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AbstractThe order Hymenoptera is one of the most species-rich insect orders, with more than 150,000 described extant species. Many hymenopteran insects have very different mitochondrial genome (mitogenome) organizations compared to the putative ancestral organization of insects. In this study, we sequenced 18 mitogenomes of representatives in the order Hymenoptera to increase taxonomic sampling. A total of 475 species were used in phylogenetic analyses, including 18 new mitogenomes and 457 existing mitogenomes. Using a site-heterogeneous model, Bayesian’s inference from amino acid data yielded more resolved relationships among Hymenoptera than maximum-likelihood analysis and coalescent-based species analyses. The monophyly of Symphyta was not supported. The Xyeloidea was the earliest branching clade in the Hymenoptera. The Orussoidea was closely related to Apocrita. Within Apocrita, the Parasitoida was non-monophyletic. The monophyly of most Parasitoida superfamilies received strong support. The Proctotrupomorpha clade was supported in Bayesian’s analysis. The Apoidea was monophyletic when excluding Ampulex compressa from consideration. The superfamilies Vespoidea and Chrysidoidea were found to be non-monophyletic. Comparisons of mitochondrial gene order revealed a higher frequency of gene rearrangement among lineages with a parasitoid lifestyle, particularly prominent in Chalcidoidea. The degree of gene rearrangement ranked second in specific taxa of Cynipoidea and Ichneumonoidea. [ABSTRACT FROM AUTHOR]

Adaptive evolution following colonization can affect the impact of invasive species. The fall webworm (FWW) invaded China 40 years ago through a single introduction event involving a severe bottleneck and subsequently diverged into two genetic groups. The well‐recorded invasion history of FWW, coupled with a clear pattern of genetic divergence, provides an opportunity to investigate whether there is any sign of adaptive evolution following the invasion. Based on genome‐wide SNPs, we identified genetically separated western and eastern groups of FWW and correlated spatial variation in SNPs with geographical and climatic factors. Geographical factors explained a similar proportion of the genetic variation across all populations compared with climatic factors. However, when the two population groups were analysed separately, environmental factors explained more variation than geographical factors. SNP outliers in populations of the western group had relatively stronger response to precipitation than temperature‐related variables. Functional annotation of SNP outliers identified genes associated with insect cuticle protein potentially related to desiccation adaptation in the western group and genes associated with lipase biosynthesis potentially related to temperature adaptation in the eastern group. Our study suggests that invasive species may maintain the evolutionary potential to adapt to heterogeneous environments despite a single invasion event. The molecular data suggest that quantitative trait comparisons across environments would be worthwhile. [ABSTRACT FROM AUTHOR]

Following invasion, insects can become adapted to conditions experienced in their invasive range, but there are few studies on the speed of adaptation and its genomic basis. Here, we examine a small insect pest, Thrips palmi , following its contemporary range expansion across a sharp climate gradient from the subtropics to temperate areas. We first found a geographically associated population genetic structure and inferred a stepping-stone dispersal pattern in this pest from the open fields of southern China to greenhouse environments of northern regions, with limited gene flow after colonization. In common garden experiments, both the field and greenhouse groups exhibited clinal patterns in thermal tolerance as measured by critical thermal maximum (CTmax) closely linked with latitude and temperature variables. A selection experiment reinforced the evolutionary potential of CTmax with an estimated h 2 of 6.8% for the trait. We identified 3 inversions in the genome that were closely associated with CTmax, accounting for 49.9%, 19.6%, and 8.6% of the variance in CTmax among populations. Other genomic variations in CTmax outside the inversion region were specific to certain populations but functionally conserved. These findings highlight rapid adaptation to CTmax in both open field and greenhouse populations and reiterate the importance of inversions behaving as large-effect alleles in climate adaptation. [ABSTRACT FROM AUTHOR]

The genome-level features are crucial genetic resources for species identification and phylogenetic analysis. Here, the complete mitochondrial genome of Aphidius colemani Viereck 1912 (Hymenoptera: Braconidae: Aphidiinae) was sequenced, determined and analyzed. The circular genome is 16,372 bp in length with an overall base composition of 38.9% for A, 46.2% for T, 6.7% for C, and 8.2% for G. The mitochondrial genome of A. colemani contained 13 protein-coding genes that initiated by the ATN codon, 22 transfer RNA genes, two ribosomal RNA genes (rRNAs), and a control region (CR). It shared the same gene arrangement patterns that occurred in two tRNA clusters of trnI-trnQ-trnM and trnW-trnC-trnY with Aphidius gifuensis. Phylogenetic analyses using Bayesian inference and Maximum-likelihood methods supported that the two species of Aphidiinae formed a clade and sister to other subfamilies of Braconidae. [ABSTRACT FROM AUTHOR]

