The complete mitochondrial genome of Epicauta chinensis (Coleoptera: Meloidae) and phylogenetic analysis among Coleopteran insects

Comparative Analysis of the Complete Mitochondrial Genomes of Three Sisoridae (Osteichthyes, Siluriformes) and the Phylogenetic Relationships of Sisoridae

The family Sisoridae is one of the largest and most diverse Asiatic catfish families, with most species occurring in the water systems of the Qinhai-Tibetan Plateau and East Himalayas. At present, the phylogenetic relationship of the Sisoridae is relatively chaotic. In this study, the mitochondrial genomes (mitogenomes) of three species Creteuchiloglanis kamengensis, Glaridoglanis andersonii, and Exostoma sp. were systematically investigated, the phylogenetic relationships of the family were reconstructed and to determine the phylogenetic position of Exostoma sp. within Sisoridae. The lengths of the mitogenomes' sequences of C. kamengensis, G. andersonii, and Exostoma sp. were 16,589 bp, 16,531 bp, and 16,529 bp, respectively. They all contained one identical control region (D-loop), two ribosomal RNAs (rRNAs), 13 protein-coding genes (PCGs) and 22 transfer RNA (tRNA) genes. We applied two approaches, Bayesian Inference (BI) and Maximum Likelihood (ML), to construct phylogenetic trees. Our findings revealed that the topological structure of both ML and BI trees exhibited significant congruence. Specifically, the phylogenetic tree strongly supports the monophyly of Sisorinae and Glyptosternoids and provides new molecular biological data to support the reconstruction of phylogenetic relationships with Sisoridae. This study is of great scientific value for phylogenetic and genetic variation studies of the Sisoridae.

Mitochondrial genomes of three Mylabris (Pseudabris) species (Coleoptera: Meloidae, Mylabrini) and their phylogenetic implications

The complete mitogenomes of the subgenus Mylabris (Pseudabris) Fairmaire, 1894, endemic to the Qinghai-Xizang Plateau, are reported for the first time. Three species out of seven, M. hingstoni Blair, 1927, M. longiventris Blair, 1927, and M. przewalskyi (Dokhtouroff, 1887), were sequenced. The sequencing results of mitogenomes were annotated and analyzed. The gene arrangements were consistent with the putative ancestral insect mitogenomes as understood today, including 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, and a noncoding internal control region (CR). The PCGs used the typical start ATN codon and TAA/TAG stop codons. The lengths of three mitogenomes were 15,692 bp, 15,685 bp, and 15,685 bp, with an A + T content of 71.29%, 71.67%, and 71.53%, respectively. The evolution rates of 13 PCGs were compared: The evolution rate of ATP8 was the highest, and that of COX1 was the lowest. Furthermore, the phylogenetic relationships among the genera and tribes of Meloidae were discussed.

Comparative Mitogenomic Analyses of Darkling Beetles (Coleoptera: Tenebrionidae) Provide Evolutionary Insights into tRNA-like Sequences

Tenebrionidae is widely recognized owing to its species diversity and economic importance. Here, we determined the mitochondrial genomes (mitogenomes) of three Tenebrionidae species (Melanesthes exilidentata, Anatolica potanini, and Myladina unguiculina) and performed a comparative mitogenomic analysis to characterize the evolutionary characteristics of the family. The tenebrionid mitogenomes were highly conserved with respect to genome size, gene arrangement, base composition, and codon usage. All protein-coding genes evolved under purifying selection. The largest non-coding region (i.e., control region) showed several unusual features, including several conserved repetitive fragments (e.g., A+T-rich regions, G+C-rich regions, Poly-T tracts, TATA repeat units, and longer repetitive fragments) and tRNA-like structures. These tRNA-like structures can bind to the appropriate anticodon to form a cloverleaf structure, although base-pairing is not complete. We summarized the quantity, types, and conservation of tRNA-like sequences and performed functional and evolutionary analyses of tRNA-like sequences with various anticodons. Phylogenetic analyses based on three mitogenomic datasets and two tree inference methods largely supported the monophyly of each of the three subfamilies (Stenochiinae, Pimeliinae, and Lagriinae), whereas both Tenebrioninae and Diaperinae were consistently recovered as polyphyletic. We obtained a tenebrionid mitogenomic phylogeny: (Lagriinae, (Pimeliinae, ((Tenebrioninae + Diaperinae), Stenochiinae))). Our results provide insights into the evolution and function of tRNA-like sequences in tenebrionid mitogenomes and contribute to our general understanding of the evolution of Tenebrionidae.

