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Extreme weather poses huge challenges for animals that must adapt to wide variations in environmental temperature and, in many cases, it can lead to the local extirpation of populations or even the extinction of an entire species. Previous studies have found that one element of amphibian adaptation to environmental stress involves changes in mitochondrial gene expression at low temperatures. However, to date, comparative studies of gene expression in organisms living at extreme temperatures have focused mainly on nuclear genes. This study sequenced the complete mitochondrial genomes of five Asian hylid frog species: Dryophytes japonicus, D. immaculata, Hyla annectans, H. chinensis and H. zhaopingensis. It compared the phylogenetic relationships within the Hylidae family and explored the association between mitochondrial gene expression and evolutionary adaptations to cold stress. The present results showed that in D. immaculata, transcript levels of 12 out of 13 mitochondria genes were significantly reduced under cold exposure (p < 0.05); hence, we put forward the conjecture that D. immaculata adapts by entering a hibernation state at low temperature. In H. annectans, the transcripts of 10 genes (ND1, ND2, ND3, ND4, ND4L, ND5, ND6, COX1, COX2 and ATP8) were significantly reduced in response to cold exposure, and five mitochondrial genes in H. chinensis (ND1, ND2, ND3, ND4L and ATP6) also showed significantly reduced expression and transcript levels under cold conditions. By contrast, transcript levels of ND2 and ATP6 in H. zhaopingensis were significantly increased at low temperatures, possibly related to the narrow distribution of this species primarily at low latitudes. Indeed, H. zhaopingensis has little ability to adapt to low temperature (4 °C), or maybe to enter into hibernation, and it shows metabolic disorder in the cold. The present study demonstrates that the regulatory trend of mitochondrial gene expression in amphibians is correlated with their ability to adapt to variable climates in extreme environments. These results can predict which species are more likely to undergo extirpation or extinction with climate change and, thereby, provide new ideas for the study of species extinction in highly variable winter climates. [ABSTRACT FROM AUTHOR]

Simple Summary: As one of the burrowing mayfly groups with large mandibular tusks, the phylogenetic relationships within Potamanthidae are always controversial. There are at least two opposite hypotheses for mayfly grouping: Potamanthidae + (Ephemeridae + Polymitarcyidae) and (Potamanthidae + Ephemeridae) + Polymitarcyidae. Because of the indeterminate origin time of this group, the present study aimed to reconstruct the phylogenetic relationship and explore the origin time of Potamanthidae based on mitochondrial (mt) genomes. In addition, the protein-coding genes (PCGs) of these mt genomes may undergo positive selection when these species live in low-temperature environments. Potamanthidae belongs to the superfamily Ephemeroidea but has no complete mt genome released in the NCBI (except for two unchecked and one partial mt genome). Since the sister clade to Potamanthidae has always been controversial, we sequenced seven mt genomes of Potamanthidae (two species from Rhoenanthus and five species from Potamanthus) in order to rebuild the phylogenetic relationships of Potamanthidae in this study. The divergence time of Potamanthidae was also investigated by utilizing five fossil calibration points because of the indeterminate origin time. In addition, because Rhoenanthus coreanus and Potamanthus luteus are always in low-temperature environments, we aimed to explore whether these two species were under positive selection at the mt genome level. Amongst the 13 PCGs, CGA was used as the start codon in COX1, whereas other genes conformed to initiating with an ATN start codon. From this analysis, UUA (L), AUU (I), and UUU (F) had the highest usage. Furthermore, the DHU arm was absent in the secondary structure of S1 in all species. By combining the 13 PCGs and 2 rRNAs, we reconstructed the phylogenetic relationship of Potamanthidae within Ephemeroptera. The monophyly of Potamanthidae and the monophyly of Rhoenanthus and Potamanthus were supported in the results. The phylogenetic relationship of Potamanthidae + (Ephemeridae + Polymitarcyidae) was also recovered with a high prior probability. The divergence times of Potamanthidae were traced to be 90.44 Mya (95% HPD, 62.80–121.74 Mya), and the divergence times of Rhoenanthus and Potamanthus originated at approximately 64.77 Mya (95% HPD, 43.82–88.68 Mya), thus belonging to the late Pliocene Epoch or early Miocene Epoch. In addition, the data indicated that R. coreanus was under negative selection and that ATP8 and ND2 in Potamanthidae had a high evolutionary rate. [ABSTRACT FROM AUTHOR]

