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The frequency and severity of outbreaks by pestiferous insects is increasing globally, likely as a result of human-mediated introductions of non-native organisms. However, it is not always apparent whether an outbreak is the result of a recent introduction of an evolutionarily naïve population, or of recent disturbance acting on an existing population that arrived previously during natural range expansion.  Here we use approximate Bayesian computation to infer the colonization history of a pestiferous insect, the winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), which has caused widespread defoliation in northern Fennoscandia. We generated genotypes using a suite of 24 microsatellite loci and find that populations of winter moth in northern Europe can be assigned to five genetically distinct clusters that correspond with 1) Iceland, 2) the British Isles, 3) Central Europe and southern Fennoscandia, 4) Eastern Europe, and 5) northern Fennoscandia. We find that the northern Fennoscandia winter moth cluster is most closely related to a population presently found in the British Isles, and that these populations likely diverged around 2,900 years ago. This result suggests that current outbreaks are not the result of a recent introduction, but rather that recent climate or habitat disturbance is acting on existing populations that may have arrived to northern Fennoscandia via pre-Roman traders from the British Isles, and/or by natural dispersal across the North Sea likely using the Orkney Islands of northern Scotland as a stepping-stone before dispersing up the Norwegian coast.

Adelges (Cholodkovskya) viridanus (Cholodkovsky 1896) (Hemiptera: Adelgidae) is found throughout Eurasia where it is understood to be anholocyclic, feeding on species of larch (Larix), without host alternation. For the first time, we report this species in North America, outside of its native range, from specimens collected in an arboretum in Ohio, USA. Molecular phylogenetic analysis was inconclusive as to whether it was introduced from Europe or Asia. In addition, specimens collected from Picea jezoensis in Japan were confirmed for the first time as A. (C.) viridanus by matching DNA sequences to specimens collected on Larix. Therefore, A. (C.) viridanus is either capable of completing a host‐alternating holocycle in Japan, or includes very recently diverged anholocyclic populations on Picea. Finally, we describe the adult fundatrix form, which was previously unknown. [ABSTRACT FROM AUTHOR]

The European winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), was accidentally introduced to North America on at least 4 separate occasions, where it has been hybridizing with the native Bruce spanworm, O. bruceata Hulst, at rates up to 10% per year. Both species are known to respond to the same sex pheromones and to produce viable offspring, but whether they differ in the seasonal timing of their mating flights is unknown. Therefore, we collected adult male moths weekly along 2 transects in the northeastern United States and genotyped individuals using polymorphic microsatellite markers as males of these 2 species cannot be differentiated morphologically. Along each transect, we then estimated the cumulative proportions (i.e. the number of individuals out of the total collected) of each species on each calendar day. Our results indicate that there are significant differences between the species regarding their seasonal timing of flight, and these allochronic differences likely are acting to promote reproductive isolation between these 2 species. Lastly, our results suggest that the later flight observed by winter moth compared to Bruce spanworm may be limiting its inland spread in the northeastern United States because of increased exposure to extreme winter events. [ABSTRACT FROM AUTHOR]

Sympatric host-associated genetic differentiation is a prominent pattern that could lead to speciation. In insects, there are numerous examples of host-associated differentiation among herbivores that prefer different plants, and parasitoids that prefer different hosts, but few examples for specialist predators. We developed new microsatellite loci for two species of silver fly, Leucotaraxis argenticollis (Zetterstedt) and L. piniperda (Malloch) (Diptera: Chamaemyiidae), being evaluated as biological control agents for the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), in eastern North America where it is a nonnative pest. We obtained DNA from specimens of both fly species feeding on native A. tsugae in western North America, as well as on other western and eastern adelgid species. We performed population genetic analyses using the new loci and DNA barcode sequences. Our results confirmed east–west allopatric divergence and uncovered nested genetic differentiation associated with different adelgid prey species and their host plants in western North America for both species of silver flies. For both species, there is also evidence for a longer history of diversification in the west, with ancestral specialization of feeding on pine adelgids, which was retained after range expansion to the east. More recently, divergence to feeding on new adelgid prey species occurred in the west. Our findings are consistent with the hypothesis that host-alternating life cycles in Adelgidae may provide temporary escape from specialist predators. We discuss the implications for biological control efficacy and potential for lineage hybridization as western flies are released in the east to control A. tsugae. [ABSTRACT FROM AUTHOR]

Some introduced species cause severe damage, although the majority have little impact. Robust predictions of which species are most likely to cause substantial impacts could focus efforts to mitigate those impacts or prevent certain invasions entirely. Introduced herbivorous insects can reduce crop yield, fundamentally alter natural and managed forest ecosystems, and are unique among invasive species in that they require certain host plants to succeed. Recent studies have demonstrated that understanding the evolutionary history of introduced herbivores and their host plants can provide robust predictions of impact. Specifically, divergence times between hosts in the native and introduced ranges of a nonnative insect can be used to predict the potential impact of the insect should it establish in a novel ecosystem. However, divergence time estimates vary among published phylogenetic datasets, making it crucial to understand if and how the choice of phylogeny affects prediction of impact. Here, we tested the robustness of impact prediction to variation in host phylogeny by using insects that feed on conifers and predicting the likelihood of high impact using four different published phylogenies. Our analyses ranked 62 insects that are not established in North America and 47 North American conifer species according to overall risk and vulnerability, respectively. We found that results were robust to the choice of phylogeny. Although published vascular plant phylogenies continue to be refined, our analysis indicates that those differences are not substantial enough to alter the predictions of invader impact. Our results can assist in focusing biosecurity programs for conifer pests and can be more generally applied to nonnative insects and their potential hosts by prioritizing surveillance for those insects most likely to be damaging invaders. [ABSTRACT FROM AUTHOR]