Comparative mitochondrial genomic analysis provides new insights into the evolution of the subfamily Lamiinae (Coleoptera: Cerambycidae)

The genus Monochamus within the subfamily Lamiinae is the main vector of Bursaphelenchus xylophilus, which causes pine wilt disease and induces substantial economic and ecological losses. Only three complete mitochondrial genomes of the genus Monochamus have been sequenced to date, and no comparative mitochondrial genomic studies of Lamiinae have been conducted. Here, the mitochondrial genomes of two Monochamus species, M. saltuarius and M. urussovi, were newly sequenced and annotated. The composition and order of genes in the mitochondrial genomes of Monochamus species are conserved. All transfer RNAs exhibit the typical clover-leaf secondary structure, with the exception of trnS1. Similar to other longhorn beetles, Lamiinae mitochondrial genomes have an A + T bias. All 13 protein-coding genes have experienced purifying selection, and tandem repeat sequences are abundant in the A + T-rich region. Phylogenetic analyses revealed congruent topologies among trees inferred from the five datasets, with the monophyly of Acanthocinini, Agapanthiini, Batocerini, Dorcaschematini, Pteropliini, and Saperdini receiving high support. The findings of this study enhance our understanding of mitochondrial genome evolution and will provide a basis for future studies of population genetics and phylogenetic investigations in this group.

The complete mitochondrial genome of Meloeproscarabaeus (Coleoptera, Meloidae): genome descriptions and phylogenetic inferences

Oil beetles are meloids, which are characterised for their cleptoparasitic habits in bee nests and oily fluid of cantharidin that causes blistering and swelling of the skin. The complete mitochondrial genome of Meloeproscarabaeus is determined using the next-generation sequencing technology and its genomic characteristics are described. The 15,653-bp long genome is a circular molecule consisting of 13 protein-coding genes (PCG), 22 transport RNA, two ribosomal RNA, and a control region. The A + T bias of the mitochondrial genome is manifested in the complete sequence and the codon usage of protein-coding genes. The genetic distance within and between genera is calculated to confirm the taxonomic status of M.proscarabaeus. The phylogenetic relationships among 15 available meloid taxa are inferred by the maximum likelihood (ML) method based on 13 mitochondrial PCGs. The ML trees resulting from nucleotide and amino acid datasets recover both the monophyly of Meloe and Epicauta and the polyphyly comprising Hycleus and Mylabris. This study provides the first description of a mitochondrial genome belonging to the genus Meloe. The mitochondrial genome sequence and its characteristics are expected to be conducive to future studies on taxonomy, systematics, and molecular phylogenetics of the family Meloidae.

Phylogenetic Implication of Large Intergenic Spacers: Insights from a Mitogenomic Comparison of Prosopocoilus Stag Beetles (Coleoptera: Lucanidae)

Simple Summary

Insect mitochondrial genomes (mitogenomes) show high diversity in some lineages. In the mitogenome of some Coleoptera species, a large intergenic spacer (IGS) has been identified. However, very little is known about mitogenomes of lucanid beetles. In this work, to provide further insight into the phylogenic relationships among species in lucanid beetles (genus Prosopocoilus), two Prosopocoilus species (Prosopocoilus castaneus and Prosopocoilus laterotarsus) were newly sequenced and comparatively analyzed. Significantly, the two newly sequenced Prosopocoilus species contained a large IGS located between trnI and trnQ. Our phylogenomic analyses showed that P. castaneus and P. laterotarsus were clustered in a clade with typical Prosopocoilus species (Prosopocoilus confucius, Prosopocoilus blanchardi, and Prosopocoilusastacoides). These results provide valuable data for the future study of the phylogenetic relationships in this genus.

