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The fruit fly, Drosophila melanogaster, is a model species in evolutionary studies. However, population processes of this species in East Asia are poorly studied. Here we examined the population genetic structure of D. melanogaster across China. There were 14 mitochondrial haplotypes with 10 unique ones out of 23 known from around the globe. Pairwise F(ST) values estimated from 15 novel microsatellites ranged from 0 to 0.11, with geographically isolated populations showing the highest level of genetic uniqueness. STRUCTURE analysis identified high levels of admixture at both the individual and population levels. Mantel tests indicated a strong association between genetic distance and geographical distance as well as environmental distance. Full redundancy analysis (RDA) showed that independent effects of environmental conditions and geography accounted for 62.10% and 31.58% of the total explained genetic variance, respectively. When geographic variables were constrained in a partial RDA analysis, the environmental variables bio2 (mean diurnal air temperature range), bio13 (precipitation of the wettest month), and bio15 (precipitation seasonality) were correlated with genetic distance. Our study suggests that demographic history, geographical isolation, and environmental factors have together shaped the population genetic structure of D. melanogaster after its introduction into China.

Putative mechanisms underlying spinosyn resistance have been identified in controlled studies on many species; however, mechanisms underlying field-evolved resistance and the development of a molecular diagnostic method for monitoring field resistance have lagged behind. Here, we examined levels of resistance of melon thrips, Thrips palmi Karny (Thysanoptera:Thripidae), to spinetoram as well as target site mutations in field populations across China to identify potential mechanisms and useful molecular markers for diagnostic and quantifying purposes. In resistant populations, we identified the G275E mutation, which has previously been linked to spinosyns resistance, and F314V mutation, both located in the α6 subunit of the nicotinic acetylcholine receptor. There was a strong correlation between levels of spinetoram resistance and allele frequency of G275E mutation in field-collected populations (r2 = 0.84) and those reared under laboratory conditions for two to five generations (r2 = 0.91). LC50 ranged from 0.12 to 0.66 mg/liter in populations without G275E mutation, whereas it ranged from 33.12 to 39.91 mg/liter in most populations with a G275E mutation frequency more than 90%. Our results indicate that the field-evolved resistance of T. palmi to spinetoram in China is mainly conferred by the G275E mutation. The frequency of the G275E mutation provides a useful diagnostic for quantifying resistance levels in field populations of T. palmi.

Aphidius gifuensis is a parasitoid wasp that has been commercially bred and released in large scale as a biocontrol agent for the management of aphid pests. As a highly efficient endoparasitoid, it is also an important model for exploring mechanisms of parasitism. Currently, artificially bred populations of this wasp are facing rapid decline with undetermined cause, and mechanisms underlying its parasitoid strategy remain poorly understood. Exploring the mechanism behind its population decline and the host–parasitoid relationship is impeded partly due to the lack of a comprehensive genome data for this species. In this study, we constructed a high‐quality reference genome of A. gifuensis using Oxford Nanopore sequencing and Hi‐C (proximity ligation chromatin conformation capture) technology. The final genomic assembly was 156.9 Mb, with a contig N50 length of 3.93 Mb, the longest contig length of 10.4 Mb and 28.89% repetitive sequences. 99.8% of genome sequences were anchored onto six linkage groups. A total of 11,535 genes were predicted, of which 90.53% were functionally annotated. Benchmarking Universal Single‐Copy Orthologs (BUSCO) analysis showed the completeness of assembled genome is 98.3%. We found significantly expanded gene families involved in metabolic processes, transmembrane transport, cell signal communication and oxidoreductase activity, in particular ATP‐binding cassette (ABC) transporter, Cytochrome P450 and venom proteins. The olfactory receptors (ORs) showed significant contraction, which may be associated with the decrease in host recognition. Our study provides a solid foundation for future studies on the molecular mechanisms of population decline as well as host–parasitoid relationship for parasitoid wasps.

The fall webworm (FWW) Hyphantria cunea, native to North America, is a globally invasive pest of a wide range of forest and fruit trees. Spraying of pesticides is the primary method for the control of FWW. In this study, toxicity and feeding cessation of two potential pesticides against the FWW, chlorantraniliprole, and chromafenozide, were evaluated. Both pesticides were slow to affect FWW. For chlorantraniliprole, the highest mortality of third instar larvae occurred at 72 hours with an LC50 of 10.34 mg/L, while for chromafenozide, the highest mortality occurred at 72 hours with an LC50 value 74.0950 mg/L. Low concentrations of both pesticides led to larvae ceasing to feed after six hours (chlorantraniliprole) and 24 hours (chromafenozide). Both pesticides had persistent effects; thirty days after being applied at concentrations of 16, 26.67, and 35.56 mg/L to leaves, 93.33% of newly contacted larvae died after seven days. Our study showed that chlorantraniliprole and chromafenozide could be alternatively used against FWW and form a component of integrated control programs. The results provide information to guide the usage of chlorantraniliprole and chromafenozide in FWW control.

