Comparative analysis of mitochondrial genomes of geographic variants of the gypsy moth, Lymantria dispar, reveals a previously undescribed genotypic entity

Characterization and Molecular Phylogenetic Analysis of Subfamily Erebinae (Lepidoptera: Noctuoidea: Erebidae) Using Five Complete Mitochondrial Genomes

In this study, the complete mitogenomes of Sympis rufibasis, Lacera noctilio, Oxyodes scrobiculata, Mocis undata, and Artena dotata were newly sequenced to bring up-to-date the database using the next-generation sequencing methods. The gene order of all sequenced mitogenomes was identical consisting of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a non-coding A+T-rich region, which were common to other Lepidopteran insects. All protein-coding genes (PCGs) initiated with a canonical ATN codon and ended with TAN or an incomplete stop codon, single T. The A+T-rich region of S. rufibasis, L. noctilio, O. scrobiculata, M. undata, and A. dotata are 406 bp, 462 bp, 372 bp, 410 bp, and 406 bp long, respectively, containing number of characteristics that are distinctive to Noctuoidea moths. We analyzed concatenated amino acid sequences of protein-coding genes not including rRNAs, using Maximum Likelihood and Bayesian Inference methods. The phylogenetic analyses indicated that the tribe relationships within Erebinae were reconstructed as (Sypnini+((Erebini 1+Poaphilini 1)+((Euclidiini+Catocalini+(Hypopyrini+Erebini 2))+((Hulodini+(Poaphilini 2+Ophiusini))))). Phylogenetic analyses supported and confirmed the monophyly of the subfamilies' relationships as follows: (Hypeninae+Lymantriinae)+((Scoliopterginae+((Calpinae+Erebinae)+((Herminiinae+Aganainae)+Arctiinae)))) within Erebidae.

Mitochondrial genomes of four slug moths (Lepidoptera, Limacodidae): Genome description and phylogenetic implications

The family Limacodidae belongs to the superfamily Zygaenoidea, which includes 1672 species commonly referred to as slug moths. Limacodidae larvae are major pests for many economically important plant species and can cause human dermatitis. At present, the structure of the mitochondrial genome (mitogenome), phylogenetic position, and adaptive evolution of slug moths are poorly understood. Herein, the mitogenomes of Parasa lepida, Phlossa conjuncta, Thosea sinensis, and Setora sinensis were sequenced and compared with other available mitogenome sequences to better characterize the mitogenomic diversity and evolution of this moth family. The mitogenomes of P. lepida, P. conjuncta, T. sinensis, and S. sinensis were confirmed to be circular in structure with lengths of 15,575 bp, 15,553 bp, 15,535 bp, and 15,529 bp, respectively. The Limacodidae mitogenomes exhibited similar nucleotide composition, codon usage, RNA structure, and control region patterns, indicating the conservation of the mitogenome in the family Limacodidae. A sliding window, Ka/Ks, and genetic distance analyses revealed that the atp8 and nad6 genes exhibited the highest levels of variability and the most rapid evolutionary rates among the 13 protein-coding genes (PCGs) encoded in these Limacodidae mitogenomes, suggesting that they may offer value as candidate DNA markers. The phylogenetic analysis recovered the overall relationship as Tortricoidea + (Sesiidae + (Zygaenoidea + (Cossoidea/+Choreutoidea + (others)))). Within Zygaenoidea, Limacodidae was recovered as monophyletic, and the phylogenetic relationships were recovered as (Phaudidae + Zyganidae) + Limacodidae in all six phylogenetic trees. The analysis indicated that P. lepida, P. conjuncta, T. sinensis, and S. sinensis are members of the Limacodidae.

