The mitochondrial genome of Ruspolia dubia (Orthoptera: Conocephalidae) contains a short A+T-rich region of 70 bp in length

Relaxed purifying selection pressure drives accelerated and dynamic gene rearrangements in thrips (Insecta: Thysanoptera) mitochondrial genomes

Insect mitochondrial genomes (mitogenome) generally present a typical gene order, which is considered as the ancestral arrangement. All sequenced mitogenomes in the Thysanoptera display high levels of gene rearrangement. Due to limited number of thrips mitogenomes sequenced, how gene rearrangement may be shaped by evolution remain unclear. Here, we analyzed 33 thrips mitogenomes, including 14 newly sequenced. These mitogenomes were diverse in organization, nucleotides substitution and gene arrangements. We found 28 highly rearranged gene orders with the breakpoints of gene rearrangements from 25 to 33. Reconstruction of the ancestors mitochondrial gene arrangements states indicated that Tubulifera have more complex pathways than Terebrantia in the gene order evolution. Molecular calibration estimated that divergence of two suborders occurred in the middle Triassic while the radiation of thrips was associated with the arose and flourish of angiosperm. Our evolutionary hypothesis testing suggests that relaxation of selection pressure enabled the early phase of Thysanoptera evolution, followed by a stronger selective pressure fixed diversification. Our analyses found gene inversion increases the nonsynonymous substitution rates and provide an evolutionary hypothesis driving the diverse gene orders.

Mitogenomic Comparison of the Mole Crickets Gryllotalpidae with the Phylogenetic Implications (Orthoptera: Ensifera)

Owing to limited molecular data, the phylogenetic position of the family Gryllotalpidae is still controversial in the infraorder Gryllidea. Mitochondrial genome (mitogenome) plays a crucial role in reconstructing phylogenetic relationships and revealing the molecular evolution of insects. However, only four mitogenomes have been reported in Gryllotalpidae to date. Herein, we obtained the first mitogenomes of Gryllotalpa henana Cai & Niu, 1998 and the Chinese G. orientalis Burmeister, 1838, made a detailed comparison of all mitogenomes available in Gryllotalpidae and reconstructed the phylogeny of Gryllidea based on mitogenomes using Bayesian inference (BI) and maximum likelihood (ML) methods. The results show that the complete mitogenome sequences of G. henana (15,504 bp) and G. orientalis (15,497 bp) are conserved, both exhibiting the double-stranded circular structure, typical gene content and the ancestral insect gene arrangement. The complete mitogenome of G.henana exhibits the lowest average AT content ever detected in Gryllotalpidae, and even Gryllidea. The gene nad2 of both species has atypical initiation codon GTG. All tRNAs exhibit typical clover-leaf structure, except for trnS1 lacking the dihydrouridine (DHU) arm. A potential stem-loop structure, containing a (T)_n(TC)₂(T)_n sequence, is detected in the control region of all gryllotalpids investigated and is likely related to the replication initiation of the minority strand. The phylogenetic analyses recover the six families of Gryllidea as Gryllotalpidae + (Myrmecophilidae + (Mogoplistidae + (Trigonidiidae + (Phalangopsidae + Gryllidae)))), similar to the trees based on transcriptomic and mitogenomic data. However, the trees are slightly different from the multilocus phylogenies, which show the sister-group relationship of Gryllotalpidae and Myrmecophilidae. The contradictions between mitogenomic and multilocus trees are briefly discussed.

Positive Correlation of the Gene Rearrangements and Evolutionary Rates in the Mitochondrial Genomes of Thrips (Insecta: Thysanoptera)

Simple Summary

Aeolothrips, commonly known as banded thrips, is the largest genus of the family Aeolothripidae (predatory thrips). In the current study, we sequenced the mitochondrial genome (mitogenome) of the banded thrip species Aeolothrips xinjiangensis. We found a novel gene arrangement in this mitogenome that has not been reported in Thysanoptera. By comparing the gene order and rearrangement patterns, we found seven identical gene blocks and three identical rearrangement events in two mitogenomes of banded thrips. There was marked variation in the mitochondrial gene order across thrip species, with only two conserved gene blocks shared by all 14 thrips. In addition, we found a positive correlation between the degree of gene rearrangement and evolutionary rate. Our results suggested that the mitogenomes of thrips have tended to be stable since their massive rearrangement.

Abstract

Extensive gene rearrangement is characteristic in the mitogenomes of thrips (Thysanoptera), but the historical process giving rise to the contemporary gene rearrangement pattern remains unclear. To better understand the evolutionary processes of gene rearrangement in the mitogenomes of thrips, we sequenced the mitogenome of the banded thrip species Aeolothrips xinjiangensis. First, we found a novel mitochondrial gene order in this species. This mitogenome is 16,947 bp in length and encodes the typical 37 coding genes (13 protein-coding genes, 22 tRNA genes, and two rRNA genes) of insects. The gene arrangement was dramatically different from the putative ancestral mitogenome, with 26 genes being translocated, eight of which were inverted. Moreover, we found a novel, conserved gene block, trnC-trnY, which has not been previously reported in the mitogenomes of thrips. With this newly assembled mitogenome, we compared mitogenome sequences across Thysanoptera to assess the evolutionary processes giving rise to the current gene rearrangement pattern in thrips. Seven identical gene blocks were shared by two sequenced banded thrip mitogenomes, while the reversal of ND2 combined with TDRL events resulted in the different gene orders of these two species. In phylogenetic analysis, the monophyly of the suborders and families of Thysanoptera was well supported. Across the gene orders of 14 thrips, only two conserved gene blocks, ATP8-ATP6 and ND4-ND4L, could be found. Correlation analysis showed that the degree of gene rearrangement was positively correlated with the non-synonymous substitution rate in thrips. Our study suggests that the mitogenomes of thrips remain stable over long evolutionary timescales after massive rearrangement during early diversification.

Comparative mitochondrial genomes of the Rhus gall aphid Kaburagia rhusicola subspecies with variable gall shapes

Rhus gall aphids (Hemiptera: Aphididae: Eriosomatinae) stimulate the formation of galls on their primary host plants (sumacs: Rhus spp., Anacardiaceae). The shapes of galls are often used as an extended phenotype to identify the aphid species and subspecies. We collected four Rhus galls with conspicuously different shapes formed by Kaburagia rhusicola aphids, whose sequences of the complete mitochondrial genomes (mitogenomes) were obtained by high-throughput sequencing. Each mitogenome was assembled into a circular molecule containing 13 protein-coding genes, two rRNAs, 22 tRNAs and one control region. All the protein-coding genes had a typical ATN initiation codon and TAA termination codon except for cox1 and nad4, which had a single T as stop codon. All the tRNAs could be folded as a typical clover-leaf secondary structure, except for trnS1 lacking a dihydrouridine (DHU) arm. The relative synonymous codon usage and ratio of nonsynonymous to synonymous substitution rates showed that the four K. rhusicola samples were highly similar to the subspecies K. r. ovogallis. The phylogenetic analyses grouped these samples with K. r. ovogallis in a clade sister to K. r. rhusicola. All these molecular analyses demonstrated that our current samples represented one subspecies of Kaburagia rhusicola, i.e., K. r. ovogallis, and the gall shape was variable even at the subspecies level in Kaburagia gall aphids.