Hybridization plays an important and underappreciated role in shaping the evolutionary trajectories of species. Following the introduction of a non‐native organism to a novel habitat, hybridization with a native congener may affect the probability of establishment of the introduced species. In most documented cases of hybridization between a native and a non‐native species, a mosaic hybrid zone is formed, with hybridization occurring heterogeneously across the landscape. In contrast, most naturally occurring hybrid zones are clinal in structure. Here, we report on a long‐term microsatellite data set that monitored hybridization between the invasive winter moth, Operophtera brumata (Lepidoptera: Geometridae), and the native Bruce spanworm, O. bruceata, over a 12‐year period. Our results document one of the first examples of the real‐time formation and geographic settling of a clinal hybrid zone. In addition, by comparing one transect in Massachusetts where extreme winter cold temperatures have been hypothesized to restrict the distribution of winter moth, and one in coastal Connecticut, where winter temperatures are moderated by Long Island Sound, we found that the location of the hybrid zone appeared to be independent of environmental variables and maintained under a tension model wherein the stability of the hybrid zone was constrained by population density, reduced hybrid fitness, and low dispersal rates. Documenting the formation of a contemporary clinal hybrid zone may provide important insights into the factors that shaped other well‐established hybrid zones. [ABSTRACT FROM AUTHOR]

The hemlock woolly adelgid (Adelges tsugae (Annand)) is a serious invasive pest of hemlock trees in eastern North America. Multiple biological control agents have been the focus of research aimed at pest management and conserving hemlock communities. Three promising A. tsugae specialist predators are the beetle Laricobius nigrinus (Fender) (Coleoptera: Derodontidae) and flies in the genus Leucotaraxis (Diptera: Chamaemyiidae), Leucotaraxis argenticollis (Zetterstedt), and Leucotaraxis piniperda (Malloch). However, these flies are vulnerable to parasitism by wasps in the genera Pachyneuron (Walker) (Hymenoptera: Pteromalidae) and Melanips (Walker) (Hymenoptera: Figitidae). This study explores parasitoid wasp interactions with these Leucotaraxis species in their native western North American range and potential impacts on the biological control program in the East. Leucotaraxis , La. nigrinus , and parasitoid emergences were observed from adelgid-infested foliage collected from Washington State and British Columbia in 2018, 2019, and 2020. Undescribed species of Pachyneuron and Melanips emerged from puparia as solitary parasitoids. Parasitoid emergence was positively correlated with Leucotaraxis emergence. Percent parasitism increased between February and July, with the months of June and July experiencing higher parasitoid emergence than Leucotaraxis. Differences in emergence patterns suggest that Pachyneuron may be more closely associated with Le. argenticollis as a host, and that Melanips may be associated with Le. piniperda. High parasitism in Leucotaraxis had no effect on La. nigrinus larval abundance, whereas the combined emergence of parasitoids and Leucotaraxis was positively correlated with La. nigrinus. This suggests that there is limited competition among these predators. [ABSTRACT FROM AUTHOR]

The southern pine beetle, Dendroctonus frontalis, is a native pest of pine trees that has recently expanded its range into the northeastern United States. Understanding its colonization, dispersal, and connectivity will be critical for mitigating negative economic and ecological impacts in the newly invaded areas. Characterization of spatial-genetic structure can contribute to this; however, previous studies have reached different conclusions about regional population genetic structure, with one study reporting a weak east-west pattern, and the most recent reporting an absence of structure. Here we systematically assessed several explanations for the absence of spatial-genetic structure. To do this, we developed nine new microsatellite markers and combined them with an existing 24-locus data matrix for the same individuals. We then reanalyzed this full dataset alongside datasets in which certain loci were omitted with the goal of creating more favorable signal to noise ratios. We also partitioned the data based on the sex of D. frontalis individuals, and then employed a broad suite of genotypic clustering and isolation-by-distance (IBD) analyses. We found that neither inadequate information content in the molecular marker set, nor unfavorable signalto-noise ratio, nor insensitivity of the analytical approaches could explain the absence of structure. Regardless of dataset composition, there was little evidence for clusters (i.e., distinct geo-genetic groups) or clines (i.e., gradients of increasing allele frequency differences over larger geographic distances), with one exception: significant IBD was repeatedly detected using an individual-based measure of relatedness whenever datasets included males (but not for female-only datasets). This is strongly indicative of broadscale female-biased dispersal, which has not previously been reported for D. frontalis, in part owing to logistical limitations of direct approaches (e.g., capture-mark-recapture). Weak spatial-genetic structure suggests long-distance connectivity and that gene flow is high, but additional research is needed to understand range expansion and outbreak dynamics in this species using alternate approaches. [ABSTRACT FROM AUTHOR]

Reconstructing the geographic origins of non‐native species is important for studying the factors that influence invasion success, however; these analyses can be constrained by the amount of diversity present in the native and invaded regions, and by changes in the genetic background of the invading population following bottlenecks and/or hybridization events. Here we explore the geographical origins of the invasive winter moth (Operopthera brumata L.) that has caused widespread defoliation to forests, orchards, and crops in Nova Scotia, British Columbia, Oregon, and the northeastern United States. It is not known whether these represent independent introductions to North America, or a "stepping stone" spread among regions. Using a combination of Bayesian assignment and approximate Bayesian computation methods, we analysed a population genetic data set of 24 microsatellite loci. We estimate that winter moth was introduced to North America on at least four occasions, with the Nova Scotian and British Columbian populations probably being introduced from France and Sweden, respectively; the Oregonian population probably being introduced from either the British Isles or northern Fennoscandia; and the population in the northeastern United States probably being introduced from somewhere in Central Europe. We discuss the impact of genetic bottlenecks on analyses meant to determine region of origin. [ABSTRACT FROM AUTHOR]