The barley yellow dwarf virus (BYDV) of cereals is thought to substantially increase the high-temperature tolerance of its aphid vector, Rhopalosiphum padi, which may enhance its transmission efficiency. This is based on experiments with North American strains of BYDV and R. padi. Here, we independently test these by measuring the temperature tolerance, via Critical Thermal Maximum (CTmax) and knockdown time, of Australian R. padi infected with a local BYDV isolate. We further consider the interaction between BYDV transmission, the primary endosymbiont of R. padi (Buchnera aphidicola), and a transinfected secondary endosymbiont (Rickettsiella viridis) which reduces the thermotolerance of other aphid species. We failed to find an increase in tolerance to high temperatures in BYDV-infected aphids or an impact of Rickettsiella on thermotolerance. However, BYDV interacted with R. padi endosymbionts in unexpected ways, suppressing the density of Buchnera and Rickettsiella. BYDV density was also fourfold higher in Rickettsiella-infected aphids. Our findings indicate that BYDV does not necessarily increase the temperature tolerance of the aphid transmission vector to increase its transmission potential, at least for the genotype combinations tested here. The interactions between BYDV and Rickettsiella suggest new ways in which aphid endosymbionts may influence how BYDV spreads, which needs further testing in a field context. [ABSTRACT FROM AUTHOR]

