Northern Range Boundary Research Articles

Spatio-temporal shifts in British wild bees in response to changing climate.

Climate plays a major role in determining where species occur, and when they are active throughout the year. In the face of a changing climate, many species are shifting their ranges poleward. Many species are also shifting their emergence phenology. Wild bees in Great Britain are susceptible to changes in climatic conditions but little is known about historic or potential future spatio-temporal trends of many species. This study utilized a sliding window approach to assess the impacts of climate on bee emergence dates, estimating the best temperature window for predicting emergence dates for 88 species of wild bees. Using a 'middle-of-the-road' (RCP 4.5) and 'worst-case' (RCP 8.5) climate scenario for the period 2070-2079, predictions of future emergence dates were made. In general, the best predicting climate window occurred in the 0-3 months preceding emergence. Across the 40 species that showed a shift in emergence dates in response to a climate window, the mean advance was 13.4 days under RCP 4.5 and 24.9 days under RCP 8.5. Species distribution models (SDMs) were used to predict suitable climate envelopes under historic (1980-1989), current (2010-2019) and future (2070-2079 under RCP 4.5 and RCP 8.5 scenarios) climate conditions. These models predict that the climate envelope for 92% of studied species has increased since the 1980s, and for 97% and 93% of species under RCP 4.5 and RCP 8.5 respectively, this is predicted to continue, due to extension of the northern range boundary. While any range changes will be moderated by habitat availability, it highlights that Great Britain will likely experience northward shifts of bee populations in the future. By combining spatial and temporal trends, this work provides an important step towards informing conservation measures suitable for future climates, directing how interventions can be provided in the right place at the right time.

Using mechanistic insights to predict the climate‐induced expansion of a key aquatic predator

AbstractAmeliorating the impacts of climate change on communities requires understanding the mechanisms of change and applying them to predict future responses. One way to prioritize efforts is to identify biotic multipliers, which are species that are sensitive to climate change and disproportionately alter communities. We first evaluate the mechanisms underlying the occupancy dynamics of marbled salamanders, a key predator in temporary ponds in the eastern United States We use long‐term data to evaluate four mechanistic hypotheses proposed to explain occupancy patterns, including autumn flooding, overwintering predation, freezing, and winterkill from oxygen depletion. Results suggest that winterkill and fall flooding best explain marbled salamander occupancy patterns. A field introduction experiment supports the importance of winterkill via hypoxia rather than freezing in determining overwinter survival and rejects dispersal limitation as a mechanism preventing establishment. We build climate‐based correlative models that describe salamander occupancy across ponds and years at two latitudinally divergent sites, a southern and middle site, with and without field‐collected habitat characteristics. Correlative models with climate and habitat variation described occupancy patterns better than climate‐only models for each site, but poorly predicted occupancy patterns at the site not used for model development. We next built hybrid mechanistic metapopulation occupancy models that incorporated flooding and winterkill mechanisms. Although hybrid models did not describe observed site‐specific occupancy dynamics better than correlative models, they better predicted the other site's dynamics, revealing a performance trade‐off between model types. Under future climate scenarios, models predict an increased occupancy of marbled salamanders, especially at the middle site, and expansion at a northern site beyond the northern range boundary. Evidence for the climate sensitivity of marbled salamanders combined with their disproportionate ecological impacts suggests that they might act as biotic multipliers of climate change in temporary ponds. More generally, we predict that top aquatic vertebrate predators will expand into temperate‐boreal lakes as climate change reduces winterkill worldwide. Predaceous species with life histories sensitive to winter temperatures provide good candidates for identifying additional biotic multipliers. Building models that include biological mechanisms for key species such as biotic multipliers could better predict broad changes in communities and design effective conservation actions.