The Adelges (Dreyfusia) piceae (Ratzeburg) species complex is a taxonomically unstable group of six species. Three of the species are cyclically parthenogenetic [Ad. nordmannianae (Eckstein), Ad. prelli (Grossmann), and Ad. merkeri (Eichhorn)] and three are obligately asexual [Ad. piceae, Ad. schneideri (Börner), and Ad. nebrodensis (Binazzi & Covassi)]. Some species are high‐impact pests of fir (Abies) trees, so stable species names are needed to communicate effectively about management. Therefore, to refine species delimitation, guided by a reconstruction of their biogeographic history, we genotyped adelgids from Europe, North America, and the Caucasus Mountains region with 19 microsatellite loci, sequenced the COI DNA barcoding region, and compared morphology. Discriminant analysis of principal components of microsatellite genotypes revealed four distinct genetic clusters. Two clusters were morphologically consistent with Ad. nordmannianae. One of these clusters consisted of samples from the Caucasus Mountains and northern Turkey, and the other included samples from this region as well as from Europe and North America, where Ad. nordmannianae is invasive. A third cluster was morphologically consistent with Ad. piceae, and included individuals from Europe, where it is native, and North America, where it is invasive. In North America, the majority of Ad. piceae individuals were assigned to two geographically widespread clones, suggesting multiple introductions. The fourth cluster included individuals morphologically consistent with Ad. prelli or Ad. merkeri. However, based on genetic assignments, hybrid simulations, and approximate Bayesian computation, we find it likely that these are contemporary hybrids between Ad. nordmannianae and Ad. piceae that arose independently in Europe and North America, so we propose that Ad. prelli and Ad. merkeri are invalid. Finally, we synonymise Ad. schneideri(syn.n.) with Ad. nordmannianae and designate Ad. nebrodensis as subspecies Ad. piceae nebrodensis(stat.n.). Our revised taxonomy therefore recognises two species: Ad. nordmannianae and Ad. piceae, which we estimate to have diverged recently, during one of the last two interglacial periods. Finally, we comment on this species complex being in the midst of transition between sexual and asexual reproduction, a pattern that is probably common in Adelgidae. [ABSTRACT FROM AUTHOR]

Winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), causes widespread defoliation in both its native and introduced distributions. Invasive populations of winter moth are currently established in the United States and Canada, and pheromone-baited traps have been widely used to track its spread. Unfortunately, a native species, the Bruce spanworm, O. bruceata (Hulst), and O. bruceata × brumata hybrids respond to the same pheromone, complicating efforts to detect novel winter moth populations. Previously, differences in measurements of a part of the male genitalia called the uncus have been utilized to differentiate the species; however, the accuracy of these measurements has not been quantified using independent data. To establish morphological cutoffs and estimate the accuracy of uncus-based identifications, we compared morphological measurements and molecular identifications based on microsatellite genotyping. We find that there are significant differences in some uncus measurements, and that in general, uncus measurements have low type I error rates (i.e. the probability of having false positives for the presence of winter moth). However, uncus measurements had high type II error rates (i.e. the probability of having false negatives for the presence of winter moth). Our results show that uncus measurements can be useful for performing preliminary identifications to monitor the spread of winter moth, though for accurate monitoring, molecular methods are still required. As such, efforts to study the spread of winter moth into interior portions of North America should utilize a combination of pheromone trapping and uncus measurements, while maintaining vouchers for molecular identification. [ABSTRACT FROM AUTHOR]

Two species of silver fly, Leucopis argenticollis (Zetterstedt) and Leucopis piniperda (Malloch) (Diptera: Chamaemyiidae), from the Pacific Northwest region of North America have been identified as potential biological control agents of hemlock woolly adelgid (Hemiptera: Adelgidae: Adelges tsugae Annand) in eastern North America. The two predators are collectively synchronized with A. tsugae development. To determine whether adult emergence of the two species of silver fly are also synchronized with one another, we collected adult Leucopis which emerged from A. tsugae- infested western hemlock [Pinaceae: Tsuga heterophylla (Raf.) Sarg.] from four sites in the Pacific Northwest over a 29-d period. Specimens were collected twice daily in the laboratory and identified to species using DNA barcoding. The study found that more adult Leucopis were collected in the evening than the morning. Additionally, the daily emergences of adults over the 29-d sampling period exhibited sinusoidal-like fluctuations of peak abundance of each species, lending evidence to a pattern of temporal partitioning. This pattern could have logistical implications for their use as biological control agents in eastern North America, namely the need to release both species for maximum efficacy in decreasing A. tsugae populations. [ABSTRACT FROM AUTHOR]

Here we compare the environmental niche of a highly polyphagous forest Lepidoptera species, the winter moth (Operophtera brumata), in its native and invaded range. During the last 90 years, this European tree folivore has invaded North America in at least three regions and exhibited eruptive population behavior in both its native and invaded range. Despite its importance as both a forest and agricultural pest, neither the potential extent of this species' invaded range nor the geographic source of invading populations from its native range are known. Here we fit a climatic niche model, based on the MaxEnt algorithm, to historical records of winter moth occurrence in its native range and compare predictions of suitable distributions to records from the invaded range. We modeled this distribution using three spatial bins to overcome sampling bias for data obtained from public databases and averaged the multi-continental suitable habitat prediction. Results indicate that this species is distributed across a wide range of climates in its native range but occupies a narrower range in its invaded habitat. Furthermore, the lack of a close fit between climatic conditions in parts of its invaded range and its known native range suggests the possibility that this species has adapted to new climatic conditions during the invasion process. These models can be used to predict suitable habitats for winter moth invasions worldwide and to gain insight into possible origins of North American populations. [ABSTRACT FROM AUTHOR]