Abstract

To explore the characteristics of mitogenomes and discuss the phylogenetic relationships within the genus Prosopocoilus, the mitogenomes of two species (P. castaneus and P. laterotarsus) were newly sequenced and comparatively analyzed. The arrangement of the mitogenome in these two lucanid beetles was the same as that in the inferred ancestral insect, and the nucleotide composition was highly biased towards A + T as in other lucanids. The evolutionary rates of 13 protein-coding genes (PCGs) suggested that their evolution was based on purifying selection. Notably, we found evidence of the presence of a large IGS between trnI and trnQ genes, whose length varied from 375 bp (in P. castaneus) to 158 bp (in P. laterotarsus). Within the large IGS region, a short sequence (TAAAA) was found to be unique among these two species, providing insights into phylogenomic reconstruction. Phylogenetic analyses were performed using the maximum likelihood (IQ-TREE) and Bayesian (PhyloBayes) methods based on 13 protein-coding genes (PCGs) in nucleotides and amino acids (AA) from published mitogenomes (n = 29). The genus Prosopocoilus was found to constitute a distinct clade with high nodal support. Overall, our findings suggested that analysis of the characteristics of the large IGS (presence or absence, size, and location) in mitogenomes of the genus Prosopocoilus may be informative for the phylogenetic and taxonomic analyses and for evaluation of the genus Prosopocoilus, despite the dense sampling materials needed.

The mitochondrial genome of Mylabris mongolica Dokhtouroff, 1887 (Coleoptera: Meloidae)

Mylabris mongolica Dokhtouroff, 1887 is a traditional medicine material and an important predator in China. The mitochondrial genome of M. mongolica is presented for the first time in this study. The mitogenome is 15,034 bp in length and comprises 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and partial control region. The nucleotide composition of M. mongolica was 36.7% of A, 18.1% of C, 11.1% of G, and 34.1% of T. The phylogenetic results divide all Meloidae species into two clades. The genus Mylabris was retrieved as a paraphyletic group, with Mylabris having a closer relationship with Hycleus than other genera within Meloidae. This study provides useful genetic data for future studies on the phylogeny and evolution of Meloidae species.

Mitogenomics and hidden-trait models reveal the role of phoresy and host shifts in the diversification of parasitoid blister beetles (Coleoptera: Meloidae)

Changes in life history traits are often considered speciation triggers and can have dramatic effects on the evolutionary history of a lineage. Here, we examine the consequences of changes in two life history traits, host‐type and phoresy, in the hypermetamorphic blister beetles, Meloidae. Subfamilies Nemognathinae and Meloinae exhibit a complex life cycle involving multiple metamorphoses and parasitoidism. Most genera and tribes are bee‐parasitoids, and include phoretic or nonphoretic species, while two tribes feed on grasshopper eggs. These different life strategies are coupled with striking differences in species richness among clades. We generated a mitogenomic phylogeny for Nemognathinae and Meloinae, confirming the monophyly of these two clades, and used the dated phylogeny to explore the association between diversification rates and changes in host specificity and phoresy, using state‐dependent speciation and extinction (SSE) models that include the effect of hidden traits. To account for the low taxon sampling, we implemented a phylogenetic‐taxonomic approach based on birth‐death simulations, and used a Bayesian framework to integrate parameter and phylogenetic uncertainty. Results show that the ancestral hypermetamorphic Meloidae was a nonphoretic bee‐parasitoid, and that transitions towards a phoretic bee‐parasitoid and grasshopper parasitoidism occurred multiple times. Nonphoretic bee‐parasitoid lineages exhibit significantly higher relative extinction and lower diversification rates than phoretic bee‐and grasshopper‐parasitoids, but no significant differences were found between the latter two strategies. This suggests that Orthopteran host shifts and phoresy contributed jointly to the evolutionary success of the parasitoid meloidae. We also demonstrate that SSE models can be used to identify hidden traits coevolving with the focal trait in driving a lineage's diversification dynamics.

Structural Features and Phylogenetic Implications of Three New Mitochondrial Genomes of Blister Beetles (Coleoptera: Meloidae)