Comparative mitochondrial genomes of four species of Sinopodisma and phylogenetic implications (Orthoptera, Melanoplinae)

In this study, the whole mitochondrial genomes (mitogenomes) from four species were sequenced. The complete mitochondrial genomes of Sinopodisma pieli, S. houshana, S. qinlingensis, and S. wulingshanensis are 15,857 bp, 15,818 bp, 15,843 bp, and 15,872 bp in size, respectively. The 13 protein-coding genes (PCGs) begin with typical ATN codons, except for COXI in S. qinlingensis, which begins with ACC. The highest A+T content in all the sequenced orthopteran mitogenomes is 76.8% (S. qinlingensis), followed by 76.5% (S. wulingshanensis), 76.4% (S. pieli) and 76.4% (S. houshana) (measured on the major strand). The long polythymine stretches (T-stretch) in the A+T-rich region of the four species are not adjacent to the trnI locus but are inside the stem-loop sequences on the major strand. Moreover, several repeated elements are found in the A+T-rich region of the four species. Phylogenetic analysis based on 53 mitochondrial genomes using Bayesian Inference (BI) and Maximum Likelihood (ML) revealed that Melanoplinae (Podismini) was a monophyletic group; however, the monophyly of Sinopodisma was not supported. These data will provide important information for a better understanding of the phylogenetic relationship of Melanoplinae.

The complete mitochondrial genome of Euconocephalus Nasutus and its phylogenetic analysis

In this study, the first complete mitochondrial genome of genus Euconocephalus (Euconocephalus nasutus) was determined. The mitochondrial genome is 14,999 bp in length, including 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes, and an A + T-rich region. Phylogenetic analysis highly supported that E. nasutus showed a close relationship with Ruspolia dubia. The complete mitochondrial genome sequence of E. nasutus will provide fundamental data for the phylogenetic and biogeographic studies of the Tettigoniidae.

Comparative analysis of the Liriomyza chinensis mitochondrial genome with other Agromyzids reveals conserved genome features

Liriomyza chinensis is a serious pest of onions in many countries, especially in East Asia. We sequenced the complete mitochondrial genome of this species and compared it with five other Agromyzidae species. The L. chinensis mitogenome is a double-stranded 16,175 bp circular molecule with an A + T content of 78.3%. It contains 37 genes and a control region as do the sequenced Liriomyza species. The mitogenomes of L. chinensis and other Agromyzidae species showed a clear bias in nucleotide composition with a positive AT-skew. Most PCGs used standard ATN as start codons, and TAN as termination codons. The tRNAs exhibited the typical clover-leaf structure, except for tRNASer^(AGN) and the two rRNA genes are conserved with those of other Agromyzids. The L. chinensis mitogenome control region included several conserved regions, including a poly-T, two (TA)n and one poly-A stretch, which are considered important replication and transcription. The 13 PCGs were used to study the phylogeny of L. chinensis and five related Agromyzids. Analysis by maximum likelihood, Bayesian inference and genetic distance suggest congruent phylogenetic relationships in Liriomyza spp. and provide a useful supplement to taxonomic classification by morphology.

Complete mitochondrial genome of bamboo grasshopper, Ceracris fasciata, and the phylogenetic analyses and divergence time estimation of Caelifera (Orthoptera)

The bamboo grasshopper Ceracris fasciata is regarded as a major pest species because of the damage it causes to bamboo, and its classification within the families and subfamilies of the suborder Caelifera remains unclear. Thus, we attempted to resolve these questions using molecular biology methods and analyses. Our results are as follows: (1) the complete mitochondrial genome of C. fasciata is 15,569 bp in length. The mitochondrial genome contains a standard set of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and an A + T-rich region in the same order as those of the other analysed Caeliferan species. The putative start codon for the COX1 gene in C. fasciata is ACC, although it is not defined in other genes. The presence of tandem repeats of different sizes in the A + T-rich region may lead to size differences in other mitochondrial genomes. The mitochondrial genome of C. fasciata harbours the typical 37 genes and an A + T-rich region, and it shows similar characteristics to those of other grasshopper species. Characterization of the mitochondrial genome has enriched our knowledge of the mitochondrial genomes of Orthoptera around the world. Therefore, the phylogenetic relationships in Orthoptera can be re-examined. (2) In phylogenetic analyses, the monophyly of Orthoptera and its two suborders (Caelifera and Ensifera) has been consistently recovered based on most of the datasets selected, regardless of the optimal criteria. Our results do not support the monophyly of the subfamily Oedipodinae of Caelifera. We found that Phlaeoba albonema of the Acridinae is sorted into a clade with Ceracris in all our phylogenetic trees, and field experiments show that Phlaeoba always lives with Ceracris in the same ecotopes. Therefore, we suggest that Phlaeoba should be classified as a member of the Oedipodinae. We found that C. fasciata always clustered with Ceracris kiangsu, and both were sisters to Ceracris versicolor. Therefore, the genetic relationship between C. fasciata and C. kiangsu is closer than that between C. fasciata and C. versicolor. (3) The oldest estimated time of divergence of Ensifera in this context was determined to be 146.16 million years ago (Mya), or around the late Jurassic or early Cretaceous. We estimated that katydids (Grylloidea) likely diverged from other groups in the early Cretaceous. According to our divergence time analyses, we concluded that the ancestral Acrididae probably originated in the early Paleogene, and it is likely that the major diversification events happened at the middle Paleogene, well into the next geologic time. We estimated that crickets (Tettigoniidae) likely diverged from other groups in the early Cretaceous. Acrididae and Romaleinae group, Pyrgacrididae and Ommexechidae group, the youngest two clades we observed, were estimated to have diverged 58.79 Mya, between the middle and early Paleogene. C. versicolor is a sister to the group containing C. kiangsu and C. fasciata. First, C. versicolor diverged from the sister group (C. kiangsu + C. fasciata) around 44.81 Mya, and then the C. kiangsu and C. fasciata group separated at 43.04 Mya.

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.

Characterization of the mitochondrial genome of Phyllomimus sp. (Orthoptera: Pseudophyllidae)

The nearly complete mitochondrial genome (mitogenome) without tRNA-Met and with a partial A + T-rich region of phyllomimus sp. has been sequenced with the length of 15,543 bp. We found 140 bp-long intergenic spacers (IGSs) which located between tRNA-Gln and ND2, while this region should be tRNA-Met in most orthopteran mitogenomes. The content of As, Ts, Cs Gs and AT in the mitogenome is 37.3%, 32.5%, 20.6%, 9.5% and 69.8%, respectively. All protein-coding genes start with typical ATN codon except for ND1, which initiates with TTG codon instead, and end with either complete TAA/TAG codons or incomplete T(aa) codons. Phylogenetic analysis indicated that genetic distances of phyllomimus sp. and Orophyllus montanus was closer than other species.