Simple Summary: Lamiinae is the largest subfamily among the Cerambycidae (longhorn beetles), and its members are distributed worldwide. The monophyly of Lamiinae is generally recognized, but there are still diverse ideas as to whether the tribes belonging to Lamiinae are monophylic. Ambiguous classification boundaries and the existence of synonyms are major issues leading to controversies over Lamiinae classification. It is not enough to conduct research solely on the morphological characteristics and simple molecular loci of longhorn beetles. Mitochondrial genomes have proven to be reliable markers and can shed more light on phylogenetic relationships among Lamiinae. The present study resolved infra-subfamilial relationships among Lamiinae and provides more mitochondrial data for further phylogenetic research on longhorn beetles. Lamiinae is the largest subfamily of the Cerambycidae (longhorn beetles), with approximately 21,863 described species. Previous phylogenetic studies of Lamiinae showed that this subfamily was monophyletic, but the relationship between the tribes of Lamiinae is still controversial. Partial molecular data and species morphological characteristics are not sufficient to resolve species phylogenetic studies perfectly. At the same time, the full mitochondrial genome contains more comprehensive genetic data. Benefiting from the development of next-generation sequencing (NGS), mitochondrial genomes can be easily acquired and used as reliable molecular markers to investigate phylogenetic relationships within Cerambycidae. Using NGS technology, we obtained 11 mitochondrial genome sequences of Lamiinae species. Based on this newly generated mitochondrial genome dataset matrix, we reconstructed the phylogeny of Lamiinae. The Bayesian Inference and Maximum Likelihood analyses strongly support the monophyly of four tribes (Lamiini, Batocerini, Mesosini, and Saperdini), whereas the tribe Acanthocinini was identified as paraphyletic. Other mitochondrial structural features were also observed: the start codon in the nad1 gene of all 11 mitochondrial genomes is TTG; 17–22 bp intergenic spacers (IGS) with a 'TACTA' motif were found between trnS2 and nad1. Moreover, two long IGS were found in Mesosa myops and Batocera sp. Tandem repeats were found in the IGS of Batocera sp. [ABSTRACT FROM AUTHOR]

Simple Summary: The tropical and subtropical paddy frog, Fejervarya kawamurai (Anura: Dicroglossidae), is a common and widespread species in Asia. Amphibians can adapt to small changes in climate, but extreme temperature changes can lead to metabolic abnormalities affecting numerous cell functions. Damage or disruption of mitochondrial respiratory chain complexes can be lethal. The present study characterizes the mitochondrial genome of F. kawamurai to evaluate its evolutionary relationship within Dicroglossidae and to analyze the effects of extreme temperature change on mitochondrial gene expression of proteins involved in oxidative phosphorylation. Unusual climates can lead to extreme temperatures. Fejervarya kawamurai, one of the most prevalent anurans in the paddy fields of tropical and subtropical regions in Asia, is sensitive to climate change. The present study focuses primarily on a single question: how do the 13 mitochondrial protein-coding genes (PCGs) respond to extreme temperature change compared with 25 °C controls? Thirty-eight genes including an extra tRNA-Met gene were identified and sequenced from the mitochondrial genome of F. kawamurai. Evolutionary relationships were assessed within the Dicroglossidae and showed that Dicroglossinae is monophyletic and F. kawamurai is a sister group to the clade of (F. multistriata + F. limnocharis). Transcript levels of mitochondrial genes in liver were also evaluated to assess responses to 24 h exposure to low (2 °C and 4 °C) or high (40 °C) temperatures. Under 2 °C, seven genes showed significant changes in liver transcript levels, among which transcript levels of ATP8, ND1, ND2, ND3, ND4, and Cytb increased, respectively, and ND5 decreased. However, exposure to 4 °C for 24 h was very different in that the expressions of ten mitochondrial protein-coding genes, except ND1, ND3, and Cytb, were significantly downregulated. Among them, the transcript level of ND5 was most significantly downregulated, decreasing by 0.28-fold. Exposure to a hot environment at 40 °C for 24 h resulted in a marked difference in transcript responses with strong upregulation of eight genes, ranging from a 1.52-fold increase in ND4L to a 2.18-fold rise in Cytb transcript levels, although COI and ND5 were reduced to 0.56 and 0.67, respectively, compared with the controls. Overall, these results suggest that at 4 °C, F. kawamurai appears to have entered a hypometabolic state of hibernation, whereas its mitochondrial oxidative phosphorylation was affected at both 2 °C and 40 °C. The majority of mitochondrial PCGs exhibited substantial changes at all three temperatures, indicating that frogs such as F. kawamurai that inhabit tropical or subtropical regions are susceptible to ambient temperature changes and can quickly employ compensating adjustments to proteins involved in the mitochondrial electron transport chain. [ABSTRACT FROM AUTHOR]