Assessing the ecological and economic impacts of non-native species is crucial to providing managers and policymakers with the information necessary to respond effectively. Most non-native species have minimal impacts on the environment in which they are introduced, but a small fraction are highly deleterious. The definition of 'damaging' or 'high-impact' varies based on the factors determined to be valuable by an individual or group, but interpretations of whether non-native species meet particular definitions can be influenced by the interpreter's bias or level of expertise, or lack of group consensus. Uncertainty or disagreement about an impact classification may delay or otherwise adversely affect policymaking on management strategies. One way to prevent these issues would be to have a detailed, nine-point impact scale that would leave little room for interpretation and then divide the scale into agreed upon categories, such as low, medium, and high impact. Following a previously conducted, exhaustive search regarding non-native, coniferspecialist insects, the authors independently read the same sources and scored the impact of 41 conifer-specialist insects to determine if any variation among assessors existed when using a detailed impact scale. Each of the authors, who were selected to participate in the working group associated with this study because of their diverse backgrounds, also provided their level of expertise and uncertainty for each insect evaluated. We observed 85% congruence in impact rating among assessors, with 27% of the insects having perfect inter-rater agreement. Variance in assessment peaked in insects with a moderate impact level, perhaps due to ambiguous information or prior assessor perceptions of these specific insect species. The authors also participated in a joint fact-finding discussion of two insects with the most divergent impact scores to isolate potential sources of variation in assessor impact scores. We identified four themes that could be experienced by impact assessors: ambiguous information, discounted details, observed versus potential impact, and prior knowledge. To improve consistency in impact decision-making, we encourage groups to establish a detailed scale that would allow all observed and published impacts to fall under a particular score, provide clear, reproducible guidelines and training, and use consensus-building techniques when necessary. [ABSTRACT FROM AUTHOR]

Numerous studies have shown that the genetic diversity of species inhabiting temperate regions has been shaped by changes in their distributions during the Quaternary climatic oscillations. For some species, the genetic distinctness of isolated populations is maintained during secondary contact, while for others, admixture is frequently observed. For the winter moth (Operophtera brumata), an important defoliator of oak forests across Europe and northern Africa, we previously determined that contemporary populations correspond to genetic diversity obtained during the last glacial maximum (LGM) through the use of refugia in the Iberian and Aegean peninsulas, and to a lesser extent the Caucasus region. Missing from this sampling were populations from the Italian peninsula and from North Africa, both regions known to have played important roles as glacial refugia for other species. Therefore, we genotyped field‐collected winter moth individuals from southern Italy and northwestern Tunisia—the latter a region where severe oak forest defoliation by winter moth has recently been reported—using polymorphic microsatellite. We reconstructed the genetic relationships of these populations in comparison to moths previously sampled from the Iberian and Aegean peninsulas, the Caucasus region, and western Europe using genetic distance, Bayesian clustering, and approximate Bayesian computation (ABC) methods. Our results indicate that both the southern Italian and the Tunisian populations are genetically distinct from other sampled populations, and likely originated in their respective refugium during the LGM after diverging from a population that eventually settled in the Iberian refugium. These suggest that winter moth populations persisted in at least five Mediterranean LGM refugia. Finally, we comment that outbreaks by winter moth in northwestern Tunisia are not the result of a recent introduction of a nonnative species, but rather are most likely due to land use or environmental changes. [ABSTRACT FROM AUTHOR]

A long‐standing goal of invasion biology is to identify factors driving highly variable impacts of non‐native species. Although hypotheses exist that emphasize the role of evolutionary history (e.g., enemy release hypothesis & defense‐free space hypothesis), predicting the impact of non‐native herbivorous insects has eluded scientists for over a century.Using a census of all 58 non‐native conifer‐specialist insects in North America, we quantified the contribution of over 25 factors that could affect the impact they have on their novel hosts, including insect traits (fecundity, voltinism, native range, etc.), host traits (shade tolerance, growth rate, wood density, etc.), and evolutionary relationships (between native and novel hosts and insects).We discovered that divergence times between native and novel hosts, the shade and drought tolerance of the novel host, and the presence of a coevolved congener on a shared host, were more predictive of impact than the traits of the invading insect. These factors built upon each other to strengthen our ability to predict the risk of a non‐native insect becoming invasive. This research is the first to empirically support historically assumed hypotheses about the importance of evolutionary history as a major driver of impact of non‐native herbivorous insects.Our novel, integrated model predicts whether a non‐native insect not yet present in North America will have a one in 6.5 to a one in 2,858 chance of causing widespread mortality of a conifer species if established (R2 = 0.91)Synthesis and applications. With this advancement, the risk to other conifer host species and regions can be assessed, and regulatory and pest management efforts can be more efficiently prioritized. [ABSTRACT FROM AUTHOR]

We collected data on mortality of late-instar gypsy moth, Lymantria dispar (L.), from outbreak populations over 4 wk in June 2017 at 10 sites in the New England region of the United States, along with estimated rainfall at these sites. Deposition of airborne conidia of the fungal pathogen, Entomophaga maimaiga Humber, Shimazu & R.S. Soper, was measured at these same sites as well as at seven other locations in New England. We also quantified the geographical distribution of gypsy moth-caused defoliation in New England in 2017 and 2018 from Landsat imagery. Weekly mortality of gypsy moth larvae caused by E. maimaiga correlated with local deposition of conidia from the previous week, but not with rainfall. Mortality from this pathogen reached a peak during the last 2 wk of gypsy moth larval development and always exceeded that caused by LdNPV , the viral pathogen of gypsy moth that has long been associated with gypsy moth outbreaks, especially prior to 1989. Cotesia melanoscela (Ratzeburg) was by far the most abundant parasitoid recovered and caused an average of 12.6% cumulative parasitism, but varied widely among sites. Deposition of E. maimaiga conidia was highly correlated with percent land area defoliated by gypsy moths within distances of 1 and 2 km but was not significantly correlated with defoliation at distances greater than 2 km. This is the first study to relate deposition of airborne conidia of E. maimaiga to mortality of gypsy moths from that agent. [ABSTRACT FROM AUTHOR]