Mitochondrial genomic variation and phylogenetic relationships of three groups in the genus Scaphoideus (Hemiptera: Cicadellidae: Deltocephalinae)

The widespread leafhopper genus Scaphoideus Uhler is the most diverse genus in Scaphoideini and includes some species that are serious pests and vectors of plant pathogens. Here the first Scaphoideus mitogenome sequences are provided for three species, S. maai, S. nigrivalveus and S. varius, representing three main species groups in the Oriental region based on color pattern. The lengths of these three mitogenomes were 15,188, 15,235 and 15,207 bp, respectively. Gene order of three mitogenomes is highly conserved and identical to that of the putative ancestral insect. All three mitogenomes exhibited similar AT nucleotide bias, AT-, GC-skews and codon usage. One large 101 bp intergenic spacer between trnY and cox1 was in S. varius. All 22 tRNA genes had typical cloverleaf secondary structures, except for trnS1 (AGN) which appears to lack the dihydrouridine arm. Genes atp8, nad6 and nad2 were highly variable while cox1 showed the lowest nucleotide diversity. Phylogenetic analyses of three concatenated nucleotide datasets using maximum likelihood and Bayesian methods, comprising all 13 mitogenomes currently available for Membracoidea plus mitogenomes for eight outgroup species representing other cicadomorphan superfamilies, yielded the same topology in which Scaphoideus species formed a monophyletic group within a larger clade comprising three other included Deltocephalinae.

The comparative mitogenomics and phylogenetics of the two grouse-grasshoppers (Insecta, Orthoptera, Tetrigoidea)

OBJECTIVE

This study aimed to reveal the mitochondrial genomes (mtgenomes) of Tetrix japonica and Alulatettix yunnanensis, and the phylogenetics of Orthoptera species.

METHODS

The mtgenomes of A. yunnanensis and T. japonica were firstly sequenced and assembled through partial sequences amplification, and then the genome organization and gene arrangement were analyzed. Based on nucleotide/amino acid sequences of 13 protein-coding genes and whole mtgenomes, phylogenetic trees were established on 37 Orthoptera species and 5 outgroups, respectively.

RESULTS

Except for a regulation region (A+T rich region), a total of 37 genes were found in mtgenomes of T. japonica and A. yunnanensis, including 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes, which exhibited similar characters with other Orthoptera species. Phylogenetic tree based on 13 concatenated protein-coding nucleotide sequences were considered to be more suitable for phylogenetic reconstruction of Orthoptera species than amino acid sequences and mtgenomes. The phylogenetic relationships of Caelifera species were Acridoidea and Pamphagoidea > Pyrgomorphoidea > Pneumoroidea > Eumastacoidea > Tetrigoidea > Tridactyloidea. Besides, a sister-group relationship between Tettigonioidea and Rhaphidophoroidea was revealed in Ensifera.

CONCLUSION

Concatenated protein-coding nucleotide sequences of 13 genes were suitable for reconstruction of phylogenetic relationship in orthopteroid species. Tridactyloidea was a sister group of Tetrigoidea in Caelifera, and Rhaphidophoroidea was a sister group of Tettigonioidea in Ensifera.

Novel insights into mitochondrial gene rearrangement in thrips (Insecta: Thysanoptera) from the grass thrips, Anaphothrips obscurus

We sequenced the mitochondrial (mt) genome of the grass thrips, Anaphothrips obscurus, which is highly rearranged and differs from the four thrips species reported previously in the arrangement of both tRNA genes and a protein-coding gene, nad3, and in the copy number of the control region (CR). We reconstructed the phylogeny of the thrips with mt genome sequences, and used it as a framework to gain insights into mt genome evolution in thrips. It is evident that A. obscurus is less rearranged in mt genome organization than the other four known thrips. nad3 is in its ancestral location in A. obscurus but was translocated in other four thrips. Also, A. obscurus has one CR, which is ancestral to hexapods whereas other thrips have two or three CRs. All of the five thrips whose mt genomes have been sequenced to date are from the subfamily Thripinae, which represents about a quarter of the species richness in the order Thysanoptera. The high variation in mt genome organization observed in a subfamily challenges our knowledge about animal mt genomes. It remains to be investigated why mt genomes evolved so fast in the subfamily Thripinae and how mt genomes evolved in other lineages of thrips.

Towards a higher-level Ensifera phylogeny inferred from mitogenome sequences

Although mitogenomes are useful tools for inferring evolutionary history, only a few representative ones can be used for most Ensifera lineages. Thirty-two ensiferan mitogenomes were determined using ABI Sanger sequencing and standard primer walking of 2-3 overlapping Long-PCR fragments, or Illumina® HiSeq2000 for "shotgun" sequenced long-PCR-amplified mitochondrial or total genomic DNA. Six patterns of gene arrangements, including the novel trnR-trnS^AGN-trnA-trnN-trnG-nad3 in Lipotactes tripyrga (Lipotactinae), were identified from 59 ensiferan mitogenomes. The results suggest that trnM-trnI-trnQ and trnA-trnR-trnE-trnS^AGN-trnN-trnF rearrangements might be a shared derived character in Pseudophyllinae and Gryllidae, respectively. We found base composition biases in our dataset, which potentially complicate the inference of higher-level ensiferan phylogeny. Site-heterogeneous Bayesian inference (BI) and site-homogeneous maximum likelihood (ML) analyses recovered all ensiferan superfamilies as monophyletic. The site-homogeneous BI analysis failed to recover the monophyly of Stenopelmatoidea. As Schizodactyloidea was only represented by Comicus campestris, its monophyly could not be tested. In the Triassic/Jurassic boundary, Ensifera diverged into grylloid and non-grylloid clades. All analyses confirmed Grylloidea and Gryllotalpoidea as sister groups. Site-heterogeneous BI analysis found Schizodactyloidea as the most basal lineage and sister to the clade formed by Grylloidea and Gryllotalpoidea, but the site-homogeneous analyses placed it basally to the non-grylloid clade and recovered a sister relationship between Tettigonioidea and (Hagloidea, Rhaphidophoroidea, Stenopelmatoidea), although this clade had a low support. The site-heterogeneous BI analysis found Tettigonioidea and Hagloidea were sister groups (posterior probability (PP)=0.99), Stenopelmatoidea was sister to (Tettigonioidea, Hagloidea) (PP>0.91), and Rhaphidophoroidea was basal to the non-grylloid clade. At a lower level, all analyses divided Tettigonioidea into Phaneropteridae and Tettigoniidae.