Simple Summary: The spot-legged treefrog Polypedates megacephalus (Anura: Rhacophoridae) is widely distributed in Asia. In previous studies, it has been noted that the mitochondrial gene ATP8 has not been confidently annotated in any sequenced Polypedates to date. Duplications of control regions (CRs) are often observed in the tree frog family Rhacophoridae, and in most cases the copied CRs are highly similar to one another. This feature may lead to sequence assembly errors. Our findings are the first to detect two copies of the ND5 genes and three copies of the CRs in P. megacephalus by employing a "primer bridging" approach and allude to the presence of ATP8 via bioinformatic analyses and RT-qPCR. However, the question of whether the ATP8 is functional needs to be addressed in future studies. In prior research on the mitochondrial genome (mitogenome) of Polypedates megacephalus, the one copy of ND5 gene was translocated to the control region (CR) and the ATP8 gene was not found. Gene loss is uncommon among vertebrates. However, in this study, we resequenced the mitogenomes of P. megacephalus from different regions using a "primer bridging" approach with Sanger sequencing technologies, which revealed the "missing" ATP8 gene in P. megacephalus as well as three other previously published Polypedates. The mitogenome of this species was found to contain two copies of the ND5 genes and three copies of the control regions. Furthermore, multiple tandem repeats were identified in the control regions. Notably, we observed that there was no correlation between genetic divergence and geographic distance. However, using the mitogenome, gene expression analysis was performed via RT-qPCR of liver samples and it was thus determined that COIII, ND2, ND4, and ND6 were reduced to 0.64 ± 0.24, 0.55 ± 0.34, 0.44 ± 0.21 and 0.65 ± 0.17, respectively, under low-temperature stress (8 °C) as compared with controls (p < 0.05). Remarkably, the transcript of long non-coding RNA (lncRNA) between positions 8029 and 8612 decreased significantly with exposure to low-temperature stress (8 °C). Antisense ND6 gene expression showed a downward trend, but this was not significant. These results reveal that modulations of protein-coding mitochondrial genes and lncRNAs of P. megacephalus play a crucial role in the molecular response to cold stress. [ABSTRACT FROM AUTHOR]

Simple Summary: Hylidae is a rich family of Anura that is widely distributed across the world. Previous studies have shown that the Hyla and Dryophytos genera in the Hylidae used to belong to the same genus. The Eurasian species (including Hyla sanchiangensis) originated in North America and spread through the Beringian Land Bridge to Asia during the last ice age. Adaptation to low temperatures may require more energy expenditure. Mitochondria are the center of energy metabolism and, through oxidative phosphorylation, provide most of the ATP energy for the physiological and biochemical activities of the body. The mitogenome was used to investigate whether Hyla and Dryophytos genera are subject to positive selection. In addition, as a unique species in China, the distinction between Hyla sanchiangensis (Anura: Hylidae) and two different sites was also compared and analyzed in this paper. Hyla sanchiangensis (Anura: Hylidae) is endemic to China and is distributed across Anhui, Zhejiang, Fujian, Guangdong, Guangxi, Hunan, and Guizhou provinces. The mitogenomes of H. sanchiangensis from two different sites (Jinxiu, Guangxi, and Wencheng, Zhejiang) were sequenced. Phylogenetic analyses were conducted, including 38 mitogenomes of Hylidae from the NCBI database, and assessed the phylogenetic relationship of H. sanchiangensis within the analyzed dataset. Two mitogenomes of H. sanchiangensis showed the typical mitochondrial gene arrangement with 13 protein-coding genes (PCGs), two ribosomal RNA genes (12S rRNA and 16S rRNA), 22 transfer RNA (tRNA) genes, and one non-coding control region (D-loop). The lengths of the 12S rRNA and 16S rRNA genes from both samples (Jinxiu and Wencheng) were 933 bp and 1604 bp, respectively. The genetic distance (p-distance transformed into percent) on the basis of the mitogenomes (excluding the control region) of the two samples was calculated as 4.4%. Hyla sanchiangensis showed a close phylogenetic relationship with the clade of (H. annectans + H. tsinlingensis), which was supported by ML and BI analyses. In the branch-site model, five positive selection sites were found in the clade of Hyla and Dryophytes: Cytb protein (at position 316), ND3 protein (at position 85), and ND5 protein (at position 400) have one site, respectively, and two sites in ND4 protein (at positions 47 and 200). Based on the results, we hypothesized that the positive selection of Hyla and Dryophytes was due to their experience of cold stress in historical events, but more evidence is needed to support this conclusion. [ABSTRACT FROM AUTHOR]

In this study, the mitochondrial (mt) genomes of Siphluriscus chinensis (Ephemeroptera: Siphluriscidae) were evaluated in specimens collected from two sites in China: Niutou Mountain, Zhejiang Province (S. chinensis NTS) and Leigong Mountain, Guizhou Province (S. chinensis LGS) and were successfully sequenced. The lengths of the mt genomes of S. chinensis NTS and S. chinensis LGS were 15,904 bp (ON729390) and 15,212 bp (ON729391), respectively. However, an in-depth comparison of the two mt genomes showed significant differences between the specimens collected from the two sites. A detailed analysis of the genetic distance between S. chinensis NTS and S. chinensis LGS was undertaken to further achieve an accurate delimitation of S. chinensis. The genetic distance between S. chinensis NTS and the other three species within Siphluriscidae was a high value, above 12.2%. The two mt genomes were used to reconstruct phylogenetic relationships and estimate divergence time. The results demonstrated robust differences between S. chinensis NTS and S. chinensis LGS, which revealed that a kind of cryptic species existed. Maximum likelihood (ML) and Bayesian inference (BI) analyses produced well-supported phylogenetic trees that showed evolutionary relationships between Siphluriscidae (((S. chinensis HQ875717 + S. chinensis MF352165) + S. chinensis LGS) + S. chinensis NTS). The most recent common ancestor (MRCA) of four species within Siphluriscidae began to diversify during the Neogene [11.80 million years ago (Mya); 95% highest posterior densities (HPD) = 6.17–19.28 Mya], and S. chinensis NTS was first to diverge from the branches of S. chinensis LGS. In short, based on mitochondrial genomes, our results showed that the specimens collected from Leigong Mountain, Guizhou Province (S. chinensis LGS) belonged to S. chinensis, and the specimens collected from Niutou Mountain, Zhejiang Province (S. chinensis NTS) were a cryptic species of S. chinensis. [ABSTRACT FROM AUTHOR]