Phenological Features of the Spongy Moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), in the Northernmost Portions of Its Eurasian Range

The spongy moth, Lymatria dispar, is a classic example of an invasive pest accidentally introduced from Europe to North America, where it has become one of the most serious forest defoliators, as in its native range. The present study was aimed at (i) identifying the current northern limit of L. dispar's Eurasian range and exploring its northward expansion in Canada using pheromone trap data, and (ii) comparing northern Eurasian populations with those from central and southern regions with respect to male flight phenology, the sums of effective temperatures (SETs) above the 7 °C threshold necessary for development to the adult stage, and heat availability. We show that the range of L. dispar in Eurasia now reaches the 61st parallel, and comparisons with historical data identify the average speed of spread as 50 km/year. We also document the northern progression of L. dispar in southern Canada, where the actual northern boundary of its range remains to be identified. We show that the median date of male flight does not vary greatly between northern and southern regions of the spongy moth range in Eurasia despite climate differences. Synchronization of flight at different latitudes of the range is associated with an acceleration of larval development in northern Eurasian populations. Similar changes in developmental rate along a latitudinal gradient have not been documented for North American populations. Thus, we argue that this feature of spongy moths from northern Eurasia poses a significant invasive threat to North America in terms of enhanced risks for rapid northward range expansion.

Characterization of four mitochondrial genomes from superfamilies Noctuoidea and Hyblaeoidea with their phylogenetic implications

In the present study, the newly sequenced mitogenomes of three Noctuoid and one Hyblaeoid (Insecta: Lepidoptera) species were annotated based on next-generation sequence data. The complete mitogenome lengths of Oraesia emarginata, Actinotia polyodon, Odontodes seranensis, and Hyblaea puera were 16,668 bp, 15,347 bp, 15,419 bp, and 15,350 bp, respectively. These mitogenomes were found to encode 37 typical mitochondrial genes (13 protein-coding, 22 transfer RNA, 2 ribosomal RNA) and a control region, similar to most Lepidoptera species. Maximum likelihood (ML) methods and Bayesian inference (BI) were used to reconstruct the phylogenetic relationships of the moths. This study showed the relationships of Noctuoid families as follows: (Notodontidae + (Erebidae + (Nolidae + (Euteliidae + Noctuidae)))). Furthermore, the species H. puera was separately clustered from the Noctuoidea member groups. Till now, the species from the superfamily Hyblaeoidea have not been discussed for their phylogenetic relationships. In this study, the complete mitochondrial genome of one species from the superfamily Hyblaeoidea was analysed.

Analyses of adult transcriptomes from four different populations of the spongy moth, Lymantria dispar L., from China and the USA

The spongy moth Lymantria dispar, formerly known as the gypsy moth, is a forest pest that occurs as two different biotypes: the European spongy moth (ESM), Lymantria dispar dispar, which is distributed in Europe and North America; and the Asian spongy moth (ASM), which consists of subspecies Lymantria dispar asiatica and Lymantria dispar japonica and is distributed in China, Russia, Korea, and Japan. The Asian biotype is classified as a quarantine pest by the U.S. Department of Agriculture because of the superior flight ability of adult females compared to females of the European biotype. To identify genes that potentially account for differences in female flight capability between the two biotypes, we assembled and compared transcriptional profiles of two North American populations of ESM and two Chinese populations of ASM, including samples of unmated female adults and females after mating and oviposition. Of 129,286 unigenes identified, 306 were up-regulated in ASM samples relative to ESM, including genes involved in egg production. In contrast, 2309 unigenes were down-regulated in ASM samples, including genes involved in energy production. Although a previous study found that ASM female flight was reduced after oviposition, a comparison of gene expression before and after mating and oviposition did not reveal any genes which were consistently up- or down-regulated in the two ASM populations.

Lymantria dispar (L.) (Lepidoptera: Erebidae): Current Status of Biology, Ecology, and Management in Europe with Notes from North America

The European Spongy moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), is an abundant species found in oak woods in Central and Southern Europe, the Near East, and North Africa and is an important economic pest. It is a voracious eater and can completely defoliate entire trees; repeated severe defoliation can add to other stresses, such as weather extremes or human activities. Lymantria dispar is most destructive in its larval stage (caterpillars), stripping away foliage from a broad variety of trees (>500 species). Caterpillar infestation is an underestimated problem; medical literature reports that established populations of caterpillars may cause health problems to people and animals. Inflammatory reactions may occur in most individuals after exposure to setae, independent of previous exposure. Currently, chemical and mechanical methods, natural predators, and silvicultural practices are included for the control of this species. Various insecticides have been used for its control, often through aerial sprayings, which negatively affect biodiversity, frequently fail, and are inappropriate for urban/recreational areas. However, bioinsecticides based on various microorganisms (e.g., entomopathogenic viruses, bacteria, and fungi) as well as technologies such as mating disruption using sex pheromone traps have replaced insecticides for the management of L. dispar.