The pine bark adelgid, Pineus strobi (Hartig) (Hemiptera: Adelgidae), is an herbivore native to eastern North America that specialises on eastern white pine, Pinus strobus Linnaeus (Pinaceae). Little is known about P. strobi , especially in its southern range in the Appalachian Mountains, United States of America, and the composition of its predator complex has not yet been documented in this region. The current study identifies arthropod predators associated with P. strobi in Appalachian forests of Virginia based on a two-year survey. Predators were identified using morphology and DNA barcoding. Predator species include: Laricobius rubidus LeConte (Coleoptera: Derodontidae), Leucopis piniperda Malloch (Diptera: Chamaemyiidae), and Leucopis argenticollis Zetterstedt (Diptera: Chamaemyiidae), that are known adelgid specialists. Also found were predators from the families Cecidomyiidae (Diptera), Coccinellidae (Coleoptera), Chrysopidae (Neuroptera), Hemerobiidae (Neuroptera), and Syrphidae (Diptera). The Cecidomyiidae were especially diverse, with 14 different species inferred from their DNA barcodes. Knowledge of this predator complex is particularly valuable for anticipation and detection of potential interactions between native predator species and those that are being considered for the introduction for biological control of invasive adelgid pests within the southern Appalachian ecosystem. [ABSTRACT FROM AUTHOR]

Bacterial endosymbionts of sap‐sucking insects provide their host with a number of beneficial qualities, including the supply of nutrition, defense against parasitoids, and protection from heat stress. Damage to these bacterial associates can therefore have a negative impact on the fitness of their insect host. We evaluated observational and experimental factors regarding the nonnative hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera: Adelgidae) to help understand the roles of its three recently identified symbionts, including under heat stress conditions. The prevalence of A. tsugae's facultative symbiont (Serratia symbiotica) was examined at different spatial scales to determine how variable infection rates are for this symbiont. There was no significant difference found in infection rates between adelgids on a tree, within a plot, or within a state. However, significantly more adelgids in Georgia (95%) had S. symbiotica compared to those in New York (68%). Microsatellite genotyping of the adelgids found that this difference was most likely not the result of a second introduction of A. tsugae into eastern North America. Comparison of S. symbiotica proportions between first and fourth instars showed that symbiont absence did not affect the ability of A. tsugae to survive aestivation. Evaluations of symbiont densities within each adelgid found that when S. symbiotica was absent, the density of obligate symbionts was significantly higher. Exposure to heat stress (32.5 °C) was not consistently correlated with changes in symbiont densities over a 4‐d period. Overall, we have shown that symbiont prevalence and densities vary within the broad population of A. tsugae in eastern North America, with potentially significant effects upon the ecology of this important pest. [ABSTRACT FROM AUTHOR]

The hemlock woolly adelgid (HWA), Adelges tsugae, is an invasive pest of Tsuga spp. in eastern North America. Scymnus coniferarum is a predaceous beetle that was collected from HWA in the western United States. Limited knowledge of this insect in its native habitat led to studies to evaluate its potential for biological control of HWA. Seasonal abundance was sampled at six sites in Tacoma, WA, twice monthly, for one year on different host trees of potential adelgid prey. Tree species included Pseudotsuga menziesii, Pinus contorta, Pinus monticola, and Tsuga heterophylla. Scymnus coniferarum adults were found on all conifer species, except P. menziesii. Each conifer species supported a different adelgid species, suggesting S. coniferarum feeds on multiple adelgid species. More S. coniferarum were found on pine than hemlock. DNA barcoding of S. coniferarum found two distinct clusters that differed by 6% divergence. Beetles in each cluster were co-habiting the same conifer species, and they could not be distinguished morphologically. Further taxonomic studies are needed to understand the significance of DNA barcode sequence divergence. Because S. coniferarum was more frequently associated with pine adelgids than HWA, and because of remaining taxonomic uncertainty, S. coniferarum may not be suitable for HWA biological control. [ABSTRACT FROM AUTHOR]

Nutritional bacterial symbionts enhance the diets of sap-feeding insects with amino acids and vitamins missing from their diets. In many lineages, an ancestral senior symbiont is joined by a younger junior symbiont. To date, an emergent pattern is that senior symbionts supply a majority of amino acids, and junior symbionts supply a minority. Similar to other hemipterans, adelgids harbor obligate symbionts, but have higher diversity of bacterial associates, suggesting a history of symbiont turnover. The metabolic roles of dual symbionts in adelgids and their contributions to the consortium are largely unexplored. Here, we investigate the symbionts of Adelges tsugae, the hemlock woolly adelgid (HWA), an invasive species introduced from Japan to the eastern United States, where it kills hemlock trees. The response of hemlocks to HWA feeding has aspects of a defensive reaction against pathogens, and some have speculated that symbionts may be involved. We sequenced the genomes of "Ca. Annandia adelgestsuga" and "Ca. Pseudomonas adelgestsugas" symbionts to detail their metabolic capabilities, infer ages of relationship, and search for effectors of plant defenses. We also tested the relationship of "Ca. Annandia" to symbionts of other insects. We find that both symbionts provide nutrients, but in more balanced proportions than dual symbionts of other hemipterans. The lesser contributions of the senior "Ca. Annandia" support our hypothesis for symbiont replacements in adelgids. Phylogenomic results were ambiguous regarding the position of "Ca. Annandia". We found no obvious effectors of plant defenses related to insect virulence, but hypothetical proteins in symbionts are unknown players. [ABSTRACT FROM AUTHOR]