The peach fruit moth (PFM), Carposina sasakii Matsumura, is a major phytophagous orchard pest widely distributed across Northeast Asia. Here, we report the chromosome-level genome for the PFM, representing the first genome for the family Carposinidae, from the lepidopteran superfamily Copromorphoidea. The genome was assembled into 404.83 Mb sequences using PacBio long-read and Illumina short-read sequences, including 275 contigs, with a contig N50 length of 2.62 Mb. All contigs were assembled into 31 linkage groups assisted by the Hi-C technique, including 30 autosomes and a Z chromosome. BUSCO analysis showed that 98.3% of genes were complete and 0.4% of genes were fragmented, while 1.3% of genes were missing in the assembled genome. In total, 21,697 protein-coding genes were predicted, of which 84.80% were functionally annotated. Because of the importance of diapause triggered by photoperiod in PFM, five circadian genes in the PFM as well as in the other related species were annotated, and potential genes related to diapause and photoperiodic reaction were also identified from transcriptome sequencing. In addition, manual annotation of detoxification gene families was undertaken and showed a higher number of glutathione S-transferase (GST) gene in PFM than in most other lepidopterans, in contrast to a lower number of uridine diphosphate (UDP)-glycosyltransferase (UGT) gene, carboxyl/cholinesterases (CCE) gene and cytochrome P450 monooxygenase (P450) gene, suggesting different detoxication pathways in this moth. The high-quality genome provides a resource for comparative evolutionary studies of this moth and its relatives within the context of radiations across Lepidoptera.

The melon thrips, Thrips palmi, is an increasingly important pest of vegetables in northern China. Some populations have developed resistance in the field to the insecticide spinetoram. Understanding the origin and dispersal of insecticide‐resistant populations can shed light on resistance management strategies. In this study, we tested susceptibility of seven greenhouse populations of T. palmi to spinetoram collected from a small area of about 300 km2 in Shandong Province and examined population genetic structure across the area based on a segment of mitochondrial cox1 gene and 22 microsatellite loci to infer the possible origin and dispersal of insecticide resistance. Levels of resistance to spinetoram differed among seven populations, which included one population with high resistance (LC50 = 759.34 mg/L), three populations with medium resistance (LC50 ranged from 28.69 to 34.79 mg/L), and three populations with low resistance (LC50 ranged from 7.61 to 8.97 mg/L). The populations were genetically differentiated into two groups unrelated to both levels of resistance and geographic distance. The molecular data indicated high levels of gene flow between populations with different levels of resistance to spinetoram and low gene flow among populations with the same level of resistance, pointing to a likely separate history of resistance evolution. Resistance levels of two tested populations to spinetoram decreased 23 and 4.6 times after five generations without any exposure to the pesticide. We therefore suspect that resistance of T. palmi most likely evolved in response to local applications of the insecticide. Our study suggests that the development of resistance could be avoided or resistance even reversed by reducing usage of spinetoram.

The long-armed scarab (Cheirotonus gestroi) is an endangered large insect in southwestern China and neighboring countries; however, limited information is available regarding its population genetics, hindering conservation efforts. Therefore, we investigated the population genetic structure and evolutionary history of C. gestroi in southwestern China. Twenty-five haplotypes were obtained from 47 specimens across five populations. The Dawei Mountain (DWS) population differed from other populations by a high genetic distance. Population structure analysis generated three distinct clades, corresponding to Hengduan Mountains (HM), Ailao Mountains (AM), and Dawei Mountains (DM), and high-level genetic diversity was found in two HM populations. Collectively, the strong genetic differentiation among populations might be due to limited gene flow, geographical isolation, and habitat fragmentation. Therefore, while developing a conservation strategy, HM, AM, and DM groups should be defined as separate management units. Additionally, the DWS population should be given priority protection due to its uniqueness and low genetic diversity.

The dobsonfly species Neoneuromus ignobilis Navas (Megaloptera: Corydalidae) is endemic to but widely distributed from eastern and southeastern Asia, being an important insect indicator for freshwater biomonitoring. At present, there is no report on the development of microsatellites of Megaloptera. Here, we developed 27 novel microsatellite markers of N. ignobilis from 850,920 candidate microsatellites with the stringent screening criteria considering the amplification success rate, the presence or absence of stutter peaks, the peak intensity, the polymorphism of the loci, the heterozygosity, and the number of alleles. The allele number of 27 microsatellite markers ranges from 3 to 12 with an average value of 6.19 per locus. The observed heterozygosity (HO) and expected heterozygosity (HE) revealed a range from 0.000 to 0.947 and 0.000 to 0.842, respectively. We constructed three panels (MP panel, most polymorphic; SS panel, most stringent strategy; ALL panel, total 27 microsatellite markers) and compared the analyses on population genetic diversity and structure. The result showed that the MP panel can significantly improve the analyses of individual assignment and genetic diversity. Accordingly, we advocate selecting the most polymorphic microsatellite marker for analyzing population genetics based on microsatellite data. The present work represents the first study on the microsatellite development of Megaloptera.

Biological invasions of pests into climatically unsuitable areas can be facilitated by human‐regulated environments, in which case there may be an impact on genetic structure through population processes and/or adaptation. Here, we investigated the population genetic structure of an invasive agricultural pest, Thrips palmi, in China, which has expanded its distribution range through using greenhouses. Early invaded populations showed a relatively higher level of genetic diversity than recently expanded greenhouse populations. Strong population genetic structure corresponded to a pattern of isolation by distance, with no recent gene flow and low historical gene flow among populations, reflecting limited ongoing dispersal. A genetic signature of population expansion was detected in early invaded populations and three northern populations from greenhouses, suggesting that the greenhouse environments facilitated expansion of this species. Redundancy analysis showed that the independent effects of environment and geography could explain 51.68% and 32.06% of the genetic variance, respectively. These findings point to climate‐ and greenhouse‐related spatial expansion, with the potential for adaptation by T. palmi. They emphasize the contribution of human‐regulated environments on the successes of this invasive species, a situation likely to apply to other invasive species that use greenhouse environments.