Genome Organization and Comparative Evolutionary Mitochondriomics of Brown Planthopper, Nilaparvata lugens Biotype 4 Using Next Generation Sequencing (NGS)

Nilaparvata lugens is the main rice pest in India. Until now, the Indian N. lugens mitochondrial genome has not been sequenced, which is a very important basis for population genetics and phylogenetic evolution studies. An attempt was made to sequence two examples of the whole mitochondrial genome of N. lugens biotype 4 from the Indian population for the first time. The mitogenomes of N. lugens are 16,072 and 16,081 bp long with 77.50% and 77.45% A + T contents, respectively, for both of the samples. The mitochondrial genome of N. lugens contains 37 genes, including 13 protein-coding genes (PCGs) (cox1-3, atp6, atp8, nad1-6, nad4l, and cob), 22 transfer RNA genes, and two ribosomal RNA (rrnS and rrnL) subunits genes, which are typical of metazoan mitogenomes. However, both samples of N. lugens mitogenome in the present study retained one extra copy of the trnC gene. Additionally, we also found 93 bp lengths for the atp8 gene in both of the samples, which were 60–70 bp less than that of the other sequenced mitogenomes of hemipteran insects. The phylogenetic analysis of the 19 delphacids mitogenome dataset yielded two identical topologies when rooted with Ugyops sp. in one clade, and the remaining species formed another clade with P. maidis and M. muiri being sisters to the remaining species. Further, the genus Nilaparvata formed a separate subclade with the other genera (Sogatella, Laodelphax, Changeondelphax, and Unkanodes) of Delphacidae. Additionally, the relationship among the biotypes of N. lugens was recovered as the present study samples (biotype-4) were separated from the three biotypes reported earlier. The present study provides the reference mitogenome for N. lugens biotype 4 that may be utilized for biotype differentiation and molecular-aspect-based future studies of N. lugens.

Association of the Female Flight Ability of Asian Spongy Moths (Lymantria dispar asiatica) with Locality, Age and Mating: A Case Study from China

The spongy moth (formerly known as a gypsy moth), Lymantria dispar L. (Lepidoptera: Erebidae), is a polyphagous pest that defoliates various species of trees in the genera Populus, Salix, Quercus, Acer and Pinus. Egg masses of Asian spongy moths (Lymantria dispar asiatica) were obtained from five geographically distinct locations in China (Chengdu, Xifeng, Heilongjiang, Kuduer and Longhua regions) and were carried to the lab for incubation and rearing larvae up to adult emergence. The aim was to see how locality, age and mating status influenced the flying activity of female Asian spongy moths. The findings demonstrate that age significantly affects L. dispar asiatica flying activity, with flight period and distance decreasing dramatically as age increases. Locality also significantly impacts flight ability, and mating status does not affect the L. dispar asiatica female flight ability (p > 0.05). The maximum speed was observed for females from Xifeng (7.19 ± 0.34 km/h). The females from Heilongjiang were recorded as having the maximum average speed (2.35 ± 0.08 km/h). Females from Xifeng exhibited the maximum flight duration and distance (0.94 ± 0.04 h and 1.87 ± 0.18 km). Morphological features, i.e., thorax width (cm) and wing loading, significantly influenced the L. dispar asiatica flight ability (R2 = 0.93 and R2 = −0.98). The overall pattern observed for female L. dispar asiatica flight duration was Xifeng > Kuder > Chengdu > Heilongjiang > Longhua, and for flight distance, it was Xifeng > Longhua > Heilongjiang > Kuder > Chengdu. This research offers detailed information on the dispersion rate of Spongy moths in a known or newly introduced habitat, which can help us limit the spread of this polyphagous pest.