The mitochondrial genome sequences of Denierella emmerichi, Epicauta curvispina, and Meloe poggii were determined. Their mitochondrial genomes were found to contain 37 genes (13 protein-coding genes [PCGs], 22 tRNA genes, and 2 rRNAs), of which 4 PCGs, 8 tRNA genes, and 2 rRNAs are encoded by the N-strand, and the remaining genes are encoded by the J-strand. The mitochondrial genomes of D. emmerichi, E. curvispina, and M. poggii are 15,702 bp, 15,813 bp, and 15,626 bp in length, respectively, and their guanine-cytosine contents are 28%, 33%, and 36%, respectively. The 13 PCGs of D. emmerichi, E. curvispina, and M. poggii use ATN as the standard start codon and TAA, TAG, and T as the stop codons. The Bayesian inference and maximum likelihood phylogenetic analysis results based on the 13 PCGs and 13 PCGs + 2rRNAs datasets of the mitochondrial genomes of the Meloidae support Epicauta (Coleoptera: Meloidae) ([D. emmerichi, E. curvispina, E. ruficeps, E. aptera] + [E. chinensis, E. impressicornis, E. gorhami, E. tibialis]). We believe that this research enriches the literature on the mitochondrial genomics of Meloidae and serves as a foundation for the further study of the phylogenetic relationships and characterization of Meloidae and Coleoptera.

De novo transcriptome assemblies of Epicauta tibialis provide insights into the sexual dimorphism in the production of cantharidin

Blister beetles have medicinal uses for their defensive secretion cantharidin, which has curative effects on many cancers and other diseases. It was demonstrated that sexual dimorphism exists in the production of cantharidin between male and female adults. This study performed a de novo assembly of Epicauta tibialis transcriptomes and analyzed the differentially expressed genes (DEGs) between male and female adults to help to find genes and pathways associated with cantharidin biosynthesis. A total of 99,295,624 paired reads were generated, and more than 7 Gb transcriptome data for each sample were obtained after trimming. The clean data were used to de novo assemble and then cluster into 27,355 unigenes, with a mean length of 1442 bp and an N50 of 2725 bp. Of these, 14,314 (52.33%) unigenes were annotated by protein databases. Differential expression analysis identified 284 differentially expressed genes (DEGs) between male and female adults. Nearly 239 DEGs were up-regulated in male adults than in female adults, while 45 DEGs were down-regulated. The Kyoto Encyclopedia of Gene and Genomes pathway enrichment manifested that seven up-regulated DEGs in male adults were assigned to the terpenoid biosynthesis pathway, to which 19 unigenes were annotated. The DEGs in the terpenoid biosynthesis pathway between male and female adults may be responsible for the sexual dimorphism in cantharidin production. The up-regulated genes assigned to the pathway in male adults may play a significant role in cantharidin biosynthesis, and its biosynthesis process is probably via the mevalonate pathway. The results would be helpful to better understand and reveal the complicated mechanism of the cantharidin biosynthesis.

First Complete Mitochondrial Genome of Melyridae (Coleoptera, Cleroidea): Genome Description and Phylogenetic Implications

To explore the characteristics of the mitogenome of Melyridae and reveal phylogenetic relationships, the mitogenome of Cordylepherus sp. was sequenced and annotated. This is the first time a complete mitochondrial genome has beengenerated in this family. Consistent with previous observations of Cleroidea species, the mitogenome of Cordylepherus sp. is highly conserved in gene size, organization and codon usage, and secondary structures oftRNAs. All protein-coding genes(PCGs) initiate withthe standard start codon ATN,except ND1, which starts with TTG, and terminate with the complete stop codons of TAA and TAG, or incomplete forms, TA- and T-. MosttRNAs have the typical clover-leaf structure, except trnS1 (Ser, AGN), whose dihydrouridine (DHU) armis reduced. In the A+T-rich region, three types of tandem repeat sequence units are found, including a 115 bp sequence tandemly repeated twice, a 16 bp sequence tandemly repeated three timeswith a partial third repeat and a 10 bp sequence tandemly repeated seven times. Phylogenetic analyses based on 13 protein-coding genes by both Bayesian inference (BI) and maximum likelihood (ML) methods suggest that Melyridae sensu lato is polyphyletic, and Dasytinae and Malchiinae are supported as independent families.