Chalcidoidea is one of the most diverse group in Hymenoptera by possessing striking mitochondrial gene arrangement. By using next generation sequencing method, the first two nearly complete mitochondrial genomes in the family Aphelinidae (Insecta, Hymenopetra, Chalcidoidea) were obtained in this study. Almost all previously sequenced mitochondrial genome of Chalcidoidea species have a large inversion including six genes (atp6-atp8-trnD-trnK-cox2-trnL2-cox1) as compared with ancestral mitochondrial genome, but these two Encarsia mitochondrial genomes had a large inversion including nine genes (nad3-trnG-atp6-atp8-trnD-trnK-cox2-trnL2-cox1), which was only congruent with the species in the genus Nasonia. Moreover, we found that one shuffling changes (trnD and trnK) happened in the species E. obtusiclava but not in another species E. formosa within the same genus, of which such shuffling within the same genus at this region was only detected in Polisters within Insecta. Phylogenetic analysis displayed that different data matrix (13PCG+ 2 rRNA or 13 PCG) and inference methods (BI or ML) indicate the identical topology with high nodal supports that Aphelinidae formed a sister group with (Trichogrammatidae + Aganoidae) and the monophyly of Pteramalidae. Our results also indicated the validity of assembling and feasibility of next-generation technology to obtain the mitochondrial genomes of parasitic Hymenoptera.

Parasitic wasps produce several factors including venom, polydnaviruses (PDVs) and specialized wasp cells named teratocytes that benefit the survival of offspring by altering the physiology of hosts. However, the underlying molecular mechanisms for the alterations remain unclear. Here we find that the teratocytes of Cotesia vestalis, an endoparasitoid of the diamondback moth Plutella xylostella, and its associated bracovirus (CvBV) can produce miRNAs and deliver the products into the host via different ways. Certain miRNAs in the parasitized host are mainly produced by teratocytes, while the expression level of miRNAs encoded by CvBV can be 100-fold greater in parasitized hosts than non-parasitized ones. We further show that one teratocyte-produced miRNA (Cve-miR-281-3p) and one CvBV-produced miRNA (Cve-miR-novel22-5p-1) arrest host growth by modulating expression of the host ecdysone receptor (EcR). Altogether, our results show the first evidence of cross-species regulation by miRNAs in animal parasitism and their possible function in the alteration of host physiology during parasitism., The moth Plutella xylostella during its larval stage is the host of the endoparasitic wasp Cotesia vestalis. Here the authors show that the parasitoids deliver microRNAs to their hosts through their symbiotic virus and specialized cells leading to induced developmental delay.

For the first time the mitochondrial genome of a Dolichovespula species, D. panda Archer (Hymenoptera: Vespidae), was sequenced with a next-generation sequencing approach. The sequenced mitochondrial genome is 17137 bp long and consists of 13 protein-coding, 22 tRNA and two rRNA genes, as well as a partial A + T-rich region. Twenty-two of the genes are encoded on the majority strand and 15 genes on the minority strand. All protein-coding genes start with ATN codons and have a TAA termination codon, except for one with a TA codon. Compared with the putative ancestral arrangement of insects, the D. panda mitochondrial genome shows the shuffling of trnN and trnE, and of trnQ and trnM, the translocation of trnY to upstream of trnI, and of trnL1 to the region between trnS2 and nad1 and a reversal of trnS1. A phylogenetic tree within the Vespidae was reconstructed using the 13 protein-coding mitochondrial genes. This shows a sister group relationship between Dolichovespula and a clade formed by Vespa and Vespula. It also corroborated the position of Eumeninae as sister group of the clade Polistinae + Vespinae.

Thrips are tiny insects from the order Thysanoptera (Hexapoda: Condylognatha), including many sap-sucking pests that are causing increasing damage to crops worldwide. In contrast to their closest relatives of Hemiptera (Hexapoda: Condylognatha), including numerous sap-sucking species, there are few genomic resources available for thrips. In this study, we assembled the first thrips genome at the chromosomal level from the melon thrips, Thrips palmi, a notorious pest in agriculture, using PacBio long-read and Illumina short-read sequences. The assembled genome was 237.85 Mb in size, with 1,324 contigs and a contig N50 of 567 kb. All contigs were assembled into 16 linkage groups assisted by the Hi-C technique. In total, 16,333 protein-coding genes were predicted, of which 88.13% were functionally annotated. Among sap-sucking insects, polyphagous species (e.g., T. palmi and Bemisia tabaci) usually possess more detoxification genes than oligophagous species (e.g., Diaphorina citri). The polyphagous thrips genomes characterized so far have relatively more detoxification genes in the GST and CCE families than polyphagous aphids, but they have fewer UGTs. HSP genes, especially from the Hsp70s group, have expanded in thrips compared to other hemipterans. These differences point to different genetic mechanisms associated with detoxification and stress responses in these two groups of sap-sucking insects. The expansion of these gene families may contribute to the rapid development of pesticide resistance in thrips, as supported by a transcriptome comparison of resistant and sensitive populations of T. palmi. The high-quality genome developed here provides an invaluable resource for understanding the ecology, genetics, and evolution of thrips as well as their relatives more generally.

The stinging wasps (Hymenoptera: Aculeata) include diverse groups such as vespid wasps, ants and bees. Phylogenetic relationships among major lineages of stinging wasps have been inferred from molecular and morphological data. However, the genomic features of the mitochondrial genomes and their phylogenetic utility remain to be explored. In this study, we determined 23 mitochondrial genomes from the Aculeata. Four Mutillidae species showed relatively low A + T content compared to other species of the Aculeata (69.7%-77.4%). Eleven out of 44 species, mainly from the Chrysididae and the Pompilidae, showed reversals of GC skews. Gene rearrangements occurred across the species. Patterns of tRNA rearrangement were conserved in some groups, including the Chrysididae, Bethylidae, Pompilidae, Scolioidea and Vespoidea. Rearrangement of protein-coding genes were found in 12 out of 44 species of the Aculeata, including all four species from the Chrysididae, both species from the Bethylidae, one species from the Dryinidae, all three Scolioidea species and two Apoidea species. Phylogenetic inference showed a long branch in species with unusual genomic features, such as in the Mutillidae and Bethylidae. By excluding these species, we found paraphyly of the Chrysidoidea and a sister group relationship between the Formicoidea and Vespoidea. These results improve our understanding of the evolution of mitochondrial genomes in the Aculeata and, in general, the evolution across this subclade.

