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Climate change increases the insect abundance, especially in Arctic ecosystems. Insect herbivory also significantly increases plant emissions of volatile organic compounds (VOCs), which are highly reactive in the atmosphere and play a crucial role in atmospheric chemistry and physics. However, it is unclear how the effects of insect herbivory on VOC emissions interact with climatic changes, such as warming and increased cloudiness. We assessed how experimental manipulations of temperature and light availability in subarctic tundra, that had been maintained for 30 years at the time of the measurements, affect the VOC emissions from a widespread dwarf birch (Betula nana) when subjected to herbivory by local geometrid moth larvae, the autumnal moth (Epirrita autumnata) and the winter moth (Operophtera brumata). Warming and insect herbivory on B. nana stimulated VOC emission rates and altered the VOC blend. The herbivory‐induced increase in sesquiterpene and homoterpene emissions were climate‐treatment‐dependent. Many herbivory‐associated VOCs were more strongly induced in the shading treatment than in other treatments. We showed generally enhanced tundra VOC emissions upon insect herbivory and synergistic effects on the emissions of some VOC groups in a changing climate, which can have positive feedbacks on cloud formation. Furthermore, the acclimation of plants to long‐term climate treatments affects VOC emissions and strongly interacts with plant responses to herbivory. Such acclimation complicates predictions of how climate change, together with interacting biotic stresses, affects VOC emissions in the high latitudes., Climate change increases the insect abundance, especially in arctic ecosystems. Insect herbivory also significantly increases plant emissions of volatile organic compounds (VOCs), which are highly reactive in the atmosphere and play a crucial role in atmospheric chemistry and physics. We showed generally enhanced tundra VOC emissions upon insect herbivory and synergistic effects on the emissions of some VOC groups in a changing climate, which can have positive feedbacks on cloud formation.

Moths (Lepidoptera) are major agricultural and forest pests in many parts of the world, including Europe, with many causing great economic damage to crops, horticultural plants, stored items, and wool products. Here, we focus on two ecologically similar inchworms, Operophtera brumata and Erannis defoliaria, known for their high foliage consumption during the spring emergence of caterpillars. We hypothesise that bats could play a role in reducing pests such as caterpillars by switching to this abundant emerging prey. At two infested and one control forest sites, caterpillars were sampled during spring to determine levels of infestation. At the same time, bat flight activity was monitored during the peak in caterpillar abundance. During the spring caterpillar outbreak, we collected faecal samples of forest-dwelling bats capable of using gleaning. The majority of samples were positive for our focus species, being 51.85% for O. brumata and 29.63% for E. defoliaria faecal samples. The foraging activity of two gleaning bats, Myotis nattereri and Myotis bechsteinii, increased at both infested sites, but not at the control site, during caterpillar emergence, as did foraging of Plecotus auritus/austriacus, which used both gleaning and aerial hawking. We conclude that both specialists and occasional gleaners, which prefer different prey but are able to switch their foraging strategies, aggregate at sites during pest emergence and, as such, our results confirm the high potential of bats to reduce numbers of pest species such as caterpillars.

Key message Whereas cold temperatures and artificial smoke pollution (during World War II) cause negative pointer years in northern Fennoscandian downy birches, mass outbreaks of Epirrita autumnata L. and Operophtera brumata Bkh. are the strongest growth-influencing and -synchronizing factor. Abstract Variations in radial tree growth of downy birch can be affected by short-term environmental changes. Here we examine the tree-ring width of downy birch trees for signals caused by three different disturbance factors: climatic extremes, insect outbreaks, and artificial smoke employed to hide the German battleship Tirpitz during World War II at the Kåfjord in northern Norway. Besides growth/climate response analysis using gridded climate data and a tree ring width-chronology of the studied birch trees, we analyze missing rings, pointer years, and the ability of recovery after severe disturbances on an individual tree basis using the percent change of the trees’ basal area increment with respect to a reference period. The downy birches reveal (1) a significant positive correlation with May and June temperatures, (2) a high growth sensitivity to moth epidemics (Epirrita autumnata L. and Operophtera brumata Bkh.), and (3) a distinct growth deviation in the year of intense but short-term artificial smoke pollution. We conclude that downy birches are not exclusively sensitive to unusual cold temperatures, but short-term artificial pollution and insect outbreaks cause similar growth declines in the year of occurrence. Whereas for temperature and pollution, the growth response is less coherent among trees, and fades within 2 years, the insect outbreaks synchronize growth among all downy birches. Growth declines during years of mass insect outbreaks can further be amplified by cold May and June temperatures. Our findings thereby improve the understanding of competing disturbance factors on single birch trees but also on the growth of a whole site in Fennoscandia and facilitates the detection of disturbances in birch chronologies.