Background: Several agricultural fungicides are known to affect insect pests directly and these effects may be transgenerational and mediated through impacts on endosymbionts, providing opportunities for pest control. The cotton aphid Aphis gossypii is a polyphagous pest that can cause large crop yield losses. Here, we tested the effects of three fungicides, pyraclostrobin, trifloxystrobin and chlorothalonil, on the fitness and Buchnera endosymbiont of A. gossypii. Results: The formulations of trifloxystrobin and pyraclostrobin, and the active ingredient of pyraclostrobin produced dose‐dependent mortality in A. gossypii, whereas there was no dose‐dependent mortality for chlorothalonil. The formulations of trifloxystrobin and pyraclostrobin significantly reduced the lifespan and fecundity of A. gossypii, and increased the density of Buchnera in the parental generation but not the (unexposed) F1. When the active ingredient of pyraclostrobin was tested, the lifespan of the F0 generation was also reduced, but the density of Buchnera was not, indicating that non‐insecticidal chemicals in the fungicide formulation may affect the density of the endosymbiont of A. gossypii. There was no transgenerational effect of the active ingredient of pyraclostrobin on the lifespan and Buchnera of (unexposed) F1. Conclusions: Our results suggest that formulations of two strobilurin fungicides have immediate impacts on the fitness of A. gossypii, and chemicals in the formulation impact the density of the primary Buchnera endosymbiont. Our study highlights the potential effects of non‐insecticidal chemicals of fungicides on aphid pests and their primary endosymbionts but direct connections between fitness and Buchnera densities remain unclear. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Field control of pest thrips mainly relies on insecticides, but the toxicity of insecticides can vary among thrips species and populations. In this study, we examined the susceptibility of multiple field populations of two thrips pests, Frankliniella occidentalis, and Thrips palmi, that often co‐occur on vegetables, to nine insecticides belonging to seven subgroups. RESULTS: The highest level of variation in susceptibility among F. occidentalis populations was for spinetoram (73.92 fold difference between most resistant and most susceptible population), followed by three neonicotinoids (8.06–15.99 fold), while among T. palmi populations, it was also for spinetoram (257.19 fold), followed by emamectin benzoate, sulfoxaflor, and acetamiprid (23.64–45.50 fold). These findings suggest evolved resistance to these insecticides in some populations of the two thrips. One population of F. occidentalis had a particularly high level of resistance overall, being the most resistant for five of the nine insecticides tested. Likewise, a population of T. palmi had high resistance to all nine insecticides, again suggesting the evolution of resistance to multiple chemicals. For F. occidentalis, the LC95 values of most populations were higher than the field‐recommended dosage for all insecticides except chlorfenapyr and emamectin benzoate. For several T. palmi populations, the LC95 values also tended to be higher than recommended dosages, except in the case of emamectin benzoate and spinetoram. CONCLUSIONS: Our study found interspecific and intraspecific variations in the susceptibility of two thrips to nine insecticides and multiple resistance in some populations, highlighting the need for ongoing monitoring and resistance management. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Pesticide resistance is a long‐standing and growing problem in the chemical control of invertebrate pests. Molecular diagnostic methods can facilitate pesticide resistance management by accurately and efficiently detecting resistant mutations and their frequency. In this study, the kompetitive allele specific PCR (KASP) approach, a technology for high‐throughput single nucleotide polymorphism (SNP) genotyping, is validated as a useful method for characterizing genotypes at a pesticide‐resistance locus for the first time. We focus on the spinetoram resistance mutation of G275E in the nicotinic acetylcholine receptor alpha 6 (nAChR α6) subunit gene of Thrips palmi. RESULTS: Of the 341 individuals of Thrips palmi tested, 98.24% were successfully genotyped, with 100% concordance with Sanger sequencing results. We then quantitatively mixed genomic DNA of known genotypes to establish 21 DNA mixtures with a resistant allele frequency ranging from 0 to 100% at steps of 5%. The linear discriminant analysis (LDA) showed that 75.8% of original grouped cases were correctly classified; six groups had no overlap in membership (resistant allele frequency: 0%, 5%, 10–75%, 80–85%, 90–95%, and 100%). When we chose 11 pooled samples with 10% steps for LDA, 84.4% of original grouped cases were correctly classified; seven groups had no overlap in membership (0%, 10%, 20–30%, 40–70%, 80%, 90%, 100%). The results indicated that KASP applied to pooled samples may provide a semi‐quantitative estimate of resistance. CONCLUSIONS: Our study points to the suitability of KASP for high‐throughput genotyping of genotypes affecting pesticide resistance and semi‐quantitative assessments of resistance allele frequencies in populations. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Background: The two‐spotted spider mite (TSSM), Tetranychus urticae (Acari: Tetranychidae), is a cosmopolitan phytophagous pest in agriculture and horticulture. It has developed resistance to many acaricides by target‐site mutations. Understanding the status and evolution of resistant mutations in the field is essential for resistance management. Here, we applied a high‐throughput Kompetitive allele‐specific polymerase chain reaction (KASP) method for detecting six mutations conferring resistance to four acaricides of the TSSM. We genotyped 3274 female adults of TSSM from 43 populations collected across China in 2017, 2020, and 2021. Results: The KASP genotyping of 24 testing individuals showed 99% agreement with Sanger sequencing results. KASP assays showed that most populations had a high frequency of mutations conferring avermectin (G314D and G326E) and pyridaben (H92R) resistance. The frequency of mutation conferring bifenazate (A269V and G126S) and etoxazole (I1017F) resistance was relatively low. Multiple mutations were common in the TSSM, with 70.2% and 24.6% of individuals having 2–6 and 7–10 of 10 possible resistant alleles, respectively. No loci were linked in most populations among the six mutations, indicating the development of multiple resistance is mainly by independent selection. However, G314D and I1017F on the nuclear genome deviated from Hardy–Weinberg equilibrium in most populations, indicating significant selective pressure on TSSM populations by acaricides or fitness cost of the mutations in the absence of acaricide selection. Conclusion: Our study revealed that the high frequency of TSSMs evolved multiple resistant mutations in population and individual levels by independent selection across China, alarming for managing multiple‐acaricides resistance. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Simple Summary: Ericerus pela Chavannes (Hemiptera: Coccoidea) is one of the most economically valuable resource insects in China. Its mitochondrial genome provides essential information for the molecular identification and genetic study of this species. In this paper, we assembled the mitochondrial genome of E. pela. Gene rearrangement analysis showed that compared to other scale insects, E. pela's atp6, atp8, and a few tRNAs were obviously rearranged. Moreover, there were nine tRNAs identified to have obvious truncated structures. Synteny analysis based on the whole mitochondrial genomes showed that a significant rearrangement of homologous blocks had occurred within this Coccoidea species. The results revealed great variations in the intergenic regions among Coccoidea species and novel gene arrangement and truncated tRNA genes in the mitochondrial genome of E. pela. The Chinese white wax scale insect, Ericerus pela Chavannes (Hemiptera: Coccidae), is one of the scale insects with great economic value and has been dispersed and reared in China for over one thousand years. Its mitochondrial genome provides essential information for the molecular identification and genetic study of this species. We assembled the complete mitochondrial genome of E. pela based on PacBio sequencing and analyzed its genomic features. The genome was 17,766 bp in length with 13 protein-coding genes, 22 tRNAs, and two rRNA genes. The analysis results showed E. pela had significant gene rearrangements involving tRNAs compared with other Coccoidea species. Furthermore, E. pela's nine tRNAs were identified to have obvious truncated structures. The phylogenetic tree compiled of the species showed a long branch of the Coccoidea lineage, which indicated the high evolutionary rate in this group. Our study revealed the mitochondrial characteristics of E. pela and enriched the mitochondrial genetic information on Coccoidea species. It also determined the occurrence of gene rearrangement for the species in this superfamily. [ABSTRACT FROM AUTHOR]