Complete Mitochondrial Genome of the Citrus Spiny Whitefly Aleurocanthus spiniferus (Quaintance) (Hemiptera: Aleyrodidae): Implications for the Phylogeny of Whiteflies

In this study, we sequenced the complete mitochondrial genome (15,220 bp) of the citrus spiny whitefly, Aleurocanthus spiniferus (Quaintance), a well-known pest from the superfamily Aleyrodidae. The A. spiniferus mitogenome contains 36 genes, including 13 protein-coding genes (PCGs), 21 transfer RNAs (tRNA), two ribosomal RNAs (rRNA) and a large non-coding region (control region, CR). Like most whiteflies, the A. spiniferus mitogenome had a large degree of rearrangement due to translocation of the nad3-trnG-cox3 gene cluster. The 13 PCGs initiated with ATN and generally terminated with TAA, although some used TAG or T as stop codons; atp6 showed the highest evolutionary rate, whereas cox2 appeared to have the lowest rate. The A. spiniferus mitogenome had 21 tRNAs with a typical cloverleaf secondary structure composed of four arms. Modeling of the two rRNA genes indicated that their secondary structure was similar to that of other insects. The CR of A. spiniferus was 920 bp and mapped between the nad3-trnG-cox3 and trnI-trnM gene clusters. One potential stem-loop structure and five tandem repeats were identified in the CR. Phylogenetic relationships of 11 species from the Aleyrodidae were analyzed based on the deduced amino acid sequences of the 13 PCGs and evolutionary characteristics were explored. Species with more genetic rearrangements were generally more evolved within the Aleyrodidae.

The Complete Mitochondrial Genome and Song Evolution of the Monotypic Genus U. Tarbinsky, 1932 (Orthoptera: Tettigoniidae)

The insect Uvarovites inflatus Uvarov is highly appreciated in China. It is known for its distinctive songs and horn-like forewings and is raised commercially for insect lovers. U. inflatus was previously categorized as part of the monotypic genus Uvarovites; however, there was little molecular evidence to support this taxonomic classification. This study obtained and investigated the mitogenome of U. inflatus, and its songs were characterized and compared with other Ensifera species whose mitogenomes are available. By performing the mitochondrial analysis, we were able to assess the phylogenetic relationships between these species and discuss the evolution of Ensifera calling songs. The mitogenome of U. inflatus is 15,956 bp in length and contains 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 1 control region. The organization and orientation of the U. inflatus mitogenome are similar to those of other Tettigonioidea species. Phylogenetic analysis based on 13 protein-coding genes showed that the superfamily Tettigonioidea is monophyletic, as are the other six tested subfamilies from Tettigonioidea. Our results also indicated that Grylloidea is monophyletic. A Bayesian relaxed clock analysis showed that the differentiation of U. inflatus and Gampsocleis gratiosa Brunner occurred in the middle Miocene, suggesting that their speciation occurred over a long evolutionary period. The results provide significant support for the establishment of the monotypic genus Uvarovites. Calling song analysis showed that at least two discrete steps of independent evolution occurred during the change from pure tone to broadband noise, and that the ancestor of existing Ensifera was more likely to have emitted pure-tone songs than broadband signals. Together, the mitogenome, molecular clock, and acoustic data allowed us to clarify the taxonomic state of U. inflatus and propose a timeline for the evolution of Ensifera songs.

Characterization of the complete mitogenomes of two Neoscona spiders (Araneae: Araneidae) and its phylogenetic implications

The complete mitogenomes of two orb-weaving spiders Neoscona doenitzi and Neoscona nautica were determined and a comparative mitogenomic analysis was performed to depict evolutionary trends of spider mitogenomes. The circular mitogenomes are 14,161bp with A+T content of 74.6% in N. doenitzi and 14,049bp with A+T content of 78.8% in N. nautica, respectively. Both mitogenomes contain a standard set of 37 genes typically presented in metazoans. Gene content and orientation are identical to all previously sequenced spider mitogenomes, while gene order is rearranged by tRNAs translocation when compared with the putative ancestral gene arrangement pattern presented by Limulus polyphemus. A comparative mitogenomic analysis reveals that the nucleotide composition bias is obviously divergent between spiders in suborder Opisthothelae and Mesothelae. The loss of D-arm in the trnS(UCN) among all of Opisthothelae spiders highly suggested that this common feature is a synapomorphy for entire suborder Opisthothelae. Moreover, the trnS(AGN) in araneoids preferred to use TCT as an anticodon rather than the typical anticodon GCT. Phylogenetic analysis based on the 13 protein-coding gene sequences consistently yields trees that nest the two Neoscona spiders within Araneidae and recover superfamily Araneoidea as a monophyletic group. The molecular information acquired from the results of this study should be very useful for future research on mitogenomic evolution and genetic diversities in spiders.

DNA barcoding reveals polymorphism in the pygmy grasshopper Tetrix bolivari (Orthoptera, Tetrigidae)

Many pygmy grasshopper species exhibit colour-marking polymorphism. However, this polymorphism in some species, such as Tetrixbolivari, is almost unknown. The aim of this work is to identify using DNA barcoding the colour-marking polymorphic morphs of this pygmy grasshopper species collected from both grass and sand microhabitats. Analysis by NJ clustering and pairwise distances indicated that all specimens collected showing colour-marking polymorphism are species of Tetrixbolivari. Haplotype network construction showed ten different haplotypes from a total of 57 Tetrixbolivari individuals with H1(82.5%) being the most common type and it also displayed low divergence within Tetrixbolivari population. The haplotype analyses were consistent with the NJ clustering. Our field census showed the frequency of Tetrixbolivari morphs differed significantly, with the rank order of morphs (from high to low) typeA₁, type B₁, type A₂, type A₃, type A₄, type A₅, type A₆, type A₇, type B₂, type B₃, and type B₄. The most common type A morphs were without contrasting markings, while the rarer type B morphs have contrasting white markings. We suggest that type B morphs have greater camouflage effects against natural backgrounds such as grass or sand than type A morphs. Both our field census and haplotype analysis revealed that type A has higher frequency and more haplotypes than type B.

The complete mitochondrial genome sequence of the tubeworm Lamellibrachia satsuma and structural conservation in the mitochondrial genome control regions of Order Sabellida

The control region of the mitochondrial genomes shows high variation in conserved sequence organizations, which follow distinct evolutionary patterns in different species or taxa. In this study, we sequenced the complete mitochondrial genome of Lamellibrachia satsuma from the cold-seep region of Kagoshima Bay, as a part of whole genome study and extensively studied the structural features and patterns of the control region sequences. We obtained 15,037 bp of mitochondrial genome using Illumina sequencing and identified the non-coding AT-rich region or control region (354 bp, AT=83.9%) located between trnH and trnR. We found 7 conserved sequence blocks (CSB), scattered throughout the control region of L. satsuma and other taxa of Annelida. The poly-TA stretches, which commonly form the stem of multiple stem-loop structures, are most conserved in the CSB-I and CSB-II regions. The mitochondrial genome of L. satsuma encodes a unique repetitive sequence in the control region, which forms a unique secondary structure in comparison to Lamellibrachia luymesi. Phylogenetic analyses of all protein-coding genes indicate that L. satsuma forms a monophyletic clade with L. luymesi along with other tubeworms found in cold-seep regions (genera: Lamellibrachia, Escarpia, and Seepiophila). In general, the control region sequences of Annelida could be aligned with certainty within each genus, and to some extent within the family, but with a higher rate of variation in conserved regions.