Seven species of tachinid flies reared from herbivorous lepidopterans collected from the deciduous forest canopy at Hokkaido University Tomakomai Experimental Forest (0.2 ha plot), Hokkaido, Japan, are recorded and described: Blepharomyia brevicornis sp. nov. ex Erannis golda Djakonov (Geometridae), Catocala lara Bremer and Orthosia odiosa (Butler) (both Noctuidae); Ctenophorinia grisea Mesnil ex Himeropteryx miraculosa Staudinger (Notodontidae); Blepharipa carbonata (Mesnil) ex Marumba jankowskii (Oberthür) (Sphingidae); Cyzenis equifacialis sp. nov. ex Faristenia geminisignella Ponomarenko (Gelechiidae), Archips crataegana (Hübner), A. nigricauda Walshingham, Epinotia exquisitana Christoph and Pseudohedya gradana Christo (all Tortricidae); Cyzenis tetrasetosa sp. nov. ex Lomographa simplicior (Butler), Operophtera brunnea Nakajima and O. relegata Prout (Geometridae); Eulasiona zimini Mesnil ex Archips crataegana (Hübner), Pseudohedya gradana (Christoph), Rhopobota naevana (Hübner) and Rhopobota sp. (all Tortricidae); Panzeria sp. (nr. japonica Shima) ex Erannis golda Djakonov (Geometridae). The genus Eulasiona Townsend is moved to the subfamily Tachininae from its present position in the subfamily Dexiinae, and the female and puparium of Eulasiona zimini Mesnil are described for the first time. The parasitization rates and life habits of these tachinids are briefly discussed.

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.

In North America the invasive winter moth (Operopthera brumata) has caused defoliation in forest and fruit crop systems in British Columbia, Nova Scotia, Oregon, and in the northeastern United States (the “Northeast”). In the Northeast, it was previously shown that hybridization is occurring with a native congener, Bruce spanworm (O. bruceata)—a species that has a broad distribution across much of North America. Whether hybridization among winter moth and Bruce spanworm populations has occurred in all of regions where winter moth established is unknown. One factor that might influence hybridization between these two species is the presence of reproductive manipulating endosymbionts, such a Wolbachia. To determine the geographic extent of hybridization among populations of these two species, we classified 1400 field-collected moths from Europe and North America as either being winter moth, Bruce spanworm, or hybrids using 10–12 polymorphic microsatellite loci. We then screened each individual for the presence of Wolbachia by PCR amplification of the wsp gene fragment. For all hybrids, we determined their maternal species-lineage by PCR amplification and sequencing of the mitochondrial locus cytochrome oxidase I. We find that winter moth x Bruce spanworm hybrid individuals appear to be present in all regions of North America that winter moth has invaded, and that hybrids are of both winter moth and Bruce spanworm maternal-origins. In addition, we find Wolbachia infected individuals from all species in North America, and that winter moth individuals in North America have a much lower infection rate (11.5%) than individuals in Europe (55.1%).

Ecological communities may be resistant to invasive species through a combination of top-down and bottom-up mechanisms, including predation, competition, parasitism, and disease. In particular, natural enemies that cross over from native species to use newly introduced non-native species as hosts can influence invasive species population dynamics and may slow down invasions. However, research on parasitism in biological invasions is lagging behind research on biological invasions in general. We used the model species winter moth (Operophtera brumata) to study the effect of recruitment of native parasitoids on an invasive population of winter moth in the northeastern United States. We deployed sentinel pupae over 4 years across this population’s range, identified recovered parasitoids, and measured the rate of parasitism by native sources across years, seasons, invasion history, and host densities. Native Pimpla wasps inflicted 98% of the parasitism detected, resulting in an annual average of 15–40% mortality on pupae not depredated. Pimpla were present across all years, seasons, and sites. Where winter moth has invaded, parasitism was greatest when winter moth pupal density was high (i.e., positive density-dependent mortality) suggesting that Pimpla is helping to regulate the population. The wasps were morphologically identified as Pimpla aequalis Provancher; however, using a multilocus genetic comparison approach, they were determined to comprise two cryptic species. Overall, this study shows that recruitment of these native wasps to the invasive winter moth population is likely playing a significant role in regulating population outbreaks and is aiding in biological control of winter moth.

Reconstructing the geographic origins of invasive species is critical for establishing effective management strategies. Frequently, molecular investigations are undertaken when the source population is not known, however; these analyses are constrained both by the amount of diversity present in the native region 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 four discrete regions: Nova Scotia, British Columbia, Oregon, and the northeastern United States. It is not known whether these represent independent introductions to North America, or “stepping stone” spread among regions. Using a combination of Bayesian assignment and approximate Bayesian computation methods, we analyzed a population genetic dataset of 24 polymorphic 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 likely being introduced from France and Sweden, respectively; the Oregonian population likely being introduced from either the British Isles or northern Fennoscandia; and the population in the northeastern United States likely being introduced from somewhere in Central Europe. To our surprise, we found that hybridization has not played a large role in the establishment of winter moth populations even though previous reports have documented widespread hybridization between winter moth and a native congener. We discuss the impact of genetic bottlenecks on analyses meant to determine region of origin.