Aim To establish patterns of genetic variation associated with the well-documented history of invasion and expansion of the fall webworm (FWW), Hyphantria cunea, into China. Patterns are expected to be affected by geographical and environmental factors as well as a history of control campaigns. Location Northern and eastern China. Methods We genotyped 18 polymorphic microsatellite loci derived from 657 individuals (25 populations) collected from across the distribution range of FWW in China and a native population in USA, and we also sequenced mitochondrial DNA from a subset of 70 individuals. Population genetic structure was analysed by using three Bayesian cluster methods (structure, geneland and tess) and a multivariate principal component analysis (PCA). The scenarios of invasion history were tested using an approximate Bayesian computation (ABC) approach. A multiple matrix regression was performed to assess the relative contributions of geographical and environmental isolation. Results The average allelic richness and mitochondrial haplotype diversity of the FWW populations in China was very low compared to native populations from USA, pointing to a significant bottleneck during colonization. Based on the nuclear markers, two genetically separated groups were identified along with a contact zone between them. ABC analyses suggested a single introduction into the east with subsequent westward expansion. Geographic distance was more important than environmental distance in contributing to genetic differentiation, and geographical barriers were likely to have restricted gene flow, with the contact zone occurring in a mountainous area. Main conclusions The combination of genetic data and historical records of the expansion suggests that geographical barriers and control campaigns have affected the formation and persistence of the two genetic groups. Our study points to ways in which genetic differentiation can develop rapidly in an invasive species after its introduction.

The rapid increase in the number of mitochondrial genomes in public databases provides opportunities for insect phylogenetic studies; but it also provides challenges because of gene rearrangements and variable substitution rates among both lineages and sites. Typically, phylogenetic studies use mitochondrial sequence data but exclude other features of the mitochondrial genome from analyses. Here, we undertook large-scale sequencing of mitochondrial genomes from a worldwide collection of specimens belonging to Braconidae, one of the largest families of Metazoa. The strand-asymmetry of base composition in the mitochondrial genomes of braconids is reversed, providing evidence for monophyly of the Braconidae. We have reconstructed a backbone phylogeny of the major lineages of Braconidae from gene order of the mitochondrial genomes. Standard phylogenetic analyses of DNA sequences provided strong support for both Cyclostomes and Noncyclostomes. Four subfamily complexes, that is, helconoid, euphoroid, sigalphoid, and microgastroid, within the Noncyclostomes were reconstructed robustly, the first three of which formed a monophyletic group sister to the last one. Aphidiinae was recovered as a lineage sister to other groups of Cyclostomes, while the Ichneutinae was recovered as paraphyletic. Separate analyses of the subdivided groups showed congruent relationships, employing different matrices and methods, for the internal nodes of the Cyclostomes and the microgastroid complex of subfamilies. This research, using multiple lines of evidence from mitochondrial genomes, illustrates multiple uses of mitochondrial genomes for phylogenetic inference in Braconidae.

Background Refugial populations in Quaternary glaciations are critical to understanding the evolutionary history and climatic interactions of many extant species. Compared with the well-studied areas of Europe and Northern America, refugia of species in eastern Asia remain largely unknown. Here, we investigated the phylogeographic history of a globally important insect pest, the oriental fruit moth Grapholita molesta, in its native range of China. Results Genetic structure analyses unveiled three distinct groups and a set of populations with admixture. Approximate Bayesian Computation (ABC) analyses support range expansion of this moth from southwest groups of Yunnan and Sichuan to northern and eastern China. A set of admixed populations was found around these two ancestral groups. This pattern of genetic structure points to two refugia located in the Yunnan region and Sichuan Basin. The split of the two refugia was dated to 329.2 thousand years ago in the penultimate glacial period. One of the lineages was exclusively found around the Sichuan Basin, indicating the formation of endemic populations in this refugium. Ecological niche model analysis suggested a shrinking distribution from the LIG period to the MID period in the Sichuan lineage but a wide and stable distribution in the other lineage. Conclusions Our results for the first time suggest that Yunnan and Sichuan jointly served as two large-scale refugia in eastern Asia in Quaternary glaciations, helping to maintain genetic diversity overall. Electronic supplementary material The online version of this article (10.1186/s12862-018-1269-z) contains supplementary material, which is available to authorized users.

The insect order Hymenoptera presents marvelous morphological and ecological diversity. Higher-level hymenopteran relationships remain controversial, even after recent phylogenomic analyses, as their taxon sampling was limited. To shed light on the origin and diversification of Hymenoptera, in particular the poorly studied Parasitica, we undertook phylogenetic analyses of 40 newly and 43 previously sequenced mitochondrial genomes representing all major clades of Hymenoptera. Various Bayesian inferences using different data partitions and phylogenetic methods recovered similar phylogenetic trees with strong statistical support for almost all nodes. Novel findings of the mitogenomic phylogeny mainly affected the three infraorders Ichneumonomorpha, Proctotrupomorpha and Evaniomorpha, the latter of which was split into three clades. Basal relationships of Parasitica recovered Stephanoidea + (Gasteruptiidae + Aulacidae) as the sister group to Ichneumonomorpha + (Trigonalyoidea + Megalyroidea). This entire clade is sister to Proctotrupomorpha, and Ceraphronoidea + Evaniidae is sister to Aculeata (stinging wasps). Our divergence time analysis indicates that major hymenopteran lineages originated in the Mesozoic. The radiation of early apocritans may have been triggered by the Triassic–Jurassic mass extinction; all extant families were present by the Cretaceous.