Exploring genetic diversity within species of biological control agents can expose previously overlooked beneficial genotypes. This may be the case for two species of silver flies, Leucopis argenticollis and L. piniperda , predators of the hemlock woolly adelgid ( Adelges tsugae ) in the Pacific Northwest of North America. The same Leucopis species occur in eastern North America, where they feed on other adelgid species, but not on hemlock woolly adelgid, which became a pest in the region after its introduction from Japan earlier this century. We collected DNA sequence data from one mitochondrial and two nuclear genes for 606 Leucopis individuals to examine variation correlated with geographic origin and prey association. Specimens of L. argenticollis and L. piniperda collected from adelgids on hemlock and spruce in the West are phylogenetically divergent from conspecifics collected from adelgids on pine and spruce in the East. These results suggest that within each species, there are distinct lineages that specialize on different adelgid prey on different hosts in western versus eastern North America. The western lineages appear to be strong candidates for enhancing biological control of Japanese hemlock woolly adelgid in the eastern United States, given their widespread occurrence on western hemlock woolly adelgid in the Pacific Northwest, and the absence of these genotypes in the East. We also developed a PCR-RFLP assay based on the mitochondrial COI gene as an inexpensive and reliable way to distinguish the four genetic groups to document establishment and impact following release. [ABSTRACT FROM AUTHOR]

Sap-sucking insects typically engage in obligate relationships with symbiotic bacteria that play nutritional roles in synthesizing nutrients unavailable or in scarce supply from the plant-sap diets of their hosts. Adelgids are sap-sucking insects with complex life cycles that involve alternation between conifer tree species. While all adelgid species feed on spruce during the sexual phase of their life cycle, each adelgid species belongs to a major lineage that feeds on a distinct genus of conifers as their alternate host. Previous work on adelgid symbionts had discovered pairs of symbionts within each host species, and unusual diversity across the insect family, but left several open questions regarding the status of bacterial associates. Here, we explored the consistency of symbionts within and across adelgid lineages, and sought evidence for facultative vs. obligate symbiont status. Representative species were surveyed for symbionts using 16S ribosomal DNA gene sequencing, confirming that different symbiont pairs were consistently present within each major adelgid lineage. Several approaches were used to establish whether symbionts exhibited characteristics of long-term, obligate mutualists. Patterns of symbiont presence across adelgid species and diversification with host insects suggested obligate relationships. Fluorescent in situ hybridization and electron microscopy localized symbionts to bacteriocyte cells within the bacteriome of each species (with one previously known exception), and detection of symbionts in eggs indicated their vertical transmission. Common characteristics of long-term obligate symbionts, such as nucleotide compositional bias and pleomorphic symbiont cell shape were also observed. Superimposing microbial symbionts on the adelgid phylogeny revealed a dynamic pattern of symbiont gains and losses over a relatively short period of time compared to other symbionts associated with sap-sucking insects, with each adelgid species possessing an older, "senior" symbiont and a younger "junior"symbiont.A hypothesis relating adelgid life cycles to relaxed constraints on symbionts is proposed, with the degradation of senior symbionts and repeated acquisition of more junior symbionts creating opportunities for repeated colonization of new alternate-conifer hosts by adelgids. [ABSTRACT FROM AUTHOR]

Changes in climate conditions, particularly during the Quaternary climatic oscillations, have long been recognized to be important for shaping patterns of species diversity. For species residing in the western Palearctic, two commonly observed genetic patterns resulting from these cycles are as follows: (1) that the numbers and distributions of genetic lineages correspond with the use of geographically distinct glacial refugia and (2) that southern populations are generally more diverse than northern populations (the 'southern richness, northern purity' paradigm). To determine whether these patterns hold true for the widespread pest species the winter moth ( Operophtera brumata), we genotyped 699 individual winter moths collected from 15 Eurasian countries with 24 polymorphic microsatellite loci. We find strong evidence for the presence of two major genetic clusters that diverged ~18 to ~22 ka, with evidence that secondary contact (i.e., hybridization) resumed ~ 5 ka along a well-established hybrid zone in Central Europe. This pattern supports the hypothesis that contemporary populations descend from populations that resided in distinct glacial refugia. However, unlike many previous studies of postglacial recolonization, we found no evidence for the 'southern richness, northern purity' paradigm. We also find evidence for ongoing gene flow between populations in adjacent Eurasian countries, suggesting that long-distance dispersal plays an important part in shaping winter moth genetic diversity. In addition, we find that this gene flow is predominantly in a west-to-east direction, suggesting that recently debated reports of cyclical outbreaks of winter moth spreading from east to west across Europe are not the result of dispersal. [ABSTRACT FROM AUTHOR]

Hemlock woolly adelgid, Adelges tsugae, is an invasive pest of hemlock trees ( Tsuga) in eastern North America. We used 14 microsatellites and mitochondrial COI sequences to assess its worldwide genetic structure and reconstruct its colonization history. The resulting information about its life cycle, biogeography and host specialization could help predict invasion by insect herbivores. We identified eight endemic lineages of hemlock adelgids in central China, western China, Ulleung Island (South Korea), western North America, and two each in Taiwan and Japan, with the Japanese lineages specializing on different Tsuga species. Adelgid life cycles varied at local and continental scales with different sexual, obligately asexual and facultatively asexual lineages. Adelgids in western North America exhibited very high microsatellite heterozygosity, which suggests ancient asexuality. The earliest lineages diverged in Asia during Pleistocene glacial periods, as estimated using approximate Bayesian computation. Colonization of western North America was estimated to have occurred prior to the last glacial period by adelgids directly ancestral to those in southern Japan, perhaps carried by birds. The modern invasion from southern Japan to eastern North America caused an extreme genetic bottleneck with just two closely related clones detected throughout the introduced range. Both colonization events to North America involved host shifts to unrelated hemlock species. These results suggest that genetic diversity, host specialization and host phylogeny are not predictive of adelgid invasion. Monitoring non-native sentinel host trees and focusing on invasion pathways might be more effective methods of preventing invasion than making predictions using species traits or evolutionary history. [ABSTRACT FROM AUTHOR]

