all previously sequenced thrips mitogenomes. Both maximum likelihood (ML) and Bayesian inference (BI) phylogenetic trees resulted in similar topologies. The phylogenetic position of N. samayunkur indicates that subfamily Sericothripinae is sister to subfamily Thripinae. More molecular data from different taxonomic groups is needed to understand thrips phylogeny and evolution.

Characterization of the mitochondrial genome of Arge bella Wei & Du sp. nov. (Hymenoptera: Argidae)

We describe Arge bella Wei & Du sp. nov., a large and beautiful species of Argidae from south China, and report its mitochondrial genome based on high-throughput sequencing data. We present the gene order, nucleotide composition of protein-coding genes (PCGs), and the secondary structures of RNA genes. The nearly complete mitochondrial genome of A. bella has a length of 15,576 bp and a typical set of 37 genes (22 tRNAs, 13 PCGs, and 2 rRNAs). Three tRNAs are rearranged in the A. bella mitochondrial genome as compared to the ancestral type in insects: trnM and trnQ are shuffled, while trnW is translocated from the trnW-trnC-trnY cluster to a location downstream of trnI. All PCGs are initiated by ATN codons, and terminated with TAA, TA or T as stop codons. All tRNAs have a typical cloverleaf secondary structure, except for trnS1. H821 of rrnS and H976 of rrnL are redundant. A phylogenetic analysis based on mitochondrial genome sequences of A. bella, 21 other symphytan species, two apocritan representatives, and four outgroup taxa supports the placement of Argidae as sister to the Pergidae within the symphytan superfamily Tenthredinoidea.

The first mitogenomes of the superfamily Pamphilioidea (Hymenoptera: Symphyta): Mitogenome architecture and phylogenetic inference

The Pamphilioidea represents a small superfamily of the phytophagous suborder Symphyta (Hymenoptera). Here, nearly complete mitochondrial genomes (mitogenomes) of three pamphilioid species: Chinolyda flagellicornis (Pamphiliidae), Megalodontes spiraeae and M. cephalotes (Megalodontesidae) were newly sequenced using next generation sequencing and comparatively analysed with the previously reported symphytan mitogenomes. A positive AT skew (0.013) and a negative GC skew (-0.194) were found in pamphilioid mitogenome, and a deviation from strand asymmetry was also observed in the PCGs encoded on both strands. Several gene rearrangement events were observed in four tRNA gene clusters (WCY, IQM, ARNS1EF and TP clusters), which have not been reported from symphytan mitogenomes to date. As the most parsimonious explanation, compared with the inferred insect ancestral mitogenome architecture, the occurrence of gene rearrangements in pamphilioid mitogenomes requires totally five evolutionary steps, including four transpositions and one inversion. The predicted secondary structures of tRNAs, rrnS and rrnL genes are mostly consistent with reported hymenopteran species. Phylogenetic analyses recovered the monophyly of superfamily Pamphilioidea and indicated the relationship Tenthredinoidea + (Pamphilioidea + (Cephoidea + (Orussoidea + Apocrita))) with strong nodal supports.

Extensive gene rearrangements in the mitochondrial genomes of two egg parasitoids, Trichogramma japonicum and Trichogramma ostriniae (Hymenoptera: Chalcidoidea: Trichogrammatidae)

Animal mitochondrial genomes usually exhibit conserved gene arrangement across major lineages, while those in the Hymenoptera are known to possess frequent rearrangements, as are those of several other orders of insects. Here, we sequenced two complete mitochondrial genomes of Trichogramma japonicum and Trichogramma ostriniae (Hymenoptera: Chalcidoidea: Trichogrammatidae). In total, 37 mitochondrial genes were identified in both species. The same gene arrangement pattern was found in the two species, with extensive gene rearrangement compared with the ancestral insect mitochondrial genome. Most tRNA genes and all protein-coding genes were encoded on the minority strand. In total, 15 tRNA genes and seven protein-coding genes were rearranged. The rearrangements of cox1 and nad2 as well as most tRNA genes were novel. Phylogenetic analysis based on nucleotide sequences of protein-coding genes and on gene arrangement patterns produced identical topologies that support the relationship of (Agaonidae + Pteromalidae) + Trichogrammatidae in Chalcidoidea. CREx analysis revealed eight rearrangement operations occurred from presumed ancestral gene order of Chalcidoidea to form the derived gene order of Trichogramma. Our study shows that gene rearrangement information in Chalcidoidea can potentially contribute to the phylogeny of Chalcidoidea when more mitochondrial genome sequences are available.