The two-spotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most serious pests of strawberry worldwide. Understanding the preference of TSSM for particular cultivars of strawberry and performance on them helps identify host-plant resistance to this pest mite. In this study, we tested preference, developmental duration, fecundity and population levels of TSSM on 14 strawberry cultivars. TSSM showed strong preference for the Chinese cultivars of Yanxiang, Baixuegongzhu, and Jingtaoxiang. Development of TSSM on the cultivars varied from 32.32 to 36.82 days; it was longest on the cultivars Hongxiutianxiang and Baixuegongzhu, and shortest on Yanxiang, Jingzangxiang, and Darselect as well as on a wild variety (Wuye). TSSM had high fecundity on the cultivars Yanxiang, Taoxun, Hongxiutianxiang, Jingzangxiang, Albion and Baixuegongzhu as well as on Wuye, whereas egg production was lowest on Sweet Charlie, Portola, Akihime, and Benihoppe. After 28 days of plant infestation with 10 pairs of adults, the cultivars Yanxiang, Taoxun, Jingzangxiang, Jingtaoxiang, and Baixuegongzhu had the highest number of mites (> 1000 per plant), whereas mite numbers on Albion and Camarosa were low. The population size of TSSM was correlated with fecundity, but no correlation was found between other preference/performance measures. Our study suggests that a rapid increase of population size of TSSM on cultivars of strawberry is related to high fecundity, and also that there are substantial differences in preference and performance across cultivars.

Background Populations of herbivorous insects may become genetically differentiated because of local adaptation to different hosts and climates as well as historical processes, and further genetic divergence may occur following the development of reproductive isolation among populations. Here we investigate the population genetic structure of the orchard pest peach fruit moth (PFM) Carposina sasakii (Lepidoptera: Carposinidae) in China, which shows distinct biological differences when characterized from different host plants. Genetic diversity and genetic structure were assessed among populations from seven plant hosts and nine regions using 19 microsatellite loci and a mitochondrial sequence. Results Strong genetic differentiation was found among geographical populations representing distinct geographical regions, but not in host-associated populations collected from the same area. Mantel tests based on microsatellite loci indicated an association between genetic differentiation and geographical distance, and to a lesser extent environmental differentiation. Approximate Bayesian Computation analyses supported the scenario that PFM likely originated from a southern area and dispersed northwards before the last glacial maximum during the Quaternary. Conclusions Our analyses suggested a strong impact of geographical barriers and historical events rather than host plants on the genetic structure of the PFM; however, uncharacterized environmental factors and host plants may also play a role. Studies on adaptive shifts in this moth should take into account geographical and historical factors. Electronic supplementary material The online version of this article (10.1186/s12862-017-1116-7) contains supplementary material, which is available to authorized users.

To develop a new control method for the two-spotted spider mite (TSSM), Tetranychus urticae, we investigated the effect of controlled atmospheres of carbon dioxide (CO2) on TSSM mortality under different concentrations and treatment periods, and evaluated the impact of treatments on seedlings of five host plants of TSSM. Egg hatching rate of TSSM was reduced to 37.7, 5.4 or 0% after 24 h treatment involving concentrations of 16.7, 33.3 or 50%, respectively. Mobile stages (nymphs and adult) of TSSM were completely controlled after 24 h treatment at concentrations higher than 33.3%. After 4 h at concentrations of 33.3 or 50%, 1st-day survival rate for all mobile stages was 45.3 or 36.0%, respectively, whereas after 8 or 16 h treatments, all values were decreased to zero. Seedlings of four major host plants of TSSM (cucumber, eggplant, rape, green peppers) were damaged to varying degrees after 24 h at the three concentrations, but strawberry, another host plant, was not damaged. Cucumber suffered the most serious damage, resulting in wilting and death. In conclusion, controlled atmospheres of CO2 can kill TSSM, particularly at high concentrations and with long treatment times. It can be used to control TSSM on strawberry, but should be used cautiously on other host plants.

The Apoidea represent a large and common superfamily of the Hymenoptera including the bees and sphecid wasps. A robust phylogenetic tree is essential to understanding the diversity, taxonomy and evolution of the Apoidea. In this study, features of apoid mitochondrial genomes were used to reconstruct phylogenetic relationships. Twelve apoid mitochondrial genomes were newly sequenced, representing six families and nine subfamilies. Gene rearrangement events have occurred in all apoid mitochondrial genomes sequenced to date. Sphecid wasps have both tRNA and protein-coding gene rearrangements in 5 of 8 species. In bees, the only rearranged genes are tRNAs; long-tongued bees (Apidae + Megachilidae) are characterized by movement of trnA to the trnI-trnQ-trnM tRNA cluster. Phylogenetic analyses of mitochondrial gene sequences support the known paraphyly of sphecid wasps, with bees nested within this clade. The Ampulicidae is sister to the remaining Apoidea. Crabronidae is paraphyletic, split into Crabronidae s.s. and Philanthidae, with the latter group a sister clade to bees. The monophyletic bees are either classified into two clades, long-tongued bees (Apidae + Megachilidae) and short-tongued bees (Andrenidae + Halictidae + Colletidae + Melitidae), or three groups with the Melitidae sister to the other bees. Our study showed that both gene sequences and arrangements provide information on the phylogeny of apoid families.