Universal Mitochondrial Multi-Locus Sequence Analysis (mtMLSA) to Characterise Populations of Unanticipated Plant Pest Biosecurity Detections

Simple Summary

Agricultural and environmental sustainability requires effective biosecurity responses that prevent the establishment or spread of exotic insect pests. Understanding where new detections may have come from or if recurrent detections are connected contributes to this. Suitable population genetic markers use relatively rapidly evolving gene regions which render the PCR method species-specific at best. Because resource limitations mean these are pre-emptively developed for the highest risk species, populations of other exotic pests are unable to be characterised at the time. Here we have developed a generic method that is useful across species within the same taxonomic Order, including where there is little or no prior knowledge of their gene sequences. Markers are formed by concomitant sequencing of four gene regions. Sequence concatenation was shown to retrieve higher resolution signatures than standard DNA barcoding. The method is encouragingly universal, as illustrated across species in ten fly and 11 moth superfamilies. Although as-yet untested in a biosecurity situation, this relatively low-tech, off-the-shelf method makes a proactive contribution to the toolbox of quarantine agencies at the time of detection without the need for impromptu species-specific research and development.

Abstract

Biosecurity responses to post-border exotic pest detections are more effective with knowledge of where the species may have originated from or if recurrent detections are connected. Population genetic markers for this are typically species-specific and not available in advance for any but the highest risk species, leaving other less anticipated species difficult to assess at the time. Here, new degenerate PCR primer sets are designed for within the Lepidoptera and Diptera for the 3′ COI, ND3, ND6, and 3′ plus 5′ 16S gene regions. These are shown to be universal at the ordinal level amongst species of 14 and 15 families across 10 and 11 dipteran and lepidopteran superfamilies, respectively. Sequencing the ND3 amplicons as an example of all the loci confirmed detection of population-level variation. This supported finding multiple population haplotypes from the publicly available sequences. Concatenation of the sequences also confirmed that higher population resolution is achieved than for the individual genes. Although as-yet untested in a biosecurity situation, this method is a relatively simple, off-the-shelf means to characterise populations. This makes a proactive contribution to the toolbox of quarantine agencies at the time of detection without the need for unprepared species-specific research and development.

Comparative mitochondrial genome analysis of Eudocima salaminia (Cramer, 1777) (Lepidoptera: Noctuoidea), novel gene rearrangement and phylogenetic relationship within the superfamily Noctuoidea

The species Eudocima salaminia (Cramer, 1777) commonly known as the fruit-piercing moth belongs to family Erebidae. Its distribution varies from India and across South-east Asia, pacific islands and parts of Australia. The insect is a devastating pest of citrus, longans and lychees. In the present study, complete mitochondrial genome of Eudocima salaminia was sequenced and analyzed using Illumina sequencer. The phylogenetic tree was reconstructed based on nucleotide sequences of 13 PCGs using Maximum likelihood method-General Reversible mitochondrial (mtREV) model. The mitogenome has 15,597 base pairs (bp) in length, comprising of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes and A + T-rich region. All protein-coding genes (PCGs) initiate with canonical start codon ATN. The gene order (trnQ-trnI-trnM) of tRNA shows a different rearrangement compared to ancestral insect gene order (trnI-trnQ-trnM). Almost all tRNAs have a typical cloverleaf secondary structure except for trnS1 (AGN) which lacks the dihydrouridine arm. At the beginning of the control region, we observed a conserved polyT", motif "ATTTA" and microsatellite (TA)n element. There are 21 intergenic regions and five overlapping regions ranging from 1 to 73 bp and 1 to 8 bp, respectively. The phylogenetic relationships based on nucleotide sequences of 13 PCGs using Maximum likelihood method showed the family level relationships as (Notodontidae + (Euteliidae + Noctuidae + (Erebidae + Nolidae))). The present study represents the similarity to phylogenetic analysis of Noctuoidea mitogenome. Moreover, the family Erebidae is the sister to the families of (Euteliidae + Noctuidae + Nolidae).