The movement of individuals through continuous space is typically constrained by dispersal ability and dispersal barriers. A range of approaches have been developed to investigate these. Kindisperse is a new approach that infers recent intergenerational dispersal (σ) from close kin dyads and appears particularly useful for investigating taxa that are difficult to observe individually. This study, focusing on the mosquito Aedes aegypti , shows how the same close kin data can also be used for barrier detection. We empirically demonstrate this new extension of the method using genome-wide sequence data from 266 Ae. aegypti. First, we use the spatial distribution of full-sib dyads collected within one generation to infer past movements of ovipositing female mosquitoes. These dyads indicated the relative barrier strengths of two roads and performed favorably against alternative genetic methods for detecting barriers. We then use Kindisperse to quantify recent intergenerational dispersal (σ = 81.5 –197.1 m generation−1/2) from the difference in variance between the sib and the first cousin spatial distributions and, from this, estimate effective population density (ρ = 833 –4,864 km−2). Dispersal estimates showed general agreement with those from mark-release-recapture studies. Barriers, σ, ρ, and neighborhood size (331–526) can inform forthcoming releases of dengue-suppressing Wolbachia bacteria into this mosquito population. [ABSTRACT FROM AUTHOR]

Background: Thrips pests cause increasing damage to crops around the world. Widespread usage of some insecticides against thrips has now led to the evolution of resistance to several active ingredients, and new insecticides are required. This study examined the toxicity of the novel insecticide broflanilide to multiple populations of several thrips pests. Results: Bioassays showed that thrips populations had LC50 values ranging from 0.5 to almost 300 mg·L−1. A population of Frankliniella occidentalis had the highest LC50 value at 290.63 mg·L−1, while a population of Echinothrips americanus had the lowest LC50 value at 0.51 mg L−1. LC50 values among seven populations of Thrips palmi ranged from 2.5689 to 23.6754 mg·L−1, indicating intraspecific variation in toxicity. In this species, the toxicity of broflanilide was relatively higher in adults than in larvae. More than 90% of eggs of T. palmi could not develop into larvae when treated with 5–50 mg L−1 broflanilide. Compared to five commonly used insecticides, broflanilide showed relatively high toxicity to T. palmi. Field control tests with T. palmi showed that control efficacy (from 90.44% to 93.14%) was maintained from day three to day 14 after treatment with 22.5 and 45 ga.i hm−1 broflanilide. Conclusion: Broflanilide is potentially a useful insecticide for controlling Thrips hawaiiensis, Frankliniella intonsa, Megalurothrips usitatus. E. americanus, and some populations of T. palmi. However, the variation in toxicity of this insecticide to different species, populations, and developmental stages indicates that target species and life stages may need to be carefully considered. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

How invasive species cope with novel selective pressures with limited genetic variation is a fundamental question in molecular ecology. Several mechanisms have been proposed, but they can lack generality. Here, we addressed an alternative solution, polygenic adaptation, wherein traits that arise from multiple combinations of loci may be less sensitive to loss of variation during invasion. We tested the polygenic signal of environmental adaptation of Colorado potato beetle (CPB) introduced in Eurasia. Population genomic analyses showed declining genetic diversity in the eastward expansion of Eurasian populations, and weak population genetic structure (except for the invasion fronts in Asia). Demographic history showed that all populations shared a strong bottleneck about 100 years ago when CPB was introduced to Europe. Genome scans revealed a suite of genes involved in activity regulation functions that are plausibly related to cold stress, including some well‐founded functions (e.g., the activity of phosphodiesterase, the G‐protein regulator) and discrete functions. Such polygenic architecture supports the hypothesis that polygenic adaptation and potentially genetic redundancy can fuel the adaptation of CPB despite strong genetic depletion, thus representing a promising general mechanism for resolving the genetic paradox of invasion. More broadly, most complex traits based on polygenes may be less sensitive to invasive bottlenecks, thus ensuring the evolutionary success of invasive species in novel environments. [ABSTRACT FROM AUTHOR]