Comparative analysis of the complete mitochondrial genomes of three rockfishes (Scorpaeniformes, Sebastiscus) and insights into the phylogenetic relationships of Sebastidae

Mitochondrial genome is a powerful molecule marker to provide information for phylogenetic relationships and revealing molecular evolution in ichthyological studies. Sebastiscus species, a marine rockfish, are of essential economic value. However, the taxonomic status and phylogenetic relationships of Sebastidae have been controversial so far. Here, the mitochondrial genomes (mitogenomes) of three species, S. tertius, S. albofasciatus, and S. marmoratus, were systemically investigated. The lengths of the mitogenomes' sequences of S. tertius, S. albofasciatus, and S. marmoratus were 16910, 17056, and 17580 bp, respectively. It contained 13 protein-coding genes (PCGs), two ribosomal RNAs (rRNAs), 22 transfer RNA (tRNA) genes, and one identical control region (D-loop) among the three species. The genetic distance and Ka/Ks ratio analyses indicated 13 PCGs were suffering purifying selection and the selection pressures were different from certain deep-sea fishes, which were most likely due to the difference in their living environment. The phylogenetic tree was constructed by Bayesian Inference (BI) and Maximum Likelihood (ML). Most interestingly, the results indicated that Sebastidae and Scorpaenidae were grouped into a separate branch, so the taxonomic status of Sebastidae should be classified into subfamily Sebastinae. Our results may lead to a taxonomic revision of Scorpaenoidei.

Phylogenetic relationship and characterization of the complete mitochondrial genome of Mylabris calida (Coleoptera:Meloidae)

Beetle genus Mylabris (Meloidae) was described by Fabricius (1775) and had been well known due to its relevance to traditional medicine (e.g., cantharidin production). Here, we sequenced and annotated the mitochondrial genome (mitogenome) of Mylabris calida, one of species within Mylabris. This mitogenome was 15,149 bp long and encoded 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs) and two ribosomal RNA unit genes (rRNAs). All 13 PCGs were initiated by the ATN (ATG, ATT and ATA) codon. All PCGs terminated with the stop codon TAA or TAG except for cox1, cox2, nad5 and nad4 which end with the incomplete codon T-. Phylogenetic analysis showed that M. calida got together with the same genus species Mylabris sp., M. aulica and three Hycleus species (H. cichorii, H. phaleratus and H. marcipoli), indicating Mylabris has a closer relationship with Hycleus than other genera within Meloidae.

Fourteen complete mitochondrial genomes of butterflies from the genus Lethe (Lepidoptera, Nymphalidae, Satyrinae) with mitogenome-based phylogenetic analysis

The mitochondrial genome (mitogenome) can help us understand the phylogenetic relationships within the genus Lethe and the subfamily Satyrinae. In this study, we sequenced the complete mitogenomes of 14 Lethe species, which range in size from 15,225 to 15,271 bp, with both 37 genes (13 PCGs, 22 tRNAs, 2 rRNAs) and a noncoding A + T-rich region. The gene arrangement and orientation is similar to typical mitogenomes of Lepidoptera. The Ka/Ks ratio shows that cox1 has the slowest evolutionary rate. The secondary structure of trnN lacks the Pseudouracil loop (TψC loop) in most Lethe species. The inferred phylogenetic analyses show that Lethe is a well-supported monophyletic group, and reveal 2 major clades within the genus Lethe, which is consistent with previous morphological classifications.

Characterization of the Complete Mitochondrial Genome of Epicauta impressicornis (Coleoptera: Meloidae) and Its Phylogenetic Implications for the Infraorder Cucujiformia

The complete mitochondrial genome (mitogenome) of Epicauta impressicornis Pic (Coleoptera: Meloidae) was determined. The circular genome is 15,713-bp long, and encodes 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a control region (CR). The 13 PCGs start with the typical ATN codon and terminate with the typical stop codon TAA (ND2, ND4L, ND6, ATP6, ATP8, and CYTB), TAG (ND1 and ND3), and T- (COX1, COX2, COX3, ND4, and ND5). The two rRNA genes (rrn12S and rrn16S) are encoded on the minority strand. All tRNAs genes except trnS1 (AGN) are predicted to fold into the typical cloverleaf structure. The longest overlap (10 bp) is observed between ATP8 and ATP6. CR mainly harbors a conserved poly-T stretch (15 bp), a short repeat unit (17 bp), some universal microsatellite-like repeats, and a canonical poly-A tail. Phylogenetic analysis using Bayesian inferences and maximum likelihood based on nucleotide and corresponding amino acid sequences of the 13 PCGs showed that E. impressicornis is closely related to E. chinensis, this relationship is and supported within Cucujiformia belonging to Meloidae (Tenebrionoidea). Our results further confirmed the monophyly of Tenebrionoidea, Lymexyloidea, Curculionoidea, Chrysomeloidea, Cucujoidea, Coccinelloidea, and Cleroidea within Cucujiformia, and revealed the sister relationships of (Cleroidea + Coccinelloidea), (Lymexyloidea + Tenebrionoidea), and ((Chrysomeloidea + Cucujoidea) + Curculionoidea). We believe that the complete mitogenome of E. impressicornis will contribute to further studies on molecular bases for the classification and phylogeny of Meloidae or even Cucujiformia.