Sequencing, Assembly and Annotation of the Whole-Insect Genome of Lymantria dispar dispar, the European Gypsy Moth

The European gypsy moth, Lymantria dispar dispar (LDD), is an invasive insect and a threat to urban trees, forests and forest-related industries in North America. For use as a comparator with a previously published genome based on the LD652 pupal ovary-derived cell line, as well as whole-insect genome sequences obtained from the Asian gypsy moth subspecies L. dispar asiatica and L. dispar japonica, the whole-insect LDD genome was sequenced, assembled and annotated. The resulting assembly was 998 Mb in size, with a contig N50 of 662 Kb and GC content of 38.8%. Long interspersed nuclear elements (LINEs) constitute 25.4% of the whole-insect genome, and a total of 11,901 genes predicted by automated gene finding encoded proteins exhibiting homology with reference sequences in the NCBI NR and/or UniProtKB databases at the most stringent similarity cutoff level (i.e., the gold tier). These results will be especially useful in developing a better understanding of the biology and population genetics of L. dispar and the genetic features underlying Lepidoptera in general.

Potential Differences and Methods of Determining Gypsy Moth Female Flight Capabilities: Implications for the Establishment and Spread in Novel Habitats

The introduction of the Asian gypsy moth into novel environments continues with frequent interceptions in North America. There is a concern that these subspecies will pose a greater threat to the forests and urban environments of North America than the established gypsy moths (Lymantria dispardispar L.), due to their greater capacity for female flight. Asian gypsy moth populations vary in many key traits, including female flight capabilities. The potential impacts of female flight, in combination with the other key traits, on the ecology and spread of this insect are first discussed in this communication. This also provides the first review of most of the current literature on the variations in flight capability and flight distance of gypsy moth populations, as well as variation in other traits of concern and the potential methods of identification, with special attention paid to the Asian subspecies Lymantria dispar japonica Motschulsky and Lymantria dispar asiatica Vinkovskij. There are currently good tools for identifying the general origin of introduced gypsy moth populations, but these do not provide enough information to effectively manage introductions. Gypsy moth key traits differ among populations, even within each subspecies of the gypsy moth, so introduction of gypsy moths from other world areas into locations where the gypsy moth is already present could result in unwanted changes in gypsy moth biology. It also appears that the introduction of flight-capable females could enhance a population’s dispersal capability and require modifications to management protocols used for flightless females. Therefore, rapid tools to assess key traits in introduced populations are needed to adequately plan for, or deal with, new introductions into novel habitats.

Temporospatial modulation of Lymantria dispar immune system against an entomopathogenic fungal infection

BACKGROUND

Lymantria dispar is an economically impactful forest pest worldwide. The entomopathogenic fungi Beauveria bassiana shows great promise in pest management due to its high lethality in Lymantria dispar. A complete understanding of the immune interactions between the pest and the pathogenic fungus is essential to actualizing biological pest management.

RESULTS

Following the infection of Lymantria dispar by Beauveria bassiana spores, we performed a time-course analysis of transcriptome in Lymantria dispar fat bodies and hemocytes to explore host immune response. A total of 244 immunity-related genes including pattern recognition receptors, extracellular signal modulators, immune pathways (Toll, IMD, JNK and JAK/STAT), and response effectors were identified. We observed contrasting tissue and time-specific differences in the expression of immune genes. At the early stage of infection, several recognition receptors and effector genes were activated, while the signal modulation and effector genes were suppressed at later stages. Further enzyme activity-based assays coupled with gene expression analysis of prophenoloxidase revealed a significant upregulation of phenoloxidase activity at 48- and 72-h post-infection. Moreover, fungal infection led to dysbiosis in gut microbiota that seems to be partially attributed to reduced gut hydrogen peroxide (H₂ O₂ ) amount, which indicates a significant impact of fungal infection on host gut microbes.

CONCLUSION

Our study provides a comprehensive sequence resource and crucial new insights about an economically important forest pest. Specifically, we elucidate the complicated multipartite interaction between host and fungal pathogen and contribute to a better understanding of Lymantria dispar anti-fungal immunity, resulting in better tools for biological pest control. © 2020 Society of Chemical Industry.