Winter moth, Operophtera brumata, native to Europe, invaded the northeastern United States in the late 1990s, where it caused widespread defoliation of forests and shade trees ranging from 2,266 to 36,360 ha/yr between 2003 and 2015 in Massachusetts. In 2005, we initiated a biological control effort based on the specialist tachinid parasitoid Cyzenis albicans, which had previously been introduced along with the generalist ichneumonid parasitoid Agrypon flaveolatum to control winter moth in Nova Scotia in the 1950s and British Columbia in the 1970s. Due to concerns of possible non-target impacts by A. flaveolatum, we focused entirely on the specialist C. albicans. Each year for 14 yr, we collected several thousand individuals of C. albicans from British Columbia and released them in widely spaced sites in the northeastern United States. As of 2020, we had established C. albicans at 41 of 44 sites from coastal Maine to southeastern Connecticut. By 2016, winter moth densities (pupae/m2 ) had declined from 100-500 to 0-10 pupae/m2 at six release sites at least 10 km apart and this was coincident with the onset of 10-40% parasitism. At one site in Wellesley, Massachusetts, the decline occurred in 2012 and winter moth densities have remained low for seven subsequent years. Defoliation in Massachusetts has been reduced to undetectable levels by aerial survey since 2016. DNA sequencing of the barcoding region of the mitochondrial gene CO1 confirmed that all C. albicans reared from winter moth matched the C. albicans collected from Vancouver Island and were distinct from parasitic flies (presumably a native species) reared from a native congener of winter moth, Bruce spanworm (O. bruceata). Successful establishment of C. albicans on winter moth represents a rare, if not the only, example of the biological control of a major forest defoliator that attacks a wide range of tree species anywhere in the world by the establishment of a single specialist natural enemy.

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.

The mountain birch [Betula pubescens var. pumila (L.)] forest in the Subarctic is periodically exposed to insect outbreaks, which are expected to intensify due to climate change. To mitigate abiotic and biotic stresses, plants have evolved chemical defenses, including volatile organic compounds (VOCs) and non-volatile specialized compounds (NVSCs). Constitutive and induced production of these compounds, however, are poorly studied in Subarctic populations of mountain birch. Here, we assessed the joint effects of insect herbivory, elevation and season on foliar VOC emissions and NVSC contents of mountain birch. The VOCs were sampled in situ by an enclosure technique and analyzed by gas chromatography–mass spectrometry. NVSCs were analyzed by liquid chromatography–mass spectrometry using an untargeted approach. At low elevation, experimental herbivory by winter moth larvae (Operophtera brumata) increased emissions of monoterpenes and homoterpenes over the 3-week feeding period, and sesquiterpenes and green leaf volatiles at the end of the feeding period. At high elevation, however, herbivory augmented only homoterpene emissions. The more pronounced herbivory effects at low elevation were likely due to higher herbivory intensity. Of the individual compounds, linalool, ocimene, 4,8-dimethylnona-1,3,7-triene, 2-methyl butanenitrile and benzyl nitrile were among the most responsive compounds in herbivory treatments. Herbivory also altered foliar NVSC profiles at both low and high elevations, with the most responsive compounds likely belonging to fatty acyl glycosides and terpene glycosides. Additionally, VOC emissions from non-infested branches were higher at high than low elevation, particularly during the early season, which was mainly driven by phenological differences. The VOC emissions varied substantially over the season, largely reflecting the seasonal variations in temperature and light levels. Our results suggest that if insect herbivory pressure continues to rise in the mountain birch forest with ongoing climate change, it will significantly increase VOC emissions with important consequences for local trophic interactions and climate. biotic stress, geometrid moth, global change, plant–insect interactions, secondary metabolites, volatile organic compounds.

Insect herbivory is known to augment emissions of biogenic volatile organic compounds (BVOCs). Yet few studies have quantified BVOC responses to insect herbivory in natural populations in pan-Arctic regions. Here, we assess how quantitative and qualitative BVOC emissions change with increasing herbivore feeding intensity in the Subarctic mountain birch (Betula pubescens var pumila (L.)) forest. We conducted three field experiments in which we manipulated the larval density of geometrid moths (Operophtera brumata and Epirrita autumnata), on branches of mountain birch and measured BVOC emissions using the branch enclosure method and gas chromatography-mass spectrometry. Our study showed that herbivory significantly increased BVOC emissions from the branches damaged by larvae. BVOC emissions increased due to insect herbivory at relatively low larvae densities, causing up to 10% of leaf area loss. Insect herbivory also changed the blend composition of BVOCs, with damaged plants producing less intercorrelated BVOC blends than undamaged ones. Our results provide a quantitative understanding of the relationship between the severity of insect herbivore damage and emissions of BVOCs at larvae densities corresponding to background herbivory levels in the Subarctic mountain birch. The results have important and practical implications for modeling induced and constitutive BVOC emissions and their feedbacks to atmospheric chemistry. arctic, biotic stress, geometrid moth, insect herbivory, mountain birch, stress severity, volatile organic compounds

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.