Mitochondrial genomes of four katydids (Orthoptera: Phaneropteridae): New gene rearrangements and their phylogenetic implications

Phaneropteridae is a family of Orthoptera that displays an amazing amount of diversity in terms of both forms and species. We sequenced the mitochondrial genomes (mitogenomes) of two bush katydids: Ruidocollaris obscura and Kuwayamaea brachyptera (Phaneropterinae), and two true katydids: Orophyllus montanus and Phyllomimus detersus (Pseudophyllinae), to obtain further insight into the characteristics of the katydid mitogenomes and to investigate the taxonomic status of subfamily Pseudophyllinae and the diversity of gene arrangements among Phaneropteridae. The following general genomic characteristics were observed in the four katydids: a longer length of the mitogenomes (16,007bp-16,667bp) compared with Caelifera, abundant intergenic spacers, and accepted atypical initiation codons (GTG and TTG, found in cox1, nad1 and nad2). A new orientation of the gene arrangement "trnM-trnI-trnQ" was identified in P. detersus, which is the first representative of Polyneoptera found to carry this gene cluster. Large identical fragments (492bp) were detected in control region 1 (CR1) and control region 2 (CR2) of R. obscura. The high similarity of the duplicated CRs is likely due to a recent gene duplication or concerted evolution. Analyses of the duplicated CRs revealed one conserved stem-loop (on the N-strand) located in the identical sequences of both CRs that might be linked to replication initiation. Phylogenetic analyses based on 13 protein-coding genes and 2 ribosomal RNA genes from 20 Ensiferan species yielded the identical topologies between two different methods (maximum likelihood and bayesian inference). The newly sequenced Pseudophyllinae species was placed as the sister group of Phaneropterinae, and Mecopodinae clustered with Pseudophyllinae+Phaneropterinae. Additionally, we speculate that the species in Ruidocollaris and Sinochlora, as well as their closely related genera, may have undergone numerous rearrangement events.

Seven complete mitochondrial genome sequences of bushtits (Passeriformes, Aegithalidae, Aegithalos): the evolution pattern in duplicated control regions

The control region (CR) of the mitochondrial DNA exhibits important functions in replication and transcription, and duplications of the CR have been reported in a wide range of animal groups. In most cases, concerted evolution is expected to explain the high similarity of duplicated CRs. In this paper, we present seven complete mitochondrial genome sequences from the bushtits (genus Aegithalos), in which we discovered two duplicated CRs, and try to survey the evolution pattern of these duplicated CRs. We also found that the duplicated CRs within one individual were almost identical, and variations were concentrated in two sections, one located between a poly-C site and a potential TAS (termination associated sequence) element, the other one located at the 3' end of the duplicated CRs. The phylogenetic analyses of paralogous CRs showed that the tree topology were depending on whether the two high variable regions at the upstream of TAS element and the 3'end of duplicated CRs: when they were concluded, the orthologous copies were closely related; when they were excluded, the paralogous copies in the same lineages were closely related. This may suggest the role of recombination in the evolution of duplicated CRs. Consequently, the recombination was detected, and the breakpoints were found at ∼120 bp (the upstream of the potential TAS element) and ∼1150 bp of the alignment of duplicated CRs. According to these results, we supposed that homologous recombination occurred between paralogous CRs from different mtDNA molecule was proposed as the most suitable mechanism for concerted evolution of the duplicated CRs, and the recombination took place in every replication cycle, so that most part of the duplicated regions remain identical within an individual, while the 5' and 3'end of the duplicated CRs were not involved in recombination, and evolved independently.

Sequencing of the mitochondrial genome of the avocado lace bug Pseudacysta perseae (Heteroptera, Tingidae) using a genome skimming approach

Lace bugs (Tingidae) are a family of phytophagous heteropterans, some of which are important agricultural and forestry pests. They currently comprise around 2500 species distributed worldwide, for which only one mitochondrial genome has been described so far. We sequenced the complete mitochondrial genome and the nuclear ribosomal gene segment of the avocado lace bug Pseudacysta perseae using a genome skimming approach on an Illumina Hiseq 2000 platform. Fifty-four additional heteropteran mitogenomes, including the one of the sycamore lace bug Corythucha ciliata, were retrieved to allow for comparisons and phylogenetic analyses. P. perseae mitochondrial genome was determined to be 15,850 bp long, and presented the typical organisation of insect mitogenomes. The phylogenetic analysis placed P. perseae as a sister to C. ciliata but did not confirm the monophyly of Miroidae including Tingidae. Our results contradicted widely accepted phylogenetic hypothesis, which highlights the limits of analyses based on mitochondrial data only. Shotgun sequencing approaches should provide substantial improvements in harmonizing mitochondrial and nuclear databases.

Sequence and analysis of mtDNA control region in Cnaphalacrocis medinalis Guenée and Marasmia patnalis Bradley (Lepidoptera: Pyralidae)

Rice leaffolders Cnaphalocrocis medinalis and Marasmia patnalis (Lepidoptera: Pyralidae) are important rice pests and morphologically related with same damage methods. The control region of mitochondrial DNA (mtDNA) in two rice leaffolders C. medinalis and M. patnalis were sequenced and analyzed. The control regions of the two rice leaffolders are located between 12S ribosomal RNA and tRNA_Met, and exhibit conserved structural elements. We identified the poly T stretches, (TA)n block, and stem-loop structure. There are no long tandem repeats found in mtDNA control region in the two rice leaffolders studied. Nevertheless, we did not find the GA-rich block in mtDNA control regions of the two rice leaffolders. The molecular-based phylogenies support the traditional morphologically based view of relationships of Pyralidae within the Ditrysia. The addition of the C. medinalis and M. patnalis mtDNA control regions to the literature promotes the understanding of the molecular evolution of Pyralidae in Ditrysia.

Comparison of the complete mitochondrial genome of the stonefly Sweltsa longistyla (Plecoptera: Chloroperlidae) with mitogenomes of three other stoneflies

The complete mitochondrial genome of the stonefly, Sweltsa longistyla Wu (Plecoptera: Chloroperlidae), was sequenced in this study. The mitogenome of S. longistyla is 16,151bp and contains 37 genes including 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and a large non-coding region. S. longistyla, Pteronarcys princeps Banks, Kamimuria wangi Du and Cryptoperla stilifera Sivec belong to the Plecoptera, and the gene order and orientation of their mitogenomes were similar. The overall AT content for the four stoneflies was below 72%, and the AT content of tRNA genes was above 69%. The four genomes were compact and contained only 65-127bp of non-coding intergenic DNAs. Overlapping nucleotides existed in all four genomes and ranged from 24 (P. princeps) to 178bp (K. wangi). There was a 7-bp motif ('ATGATAA') of overlapping DNA and an 8-bp motif (AAGCCTTA) conserved in three stonefly species (P. princeps, K. wangi and C. stilifera). The control regions of four stoneflies contained a stem-loop structure. Four conserved sequence blocks (CSBs) were present in the A+T-rich regions of all four stoneflies.