Tracking invasions of a destructive defoliator, the gypsy moth (Erebidae: Lymantria dispar): Population structure, origin of intercepted specimens, and Asian introgression into North America

Genetic data can help elucidate the dynamics of biological invasions, which are fueled by the constant expansion of international trade. The introduction of European gypsy moth (Lymantria dispar dispar) into North America is a classic example of human-aided invasion that has caused tremendous damage to North American temperate forests. Recently, the even more destructive Asian gypsy moth (mainly L. d. asiatica and L. d. japonica) has been intercepted in North America, mostly transported by cargo ships. To track invasion pathways, we developed a diagnostic panel of 60 DNA loci (55 nuclear and 5 mitochondrial) to characterize worldwide genetic differentiation within L. dispar and its sister species L. umbrosa. Hierarchical analyses supported strong differentiation and recovered five geographic groups that correspond to (1) North America, (2) Europe plus North Africa and Middle East, (3) the Urals, Central Asia, and Russian Siberia, (4) continental East Asia, and (5) the Japanese islands. Interestingly, L. umbrosa was grouped with L. d. japonica, and the introduced North American population exhibits remarkable distinctiveness from contemporary European counterparts. Each geographic group, except for North America, shows additional lower-level structures when analyzed individually, which provided the basis for inference of the origin of invasive specimens. Two assignment approaches consistently identified a coastal area of continental East Asia as the major source for Asian invasion during 2014-2015, with Japan being another source. By analyzing simulation and laboratory crosses, we further provided evidence for the occurrence of natural Asian-North American hybrids in the Pacific Northwest, raising concerns for introgression of Asian alleles that may accelerate range expansion of gypsy moth in North America. Our study demonstrates how genetic data contribute to bio-surveillance of invasive species with results that can inform regulatory management and reduce the frequency of trade-associated invasions.

The importance of DNA barcode choice in biogeographic analyses - a case study on marine midges of the genus Clunio

DNA barcodes are widely used for species identification and biogeographic studies. Here, we compare the use of full mitochondrial genomes versus DNA barcodes and other mitochondrial DNA fragments for biogeographic and ecological analyses. Our dataset comprised 120 mitochondrial genomes from the genus Clunio (Diptera: Chironomidae), comprising five populations from two closely related species (Clunio marinus and Clunio balticus) and three ecotypes. We extracted cytochrome oxidase c subunit I (COI) barcodes and partitioned the mitochondrial genomes into non-overlapping windows of 750 or 1500 bp. Haplotype networks and diversity indices were compared for these windows and full mitochondrial genomes (15.4 kb). Full mitochondrial genomes indicate complete geographic isolation between populations, but do not allow for conclusions on the separation of ecotypes or species. COI barcodes have comparatively few polymorphisms, ideal for species identification, but do not resolve geographic isolation. Many of the similarly sized 750 bp windows have higher nucleotide and haplotype diversity than COI barcodes, but still do not resolve biogeography. Only when increasing the window size to 1500 bp, two windows resolve biogeography reasonably well. Our results suggest that the design and use of DNA barcodes in biogeographic studies must be carefully evaluated for each investigated species.

Comparative Mitogenomic Analysis of the Eurydema Genus in the Context of Representative Pentatomidae (Hemiptera: Heteroptera) Taxa

The family Pentatomidae, the largest within the superfamily Pentatomoidae, comprises about 5,000 species; many of which are economically important pests. Although the phylogeny of Pentatomidae species has been studied using various molecular markers, their phylogenetic relationships remain controversial. Recently, mitochondrial genomes (mitogenomes) have been extensively employed to examine the phylogenetics and evolution of different insects, and in this study, we sequenced complete/near-complete mitochondrial genomes from five shield bug species of Eurydema to gain a better understanding of phylogenetic relationships in the Pentatomidae. The five mitogenomes ranged in length from 15,500 to 16,752 bp and comprised 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), 2 ribosomal RNAs (rRNAs), and a control region. We compared mitogenomic characteristics of the Pentatomidae and constructed phylogenetic trees using Bayesian inference and maximum likelihood methods. Our results showed that gene arrangements, base composition, start/stop codons, gene overlaps, and RNA structures were conserved within the Pentatomidae and that congeneric species shared more characteristics. Saturation and heterogeneity analyses revealed that our PCGs and PCGRNA datasets were valid for phylogenetic analysis. Phylogenetic analyses showed consistent topologies based on BI and ML methods. These analyses strongly supported that Eurydema species belong to the tribe Strachiini, and formed a sister group with Pentatomini. The relationships among Eurydema species were shown to be consistent with their morphological features. (Strachiini + Pentatomini) was found to be a stable sibling of the clade comprising Cappaeini, Graphosomini, and Carpocorini. Furthermore, our results indicated that Graphosoma rubrolineatum (Heteroptera: Pentatomidae) belongs to the Pentatominae and not the Podopinae.