The success or failure of an introduced biological control agent may depend on its rate of mortality from disease, predation, and hyperparasitism. Cyzenis albicans Fallen (Diptera: Tachinidae) was introduced to the northeastern U.S. as a biocontrol agent of the invasive species winter moth, Operophtera brumata L. (Lepidoptera: Geometridae). This study aimed to determine the rates of mortality from predation by generalist ground predators and hyperparasitism of C. albicans puparia, identify any hyperparasitoids, and assess the impact of predation and hyperparasitism on the potential success of C. albicans in controlling the winter moth. Mortality of C. albicans puparia was primarily due to predation, but there was also hyperparasitism. Predation and parasitism of C. albicans puparia were consistently high across the six study sites and two years of study, but somewhat lower than was reported from British Columbia, where successful establishment of C. albicans in the 1970s was followed by a decrease in winter moth densities. In this study, three genera of ichneumonid hyperparasitoids were detected and identified using a combination of morphological and molecular approaches: Phygadeuon (1 species), Pimpla (2 species), and Gelis (2 species), all of which contain species with broad host ranges and were likely acting as facultative hyperparsitoids. We conclude that while total mortality of C. albicans puparia is high, it is unlikely to have a significant effect on biological control of winter moth in this system, although it may explain why C. albicans has been slow to establish in this region. Our study emphasizes the importance of assessing the mortality of introduced biological control agents caused by native predators and hyperparasitoids.

Ormocerus dirigoius Morin & Gates, n. sp. is described and compared to the North American O. americanus Dzhanokmen and Grissell and European species O. latus Walker and O. vernalis Walker. A range expansion into the Nearctic is reported for O. latus, previously only known from the Palearctic. Specimens were collected in Harpswell, Maine during a study of the parasitic Hymenoptera community associated with Operophtera brumata Linnaeus (Lepidoptera: Geometridae), an invasive species. The species are keyed and illustrated using macrophotography and scanning electron microphotography.

1. Population dynamics and interactions that vary over a species' range are of particular importance in the context of latitudinal clines in biological diversity. Winter moth (Operophtera brumata) and autumnal moth (Epirrita autumnata) are two species of eruptive geometrids that vary widely in outbreak tendency over their range, which generally increases from south to north and with elevation. 2. The predation pressure on geometrid larvae and pupae over an elevational gradient was tested. The effects of background larval density and bird occupancy of monitoring nest boxes on predation rates were also tested. Predation on larvae was tested through exclusion treatments at 20 replicate stations over four elevations at one site, while pupae were set out to measure predation at two elevations at three sites. 3. Larval densities were reduced by bird predation at three lower elevations, but not at the highest elevation, and predation rates were 1.9 times higher at the lowest elevation than at the highest elevation. The rate of predation on larvae was not related to background larval density or nest box occupancy, although there were more eggs and chicks at the lowest elevation. There were no consistent differences in predation on pupae by elevation. 4. These results suggest that elevational variation in avian predation pressure on larvae may help to drive elevational differences in outbreak tendency, and that birds may play a more important role in geometrid population dynamics than the focus on invertebrate and soil predators of previous work would suggest.

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.

Operophtera brumata (Winter Moth) is an invasive insect defoliator named for its early winter activity in its native and introduced ranges. In this study, we examined the relative winter densities of adult female and male Winter Moths in Harpswell, ME, an area of recent outbreak. Additionally, we measured female densities to determine whether specific host-plant species are favored for egg laying. We found that Winter Moth densities during the second winter of this study were lower than in the first, possibly in response to extreme cold temperatures during January 2014. We also found that peaks in male flight coincided with temperatures rising above freezing and that female densities were highest on Quercus rubra (Red Oak), a known preferred host species.

Insect herbivores have the potential to change both physical and chemical traits of their host plant. Although the impacts of herbivores on their hosts have been widely studied, experiments assessing changes in multiple leaf traits or functions simultaneously are still rare. We experimentally tested whether herbivory by winter moth (Operophtera brumata) caterpillars and mechanical leaf wounding changed leaf mass per area, leaf area, leaf carbon and nitrogen content, and the concentrations of 27 polyphenol compounds on oak (Quercus robur) leaves. To investigate how potential changes in the studied traits affect leaf functioning, we related the traits to the rates of leaf photosynthesis and respiration. Overall, we did not detect any clear effects of herbivory or mechanical leaf damage on the chemical or physical leaf traits, despite clear effect of herbivory on photosynthesis. Rather, the trait variation was primarily driven by variation between individual trees. Only leaf nitrogen content and a subset of the studied polyphenol compounds correlated with photosynthesis and leaf respiration. Our results suggest that in our study system, abiotic conditions related to the growth location, variation between tree individuals, and seasonal trends in plant physiology are more important than herbivory in determining the distribution and composition of leaf chemical and structural traits.

A classic system for studying trophic mismatch focuses on the timing of the spring caterpillar peak in relation to the breeding time and productivity of woodland passerine birds. Most work has been conducted in single-site oak woodlands and little is known about how insights generalise to other woodland types or across space. Here we present the results of a three-year study on the species composition and temporal distribution of the spring caterpillar peak on different tree taxa across 40 woodland sites spanning two degrees of latitude in Scotland. We used molecular barcoding to identify 62 caterpillar species, with winter moth (Operophtera brumata) the most abundant, comprising a third of the sample. Oak (Quercus sp.) and willow (Salix sp.) hosted significantly higher caterpillar abundances than other tree taxa, with winter moth exhibiting similar trends and invariantly proportionate across tree taxa. Caterpillar peak phenology was broadly similar between tree taxa.While latitude had little effect, increasing elevation increased the height of the caterpillar peak and retarded timing by 3.7 days/100m. These findings extend our understanding of how mismatch may play out spatially, with caterpillar peak date varying with elevation, and tree taxa varying in the caterpillar resource that they host.