Simple Summary: Skinks are the most species-rich group of lizards and are widely distributed around the world. The family Scincidae (Reptilia: Lacertiformes) includes limbed and limbless representatives occupying diverse habitats and showing a range of morphologies. Both limbed and limbless skinks have unique locomotion patterns in their habitats. Locomotion is the process of energy consumption, of which different modes may have different energy demands. As the center of energy metabolism in organisms, mitochondria provide most of the energy for physiological and biochemical activities via oxidative phosphorylation. Here, we employed mitochondrial genomes to investigate potential selective pressures among limbless skinks. Isopachys gyldenstolpei, as a typical limbless skink, has a different locomotion pattern compared to a limbed skink. Thus, I. gyldenstolpei can be used to study whether limb loss has a positive selection on mitochondrial genes. Two typical limbed skinks, Sphenomorphus indicus and Tropidophorus hainanus, were included in this study to compare the selective pressure analysis on mitochondrial genomes. In addition, the phylogenetic relationships within Scincidae are also discussed. In order to adapt to diverse habitats, organisms often evolve corresponding adaptive mechanisms to cope with their survival needs. The species-rich family of Scincidae contains both limbed and limbless species, which differ fundamentally in their locomotor demands, such as relying on the movement of limbs or only body swing to move. Locomotion requires energy, and different types of locomotion have their own energy requirements. Mitochondria are the energy factories of living things, which provide a lot of energy for various physiological activities of organisms. Therefore, mitochondrial genomes could be tools to explore whether the limb loss of skinks are selected by adaptive evolution. Isopachys gyldenstolpei is a typical limbless skink. Here, we report the complete mitochondrial genomes of I. gyldenstolpei, Sphenomorphus indicus, and Tropidophorus hainanus. The latter two species were included as limbed comparator species to the limbless I. gyldenstolpei. The results showed that the full lengths of the mitochondrial genomes of I. gyldenstolpei, S. indicus, and T. hainanus were 17,210, 16,944, and 17,001 bp, respectively. Three mitochondrial genomes have typical circular double-stranded structures similar to other reptiles, including 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and the control region. Three mitochondrial genomes obtained in this study were combined with fifteen mitochondrially complete genomes of Scincidae in the NCBI database; the phylogenetic relationship between limbless I. gyldenstolpei and limbed skinks (S. indicus and T. hainanus) is discussed. Through BI and ML trees, Sphenomorphinae and Mabuyinae were monophyletic, while the paraphyly of Scincinae was also recovered. The limbless skink I. gyldenstolpei is closer to the species of Tropidophorus, which has formed a sister group with (T. hainanus + T. hangman). In the mitochondrial genome adaptations between limbless I. gyldenstolpei and limbed skinks, one positively selected site was found in the branch-site model analysis, which was located in ND2 (at position 28, BEB value = 0.907). Through analyzing the protein structure and function of the selected site, we found it was distributed in mitochondrial protein complex I. Positive selection of some mitochondrial genes in limbless skinks may be related to the requirement of energy to fit in their locomotion. Further research is still needed to confirm this conclusion though. [ABSTRACT FROM AUTHOR]