Nearly complete mitogenome of hairy sawfly, Corynis lateralis (Brullé, 1832) (Hymenoptera: Cimbicidae): rearrangements in the IQM and ARNS1EF gene clusters

The Cimbicidae is a small family of the primitive and relatively less diverse suborder Symphyta (Hymenoptera). Here, nearly complete mitochondrial genome (mitogenome) of hairy sawfly, Corynis lateralis (Hymenoptera: Cimbicidae) was sequenced using next generation sequencing and comparatively analysed with the mitogenome of Trichiosoma anthracinum. The sequenced length of C. lateralis mitogenome was 14,899 bp with an A+T content of 80.60%. All protein coding genes (PCGs) are initiated by ATN codons and all are terminated with TAR or T- stop codon. All tRNA genes preferred usual anticodons. Compared with the inferred insect ancestral mitogenome, two tRNA rearrangements were observed in the IQM and ARNS1EF gene clusters, representing a new event not previously reported in Symphyta. An illicit priming of replication and/or intra/inter-mitochondrial recombination and TDRL seem to be responsible mechanisms for the rearrangement events in these gene clusters. Phylogenetic analyses confirmed the position of Corynis within Cimbicidae and recovered a relationship of Tenthredinoidea + (Cephoidea + Orussoidea) in Symphyta.

Phylogeography of the Wheat Stem Sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae): Implications for Pest Management

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is a key pest of wheat in the northern Great Plains of North America, and damage resulting from this species has recently expanded southward. Current pest management practices are inadequate and uncertainty regarding geographic origin, as well as limited data on population structure and dynamics across North America impede progress towards more informed management. We examined the genetic divergence between samples collected in North America and northeastern Asia, the assumed native range of C. cinctus using two mitochondrial regions (COI and 16S). Subsequently, we characterized the structure of genetic diversity in the main wheat producing areas in North America using a combination of mtDNA marker and microsatellites in samples collected both in wheat fields and in grasses in wildlands. The strong genetic divergence observed between North American samples and Asian congeners, in particular the synonimized C. hyalinatus, did not support the hypothesis of a recent American colonization by C. cinctus. Furthermore, the relatively high genetic diversity both with mtDNA and microsatellite markers offered additional evidence in favor of the native American origin of this pest. The genetic diversity of North American populations is structured into three genetic clusters and these are highly correlated with geography. Regarding the recent southern outbreaks in North America, the results tend to exclude the hypothesis of recent movement of damaging wheat stem sawfly populations from the northern area. The shift in host plant use by local populations appears to be the most likely scenario. Finally, the significance of these findings is discussed in the context of pest management.

Next-Generation Sequencing of Two Mitochondrial Genomes from Family Pompilidae (Hymenoptera: Vespoidea) Reveal Novel Patterns of Gene Arrangement

Animal mitochondrial genomes have provided large and diverse datasets for evolutionary studies. Here, the first two representative mitochondrial genomes from the family Pompilidae (Hymenoptera: Vespoidea) were determined using next-generation sequencing. The sequenced region of these two mitochondrial genomes from the species Auplopus sp. and Agenioideus sp. was 16,746 bp long with an A + T content of 83.12% and 16,596 bp long with an A + T content of 78.64%, respectively. In both species, all of the 37 typical mitochondrial genes were determined. The secondary structure of tRNA genes and rRNA genes were predicted and compared with those of other insects. Atypical trnS1 using abnormal anticodons TCT and lacking D-stem pairings was identified. There were 49 helices belonging to six domains in rrnL and 30 helices belonging to three domains in rrns present. Compared with the ancestral organization, four and two tRNA genes were rearranged in mitochondrial genomes of Auplopus and Agenioideus, respectively. In both species, trnM was shuffled upstream of the trnI-trnQ-trnM cluster, and trnA was translocated from the cluster trnA-trnR-trnN-trnS1-trnE-trnF to the region between nad1 and trnL1, which is novel to the Vespoidea. In Auplopus, the tRNA cluster trnW-trnC-trnY was shuffled to trnW-trnY-trnC. Phylogenetic analysis within Vespoidea revealed that Pompilidae and Mutillidae formed a sister lineage, and then sistered Formicidae. The genomes presented in this study have enriched the knowledge base of molecular markers, which is valuable in respect to studies about the gene rearrangement mechanism, genomic evolutionary processes and phylogeny of Hymenoptera.