To the Stady of a Water Vole (<i>Arvicola anphibius</i>) at the North-Western Area

We have conducted the long-term expeditionary and stationary studies in the taiga Northwest of Russia (1958–2018) to characterize the population, biotopic distribution, nutrition, reproduction, spatial and ecological structure of the population, and the dynamics of the number of water voles, including those associated with its habitat in northern range boundaries: timing, reproductive cycles, course and intensity of reproduction, participation in the reproduction of individual age groups, variations in brood size, etc. The breeding season from the first pregnant females are caught in spring to the last newly born females in autumn lasts 4–6 months. It depends on the state of the population and weather and phenological conditions of the year. The average brood in wintering and arrived female voles in our region was close to the species norm and amounted to 6.5 ± 0.37 and 5.7 ± 0.41. The main reasons for the long-term dynamics of the species abundance are changes in the hydrological regime of water bodies.

Climate tracking by freshwater fishes suggests that fish diversity in temperate lakes may be increasingly threatened by climate warming

AbstractAimMany freshwater fishes are migrating poleward to more thermally suitable habitats in response to warming climates. In this study, we aimed to identify which freshwater fishes are most sensitive to climatic changes and asked: (i) how fast are lakes warming? (ii) how fast are fishes moving? and (iii) are freshwater fishes tracking climate?LocationOntario, Canada.MethodsWe assembled a database containing time series data on climate and species occurrence data from 10,732 lakes between 1986 and 2017. We calculated the rate of lake warming and climate velocity for these lakes. Climate velocities were compared with biotic velocities, specifically the rate at which the northernmost extent of each species shifted north.ResultsLakes in Ontario warmed by 0.2°C decade−1 on average, at a climate velocity of 9.4 km decade−1 between 1986 and 2017. In response, some freshwater fishes have shifted their northern range boundaries with considerable interspecific variation ranging from species moving southwards at a rate of −58.9 km decade−1 to species ranges moving northwards at a rate of 83.6 km decade−1 over the same time period. More freshwater fish species are moving into northern lakes in Ontario than those being lost. Generally, predators are moving their range edges northwards, whereas prey fishes are being lost from northern lakes.Main ConclusionsThe concurrent loss of cooler refugia, combined with antagonistic competitive and predatory interactions with the range expanding species, has resulted in many commercially important predators moving their range edges northwards, whereas prey species have contracted their northern range edge boundaries. Trophic partitioning of range shifts highlights a previously undocumented observation of the loss of freshwater fishes from lower trophic levels in response to climate‐driven migrations.

Biodiversity of Coleoptera (Insecta) in the Middle and Lower Volga Regions (Russia)

(1) Background: The conservation of entomofauna in individual macroregions requires efforts to study the distribution and abundance of insects. For this purpose, databases are created that enumerate this information. Such databases, with the processing of significant factual material, make it possible to objectively assess the status of a species and, if necessary, take measures for its protection. The aim of the paper is to describe the modern Coleoptera fauna in nine regions of Russia on the basis of a recently published dataset. (2) Methods: We conducted our own studies in 1994, 1996, 1998–2003 and 2005–2022. The dataset also includes data from museum specimens from other years. We used a variety of methods, such as sifting through litter, searching under the bark of trees and stumps, trapping by light, soil traps, beer traps, window traps, etc. For each observation, the coordinates of the find, the number of individuals observed and the date were recorded. (3) Results: The dataset contains data on 1469 species and subspecies of Coleoptera from 85 families found in the Volga Region. In total, there are 31,433 samples and 9072 occurrences in the dataset. (4) Conclusions: The largest families in terms of species diversity are Curculionidae (202 species), Carabidae (145 species) and Chrysomelidae (142 species). There are 54 species of Coleoptera with a northern range boundary in the macroregion, two species with a southern range boundary and one species with an eastern range boundary. Twenty-one invasive Coleoptera species have been recorded in the macroregion.