Simple Summary: The sequencing of mitochondrial genomes promotes the study of cryptic species and the phylogenetic relationship of species. Thus far, only one complete mitochondrial genome of Scutigeromorpha is available in the NCBI. In this study, four specimens of Thereuonema tuberculata (Scutigeromorpha: Scutigeridae), collected from four different localities of China, were identified, and the four mitochondrial genomes of those were sequenced and annotated. Based on the gene organization and genetic diversity of the mitochondrial genomes, we hypothesized that cryptic species could exist in T. tuberculata. We further constructed BI and ML phylogenetic trees to reveal the relationship of Scutigeromorpha. Based on morphological characteristics to make species identification, the cryptic species of the Scutigeromorpha can be greatly underestimated. The mitochondrial genome provides a desirable tool for the biological identifications and the discovery of the cryptic species. The capacity to acquire mitochondrial genome sequences has substantially improved in recent years using next-generation sequencing (NGS) technology. On the basis of the next-generation sequencing, we obtained four complete mitochondrial genomes of Thereuonema tuberculata (Wood, 1862) from Nanyang, Henan Province (NY), Nanchang, Jiangxi Province (NC), Jinan, Shandong Province (JN), and Dali, Yunnan Province (DL) in China with GenBank numbers OK513221, OL449685, ON058988 and ON058989, respectively. The lengths of the four mitochondrial genomes ranged from 14,903 to 14,909 bp. The composition and order of genes of the four mitochondrial genomes were identical to the published mitochondrial genome of Scutigera coleoptrata (Linnaeus, 1758) (Scutigeromorpha: Scutigerdae). It was the first time that the tandem repeats in the control region were detected in Scutigeromorpha. We also calculated the corrected pairwise genetic distance of four complete mitochondrial genomes of T. tuberculata, ranging from 7.7 to 15.2%. The results showed that the T.tuberculata NC belonged to the typical sample of T. tuberculata, and T. tuberculata DL was hypothesized as a cryptic species of T. tuberculata. Meanwhile, T. tuberculata NY and T. tuberculata JN were hypothesized as potential cryptic species of T. tuberculata in this study. In both BI and ML trees, the monophyly of Scutigeromorpha, Scolopendromorpha, Geophilomorpha, and Lithobiomorpha was forcefully advocated. Moreover, Scutigeromorpha was recovered as the sister clade of (Scolopendromorpha + (Lithobiomorpha + Geophilomorpha)). Four specimens of T. tuberculata were clustered into one clade, which was the sister to the clade of S. coleoptrata. [ABSTRACT FROM AUTHOR]

Simple Summary: Mantodea is regarded as an excellent material to study the gene rearrangements and large non-coding regions (LNCRs) in mitochondrial genomes. Meanwhile, as a result of the convergent evolution and parallelism, the gene rearrangements and LNCRs are specific to some taxonomic groups within Mantodea, which play an important role in phylogenetic relationship research. Nine mitochondrial genomes (mitogenomes) from four newly established families of praying mantises are obtained and annotated. Eight types of gene rearrangements, including four novel types of gene rearrangements in Mantodea, are detected, which can be explained by the tandem replication-random loss (TDRL) model. Moreover, one conserved motif between trnI-trnQ is detected in Toxoderidae. This study shed light on the formation mechanisms of these gene rearrangements and LNCRs in four newly established families of praying mantises. Long non-coding regions (NCRs) and gene rearrangements are commonly seen in mitochondrial genomes of Mantodea and are primarily focused on three regions: CR-I-Q-M-ND2, COX2-K-D-ATP8, and ND3-A-R-N-S-E-F-ND5. In this study, eight complete and one nearly complete mitochondrial genomes of praying mantises were acquired for the purpose of discussing mitochondrial gene rearrangements and phylogenetic relationships within Mantodea, primarily in the newly established families Haaniidae and Gonypetidae. Except for Heterochaeta sp. JZ-2017, novel mitochondrial gene arrangements were detected in Cheddikulama straminea, Sinomiopteryx graham, Pseudovates chlorophaea, Spilomantis occipitalis. Of note is the fact that one type of novel arrangement was detected for the first time in the Cyt b-S2-ND1 region. This could be reliably explained by the tandem replication-random loss (TDRL) model. The long NCR between trnT and trnP was generally found in Iridopteryginae and was similar to the ND4L or ND6 gene. Combined with gene rearrangements and intergenic regions, the monophyly of Haaniidae was supported, whereas the paraphyly of Gonypetidae was recovered. Furthermore, several synapomorphies unique to some clades were detected that conserved block sequences between trnI and trnQ and gaps between trnT and trnP in Toxoderidae and Iridopteryginae, respectively. [ABSTRACT FROM AUTHOR]

Simple Summary: The family Vietnamellidae (Ephemeroptera) is one of the oldest insect families in the world. However, there are still controversies about the phylogenetic relationships among Vietnamellidae, Ephemerellidae, and Teloganodidae. The mitochondrial (mt) genome can be used to discuss phylogenetic relationships and cryptic species. We sequenced and annotated three complete mt genomes of Vietnamella sinensis from three different populations, identifying a cryptic species of V. sinensis and discuss the phylogenetic relationships of Vietnamellidae. Based on the genetic distance of the whole mt genomes, the phylogenetic relationship of three populations was uncovered and the divergence time of V. sinensis QY indicated that it was a cryptic species of V. sinensis. Ephemeroptera (Insecta: Pterygota) are widely distributed all over the world with more than 3500 species. During the last decade, the phylogenetic relationships within Ephemeroptera have been a hot topic of research, especially regarding the phylogenetic relationships among Vietnamellidae. In this study, three mitochondrial genomes from three populations of Vienamella sinensis collected from Tonglu (V. sinensis TL), Chun'an (V. sinensis CN), and Qingyuan (V. sinensis QY) in Zhejiang Province, China were compared to discuss the potential existence of cryptic species. We also established their phylogenetic relationship by combining the mt genomes of 69 Ephemeroptera downloaded from NCBI. The mt genomes of V. sinensis TL, V. sinensis CN, and V. sinensis QY showed the same gene arrangement with lengths of 15,674 bp, 15,674 bp, and 15,610 bp, respectively. Comprehensive analyses of these three mt genomes revealed significant differences in mt genome organization, genetic distance, and divergence time. Our results showed that the specimens collected from Chun'an and Tonglu in Zhejiang Province, China belonged to V. sinensis, and the specimens collected from Qingyuan, Zhejiang Province, China were a cryptic species of V. sinensis. In maximum likelihood (ML) and Bayesian inference (BI) phylogenetic trees, the monophyly of the family Vietnamellidae was supported and Vietnamellidae has a close relationship with Ephemerellidae. [ABSTRACT FROM AUTHOR]