The mitochondrial genome of Dastarcus helophoroides (Coleoptera: Bothrideridae) and related phylogenetic analyses

The complete mitochondrial genome of Dastarcus helophoroides (Coleoptera: Bothrideridae) which consists of 13 PCGs, 22 tRNA genes, two rRNA genes and a non-coding region (D-loop), is sequenced for its nucleotide sequence of 15,878 bp (GenBank: KF811054.1). The genome has a typical gene order which is identical to other Coleoptera species. Except for COI gene generally starts with non-canonical initial codon, all protein-coding genes start with ATN codon and terminate with the stop codon TA(A) or TAG. The secondary structure of rrnL and rrnS consists of 48 helices (contains four newly proposed helices) and 35 helices (contains two newly proposed helices) respectively. All 22 tRNAs in D. helophoroides are predicted to fold into typical cloverleaf secondary structure, except trnS1 (AGN), in which the dihydrouracil arm (DHU arm) could not form stable stem-loop structure. Thirteen protein-coding genes (nucleotide dataset and nucleic acid dataset) of the available species (29 taxa) have been used to infer the phylogenetic relationships among these orders. Tenebrionoidea and Cucujoidea form a sister group, and D. helophoroides is classified into Cucujoidea (Bothrideridae). The study first research on the phylogenetic analyses involving to the D. helophoroides mitogenome, and the results strongly bolster the current morphology-based hypothesis.

The complete mitochondrial genome and its remarkable secondary structure for a stonefly Acroneuria hainana Wu (Insecta: Plecoptera, Perlidae)

The Plecoptera (stoneflies) is a hemimetabolous order of insects, whose larvae are usually used as indicators for fresh water biomonitoring. Herein, we describe the complete mitochondrial (mt) genome of a stonefly species, namely Acroneuria hainana Wu belonging to the family Perlidae. This mt genome contains 13 PCGs, 22 tRNA-coding genes and 2 rRNA-coding genes that are conserved in most insect mt genomes, and it also has the identical gene order with the insect ancestral gene order. However, there are three special initiation codons of ND1, ND5 and COI in PCGs: TTG, GTG and CGA, coding for L, V and R, respectively. Additionally, the 899-bp control region, with 73.30% A+T content, has two long repeated sequences which are found at the 3'-end closing to the tRNA(Ile) gene. Both of them can be folded into a stem-loop structure, whose adjacent upstream and downstream sequences can be also folded into stem-loop structures. It is presumed that the four special structures in series could be associated with the D-loop replication. It might be able to adjust the replication speed of two replicate directions.

Complete mitochondrial genome of the groundhopper Erianthus versicolor (Orthoptera: Caelifera: Eumastacoidea)

The complete mitochondrial genome of Erianthus versicolor was determined. It was 15,397 bp in length and contained 73.94% AT. The gene order of tRNA(Asp) (D) and tRNA(Lys) (K) is reversed to K-D order; a trnF-like and a trnS(UCN)-like sequences are present almost in the same positions with trnF and trnS(UCN); the AT content of the A + T-rich region was low, only 59.97%.

Comparative analysis of the mitochondrial genomes of Callitettixini Spittlebugs (Hemiptera: Cercopidae) confirms the overall high evolutionary speed of the AT-rich region but reveals the presence of short conservative elements at the tribal level

The present study compares the mitochondrial genomes of five species of the spittlebug tribe Callitettixini (Hemiptera: Cercopoidea: Cercopidae) from eastern Asia. All genomes of the five species sequenced are circular double-stranded DNA molecules and range from 15,222 to 15,637 bp in length. They contain 22 tRNA genes, 13 protein coding genes (PCGs) and 2 rRNA genes and share the putative ancestral gene arrangement of insects. The PCGs show an extreme bias of nucleotide and amino acid composition. Significant differences of the substitution rates among the different genes as well as the different codon position of each PCG are revealed by the comparative evolutionary analyses. The substitution speeds of the first and second codon position of different PCGs are negatively correlated with their GC content. Among the five species, the AT-rich region features great differences in length and pattern and generally shows a 2–5 times higher substitution rate than the fastest PCG in the mitochondrial genome, atp8. Despite the significant variability in length, short conservative segments were identified in the AT-rich region within Callitettixini, although absent from the other groups of the spittlebug superfamily Cercopoidea.

The complete mitochondrial genome of Cervaphis quercus (Insecta: Hemiptera: Aphididae: Greenideinae)

The mitochondrial genome of Cervaphis quercus has been sequenced and annotated. The entire genome of 15,272 bp encodes two ribosomal RNA genes (rrnL and rrnS), 22 transfer RNA (tRNA) genes, 13 protein-coding genes and a control region. The genome has the same gene order as that found in the inferred ancestral insect. Nucleotide composition is highly A+T biased. All protein-coding genes use standard mitochondrial initiation codons. Secondary structure models of the two ribosomal RNA genes of C. quercus are similar to those proposed for other insects. All tRNAs have the classic clover-leaf structure, except for the dihydrouridine (DHU) arm of trnS (AGN), which forms a simple loop. The presence of structural elements in the control region is also discussed, with an emphasis on the possible regulation of replication and/or transcription. Comparison with mitochondrial genomes of other aphid species shows their gene arrangements are conserved; however, the variety of repeat regions in species from a different aphid subfamily, Aphidinae, suggests that they resulted from independent evolutionary events.

The mitochondrial genome of the plant bug Apolygus lucorum (Hemiptera: Miridae): Presently known as the smallest in Heteroptera

The complete mitochondrial (mt) genome of the plant bug, Apolygus lucorum, an important cotton pest, has been sequenced and annotated in this study. The entire circular genome is 14 768 bp in size and represents the smallest in presently known heteropteran mt genomes. The mt genome is encoding for two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, 13 protein coding genes and a control region, and the order, content, codon usage and base organization show similarity to a great extent to the hypothetical ancestral model. All protein coding genes use standard initiation codons ATN. Conventional stop codons TAA and TAG have been assigned to the most protein coding genes; however, COIII, ND4 and ND5 genes show incomplete terminator signal (T). All tRNA genes possess the typical clover leaf structure, but the dihydrouridine arm of tRNA(Ser(AGN)) only forms a simple loop. Secondary structure models of rRNA genes are generally in accordance with the former models, although some differences exist in certain parts. Three intergenic spacers have never been found in sequenced mt genomes of Heteroptera. The phylogenetic study based on protein coding genes is largely congruent with previous phylogenetic work. Both Bayesian inference and maximum likelihood analyses highly support the sister relationship of A. lucorum and Lygus lineolaris, and Miridae presents a sister position to Anthocoridae.