In 2003,Laricobius nigrinusFender was introduced into the eastern United States as a biological control agent of the hemlock woolly adelgid (Adelges tsugaeAnnand). Following its release, it was discovered thatL. nigrinuswas hybridising and producing viable progeny withLaricobius rubidusLeConte, a species native to eastern North America. Recently,Laricobius osakensisMontgomery and Shiyake was imported from Japan into the USA as a potential biological control agent of hemlock woolly adelgid. Hybridisation betweenL. nigrinusandL. rubidusled to interest in the outcome of interactions betweenL. osakensisand the other twoLaricobiusspp. The purpose of this study was to determine ifL. osakensiscould mate withL. nigrinus, if they could produce hybrid progeny, and whether mating interferes with reproductive output.Laricobiusspp. were observed mating directly following emergence and found to be capable of producing sterile eggs in the absence of a mating event. Laboratory and confined field studies found no evidence thatL. osakensisandL. nigrinuscould produce hybrid progeny and the interaction between the two species did not result in a lower reproduction associated with interspecific mating attempts. Interbreeding should therefore not have an impact on biological control using these species. Fecundity experiments showed thatL. osakensisproduced eggs earlier in the season and at a higher rate thanL. nigrinus, suggesting thatL. osakensismay have the potential to be an even more successful biological control agent thanL. nigrinus. [ABSTRACT FROM AUTHOR]

The predatory species Laricobius nigrinus (Fender) and Laricobius osakensis (Shiyake and Montgomery) (Coleoptera: Derodontidae) have been released for biological control of hemlock woolly adelgid (Adelges tsugae; Hemiptera: Adelgidae) in eastern North America. L. osakensis is native to Japan, whereas L. nigrinus is endemic to the Pacific Northwest of the United States and Canada. After release, L. nigrinus was found to hybridize with the native eastern species, Laricobius rubidus (LeConte). The purpose of this study is to observe prey location behaviors of these three Laricobius species and L. nigrinus L. rubidus (LnLr) hybrids. Olfactometer bioassays were used to test response to host odors of adelgid-infested eastern hemlock, uninfested eastern hemlock, and uninfested eastern white pine. Predators reacted in the olfactometer more quickly when adelgid-infested foliage was included as a choice. L. nigrinus preferred infested eastern hemlock over uninfested eastern white pine, and L. rubidus preferred uninfested eastern white pine over uninfested eastern hemlock. Laricobius hybrids did not show a preference for foliage types known to be primary adelgid hosts (eastern hemlock and eastern white pine). Unequal preference by species of Laricobius for host trees of different adelgid prey could therefore be maintaining Laricobius species barriers despite hybridization. L. osakensis for this study were reared in the laboratory, whereas other species in this study were collected from the field, yet still were attracted to infested and uninfested eastern hemlock. This species also responded most quickly in the olfactometer, which is encouraging for successful biological control with this species. [ABSTRACT FROM AUTHOR]

A taxonomic and nomenclatural Catalogue of the adelgids (Hemiptera: Adelgidae) is presented. Six family- group names are listed, five being synonyms of Adelgidae. Twenty-two genus-group names, of which nine are subjectively valid and in use, are presented with their type species, etymology, and grammatical gender. One hundred and six species-group names are listed, of which 70 are considered subjectively valid. [ABSTRACT FROM AUTHOR]

Two adelgid predators, Laricobius nigrinus Fender and Laricobius rubidus LeConte, were recently discovered to produce hybrid progeny in the eastern United States. L. rubidus is native to eastern North America where it feeds on pine bark adelgid ( Pineus strobi Hartig) and L. nigrinus is native to western North America and was introduced to the eastern United States in 2003 for biological control of hemlock woolly adelgid ( Adelges tsugae Annand). Currently, L. nigrinus and L. rubidus form a mosaic of hybrid zones throughout the eastern United States. It is not known whether these zones will be maintained over time and whether hybridization will impact the efficacy of biological control or result in displacement of L. rubidus . Sampling from 2007 to 2012 on eastern hemlock ( Tsuga canadensis Carrière) showed a clear increase in L. nigrinus , a decrease in L. rubidus , and a steady proportion of hybrids. Sampling from 2010 to 2012 on both eastern hemlock and white pine ( Pinus strobus L.) at ten sites showed that L. nigrinus was more dominant on hemlock and L. rubidus was more dominant on white pine, which may demonstrate habitat preference and promote segregation between the two species. Site factors were tested for a relationship with the proportion of hybrids. The number of years L. nigrinus had been present at the site was the only factor that showed a relationship. The results suggest that L. nigrinus may displace L. rubidus on hemlock, but not on white pine at sites where they are both present. [ABSTRACT FROM AUTHOR]