Complete Mitogenome of a Leaf-Mining Buprestid Beetle, Trachys auricollis, and Its Phylogenetic Implications

A complete mitogenome of Trachys auricollis is reported, and a mitogenome-based phylogenetic tree of Elateriformia with all protein-coding genes (PCGs), rRNAs, and tRNAs is presented for the first time. The complete mitochondrial genome of T. auricollis is 16,429 bp in size and contains 13 PCGs, two rRNA genes, 22 tRNA genes, and an A + T-rich region. The A + T content of the entire genome is approximately 71.1%, and the AT skew and GC skew are 0.10 and -0.20, respectively. According to the the nonsynonymous substitution rate to synonymous substitution rates (Ka/Ks) of all PCGs, the highest and lowest evolutionary rates were observed for atp8 and cox1, respectively, which is a common finding among animals. The start codons of all PCGs are the typical ATN. Ten PCGs have complete stop codons, but three have incomplete stop codons with T or TA. As calculated based on the relative synonymous codon usage (RSCU) values, UUA(L) is the codon with the highest frequency. Except for trnS1, all 22 tRNA genes exhibit typical cloverleaf structures. The A + T-rich region of T. auricollis is located between rrnS and the trnI-trnG-trnM gene cluster, with six 72-bp tandem repeats. Both maximum likelihood (ML) and Bayesian (BI) trees suggest that Buprestoidea is close to Byrrhoidea and that Buprestoidea and Byrrhoidea are sister groups of Elateroidea, but the position of Psephenidae is undetermined. The inclusion of tRNAs might help to resolve the phylogeny of Coleoptera.

The complete mitochondrial genomes of five longicorn beetles (Coleoptera: Cerambycidae) and phylogenetic relationships within Cerambycidae

Cerambycidae is one of the most diversified groups within Coleoptera and includes nearly 35,000 known species. The relationships at the subfamily level within Cerambycidae have not been convincingly demonstrated and the gene rearrangement of mitochondrial genomes in Cerambycidae remains unclear due to the low numbers of sequenced mitogenomes. In the present study, we determined five complete mitogenomes of Cerambycidae and investigated the phylogenetic relationship among the subfamilies of Cerambycidae based on mitogenomes. The mitogenomic arrangement of all five species was identical to the ancestral Cerambycidae type without gene rearrangement. Remarkably, however, two large intergenic spacers were detected in the mitogenome of Pterolophia sp. ZJY-2019. The origins of these intergenic spacers could be explained by the slipped-strand mispairing and duplication/random loss models. A conserved motif was found between trnS2 and nad1 gene, which was proposed to be a binding site of a transcription termination peptide. Also, tandem repeat units were identified in the A + T-rich region of all five mitogenomes. The monophyly of Lamiinae and Prioninae was strongly supported by both MrBayes and RAxML analyses based on nucleotide datasets, whereas the Cerambycinae and Lepturinae were recovered as non-monophyletic.

The mitochondrial genomes of two walnut pests, Gastrolina depressa depressa and G. depressa thoracica (Coleoptera: Chrysomelidae), and phylogenetic analyses

In this study, the mitochondrial genomes (mitogenomes) of two walnut leaf insect pests, Gastrolina depressa depressa and G. depressa thoracica, were sequenced by Sanger sequencing technology. The mitogenome of G. depressa thoracica was complete at 16,109 bp in length, while the mitogenome of G. depressa depressa (14,277 bp) was partial. The genomic analyses indicated that both mitogenomes have the typical gene content and arrangement. The formerly identified elements, 'TAGTA' between trnSer(UCN) and nad2, and 'ATGATAA' between atp8 and atp6, were more conserved than that between nad4L and nad4, which was 'ATGTTAA' in Coleoptera excluding Polyphaga. Phylogenetic analyses of the 13 protein-coding genes from 36 coleopteran species well supported a close affinity between the subfamily Chrysomelinae including G. depressa thoracica and G. depressa depressa and Galerucinae, as well as a sister relationship of ((Eumolpinae + Cryptocephalinae) + Cassidinae) within Chrysomelidae.