The first mitochondrial genome for the superfamily Hagloidea and implications for its systematic status in Ensifera

Hagloidea Handlirsch, 1906 was an ancient group of Ensifera, that was much more diverse in the past extending at least into the Triassic, apparently diminishing in diversity through the Cretaceous, and now only represented by a few extant species. In this paper, we report the complete mitochondrial genome (mitogenome) of Tarragoilus diuturnus Gorochov, 2001, representing the first mitogenome of the superfamily Hagloidea. The size of the entire mitogenome of T. diuturnus is 16144 bp, containing 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and one control region. The order and orientation of the gene arrangement pattern is identical to that of D. yakuba and most ensiferans species. A phylogenomic analysis was carried out based on the concatenated dataset of 13 PCGs and 2 rRNA genes from mitogenome sequences of 15 ensiferan species, comprising four superfamilies Grylloidea, Tettigonioidae, Rhaphidophoroidea and Hagloidea. Both maximum likelihood and Bayesian inference analyses strongly support Hagloidea T. diuturnus and Rhaphidophoroidea Troglophilus neglectus as forming a monophyletic group, sister to the Tettigonioidea. The relationships among four superfamilies of Ensifera were (Grylloidea, (Tettigonioidea, (Hagloidea, Rhaphidophoroidea))).

Comparative analysis of mitochondrial genomes of five aphid species (Hemiptera: Aphididae) and phylogenetic implications

Insect mitochondrial genomes (mitogenomes) are of great interest in exploring molecular evolution, phylogenetics and population genetics. Only two mitogenomes have been previously released in the insect group Aphididae, which consists of about 5,000 known species including some agricultural, forestry and horticultural pests. Here we report the complete 16,317 bp mitogenome of Cavariella salicicola and two nearly complete mitogenomes of Aphis glycines and Pterocomma pilosum. We also present a first comparative analysis of mitochondrial genomes of aphids. Results showed that aphid mitogenomes share conserved genomic organization, nucleotide and amino acid composition, and codon usage features. All 37 genes usually present in animal mitogenomes were sequenced and annotated. The analysis of gene evolutionary rate revealed the lowest and highest rates for COI and ATP8, respectively. A unique repeat region exclusively in aphid mitogenomes, which included variable numbers of tandem repeats in a lineage-specific manner, was highlighted for the first time. This region may have a function as another origin of replication. Phylogenetic reconstructions based on protein-coding genes and the stem-loop structures of control regions confirmed a sister relationship between Cavariella and pterocommatines. Current evidence suggest that pterocommatines could be formally transferred into Macrosiphini. Our paper also offers methodological instructions for obtaining other Aphididae mitochondrial genomes.

The phylogeny of the Orthoptera (Insecta) as deduced from mitogenomic gene sequences

Background

The phylogeny of the Orthoptera was analyzed based on 6 datasets from 47 orthopteran mitochondrial genomes (mitogenomes). The phylogenetic signals in the mitogenomes were rigorously examined under analytical regimens of maximum likelihood (ML) and Bayesian inference (BI), along with how gene types and different partitioning schemes influenced the phylogenetic reconstruction within the Orthoptera. The monophyly of the Orthoptera and its two suborders (Caelifera and Ensifera) was consistently recovered in the analyses based on most of the datasets we selected, regardless of the optimality criteria.

Results

When the seven NADH dehydrogenase subunits were concatenated into a single alignment (NADH) and were analyzed; a near-identical topology to the traditional morphological analysis was recovered, especially for BI_NADH. In both the concatenated cytochrome oxidase (COX) subunits and COX + cytochrome b (Cyt b) datasets, the small extent of sequence divergence seemed to be helpful for resolving relationships among major Orthoptera lineages (between suborders or among superfamilies). The conserved and variable domains of ribosomal (r)RNAs performed poorly when respectively analyzed but provided signals at some taxonomic levels.

Conclusions

Our findings suggest that the best phylogenetic inferences can be made when moderately divergent nucleotide data from mitogenomes are analyzed, and that the NADH dataset was suited for studying orthopteran phylogenetic relationships at different taxonomic levels, which may have been due to the larger amount of DNA sequence data and the larger number of phylogenetically informative sites.

The complete mitochondrial genome of spittlebug Paphnutius ruficeps (Insecta: Hemiptera: Cercopidae) with a fairly short putative control region

The mitochondrial genome of the spittlebug Paphnutius ruficeps is a double-strand DNA circular molecule of 14,841 bp with a total A and T content of 73.8%. It is one of the shortest genomes among published hemipteran mitogenomes and encodes 13 protein-coding genes, 2 ribosome RNA genes and 22 transfer RNA (tRNA) genes. The gene order is consistent with the hypothesized ancestral arthropod genome arrangement. Most of the protein-coding genes use ATG as start and TAA as stop codon. The codons show an evident bias toward the nucleotides T and A at the third codon position and the most commonly used codons contain more A and T than their synonymous ones. The anticodons of the 22 tRNA genes are identical to those of the mitogenome of Philaenus spumarius, another studied spittlebug. All the tRNAs could be folded into traditional clover leaf secondary structures. The putative control region (traditionally called A + T-rich region) is the main non-coding part of the mitogenome. The AT content of this region (74.5%) is not significantly higher than that of the total mitogenome (73.8%) and slightly lower than that of the N-chain protein-coding genes (75.3%). The absence of repeat sequences as well as its short length is the most obvious characteristics of the mitochondrial genome of Paphnutius ruficeps compared with those of other published hemipteran species.

The complete mitochondrial genome of the stalk-eyed bug Chauliops fallax Scott, and the monophyly of Malcidae (Hemiptera: Heteroptera)

Chauliops fallax Scott, 1874 (Hemiptera: Heteroptera: Malcidae: Chauliopinae) is one of the most destructive insect pests of soybean and rice fields in Asia. Here we sequenced the complete mitochondrial genome of this pest. This genome is 15,739 bp long, with an A+T content of 73.7%, containing 37 typical animal mitochondrial genes and a control region. All genes were arranged in the same order as most of other Heteroptera. A remarkable strand bias was found for all nine protein coding genes (PCGs) encoded by the majority strand were positive AT-skew and negative GC-skew, whereas the reverse were found in the remaining four PCGs encoded by the minority strand and two rRNA genes. The models of secondary structures for the two rRNA genes of sequenced true bugs and Lygaeoidea were predicted. 16S rRNA consisted of six domains (domain III is absent as in other known arthropod mitochondrial genomes) and 45 helices, while three domains and 27 helices for 12S rRNA. The control region consists of five subregions: a microsatellite-like region, a tandem repeats region and other three motifs. The unusual intergenic spacer between tRNA-H and ND4 only found in the species of Lygaeoidea, not in other heteropteran species, may be the synapomorphy of this superfamily. Phylogenetic analyses were carried out based on all the 13 PCGs showed that Chauliopinae was the sister group of Malcinae and the monophyly of Lygaeoidea.