The hoverflies Episyrphus balteatus and Eupeodes corollae (Diptera: Muscomorpha: Syrphidae) are important natural aphid predators. We obtained mitochondrial genome sequences from these two species using methods of PCR amplification and sequencing. The complete Episyrphus mitochondrial genome is 16,175 bp long while the incomplete one of Eupeodes is 15,326 bp long. All 37 typical mitochondrial genes are present in both species and arranged in ancestral positions and directions. The two mitochondrial genomes showed a biased A/T usage versus G/C. The cox1, cox2, cox3, cob and nad1 showed relatively low level of nucleotide diversity among protein-coding genes, while the trnM was the most conserved one without any nucleotide variation in stem regions within Muscomorpha. Phylogenetic relationships among the major lineages of Muscomorpha were reconstructed using a complete set of mitochondrial genes. Bayesian and maximum likelihood analyses generated congruent topologies. Our results supported the monophyly of five species within the Syrphidae (Syrphoidea). The Platypezoidea was sister to all other species of Muscomorpha in our phylogeny. Our study demonstrated the power of the complete mitochondrial gene set for phylogenetic analysis in Muscomorpha.

The hoverfly, Eupeodes corollae, is a worldwide natural enemy of aphids and a plant pollinator. To provide insights into the biology of this species, we examined its population genetic structure by obtaining 1.15-GB random genomic sequences using next-generation sequencing and developing genome-wide microsatellite markers. A total of 79,138 microsatellite loci were initially isolated from the genomic sequences; after strict selection and further testing of 40 primer pairs in eight individuals, 24 polymorphic microsatellites with high amplification rates were developed. These microsatellites were used to examine the population genetic structure of 96 individuals from four field populations collected across southern to northern China. The number of alleles per locus ranged from 5 to 13 with an average of 8.75; the observed and expected heterozygosity varied from 0.235 to 0.768 and from 0.333 to 0.785, respectively. Population genetic structure analysis showed weak genetic differentiation among the four geographical populations of E. corollae, suggesting a high rate of gene flow reflecting likely widespread migration of E. corollae in China.

Here, we report the mitochondrial genome sequence of the multicolored Asian lady beetle Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) (GenBank accession No. KR108208). This is the first species with sequenced mitochondrial genome from the genus Harmonia. The current length with partitial A + T-rich region of this mitochondrial genome is 16,387 bp. All the typical genes were sequenced except the trnI and trnQ. As in most other sequenced mitochondrial genomes of Coleoptera, there is no re-arrangement in the sequenced region compared with the pupative ancestral arrangement of insects. All protein-coding genes start with ATN codons. Five, five and three protein-coding genes stop with termination codon TAA, TA and T, respectively. Phylogenetic analysis using Bayesian method based on the first and second codon positions of the protein-coding genes supported that the Scirtidae is a basal lineage of Polyphaga. The Harmonia and the Coccinella form a sister lineage. The monophyly of Staphyliniformia, Scarabaeiformia and Cucujiformia was supported. The Buprestidae was found to be a sister group to the Bostrichiformia.

Genetic comparisons of parasitoids and their hosts are expected to reflect ecological and evolutionary processes that influence the interactions between species. The parasitoid wasp, Cotesia vestalis, and its host diamondback moth (DBM), Plutella xylostella, provide opportunities to test whether the specialist natural enemy migrates seasonally with its host or occurs as resident population. We genotyped 17 microsatellite loci and two mitochondrial genes for 158 female adults of C. vestalis collected from 12 geographical populations, as well as nine microsatellite loci for 127 DBM larvae from six separate sites. The samplings covered both the likely source (southern) and immigrant (northern) areas of DBM from China. Populations of C. vestalis fell into three groups, pointing to isolation in northwestern and southwestern China and strong genetic differentiation of these populations from others in central and eastern China. In contrast, DBM showed much weaker genetic differentiation and high rates of gene flow. TESS analysis identified the immigrant populations of DBM as showing admixture in northern China. Genetic disconnect between C. vestalis and its host suggests that the parasitoid did not migrate yearly with its host but likely consisted of resident populations in places where its host could not survive in winter.

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.

The oriental fruit moth (OFM)Grapholita molesta(Lepidoptera: Tortricidae) is an important economic pest of stone and pome fruits worldwide. We sequenced the OFM genome using next-generation sequencing and characterized the microsatellite distribution. In total, 56,674 microsatellites were identified, with 11,584 loci suitable for primer design. Twenty-seven polymorphic microsatellites, including 24 loci with trinucleotide repeat and three with pentanucleotide repeat, were validated in 95 individuals from four natural populations. The allele numbers ranged from 4 to 40, with an average value of 13.7 per locus. A high frequency of null alleles was observed in most loci developed for the OFM. Three marker panels, all of the loci, nine loci with the lowest null allele frequencies, and nine loci with the highest null allele frequencies, were established for population genetics analyses. The null allele influenced estimations of genetic diversity parameters but not the OFM's genetic structure. Both a STRUCTURE analysis and a discriminant analysis of principal components, using the three marker panels, divided the four natural populations into three groups. However, more individuals were incorrectly assigned by the STRUCTURE analysis when the marker panel with the highest null allele frequency was used compared with the other two panels. Our study provides empirical research on the effects of null alleles on population genetics analyses. The microsatellites developed will be valuable markers for genetic studies of the OFM.