Gene characteristics of the complete mitochondrial genomes of Paratoxodera polyacantha and Toxodera hauseri (Mantodea: Toxoderidae)

The family Toxoderidae (Mantodea) contains an ecologically diverse group of praying mantis species that have in common greatly elongated bodies. In this study, we sequenced and compared the complete mitochondrial genomes of two Toxoderidae species, Paratoxodera polyacantha and Toxodera hauseri, and compared their mitochondrial genome characteristics with another member of the Toxoderidae, Stenotoxodera porioni (KY689118). The lengths of the mitogenomes of T. hauseri and P. polyacantha were 15,616 bp and 15,999 bp, respectively, which is similar to that of S. porioni (15,846 bp). The size of each gene as well as the A+T-rich region and the A+T content of the whole genome were also very similar among the three species as were the protein-coding genes, the A+T content and the codon usages. The mitogenome of T. hauseri had the typical 22 tRNAs, whereas that of P. polyacantha had 26 tRNAs including an extra two copies of trnA-trnR. Intergenic regions of 67 bp and 76 bp were found in T. hauseri and P. polyacantha, respectively, between COX2 and trnK; these can be explained as residues of a tandem duplication/random loss of trnK and trnD. This non-coding region may be synapomorphic for Toxoderidae. In BI and ML analyses, the monophyly of Toxoderidae was supported and P. polyacantha was the sister clade to T. hauseri and S. porioni.

The complete mitochondrial genomes of hycleus cichorii and hycleus phaleratus (Coleoptera: Meloidae)

The Hycleus cichorii and Hycleus phaleratus are two species of medicinal meloids widely distributed in southwest of China. We sequenced an annotated the complete mitochondrial genomes of H. cichorii and H. phaleratus, and the mitogenomes are 15,847 and 16,004 bp in length, respectively. Every mitochondrial genome encodes 13 proteins, 2 ribosomal RNAs, 22 tRNAs, and a control region with the identical arrangement to other beetles. The preliminary phylogenetic analysis with mitochondrial genomes of nine meloid species further confirmed the status of these two species.

Dichotomius (Luederwaldtinia) schiffleri (Coleoptera: Scarabaeidae) mitochondrial genome and phylogenetic relationships within the superfamily Scarabaeoidea

The mitochondrial DNA of Dichotomius (Luederwaldtinia) schiffleri was characterized and its phylogenetic position was reconstructed in Scarabaeoidea. This mitogenome presented 14,802 bp-long, richness in AT of 77.4% and 37 genes, including 13 protein-coding, 22 transfer RNAs, and two ribosomal RNAs. In addition, it was observed intergenic spacers and reading frame overlaps. The phylogenetic trees reconstructed from protein sequences provided best resolution, indicating Scarabaeinae and Aphodiinae as a sister groups, as previously reported in other molecular phylogenies.

Mitochondrial genomes of blister beetles (Coleoptera, Meloidae) and two large intergenic spacers in Hycleus genera

BACKGROUND

Insect mitochondrial genomes (mitogenomes) exhibit high diversity in some lineages. The gene rearrangement and large intergenic spacer (IGS) have been reported in several Coleopteran species, although very little is known about mitogenomes of Meloidae.

RESULTS

We determined complete or nearly complete mitogenomes of seven meloid species. The circular genomes encode 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs) and two ribosomal RNAs (rRNAs), and contain a control region, with gene arrangement identical to the ancestral type for insects. The evolutionary rates of all PCGs indicate that their evolution is based on purifying selection. The comparison of tRNA secondary structures indicates diverse substitution patterns in Meloidae. Remarkably, all mitogenomes of the three studied Hycleus species contain two large intergenic spacers (IGSs). IGS1 is located between trnW and trnC, including a 9 bp consensus motif. IGS2 is located between trnS2 (UCN) and nad1, containing discontinuous repeats of a pentanucleotide motif and two 18-bp repeat units in both ends. To date, IGS2 is found only in genera Hycleus across all published Coleopteran mitogenomes. The duplication/random loss model and slipped-strand mispairing are proposed as evolutionary mechanisms for the two IGSs (IGS1, IGS2). The phylogenetic analyses using MrBayes, RAxML, and PhyloBayes methods based on nucleotide and amino acid datasets of 13 PCGs from all published mitogenomes of Tenebrionoids, consistently recover the monophylies of Meloidae and Tenebrionidae. Within Meloidae, the genus Lytta clusters with Epicauta rather than with Mylabris. Although data collected thus far could not resolve the phylogenetic relationships within Meloidae, this study will assist in future mapping of the Meloidae phylogeny.