Simple Summary: The family Scarabaeidae is one of the largest families in the insect order Coleoptera and is comprised of two quasi-systematics groups, Pleurosticti and Laparosticti. Pleurosticti is an economically important scarab group comprising about 20,000 species, the majority of which are phytophagous. Despite the innumerable studies based on ecological, molecular, and morphological characteristics, their taxonomy is still unclear and subject to many scientific hypotheses. The mitochondrial (mt) genome can provide tangible information to resolve the phylogenetic relationships within the family Scarabaeidae. However, the available mt genomes of Scarabaeidae in GenBank are underrepresented. Thus, we sequenced and analyzed 18 new phytophagous Scarabaeidae mitochondrial genomes from two subfamilies, Cetoniinae and Dynastinae, to conduct phylogenetic analyses within Scarabaeidae. This study contributes to increasing our knowledge about phytophagous Scarabaeidae. The availability of next-generation sequencing (NGS) in recent years has facilitated a revolution in the availability of mitochondrial (mt) genome sequences. The mt genome is a powerful tool for comparative studies and resolving the phylogenetic relationships among insect lineages. The mt genomes of phytophagous scarabs of the subfamilies Cetoniinae and Dynastinae were under-represented in GenBank. Previous research found that the subfamily Rutelinae was recovered as a paraphyletic group because the few representatives of the subfamily Dynastinae clustered into Rutelinae, but the subfamily position of Dynastinae was still unclear. In the present study, we sequenced 18 mt genomes from Dynastinae and Cetoniinae using next-generation sequencing (NGS) to re-assess the phylogenetic relationships within Scarabaeidae. All sequenced mt genomes contained 37 sets of genes (13 protein-coding genes, 22 tRNAs, and two ribosomal RNAs), with one long control region, but the gene order was not the same between Cetoniinae and Dynastinae species. All mt genomes of Dynastinae species showed the same gene rearrangement of trnQ-NCR-trnI-trnM, whereas all mt genomes of Cetoniinae species showed the ancestral insect gene order of trnI-trnQ-trnM. Phylogenetic analyses (IQ-tree and MrBayes) were conducted using 13 protein-coding genes based on nucleotide and amino acid datasets. In the ML and BI trees, we recovered the monophyly of Rutelinae, Cetoniinae, Dynastinae, and Sericinae, and the non-monophyly of Melolonthinae. Cetoniinae was shown to be a sister clade to (Dynastinae + Rutelinae). [ABSTRACT FROM AUTHOR]

Simple Summary: Bristletails (Insecta: Microcoryphia) are primarily wingless insects, some of which have been found to exhibit parthenogenesis. In the genus Coreamachilis, parthenogenesis occurs in C. coreanus, whereas sexual reproduction is found in C. songi. Therefore, after obtaining mitochondrial genome sequences of these two species, we analyzed their selection pressure, based on phylogenetic trees of Microcoryphia. However, no positive selection was found in the mitochondrial protein coding genes of either C. coreanus or C. songi. In addition, a long hairpin structure was found between ND1 and 16S rRNA genes in Machilinae and Petrobiinae, which was highly consistent with the phylogenetic results. The order Microcoryphia, commonly known as bristletails, is considered as the most primitive one among living insects. Within this order, two species, Coreamachilis coreanus and C. songi (Machilidae: Machilinae), display the following contrasting reproductive strategies: parthenogenesis occurs in C. coreanus, whereas sexual reproduction is found in C. songi. In the present study, the complete mitogenomes of C. coreanus and C. songi were sequenced to compare their mitogenome structure, analyze relationships within the Microcoryphia, and assess adaptive evolution. The length of the mitogenomes of C. coreanus and C. songi were 15,578 bp and 15,570 bp, respectively, and the gene orders were those of typical insects. A long hairpin structure was found between the ND1 and 16S rRNA genes of both species that seem to be characteristic of Machilinae and Petrobiinae species. Phylogenetic assessment of Coreamachilis was conducted using BI and ML analyses with concatenated nucleotide sequences of the 13 protein-coding genes. The results showed that the monophyly of Machilidae, Machilinae, and Petrobiinae was not supported. The genus Coreamachilis (C. coreanus and C. songi) was a sister clade to Allopsontus helanensis, and then the clade of ((C. coreanus + C. songi) + A. helanensis) was a sister clade to A. baii, which suggests that the monophyly of Allopsontus was not supported. Positive selection analysis of the 13 protein-coding genes failed to reveal any positive selection in C. coreanus or C. songi. The long hairpin structures found in Machilinae and Petrobiinae were highly consistent with the phylogenetic results and could potentially be used as an additional molecular characteristic to further discuss relationships within the Microcoryphia. [ABSTRACT FROM AUTHOR]