The mitochondrial genome of the quiet-calling katydids, Xizicus fascipes (Orthoptera: Tettigoniidae: Meconematinae)

To help determine whether the typical arthropod arrangement was a synapomorphy for the whole Tettigoniidae, we sequenced the mitochondrial genome (mitogenome) of the quiet-calling katydids, Xizicus fascipes (Orthoptera: Tettigoniidae: Meconematinae). The 16,166-bp nucleotide sequences of X. fascipes mitogenome contains the typical gene content, gene order, base composition, and codon usage found in arthropod mitogenomes. As a whole, the X. fascipes mitogenome contains a lower A+T content (70.2%) found in the complete orthopteran mitogenomes determined to date. All protein-coding genes started with a typical ATN codon. Ten of the 13 protein-coding genes have a complete termination codon, but the remaining three genes (COIII, ND5 and ND4) terminate with incomplete T. All tRNAs have the typical clover-leaf structure of mitogenome tRNA, except for tRNA(Ser(AGN)), in which lengthened anticodon stem (9 bp) with a bulged nuleotide in the middle, an unusual T-stem (6 bp in constrast to the normal 5 bp), a mini DHU arm (2 bp) and no connector nucleotides. In the A+T-rich region, two (TA)n conserved blocks that were previously described in Ensifera and two 150-bp tandem repeats plus a partial copy of the composed at 61 bp of the beginning were present. Phylogenetic analysis found: i) the monophyly of Conocephalinae was interrupted by Elimaea cheni from Phaneropterinae; and ii) Meconematinae was the most basal group among these five subfamilies.

The complete mitochondrial genomes of three grasshoppers, Asiotmethis zacharjini, Filchnerella helanshanensis and Pseudotmethis rubimarginis (Orthoptera: Pamphagidae)

The complete mitogenomes of Asiotmethis zacharjini, Filchnerella helanshanensis and Pseudotmethis rubimarginis are 15,660 bp, 15,657 bp and 15,661 bp in size, respectively. All three mitogenomes contain a standard set of 13 protein - coding genes, 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs) and an A+T-rich region in the same order as those of the other analysed caeliferan species, including the rearrangement of trnAsp and trnLys. The putative initiation codon for the cox1 gene in the three species is CCG. The long polythymine stretch (T-stretch) in the A+T-rich region of the three species is not adjacent to the trnIle but inside the stem-loop sequence in the majority strand. The mitogenomes of F. helanshanensis and P. rubimarginis have higher overall similarities. The characterization of the three mitogenomes will enrich our knowledge on the Pamphagidae mitogenome. The phylogenetic analyses indicated that within the Caelifera, Pyrgomorphoidea is a sister group to Acridoidea. The species from the Pamphagidae form a monophyletic group, as is the case for Acrididae. Furthermore, the two families cluster as sister groups, supporting the monophyly of Acridoidea. The relationships among eight acridid subfamilies were (Cyrtacanthacridinae+(Calliptaminae+(Catantopinae+(Oxyinae+(Melanopline+(Acridinae+(Oedipodinae+Gomphocerinae).

Comparative mitogenomic analysis of damsel bugs representing three tribes in the family Nabidae (Insecta: Hemiptera)

BACKGROUND

Nabidae, a family of predatory heteropterans, includes two subfamilies and five tribes. We previously reported the complete mitogenome of Alloeorhynchus bakeri, a representative of the tribe Prostemmatini in the subfamily Prostemmatinae. To gain a better understanding of architecture and evolution of mitogenome in Nabidae, mitogenomes of five species representing two tribes (Gorpini and Nabini) in the subfamily Nabinae were sequenced, and a comparative mitogenomic analysis of three nabid tribes in two subfamilies was carried out.

METHODOLOGY/PRINCIPAL FINDINGS

Nabid mitogenomes share a similar nucleotide composition and base bias, except for the control region, where differences are observed at the subfamily level. In addition, the pattern of codon usage is influenced by the GC content and consistent with the standard invertebrate mitochondrial genetic code and the preference for A+T-rich codons. The comparison among orthologous protein-coding genes shows that different genes have been subject to different rates of molecular evolution correlated with the GC content. The stems and anticodon loops of tRNAs are extremely conserved, and the nucleotide substitutions are largely restricted to TψC and DHU loops and extra arms, with insertion-deletion polymorphisms. Comparative analysis shows similar rates of substitution between the two rRNAs. Long non-coding regions are observed in most Gorpini and Nabini mtDNAs in-between trnI-trnQ and/or trnS2-nad1. The lone exception, Nabis apicalis, however, has lost three tRNAs. Overall, phylogenetic analysis using mitogenomic data is consistent with phylogenies constructed mainly form morphological traits.

CONCLUSIONS/SIGNIFICANCE

This comparative mitogenomic analysis sheds light on the architecture and evolution of mitogenomes in the family Nabidae. Nucleotide diversity and mitogenomic traits are phylogenetically informative at subfamily level. Furthermore, inclusion of a broader range of samples representing various taxonomic levels is critical for the understanding of mitogenomic evolution in damsel bugs.

[Phylogenetic relationships among Orthoptera insect groups based on complete sequences of 16S ribosomal RNA]

In order to reconstruct a robust phylogenetic relationship among major groups of Orthoptera and to explore the phylogenetic utility and performance of 16S Ribosomal RNA gene, complete sequences of 16S Ribosomal RNA were sequenced from 18 species in 9 families and 4 superfamilies of Orthoptera, and analyzed with other 40 species that have been completely sequenced. The result showed that the average length of 16S Ribosomal RNA was 1 310 bp. The positions of Tridactuloidea and Gryllotalpidae in Orthoptera were uncertain based on the 16S rRNA data, and the phylogenetic relationships of other major groups in Orthoptera were rather robust. Except for Oedipodidae and Gomphoceridae, Acrididae, Catantopidae, and Arcypteridae in Xia's taxonomic system were not monophyletic groups, and the genetic distances among the five groups were small. This indicates that the five families should be combined into one family. The genetic distances among Pamphagidae, Chrotogonidae, and Pyrgomorphidae were also small. The loops of 16S rRNA gene could provide more information than stems when they were used for phylogenetic analysis. Complete sequence of 16S rRNA gene can be used to reconstruct robust phylogenetic relationship at the taxonomic category of species, genera, and suborder in Orthoptera, but lack of resolution at family and superfamily levels.

Complete mitochondrial genome of Locusta migratoria migratoria (Orthoptera: Oedipodidae): three tRNA-like sequences on the N-strand

The complete 16053 bp mitochondrial genome (mitogenome) sequence of Locusta migratoria migratoria has been determined. This mitogenome contains the base compositional biases and codon usage typical of metazoans, and the RSCU values indicate a negative correlation with the C and G contents in codon. The orientation and gene order of the L. migratoria migratoria is identical to Locusta migratoria migratoiodes. An unusual feature of the L. migratoria migratoria mitogenome is the presence of three tRNA-like structures on the N-strand: one tRNA(Ile)-like and two tRNA(Leu(CUN))-like sequences. The tRNA-like sequences have proper folding structures and anticodons sequences. Two repeated DNA sequences, Rpt I and Rpt II, were found in the A+T-rich region of the L. migratoria migratoria mitogenome. Both repeated sequences have various features. In the 5' region of Rpt I, a 51 bp fragment is localized in the srRNA gene; and there are two tandemly sub-repeated DNA sequences (sub-Rpts), Rpt 1-4, within Rpt I and Rpt II. One stem-loop structure on the N-strand that may be involved in the N-strand replication initiation was found in the A+T-rich region.