Comparative and phylogenetic analysis of the mitochondrial genomes in basal hymenopterans

The Symphyta is traditionally accepted as a paraphyletic group located in a basal position of the order Hymenoptera. Herein, we conducted a comparative analysis of the mitochondrial genomes in the Symphyta by describing two newly sequenced ones, from Trichiosoma anthracinum, representing the first mitochondrial genome in family Cimbicidae, and Asiemphytus rufocephalus, from family Tenthredinidae. The sequenced lengths of these two mitochondrial genomes were 15,392 and 14,864 bp, respectively. Within the sequenced region, trnC and trnY were rearranged to the upstream of trnI-nad2 in T. anthracinum, while in A. rufocephalus all sequenced genes were arranged in the putative insect ancestral gene arrangement. Rearrangement of the tRNA genes is common in the Symphyta. The rearranged genes are mainly from trnL1 and two tRNA clusters of trnI-trnQ-trnM and trnW-trnC-trnY. The mitochondrial genomes of Symphyta show a biased usage of A and T rather than G and C. Protein-coding genes in Symphyta species show a lower evolutionary rate than those of Apocrita. The Ka/Ks ratios were all less than 1, indicating purifying selection of Symphyta species. Phylogenetic analyses supported the paraphyly and basal position of Symphyta in Hymenoptera. The well-supported phylogenetic relationship in the study is Tenthredinoidea + (Cephoidea + (Orussoidea + Apocrita)).

The complete mitogenomes of Calameuta filiformis (Eversmann, 1847) and Calameuta idolon (Rossi, 1794) (Hymenoptera: Cephidae): The remarkable features of the elongated A+T rich region in Cephini

Two complete mitogenomes of the stem borers, Calameuta filiformis and Calameuta idolon, and the complete A+T-rich region of Trachelus iudaicus (Hymenoptera: Cephidae), are reported. The mitogenomes of these species are the longest reported from hymenopterans to date. A remarkable increase in length of the A+T-rich region, the longest for Hymenoptera, was found and compared across the tribe Cephini. The presence of the tRNA- and rRNA-like sequences were reported in the A+T-rich region of sawflies and they were suggested to play a role in replication and/or transcription. The long and short tandem repeats were orderly located in both sides of the A+T-rich region producing stable secondary structures. We suggest that the short tandem repeats are likely to function as a replication fork barrier.

The mitochondrial genome of Tenthredo tienmushana (Takeuchi) and a related phylogenetic analysis of the sawflies (Insecta: Hymenoptera)

The mitochondrial genome sequence of Tenthredo tienmushana (Takeuchi, 1940) (Hymenoptera: Tenthredinidae) (GenBank accession KR703581) was reported. The length of the sequenced region of this mitochondrial genome is 14,943 bp, with 13 protein-coding, two rRNA, 19 tRNA (the trnI, trnQ, and trnM were failed to sequence) genes and a partial A + T-rich region. As in most other sequenced mitochondrial genomes of the suborder "Symphyta", there is no gene rearrangement in the sequenced region compared with the pupative ancestral gene arrangement of insects. All protein-coding genes start with ATN codons. Eleven, one, and one protein-coding genes stop with termination codon TAA, TA, and T, respectively. Phylogenetic analysis using the Bayesian method based on all codon positions of the 13 protein-coding genes supports the monophyly of Tenthredinoidea. Two families of the Tenthredinoidea, i.e. Tenthredinidae and Pergidae, form the basal lineage of the Hymenoptera. Within the Tenthredinidae, the subfamily Tenthrediniinae and Allantinae form a sister lineage and then sister to the Nematinae. The Orussidae was recovered to be a sister group to the Apocrita, which contains Ichneumonidae and Vespidae in our analysis. The Cephoidea is sister to the lineage of Orussoidea + Apocrita.