Simple Summary: Twenty-seven complete mitochondrial genomes of Phasmatodea have been published in the NCBI. To shed light on the intra-ordinal and inter-ordinal relationships among Phasmatodea, more mitochondrial genomes of stick insects are used to explore mitogenome structures and clarify the disputes regarding the phylogenetic relationships among Phasmatodea. We sequence and annotate the first acquired complete mitochondrial genome from the family Pseudophasmatidae (Peruphasma schultei), the first reported mitochondrial genome from the genus Phryganistria of Phasmatidae (P. guangxiensis), and the complete mitochondrial genome of Orestes guangxiensis belonging to the family Heteropterygidae. We analyze the gene composition and the structure of the three mitochondrial genomes. We recover the monophyly of Phasmatodea and show the sister-group relationship between Phasmatodea and Mantophasmatodea after removal of the Embioptera and Zoraptera species. We recover the monophyly of Heteropterygidae and the paraphyly of Diapheromeridae, Phasmatidae, Lonchodidae, Lonchodinae, and Clitumninae. Insects of the order Phasmatodea are mainly distributed in the tropics and subtropics and are best known for their remarkable camouflage as plants. In this study, we sequenced three complete mitochondrial genomes from three different families: Orestes guangxiensis, Peruphasma schultei, and Phryganistria guangxiensis. The lengths of the three mitochondrial genomes were 15,896 bp, 16,869 bp, and 17,005 bp, respectively, and the gene composition and structure of the three stick insects were identical to those of the most recent common ancestor of insects. The phylogenetic relationships among stick insects have been chaotic for a long time. In order to discuss the intra- and inter-ordinal relationship of Phasmatodea, we used the 13 protein-coding genes (PCGs) of 85 species for maximum likelihood (ML) and Bayesian inference (BI) analyses. Results showed that the internal topological structure of Phasmatodea had a few differences in both ML and BI trees and long-branch attraction (LBA) appeared between Embioptera and Zoraptera, which led to a non-monophyletic Phasmatodea. Consequently, after removal of the Embioptera and Zoraptera species, we re-performed ML and BI analyses with the remaining 81 species, which showed identical topology except for the position of Tectarchus ovobessus (Phasmatodea). We recovered the monophyly of Phasmatodea and the sister-group relationship between Phasmatodea and Mantophasmatodea. Our analyses also recovered the monophyly of Heteropterygidae and the paraphyly of Diapheromeridae, Phasmatidae, Lonchodidae, Lonchodinae, and Clitumninae. In this study, Peruphasma schultei (Pseudophasmatidae), Phraortes sp. YW-2014 (Lonchodidae), and species of Diapheromeridae clustered into the clade of Phasmatidae. Within Heteropterygidae, O. guangxiensis was the sister clade to O. mouhotii belonging to Dataminae, and the relationship of (Heteropteryginae + (Dataminae + Obriminae)) was recovered. [ABSTRACT FROM AUTHOR]

Simple Summary: The Ephemeroptera is an ancient lineage of insects, among which the Heptageniidae is one of the most species-rich families, although its phylogenetic relationships have been controversial. The mitogenomes of Heptageniidae were found gene rearrangements of CR-I-M-Q-M-ND2 and a conserved intergenic gap between trnA and trnR. Thus, 15 complete and two nearly complete mitogenomes of Heptageniidae were used to explore mitogenome structures and clarify the disputes of phylogenetic relationships among Heptageniidae. Additionally, the Heptageniidae samples collected from habitats with significant temperature differences were applied to investigate the adaptive evolution of mitochondrial PCGs under low-temperature stress. We determined 15 complete and two nearly complete mitogenomes of Heptageniidae belonging to three subfamilies (Heptageniinae, Rhithrogeninae, and Ecdyonurinae) and six genera (Afronurus, Epeorus, Leucrocuta, Maccaffertium, Stenacron, and Stenonema). Species of Rhithrogeninae and Ecdyonurinae had the same gene rearrangement of CR-I-M-Q-M-ND2, whereas a novel gene rearrangement of CR-I-M-Q-NCR-ND2 was found in Heptageniinae. Non-coding regions (NCRs) of 25–47 bp located between trnA and trnR were observed in all mayflies of Heptageniidae, which may be a synapomorphy for Heptageniidae. Both the BI and ML phylogenetic analyses supported the monophyly of Heptageniidae and its subfamilies (Heptageniinae, Rhithrogeninae, and Ecdyonurinae). The phylogenetic results combined with gene rearrangements and NCR locations confirmed the relationship of the subfamilies as (Heptageniinae + (Rhithrogeninae + Ecdyonurinae)). To assess the effects of low-temperature stress on Heptageniidae species from Ottawa, Canada, we found 27 positive selection sites in eight protein-coding genes (PCGs) using the branch-site model. The selection pressure analyses suggested that mitochondrial PCGs underwent positive selection to meet the energy requirements under low-temperature stress. [ABSTRACT FROM AUTHOR]