To identify general patterns in the effect of climate-driven changes in the outbreak frequency of forest defoliating species, we examined 60 years of records (1950–2010) of outbreaks of five defoliating species. Data on Lymantria dispar, Lymantria monacha, Bupalus piniarius, Panolis flammea, and Operophtera brumata from five Central European countries (Slovakia, Czech Republic, Austria, Hungary, and Germany), where the current climate is comparable with the projections of climate for the Eastern Baltic region by the end of the 21st century, were analyzed. Time series approach was applied to estimate the linkage between outbreaks and climate warming. Mean annual, summer, and winter deviations for the period of 1850 to 1900 were assessed as proxies of warming. To estimate the legacy effect, warming proxies were lagged by one year. Among those tested, warming proxies showed a linkage with outbreaks. Three significant outbreaks occurred in the analyzed period (at the beginning and end of the period). During the middle part of the analyzed period, the frequency and magnitude of outbreaks were low, implicating a higher insect outbreak risk with warming in Central Europe. In the latter part of the analyzed period, more frequent yet smaller outbreaks occurred, which supports the outbreak linkage with one-year lag, summer, and annual temperatures.

Disease can affect biological invasions by acting as either a synergist or antagonist. Disease-mediated invasions have important implications for understanding the spread of invasive insects, which cost billions of dollars in damages annually. One such non-native, destructive insect is the winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), which causes defoliation and mortality of deciduous trees in its introduced range. In the northeastern United States, winter moth populations overlap with a native congener, Bruce spanworm, Operophtera bruceata Hulst. Nucleopolyhedrovirus (NPV), appears to be an important natural enemy in Bruce spanworm and there is some evidence that the NPV infection found in winter moth in the northeastern U.S. may originate from Bruce spanworm. By sequencing two viral genes (the polyhedrin and p74 genes) from field-collected larvae of both species, we found that the winter moth virus (OpbuNPV) is distinct from the virus from Bruce spanworm (OpbrNPV). However, the two viruses do constitute a clade within the Alphabaculovirus Group 2 NPVs, indicating that they are more similar to each other than they are to other lepidopteran viruses, even other geometrid-derived NPVs. As far as we know, this is the first report of sequences from an NPV from Bruce spanworm. Results from cross infection trials suggest that cross infection is uncommon if it occurs at all. Our results show that these two closely related species have distinct viruses and, unlike previous suggestions, Bruce spanworm virus is not mediating the winter moth invasion.

Red autumn colouration of trees is the result of newly synthesized anthocyanin pigments in senescing autumn leaves. As anthocyanin accumulation is costly and the trait is not present in all species, anthocyanins must have an adaptive significance in autumn leaves. According to the coevolution hypothesis of autumn colours, red autumn leaves warn herbivorous insects – especially aphids that migrate to reproduce in trees in the autumn – that the tree will not be a suitable host for their offspring in spring due to a high level of chemical defence or lack of nutrients. The signalling allows trees to avoid herbivores and herbivores to choose better host trees. In this study the coevolution hypothesis was tested with four deciduous tree species that have red autumn leaf colouration – European aspen (Populus tremula L.) (Salicaceae), rowan (Sorbus aucuparia L.) (Rosaceae), mountain birch [Betula pubescens ssp. czerepanovii (NI Orlova) Hamet‐Ahti], and dwarf birch (Betula nana L.) (Betulaceae), and with two generalist herbivores, the autumnal moth [Epirrita autumnata (Borkhausen)] and the winter moth [Operophtera brumata (L.)] (both Lepidoptera: Geometridae). Anthocyanin concentrations of autumn leaves were determined from leaf samples and the growth performance parameters of the moth larvae on the study trees were measured in the spring. Trees with higher anthocyanin concentration in the autumn were predicted to be low‐quality food for the herbivores. Our results clearly showed that anthocyanin concentration was not correlated with the growth performance of the moths in any of the studied tree species. Thus, our study does not support the coevolution hypothesis of autumn colours.