Historical invasion scenarios based on observational records are usually incomplete and biased, but these can be supplemented by population genetic data. The western flower thrips (WFT), Frankliniella occidentalis, invaded China in the last 13 years and has rapidly become one of the most serious pests in the country. To assess whether this invasion involved a single event or multiple events, we examined patterns of genetic diversity and population structure of WFT across 12 Chinese populations and a native US population based on mitochondrial DNA and/or 18 microsatellite loci. The average allelic richness and haplotype diversity in Chinese populations were significantly lower than in a population from its native range. The distribution of mitochondrial haplotypes suggested multiple independent invasions of WFT into China, including two invasions into the Beijing region. Based on microsatellite data, two distinct clusters were identified, with both of them splitting further into two clusters; in the Beijing region, the microsatellite data also provided evidence for two introductions. Both the absence of isolation by distance and the fact that distant populations were similar genetically suggest patterns of WFT movement linked to human activities. Our study therefore suggests multiple introductions of WFT into China and human‐assisted spread.

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

Recent improvements in next-generation sequencing technologies have enabled investigation of microsatellites on a genome-wide scale. Faced with a huge amount of candidates, the use of appropriate marker selection criteria is crucial. Here, we used the western flower thrips Frankliniella occidentalis for an empirical microsatellite survey and validation; 132,251 candidate microsatellites were identified, 92,102 of which were perfect. Dinucleotides were the most abundant category, while (AG)n was the most abundant motif. Sixty primer pairs were designed and validated in two natural populations, of which 30 loci were polymorphic, stable, and repeatable, but not all in Hardy–Weinberg equilibrium (HWE) and linkage equilibrium. Four marker panels were constructed to understand effect of marker selection on population genetic analyses: (i) only accept loci with single nucleotide insertions (SNI); (ii) only accept the most polymorphic loci (MP); (iii) only accept loci that did not deviate from HWE, did not show SNIs, and had unambiguous peaks (SS) and (iv) all developed markers (ALL). Although the MP panel resulted in microsatellites of highest genetic diversity followed by the SNI, the SS performed best in individual assignment. Our study proposes stringent criteria for selection of microsatellites from a large-scale number of genomic candidates for population genetic studies.

The peach fruit moth Carposina sasakii is an economically important pest on dozens of fruits from Rosaceae and Rhamnaceae in Northeast Asia. We developed novel microsatellite markers for C. sasakii from randomly sequenced regions of the genome using next-generation sequencing. In total, 95,153 microsatellite markers were isolated from 4.70 GB genomic sequences. Thirty-five polymorphic markers were developed by assessing in 63 individuals from two geographical populations. The allele numbers ranged from 2 to 9 with an average value of 4.60 per locus, while the polymorphism information content ranged from 0.075 to 0.696 with an average value of 0.407. Furthermore, the observed and expected heterozygosity varied from 0.000 to 0.677 and 0.062 to 0.771, respectively. The microsatellites developed provide abundant molecular markers for investigating genetic structure, genetic diversity, and existence of host-plant associated biotypes of C. sasakii.

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

The mitochondrial genome of the German wasp Vespula germanica (Fabricius, 1793) (Hymenoptera: Vespidae) (GenBank accession no. KR703583) was sequenced in the study. It represents the first mitochondrial genome from the genus Vespula. There are totally 163 42 bp in the currently sequenced portion of the genome, containing 13 protein-coding, two rRNA, and 18 tRNA genes and a partial A + T-rich region. Four tRNA genes of trnI, trnQ, trnM and trnY located at the downstream of the A + T-rich region were failed to sequence. At least two rearrangement events occurred in the sequenced region compared with the pupative ancestral arrangement of insects, corresponding to the translocation or remote inversion of tnnY from trnW-trnC-trnY cluster to the region of trnI-trnQ-trnM cluster and translocation of trnL1 from the downstream to the upstream of nad1 gene. All protein-coding genes start with ATN codons. Twelve and one protein-coding genes stop with termination codon TAA and T, respectively. Phylogenetic analysis using the Bayesian method based on all codon positions of the 13 protein-coding genes supports the monophyly of Vespidae and Formicidae. Within the Formicidae, the Myrmicinae and Formicinae form a sister group and then sister to the Dolichoderinae, while within the Vespidae, the Eumeninae sister to the lineage of Vespinae + Polistinae.

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

The mitochondrial genome sequence of Polistes jokahamae (Radoszkowski, 1887) (Hymenoptera: Vespidae) (GenBank accession no. KR052468) was sequenced. The current length with partial A + T-rich region of this mitochondrial genome is 16,616 bp. All the typical mitochondrial genes were sequenced except for three tRNAs (trnI, trnQ, and trnY) located between the A + T-rich region and nad2. At least three rearrangement events occurred in the sequenced region compared with the pupative ancestral arrangement of insects, corresponding to the shuffling of trnK and trnD, translocation or remote inversion of tnnY and translocation of trnL1. All protein-coding genes start with ATN codons. Eleven, one, and another one protein-coding genes stop with termination codon TAA, TA, and T, respectively. Phylogenetic analysis using the Bayesian method based on all codon positions of the 13 protein-coding genes supports the monophyly of Vespidae and Formicidae. Within the Formicidae, the Myrmicinae and Formicinae form a sister lineage and then sister to the Dolichoderinae, while within the Vespidae, the Eumeninae is sister to the lineage of Vespinae + Polistinae.