CONCLUSIONS

This study presents mitogenomes of seven meloid beetles. New mitogenomes retain the genomic architecture of the Coleopteran ancestor, but contain two IGSs in the three studied Hycleus species. Comparative analyses of two IGSs suggest that their evolutionary mechanisms are duplication/random loss model and slipped-strand mispairing.

Complete mitochondrial genomes of two blattid cockroaches, Periplaneta australasiae and Neostylopyga rhombifolia, and phylogenetic relationships within the Blattaria

Complete mitochondrial genomes (mitogenomes) of two cockroach species, Periplaneta australasiae and Neostylopyga rhombifolia, 15,605 bp and 15,711 bp in length, respectively, were determined. As reported for other cockroach mitogenomes, the two mitogenomes possessed typical ancestral insect mitogenome gene composition and arrangement. Only several small intergenic spacers were found: one, which was common in all sequenced cockroach mitogenomes except for the genus Cryptocercus, was between tRNA-Ser (UCN) and ND1 and contained a 7bp highly conserved motif (WACTTAA). Three different types of short tandem repeats in the N. rhombifolia control region (CR) were observed. The homologous alignments of these tandem repeats with other six cockroach mitogenome CRs revealed a low similarity. Three conserved sequence blocks (CSB) were detected in both cockroach mitochondrial CRs. CSB1 was specific for blattinine mitogenomes and was highly conserved with 95% similarity, speculating that this block was a possible molecular synapomorphy for this subfamily. CSB3 located nearby downstream of CSB1 and has more variations within blattinine mitogenomes compared with CSB1. The CSB3 was capable of forming stable stem-loop structure with a small T-stretch in the loop portion. We assessed the influence of four datasets and two inference methods on topology within Orthopteroidea. All genes excluding the third codon positions of PCGs could generate more stable topology, and higher posterior probabilities than bootstrap values were presented at some branch nodes. The phylogenetic analysis with different datasets and analytical methods supported the monophyly of Dictyoptera and supported strongly the proposal that Isoptera should be classified as a family (Termitidae) of the Blattaria. Specifically, Shelfordella lateralis was inserted in the clade Periplaneta. Considering the K2P genetic distance, morphological characters, and the phylogenetic trees, we suggested that S. lateralis should be placed in the genus Periplaneta.

New Mitogenomes of Two Chinese Stag Beetles (Coleoptera, Lucanidae) and Their Implications for Systematics

Although conspicuous and well-studied, stag beetles have been slow to join the genomic era. In this study, mitochondrial genomes of two stag beetles, Sinodendron yunnanense and Prosopocoilus confucius, are sequenced for the first time. Both of their genomes consisted of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNAs (rRNAs), and a control region. The mitogenome of S. yunnanense was 16,921 bp in length, and P. confucius was 16,951 bp. The location of the gene trnL(UUR), between the A + T-rich and control region in S. yunnanense, is the first observed in Lucanidae. In P. confucius, an unexpected noncoding region of 580 bp was discovered. Maximum likelihood and Bayesian inference on the 13 mitochondrial PCGs were used to infer the phylogenetic relationships among 12 representative stag beetles and three scarab beetles. The topology of the two phylogenetic trees was almost identical: S. yunnanense was recovered as the most basal Lucanid, and the genus Prosopocoilus was polyphyletic due to P. gracilis being recovered sister to the genera Dorcus and Hemisodorcus. The phylogenetic results, genetic distances and mitogenomic characteristics call into question the cohesion of the genus Prosopocoilus. The genetic resources and findings herein attempts to redress understudied systematics and mitogenomics of the stag beetles.