Understanding the relationship between an insect's developmental rate and temperature is crucial to forecast insect phenology under climate change. In the winter moth Operophtera brumata timing of egg-hatching has severe fitness consequences on growth and reproduction as egg-hatching has to match bud burst of the host tree. In the winter moth, as in many insect species, egg development is strongly affected by ambient temperatures. Here we use laboratory experiments to show for the first time that the effect of temperature on developmental rate depends on the stage of development of the eggs. Building on this experimental finding, we present a novel physiological model to describe winter moth egg development in response to temperature. Our model, a modification of the existing Sharpe-Schoolfield biophysical model, incorporates the effect of developmental stage on developmental rate. Next we validate this model using a 13-year data-set from winter moth eggs kept under ambient conditions and compared this validation with a degree day model and with the Sharpe-Schoolfield model, which lacks the interaction between temperature and developmental stage on developmental rate. We show that accounting for the interaction between temperature and developmental stage improved the predictive power of the model and contributed to our understanding of annual variation in winter moth egg phenology. As climate change leads to unequal changes in temperatures throughout the year, a description of insect development in response to realistic patterns of temperature rather than an invariable degree-day approach will help us to better predict future responses of insect phenology, and thereby insect fitness, to climate change.This article is protected by copyright. All rights reserved.

The European winter moth,Operophtera brumata, is a non-native pest in the Northeastern USA causing defoliation of forest trees and crops such as apples and blueberries. This species is known to hybridize withO. bruceata, the Bruce spanworm, a native species across North America, although it is not known if there are hybrid generations beyond F1. To study winter moth population genetics and hybridization with Bruce spanworm, we developed two sets of genetic markers, single nucleotide polymorphisms (SNPs) and microsatellites, using genomic approaches. Both types of markers were validated using samples from the two species and their hybrids. We identified 1216 SNPs and 24 variable microsatellite loci. From them we developed a subset of 95 species-diagnostic SNPs and ten microsatellite loci that could be used for hybrid identification. We further validated the ten microsatellite loci by screening field collected samples of both species and putative hybrids. In addition to confirming the presence of F1 hybrids reported in previous studies, we found evidence for multi-generation asymmetric hybridization, as suggested by the occurrence of hybrid backcrosses with the winter month, but not with the Bruce spanworm. Laboratory crosses between winter moth females and Bruce spanworm males resulted in a higher proportion of viable eggs than the reciprocal cross, supporting this pattern. We discuss the possible roles of population demographics, sex chromosome genetic incompatibility, and bacterial symbionts as causes of this asymmetrical hybridization and the utility of the developed markers for future studies.

Climate change may facilitate shifts in the ranges and the spread of insect pests, but a warming climate may also affect herbivorous insects adversely if it disrupts the locally adapted synchrony between the phenology of insects and that of their host plant. The ability of a pest species to colonize new areas depends on its ability to adjust the timing of phenological events in its life cycle, particularly at high latitudes where there is marked seasonality in temperature and day length. Here we incubated eggs of three species of geometrid moth, Epirrita autumnata, Operophtera brumata and Erannis defoliaria from different geographical populations (E. autumnata and O. brumata from Northern Finland, E. autumnata and E. defoliaria from Southern Finland and all three species from Germany) in a climate chamber at a constant temperature to determine the relative importance of geographic origin in the timing of egg hatch measured in terms of cumulative temperature sums (degree days above 5°C, DD5); i.e. the relative importance of local adaptation versus phenotypic plasticity in the timing of egg hatch. In all three species, eggs from northern populations required a significantly lower temperature sum for hatching than eggs from southern populations, but the differences between them in temperature sum requirements varied considerably among species, with the differences being largest for the earliest hatching and northernmost species, E. autumnata, and smallest for the southern, late-hatching E. defoliaria. In addition, the difference in hatch timing between the E. autumnata eggs from Southern Finland and Germany was many times greater than the difference between the two Finnish populations of E. autumnata, despite the fact that the geographical distances between these populations is similar. We discuss how these differences in hatching time may be explained by the differences in hatch-budburst synchrony and its importance for different moth species and populations. We also briefly reflect on the significance of photoperiod, which is not affected by climate change. It is a controller that works parallel or in addition to temperature sum both for egg hatch in moths and bud burst of their host plants.

Forest habitats change significantly under the influence of global warming. It is important to predict the effects of these changes, especially in primeval forests which currently represent a small percentage of temperate forests. Such changes often manifest themselves in an acceleration of the frequency of mass seeding of trees, which causes cascading effects in various organisms. We evaluated changes in: tree masts (oak Quercus robur and hornbeam Carpinus betulus), rodent abundance (yellow-necked mouse Apodemus flavicollis), folivorous caterpillar abundance (winter moth Operophtera brumata), and the breeding success of a cavity-nesting songbird (collared flycatcher Ficedula albicollis) in over a 30-year period in the Białowieża Forest (E Poland). We also analysed temperature, precipitation and snow cover to determine the effects of weather on each trophic level. Previous studies have exposed the indirect effect of tree masting on songbirds breeding in open nests. Our study uniquely highlights the relationships between trees, rodents, caterpillars, and a cavity-nesting bird. Precipitation was positively correlated with the fructification of trees, abundance of caterpillars, and the breeding losses of flycatchers (in July, August, October in the previous year, in May in the current year, respectively). We found that along with the changing climate, the frequency of mast years of oak increased, which caused an increasing frequency of rodent outbreaks. The abundance of mice was positively correlated with the predation on flycatcher broods (current year) and negatively - with the abundance of caterpillars (following year). We predict that current global trends in climate change will have a negative impact on the flycatcher due to the cascading effects from the above species. Bearing in mind that F. albicollis is one of the most numerous bird species, it can be assumed that more frequent masting will result in substantial changes in the entire bird assemblage, and presumably also other groups of animals.