Simple Summary: The longicorn beetle, Monochamus alternatus, is a major vector for the transmission of pine wilt disease, which is caused by a nematode pathogen, Bursaphelenchus xylophilus (or also possibly by B. mucronatus) that is spread by the beetle as it feeds on pine trees. In this study, the mitochondrial genome sequences of four longicorn species (Coleoptera: Cerambycidae: Lamiinae) were determined to further elaborate the phylogenetic relationships of Lamiinae. RT-qPCR was also used to assess the expression of eight mitochondrial protein-coding genes in M. alternatus when carrying B. mucronatus or not, so as to explore the relationship between these two species. The results showed that expression of mitochondria-encoded genes was elevated in M. alternatus beetles that were infected with B. mucronatus, suggesting that B. mucronatus putatively activates an immune response, which significantly affects the metabolic processes of M. alternatus. These results are of significance for further understanding the phylogenetic relationships of longicorn beetles and controlling the spread of pine wilt disease. We determined the mitochondrial gene sequence of Monochamus alternatus and three other mitogenomes of Lamiinae (Insect: Coleoptera: Cerambycidae) belonging to three genera (Aulaconotus, Apriona and Paraglenea) to enrich the mitochondrial genome database of Lamiinae and further explore the phylogenetic relationships within the subfamily. Phylogenetic trees of the Lamiinae were built using the Bayesian inference (BI) and maximum likelihood (ML) methods and the monophyly of Monochamus, Anoplophora, and Batocera genera was supported. Anoplophora chinensis, An. glabripennis and Aristobia reticulator were closely related, suggesting they may also be potential vectors for the transmission of the pine wood pathogenic nematode (Bursaphelenchus xylophilus) in addition to M. alternatus, a well-known vector of pine wilt disease. There is a special symbiotic relationship between M. alternatus and Bursaphelenchus xylophilus. As the native sympatric sibling species of B. xylophilus, B. mucronatus also has a specific relationship that is often overlooked. The analysis of mitochondrial gene expression aimed to explore the effect of B. mucronatus on the energy metabolism of the respiratory chain of M. alternatus adults. Using RT-qPCR, we determined and analyzed the expression of eight mitochondrial protein-coding genes (COI, COII, COIII, ND1, ND4, ND5, ATP6, and Cty b) between M. alternatus infected by B. mucronatus and M. alternatus without the nematode. Expression of all the eight mitochondrial genes were up-regulated, particularly the ND4 and ND5 gene, which were up-regulated by 4–5-fold (p < 0.01). Since longicorn beetles have immune responses to nematodes, we believe that their relationship should not be viewed as symbiotic, but classed as parasitic. [ABSTRACT FROM AUTHOR]

Lamiinae is the largest subfamily of the Cerambycidae (longhorn beetles), with approximately 21,863 described species. Previous phylogenetic studies of Lamiinae showed that this subfamily was monophyletic, but the relationship between the tribes of Lamiinae is still controversial. Partial molecular data and species morphological characteristics are not sufficient to resolve species phylogenetic studies perfectly. At the same time, the full mitochondrial genome contains more comprehensive genetic data. Benefiting from the development of next-generation sequencing (NGS), mitochondrial genomes can be easily acquired and used as reliable molecular markers to investigate phylogenetic relationships within Cerambycidae. Using NGS technology, we obtained 11 mitochondrial genome sequences of Lamiinae species. Based on this newly generated mitochondrial genome dataset matrix, we reconstructed the phylogeny of Lamiinae. The Bayesian Inference and Maximum Likelihood analyses strongly support the monophyly of four tribes (Lamiini, Batocerini, Mesosini, and Saperdini), whereas the tribe Acanthocinini was identified as paraphyletic. Other mitochondrial structural features were also observed: the start codon in the nad1 gene of all 11 mitochondrial genomes is TTG; 17-22 bp intergenic spacers (IGS) with a 'TACTA' motif were found between trnS2 and nad1. Moreover, two long IGS were found in Mesosa myops and Batocera sp. Tandem repeats were found in the IGS of Batocera sp.