An integrated management approach is needed to maintain eastern hemlock ( Tsuga canadensis (L.) Carrière) in eastern North America and to minimize tree damage and mortality caused by the invasive hemlock woolly adelgid ( Adelges tsugae Annand). This study examined the hypothesis that chemical control with low rates of insecticide and biological control can be combined in the same stand to impact adelgid populations, prolong crown health, and allow predator proliferation. Sixty T . canadensis trees in northern Georgia were individually treated via soil injection with 0%, 10%, or 25% of the label rate of imidacloprid insecticide, and the biological control predator Laricobius nigrinus Fender was released in the stand, two and four years later. By year seven, hemlocks treated with the 25% imidacloprid rate lost their insecticide protection, had significantly better crown health and higher adelgid densities than untreated trees, and supported as many Laricobius predator larvae as untreated trees. In year seven, no residues of imidacloprid were detected in Laricobius larvae feeding on previously-treated hemlocks. Most (77%) of the predators collected on study trees were identified as L . nigrinus , 12% were the native congener Laricobius rubidus LeConte, and 11% were hybrids between the introduced and native species. The hybridization rate remained stable over time. The density of undisturbed A . tsugae ovisacs was twice as high on branches protected from predators as compared with branches exposed to predators. Results suggest that chemical and biological control of A . tsugae can be successfully integrated to help prolong hemlock health, although additional predators may be necessary to protect hemlock trees in the southern Appalachians. [ABSTRACT FROM AUTHOR]

Knowledge of intraspecific variation in symbioses may aid in understanding the ecology of widespread insects in different parts of their range. We investigated bacterial symbionts of Adelges tsugae, a pest of hemlocks in eastern North America introduced from Asia. Amplification, cloning, and sequencing of bacterial 16 S rDNA, in situ hybridizations, and electron microscopy revealed that A. tsugae harbours up to five bacterial phylotypes, according to population. Three Gammaproteobacteria species are maternally transmitted. The first, designated ' Ca. Pseudomonas adelgestsugas' resides in the haemocoel, and was detected in all populations except Taiwan. The second phylotype, ' Ca. Serratia symbiotica', resides in bacteriocytes of populations on Tsuga sieboldii in Japan and in E. North America. The third phylotype, designated ' Ca. Annandia adelgestsuga', clustered within a lineage of several insect endosymbionts that included Buchnera aphidicola. It was detected in bacteriocytes in all populations, and in salivary glands of first instars. Two Betaproteobacteria phylotypes were detected in some Japanese T. sieboldii and eastern North America populations, and were observed only in salivary glands with no evidence of maternal transmission. Our results support the ideas that symbiont gain and loss has been volatile in adelgids, and that symbionts may help to trace the source of invasive species. [ABSTRACT FROM AUTHOR]

Abstract: Hybridization between introduced biological control agents and native species has the potential to impact native biodiversity and pest control efforts. This study reports progress towards predicting the outcome of hybridization between two beetle species, the introduced Laricobius nigrinus Fender and the native L. rubidus LeConte. L. nigrinus is a predator from western North America introduced to hemlock stands in the eastern United States as a biological control of the hemlock woolly adelgid [Adelges tsugae Annand (Hemiptera: Adelgidae)]. Laricobius rubidus is a closely related eastern species that also feeds on A. tsugae but prefers pine adelgids (Pineus strobi Hartig) on white pine (Pinus strobus L.). Six microsatellite markers plus mitochondrial COI haplotypes were used to examine genetic structure of these two Laricobius species across North America. In their native ranges, major geographic features have impacted gene flow: the intermountain region in the West, and the Appalachian Mountains in the East. Analysis of 1229 individuals from adelgid-infested hemlock trees in release sites in the eastern United States found widespread hybridization with asymmetrical introgression towards L. nigrinus on hemlock. The ultimate outcome of hybridization could therefore be a complex mosaic of genetic introgression across the landscape, depending on the distribution of hemlock and pine. This study confirms the importance of evaluating the potential for introduced biological control agents to hybridize with their native relatives. This system also provides an excellent opportunity to improve our understanding of emerging hybrid zones by tracking its progress over time. [Copyright &y& Elsevier]

Gall-forming insects are commonly highly host-specific, and galling species once thought to be oligo- or polyphagous are often found to represent a complex of host-specific races or cryptic species. A recent DNA barcoding study documented that an unidentified species of the genus Adelges is a gall-former associated with four spruce species ( Picea bicolor, P. koyamai, P. maximowiczii, P. polita) as the primary hosts, with little genetic differentiation among insects on different host species. In this study, we investigated the morphology of this galling adelgid to determine its taxonomic identity. Morphological inspection of insects collected from three of the spruce species confirmed that this adelgid is a single galling species, and is identified as Adelges ( Sacchiphantes) kitamiensis, which was previously known only from the secondary host. We described the gallicola adults of this species, as well as the first-instar exules which are the offspring of gallicolae. Finally, we verified the taxonomic identity of this species and discuss its life cycle and host distribution. [ABSTRACT FROM AUTHOR]

Rhus gall aphids (Fordinae : Melaphidini) have a disjunct distribution in East Asia and North America and have specific host plant relationships. Some of them are of economic importance and all species form sealed galls which show great variation in shape, size, structure, and galling-site. We present a phylogeny incorporating ten species and four subspecies of Rhus gall aphids based on 1694 base pairs of nuclear elongation factor-1α (EF1α) and mitochondrial cytochrome oxidase subunit II (COII) DNA sequence data. The results suggest that Melaphidini is monophyletic and at the genus level, Schlechtendalia, Nurudea, and Floraphis were each monophyletic. Kaburagia and Meitanaphis were not monophyletic and therefore inconsistent with the current classification. The North American sumac gall aphid, Melaphis rhois, was most closely related to the East Asian Floraphis species, although this was poorly supported. The conservation of gall morphology with respect to aphid phylogeny rather than their host plants suggests that gall morphology is largely determined by the aphids. While there is no evidence of strict co-speciation between the aphids and their primary host plants, switching between recently diverged host plants may be involved in the speciation process in Melaphidini. [ABSTRACT FROM AUTHOR]