Genetic evidence of broad spreading of Lymantria dispar in the West Siberian Plain

Gypsy moth Lymantria dispar L. 1758 (Lepidoptera: Erebidae) is one of the most dangerous forest pests of the Holarctic region. Outbreaks of gypsy moth populations lead to significant defoliation of local forests. Within the vast territory of the West Siberian Plain, we noted the outbreak front movement in the north-east direction with a speed 100-200 km per year. The reason for the outbreak's movement is still unclear because L. dispar females are characterised by limited flight ability, which is not enough to support that movement per se. Herein, we analysed the mtDNA divergence pattern among L. dispar populations collected from the vast territory of the West Siberian Plain to determine the boundaries of populations and reveal the effect of the outbreak's front movement on mtDNA patterns of populations. The 590-bp region of the cytochrome oxidase subunit I gene of the mitochondrial genome was sequenced for 220 specimens that were collected from 18 localities along a transect line (~ 1400 km). Our results clearly show that the gypsy moth populations of the vast Siberian territory are not subdivided. This result can be explained by extensive genetic exchange among local populations. Taking into account that the flight ability of L. dispar females is rather limited, we suggest that spreading occurs through ballooning of early instar larvae. This hypothesis was confirmed by the coincidence of the outbreaks' movement direction with that of the dominant winds, complemented by the observation of ballooned larvae far from a forest edge.

Mitochondrial Gene Sequence (COI) Reveals the Genetic Structure and Demographic History of Lymantria dispar (Lepidoptera: Erebidae: Lymantriinae) in and around China

The gypsy moth, Lymantria dispar, is among the most destructive quarantine pests of forests. Here, we reconstructed the genetic structure and determined the population differentiation of gypsy moths across its distribution range at different times. This information could be used to both improve the prevention and detection of gypsy moths in the field. Using 31 newly designed species-specific primers targeting fragments of 216-1102 bp, we identified 103 full-length cytochrome oxidase subunit I (COI) gene sequences from eight fresh samples and 95 L. dispar specimens collected between 1955 and 1996, mainly in China. Combining 103 full-length COI gene sequences with 146 COI gene sequences from Genbank or DNA barcode libraries, we analyzed the genetic differentiation, gene flow and haplotypes between gypsy moth populations in order to reflect the genetic structure and population dynamics of gypsy moths. We discovered 25 previously unknown haplotypes from old gypsy moth specimens. We found that the genetic diversity among gypsy moth populations (collected in the same region at different time points) was relatively high. Furthermore, the genetic structure of Chinese geographical populations (Heilongjiang, Liaoning, Beijing) in different years was distinct. Our results suggested that some gypsy moths in China showed the genetic affinity with European gypsy moths (a sub-species of gypsy moths found mainly in Europe).

Gypsy moth genome provides insights into flight capability and virus-host interactions

Since its accidental introduction to Massachusetts in the late 1800s, the European gypsy moth (EGM; Lymantria dispar dispar) has become a major defoliator in North American forests. However, in part because females are flightless, the spread of the EGM across the United States and Canada has been relatively slow over the past 150 years. In contrast, females of the Asian gypsy moth (AGM; Lymantria dispar asiatica) subspecies have fully developed wings and can fly, thereby posing a serious economic threat if populations are established in North America. To explore the genetic determinants of these phenotypic differences, we sequenced and annotated a draft genome of L. dispar and used it to identify genetic variation between EGM and AGM populations. The 865-Mb gypsy moth genome is the largest Lepidoptera genome sequenced to date and encodes ∼13,300 proteins. Gene ontology analyses of EGM and AGM samples revealed divergence between these populations in genes enriched for several gene ontology categories related to muscle adaptation, chemosensory communication, detoxification of food plant foliage, and immunity. These genetic differences likely contribute to variations in flight ability, chemical sensing, and pathogen interactions among EGM and AGM populations. Finally, we use our new genomic and transcriptomic tools to provide insights into genome-wide gene-expression changes of the gypsy moth after viral infection. Characterizing the immunological response of gypsy moths to virus infection may aid in the improvement of virus-based bioinsecticides currently used to control larval populations.