Background Winter moth (Operophtera brumata) and mottled umber moth (Erannis defoliaria) are forest Lepidoptera species characterized by periodic high abundance in a 7–11 year cycle. During outbreak years they cause severe defoliation in many forest stands in Europe. In order to better understand the spatio-temporal dynamics and elucidate possible influences of weather, stand and site conditions, a generalized additive mixed model was developed. The investigated data base was derived from glue band catch monitoring stands of both species in Central and North Germany. From the glue bands only female moth individuals are counted and a hazard code is calculated. The model can be employed to predict the exceedance of a warning threshold of this hazard code which indicates a potential severe defoliation of oak stands by winter moth and mottled umber in the coming spring. Results The developed model accounts for specific temporal structured effects for three large ecoregions and random effects at stand level. During variable selection the negative model effect of pest control and the positive model effects of mean daily minimum temperature in adult stage and precipitation in early pupal stage were identified. Conclusion The developed model can be used for short-term predictions of potential defoliation risk in Central and North Germany. These predictions are sensitive to weather conditions and the population dynamics. However, a future extension of the data base comprising further outbreak years would allow for deeper investigation of the temporal and regional patterns of the cyclic dynamics and their causal influences on abundance of winter moth and mottled umber.

Tree mortality from insect infestations can significantly reduce carbon storage in forest soils. In subarctic birch forests (Betula pubescens), ecosystem C cycling is largely affected by recurrent outbreaks of defoliating geometrid moths (Epirrita autumnata, Operophtera brumata). Here, we show that soil C stocks in birch forests across Fennoscandia did not change up to 8 years after moth outbreaks. We found that a decrease in woody fine roots was accompanied by a lower soil CO2 efflux rate and a higher soil N availability following moth outbreaks. We suggest that a high N availability and less ectomycorrhiza likely contributed to lowered heterotrophic respiration and soil enzymatic activity. Based on proxies for decomposition (heterotrophic respiration, phenol oxidase potential activity), we conclude that a decrease in decomposition is a prime cause why soil C stocks of mountain birch forest ecosystems have not changed after moth outbreaks. Compared to disturbed temperate and boreal forests, a CO2-related positive feedback of forest disturbance on climate change might therefore be smaller in subarctic regions. Betula pubescens; disturbed subarctic forests; Epirrita autumnata; heterotrophic soil respiration; Operophtera brumata; root biomass; soil carbon sequestration; soil CO2 efflux; soil enzyme activity; structural equation modelling.

Species within the group of winter moths (Geometridae) are important oak defoliators in European forests. Adults of these species emerge either in late autumn (&lsquo, autumn species&rsquo, ) or in early spring (&lsquo, spring species&rsquo, ), and caterpillars of both &lsquo, autumn&rsquo, and &lsquo, spring&rsquo, species appear in spring. The abundance of adults assessed by regular monitoring allows the prediction of the defoliation intensity in trees by caterpillars in the following spring. &lsquo, Autumn species&rsquo, (mostly a single one, Operophtera brumata) are monitored by forestry practices as pests, whereas &lsquo, are often not paid any attention. We hypothesised that &lsquo, could also have an important share in caterpillar assemblages in oak forests. We aimed to study the proportions between &lsquo, species in adult and larval stages. In a xeric thermophilous oak forest in southern Slovakia, Central Europe, we collected adult moths using sticky bands set up on trunks of Quercus pubescens during the winter of 2014&ndash, 2015 and caterpillars from other trees belonging to the same oak species over the following spring. We also captured caterpillars from several oak species in various areas and over different years in Slovakia and Bulgaria, and we compiled relevant literature data. &lsquo, Spring species&rsquo, recorded from a unique forest as adults during winter and as caterpillars in the following spring were significantly more abundant than &lsquo, autumn species.&rsquo, Moreover, &lsquo, from Slovakian forests, regardless of the locality, the oak species and the year of sampling, reached high proportions, mostly over 50% of individuals in caterpillar assemblages. The &lsquo, Agriopis leucophaearia was the most abundant, followed by the &lsquo, Operophtera brumata. &lsquo, accounted for more than 50% of individuals in caterpillar assemblages in the Balkan Peninsula (Bulgaria) concerning one case, and they were of little importance in northern Greece. We recommend monitoring all winter moth adults (&lsquo, species together) continuously in forestry practices, using sticky bands on oak trees from late autumn to early spring.