Here we report the mitochondrial genome sequence of the garden pea leafminer Chromatomyia horticola (Goureau, 1851) (Diptera: Agromyzidae) (GenBank accession no. KR047789). This is the first species with sequenced mitochondrial genome from the genus Chromatomyia. The current length with partial A + T-rich region of this mitochondrial genome is 15,320 bp with an A + T content of 77.54%. All the 13 protein-coding, two rRNA, and 22 tRNA genes were sequenced, except for the A + T-rich region. As in most other sequenced mitochondrial genomes of Diptera, there is no rearrangement compared with the pupative ancestral arrangement of insects. All protein-coding genes start with the ATN start codon except for the gene cox1, which uses abnormal TTG. The A + T-rich region is located between rrnS and trnI with a sequenced length of 503 bp. Phylogenetic analysis using the Bayesian method based on the first and second codon positions of the 13 protein-coding genes recovered the monophyly of Agromyzidae with one species of Chromatomyia and four species of Liriomyza in our study. The superfamily Oestroidea (with Agromyzidae in analysis) is sister to the Opomyzoidea.

Here, we report the first representative mitochondrial genome of the subfamily Vespinae (Hymenopterea: Vespidae) from the Vespa bicolor Fabricius (GenBank accession No. KJ735511). Nearly complete mitochondrial genome was sequenced with a length of 16,937 bp, including 13 protein-coding genes, 2 rRNA and 20 tRNA genes, as well as a portion of A+T-rich region. Two tRNA genes, i.e. trnI and trnY, were failed to sequence, which were presumed to be located within a region between A+T-rich region and trnM-trnQ-nad2. In the V. bicolor mitochondrial genome, at least three tRNA genes were rearranged. trnY was rearranged to the unsequenced region between A+T-rich region and trnM-trnQ-nad2. trnL1 was rearranged from a location between nad1 and rrnL to the upstream of nad1 gene. trnS1 and trnE were shuffled in the tRNA cluster of trnA-trnR-trnN-trnS1-trnE-trnF. Our study showed that the mitochondrial genomes between Vespinae and Polistinae shared more arrangement pattern than that between Vespinae and Eumeninae.

The complete mitochondrial genome of the Allantus luctifer (Smith) (Hymenoptera: Tenthredinidae: Allantinae) is reported in this study (GenBank accession No. KJ713152). This is the first mitochondrial genome from the subfamily Allantinae and the first completely sequenced mitochondrial genome from the Tenthredinoidea. The length of this mitochondrial genome is 15,418 bp with an A+T content of 81.13%, including 13 protein-coding, 2 rRNA and 22 tRNA gene, and an A+T-rich region (Table 1). Gene arrangement is identical to the other two mitochondrial genomes of tenthredinoid species in nearly all region as in the pupative ancestral arrangement of insects. The ancestral pattern of "A+T-rich region-trnI(+)-trnQ(-)-trnM(+)" was rearranged to "trnM(-)-trnQ(+)-A+T-rich region-trnI(+)", which is novel to the Hymenoptera. All protein-coding genes start with ATN start codon. Eleven protein-coding genes stop with termination codon TAA, whereas one protein-coding gene uses incomplete stop codon TA and one uses T. The A+T-region is 463 bp long with an A+T content of 86.6%.

Here we report the complete mitochondrial genome sequence of the Grapholita dimorpha Komai (Lepidoptera: Tortricidae) (GenBank accession No. KJ671625). This is the second species with sequenced mitochondrial genome from the genus Grapholita. The length of this mitochondrial genome is 15,813 bp with an A+T content of 74.84%, including 13 protein-coding, 2 rRNA and 22 tRNA genes, and an A+T-rich region (Table 1). As in most other sequenced mitochondrial genomes of Lepidoptera, trnM was rearranged to the upstream of trnI-trnQ-trnM cluster compared with the pupative ancestral arrangement of insects. All protein-coding genes start with ATN start codon except for the gene cox1, which uses CGA as in other lepidopteran species. Seven protein-coding genes stop with termination codon TAA. Six protein-coding genes use incomplete stop codon T. The A+T-rich region is located between rrnS and trnM with a length of 848 bp, longer than that in most other lepidopteran species.

We report the mitochondrial genome of the Vespa mandarinia Smith (GenBank accession no. KR059904) for the subfamily Vespinae (Hymenoptera: Vespidae). This is the first completely sequenced mitochodrial genome from the genus Vespa. All of the typical mitochondrial genes were sequenced with a length of 15 902 bp. In the V. mandarinia mitochondrial genome, four rearrangement events occurred compared with the pupative ancestral arrangement of insects, corresponding to the shuffling of trnQ and trnM, translocation of trnY to the region between A + T-rich region and trnI-trnM-trnQ, shuffling of trnS1 and trnE in the tRNA cluster of trnA-trnR-trnN-trnS1-trnE-trnF, and translocation of trnL1 from a location between nad1 and rrnL to the upstream of nad1 gene. Phylogenetic analysis using the Bayesian method based on all codon positions of the 13 protein-coding genes supports the monophyly of Vespidae and Formicidae. Within the Formicidae, the Myrmicinae and Dolichoderinae form a sister group, while within the Vespidae, the Eumeninae sister to lineage of Vespinae + Polistinae. Our study showed that the mitochondrial genomes between Vespinae and Polistinae shared more arrangement patterns than that between Vespinae and Eumeninae.

The complete mitochondrial genome of the predatory bug Orius sauteri (Poppius) (Hemiptera: Anthocoridae) was sequenced and analyzed (GenBank accession No. KJ671626). The length of this mitochondrial genome is 16,246 bp with 37 typical animal mitochondrial genes; i.e., 13 protein-coding, 2 rRNA and 22 tRNA genes, and an A+T-rich region. The gene arrangement is identical to that of the pupative ancestral arrangement of insects. All protein-coding genes start with ATN start codon, i.e. five ATAs, four ATTs, three ATGs and one ATC. Ten protein-coding genes stop with termination codon TAA. Three protein-coding genes use incomplete stop codon TA. The A+T-rich region are located between rrnS and trnM with a length of 1758 bp and an A+T content of 73.49%.