Limited Genetic Structure of Gypsy Moth Populations Reflecting a Recent History in Europe

The gypsy moth, Lymantria dispar, a prominent polyphagous species native to Eurasia, causes severe impacts in deciduous forests during irregular periodical outbreaks. This study aimed to describe the genetic structure and diversity among European gypsy moth populations. Analysis of about 500 individuals using a partial region of the mitochondrial COI gene, L. dispar was characterized by low genetic diversity, limited population structure, and strong evidence that all extant haplogroups arose via a single Holocene population expansion event. Overall 60 haplotypes connected to a single parsimony network were detected and genetic diversity was highest for the coastal populations Croatia, Italy, and France, while lowest in continental populations. Phylogenetic reconstruction resulted in three groups that were geographically located in Central Europe, Dinaric Alps, and the Balkan Peninsula. In addition to recent events, the genetic structure reflects strong gene flow and the ability of gypsy moth to feed on about 400 deciduous and conifer species. Distinct genetic groups were detected in populations from Georgia. This remote population exhibited haplotypes intermediate to the European L. dispar dispar, Asian L. dispar asiatica, and L. dispar japonica clusters, highlighting this area as a possible hybridization zone of this species for future studies applying genomic approaches.

Comparative mitochondrial genome analysis of Grammodes geometrica and other noctuid insects reveals conserved mitochondrial genome organization and phylogeny

The mitochondrial genome (mitogenome) plays an important role in revealing molecular evolution. In this study, the complete mitogenome of Grammodes geometrica (G. geometrica) (Lepidoptera: Erebidae) was sequenced and characterized. The nucleotide composition of the genome is highly A + T biased, accounting for 80.49%. Most protein-coding genes (PCGs) are initiated by ATN codons except for the cytochrome oxidase subunit 1 (cox1) gene, which was initiated by CGA. The order and orientation of genes with the order trnM-trnI-trnQ-nad2 is a typical rearrangement compared with those ancestral insects in which trnM is located between trnQ and nad2. Most tRNA genes were folded into the typical cloverleaf structure except for trnS1 (AGN). The A + T-rich region contains the conserved motif "ATAGA" followed by a 19 bp poly-T stretch, which was also observed in other Noctuoidea species. In addition, we reconstructed phylogenetic trees among the nucleotide alignments of five families of Noctuoidea species except the Oenosandridae. Finally, we achieved a well-supported tree, which showed that G. geometrica belongs to the Erebidae family. Moreover, the relationships at the family-level can be displayed as follows: (Notodontidae + (Erebidae + (Nolidae + (Euteliidae + Noctuidae)))).

Mitochondrial genome characteristics of Somena scintillans (Lepidoptera: Erebidae) and comparation with other Noctuoidea insects

In this study, mitogenome of Somena scintillans (Lepidoptera: Erebidae) were sequenced and compared with other Noctuoidea species. The mitogenome is 15,410 base pairs in length. All 13 protein-coding genes (PCGs) are initiated by ATN codons except cox1 with CGA and all of PCGs terminate with TAA except nad4 with TAG. The codons ACG and CGC are absent. All the tRNA genes could be folded into the typical cloverleaf secondary structure except the trnS1 which not only loses dihydrouridine (DHU) arm but also mutates its anticodon into TCT. In the AT-rich region of the mitogenome the motif 'ATAGA' mutates to 'ATATA' and two copies of 161 bp-tandem repeats and two 'TA' short tandem repeats are founded. Phylogenetic analyses showed that S. scintillans is clustered into subfamily Lymatriinae. The phylogenetic relationships within Noctuoidea is (((Nolidae + (Euteliidae + Noctuidae)) + Erebidae) + Notodontidae).