• Insect herbivores cause substantial changes in the leaves they attack, but their effects on the ecophysiology of neighbouring, non-damaged leaves have never been quantified in natural canopies. We studied how winter moth (Operophtera brumata), a common herbivore in temperate forests, affects the photosynthetic and isoprene emission rates of its host plant, the pedunculate oak (Quercus robur). • Through a manipulative experiment, we measured leaves on shoots damaged by caterpillars or mechanically by cutting, or left completely intact. To quantify the effects at the canopy scale, we surveyed the extent and patterns of leaf area loss in the canopy. • Herbivory reduced photosynthesis both in damaged leaves and in their intact neighbours. Isoprene emission rates significantly increased after mechanical leaf damage. When scaled up to canopy-level, herbivory reduced photosynthesis by 48 ± 10%. • The indirect effects of herbivory on photosynthesis on undamaged leaves (40%) were much more important than the direct effects of leaf area loss (6%). If widespread across other plant-herbivore systems, these findings suggest that insect herbivory has major and previously underappreciated influences in modifying ecosystem carbon cycling, with potential effects on atmospheric chemistry.

The pervading paradigm in insect phenology models is that the response to a given temperature does not vary within a life stage. The developmental rate functions that have been developed for general use, or for specific insects, have for the most part been temperature-dependent but not age-dependent, except where age is an ordinal variable designating the larval instar. Age dependence, where age is a continuous variable, is not often reported (or investigated), and is rarely included in phenology models. I provide a short review of the seldom-investigated phenomenon of age dependence in developmental response to temperature, and compare the derivation of the winter moth egg phenology model by Salis et al. to the derivation of another egg phenology model with age-dependent responses to temperature I discuss some probable reasons for the discrepancies (acknowledged by Salis et al.) between modelled and observed developmental rates of the winter moth, and discuss the contribution that geographically robust phenology models can make to estimates of species distributions.

* Levels of artificial night lighting are increasing rapidly worldwide, subjecting nocturnal organisms to a major change in their environment. Many moth species are strongly attracted to sources of artificial night lighting, with potentially severe, yet poorly studied, consequences for development, reproduction and inter/intra-specific interactions. * Here, we present results of a field-based experiment where we tested effects of various types of artificial lighting on mating in the winter moth (Operophtera brumata, Lepidoptera: Geometridae). We illuminated trunks of oak trees with green, white, red or no artificial LED light at night, and caught female O. brumata on these trunks using funnel traps. The females were dissected to check for the presence of a spermatophore, a sperm package that is delivered by males to females during mating. * We found a strong reduction in the number of females on the illuminated trunks, indicating artificial light inhibition of activity. Furthermore, artificial light inhibited mating: 53% of females caught on non-illuminated trunks had mated, whereas only 13%, 16% and 28% of the females that were caught on green, white and red light illuminated trunks had mated respectively. * A second experiment showed that artificial night lighting reduced the number of males that were attracted to a synthetic O. brumata pheromone lure. This effect was strongest under red light and mildest under green light. * This study provides, for the first time, field-based evidence that artificial night lighting disrupts reproductive behaviour of moths, and that reducing short wavelength radiation only partly mitigates these negative effects.

© 2018 Saavedra, Amo., Chemical cues play a fundamental role in mate attraction and mate choice. Lepidopteran females, such as the winter moth (Operophtera brumata), emit pheromones to attract males in the reproductive period. However, these chemical cues could also be eavesdropped by predators. To our knowledge, no studies have examined whether birds can detect pheromones of their prey. O. brumata adults are part of the winter diet of some insectivorous tit species, such as the great tit (Parus major) and blue tit (Cyanistes caeruleus). We performed a field experiment aimed to disentangle whether insectivorous birds can exploit the pheromones emitted by their prey for prey location. We placed artificial larvae and a dispenser on branches of Pyrenean oak trees (Quercus pyrenaica). In half of the trees we placed an O. brumata pheromone dispenser and in the other half we placed a control dispenser. We measured the predation rate of birds on artificial larvae. Our results show that more trees had larvae with signs of avian predation when they contained an O. brumata pheromone than when they contained a control dispenser. Furthermore, the proportion of artificial larvae with signs of avian predation was greater in trees that contained the pheromone than in control trees. Our results indicate that insectivorous birds can exploit the pheromones emitted by moth females to attract males, as a method of prey detection. These results highlight the potential use of insectivorous birds in the biological control of insect pests., This work was supported by the Ministry of Economy and Competitiveness (CGL2014-58890-P).

Plant meristems were previously thought to be sterile. Today, meristem-associated shoot endophytes are mainly reported as contaminants from plant tissue cultures, the number of observed species being very low. However, the few strains characterized have the capacity for infecting host cells and affecting plant growth and development. Here we studied the communities of endophytic bacteria in the buds of mountain birch (Betula pubescens ssp. czerepanovii (N. I. Orlova) Hämet-Ahti) exposed to winter moth (Operophtera brumata L.) herbivory, to identify differences between sprouts and branches of mature birch trees. Mountain birch of the high subarctic is cyclically exposed to winter moth and produces sprouts to generate new trees as a survival mechanism. The majority (54%) of operational taxonomic units belonged to Xanthomonadaceae and Pseudomonales of Proteobacteria. Most of the observed species were classified as Xanthomonas (28%). Sprout buds had the highest diversity, containing approximately three times more species, and significantly more (43%) Pseudomonas species than the mature trees (14%). Our results demonstrate that endophytic communities of buds are richer than previously thought. We suggest that the meristem-associated endophytes should be studied further for a possible role in sprouting and aiding regeneration of trees.