Distinct temperature stressors acting on multiple ontogenetic stages influence the biogeography of Atlantic blue crabs

To understand and predict shifts in species distribution in a changing climate, it is important to consider the exposure and sensitivity of multiple life history stages, particularly for marine species with complex life cycles. In this study, we examined spatio-temporal trends in the abundance of the blue crab Callinectes sapidus and how different temperature stressors acting on multiple ontogenetic stages may affect the species’ current and future distribution across the Atlantic coast of the USA. Since 1975, crab abundance has remained constant or increased in the northeast and northern mid-Atlantic regions but declined in the southern mid-Atlantic and southeast. In the northeast, abundance changes and the location of the northern range boundary appear to be dictated primarily by lower thermal constraints on summer larval stages and may be reinforced by chronic winter cold stress on juveniles and adults. In the mid-Atlantic, acute winter cold stress on juveniles and adults may regulate crab abundance, whereas in the southeast, temperature stress is likely not limiting or directly driving abundance declines. Temperature projections suggest a potential for northward range expansion and increased abundance in the northeast. In the northern mid-Atlantic, however, changes in the duration, magnitude, and phenology of summer temperatures may have complex effects on crab reproduction. Our results highlight how past and future changes in environmental suitability can vary non-uniformly both within and beyond a species’ current range, and the value of examining multiple life history stages and aspects of temperature stress.

Steppe-runner Eremias arguta (Reptilia: Lacertidae): new encounters at the northern boundary of range in the Trans-Volga region

The information about the northern range boundary of the steppe-runner Eremias arguta (Pallas, 1773) has changed in recent decades. Based on the reliable recordins in 2001-2020 from 12 locations the northern range boundary between Volga and Ural was specified. It runs through the Engelsky District of the Saratov Region, through the Stavropolsky, Kinelsky, Bogatovsky and Borsky Districts of the Samara Region, through the Buzuluksky and Tashlinsky Districts of the Orenburg Region of Russia. The northern limit of the range should be considered the Volga above-floodplain slope in the left-bank part of the Stavropolsky district in Samara region. All specimens encountered had body coloration typical of Eremias arguta deserti (Gmelin, 1789). The locations of steppe-runner are confined to open spaces treeless and without a dense herbaceous vegetation on the southern sandy slopes.

Mosquito Distribution in Northwestern Russia: Species of the Genera Anopheles Meigen, Coquillettidia Dyar, Culex L., and Culiseta Felt (Diptera, Culicidae)

Records of 16 species of the mosquito genera Anopheles, Coquillettidia, Culex, and Culiseta (Diptera: Culicidae) in Northwestern Russia are mapped. The values of the sum of active temperatures above 0°C were shown to correlate with the position of the northern range boundaries of mosquito species, according to which 16 species were included in 4 distribution groups.

Climate Change and Local Host Availability Drive the Northern Range Boundary in the Rapid Expansion of a Specialist Insect Herbivore, Papilio cresphontes

Species distributions, abundance, and interactions have always been influenced by human activity and are currently experiencing rapid change. Biodiversity benchmark surveys traditionally require intense human labor inputs to find, identify, and record organisms limiting the rate and impact of scientific enquiry and discovery. Recent emergence and advancement of monitoring technologies have improved biodiversity data collection to a scale and scope previously unimaginable. Community science web platforms, smartphone applications, and technology assisted identification have expedited the speed and enhanced the volume of observational data all while providing open access to these data worldwide. How to integrate and leverage the data into valuable information on how species are changing in space and time requires new best practices in computational and analytical approaches. Here we integrate data from three community science repositories to explore how a specialist herbivore distribution changes in relation to host plant distributions and other environmental factors. We generate a series of temporally explicit species distribution models to generate range predictions for a specialist insect herbivore (Papilio cresphontes) and three predominant host-plant species. We find that this insect species has experienced rapid northern range expansion, likely due to a combination of the range of its larval host plants and climate changes in winter. This case study shows rapid data collection through large scale community science endeavors can be leveraged through thoughtful data integration and transparent analytic pipelines to inform how environmental change impacts where species are and their interactions for a more cost effective method of biodiversity benchmarking.

Spawning phenology of a rapidly shifting marine fish species throughout its range

Abstract Ocean warming is leading to poleward range shifts for many fish species, and while well described, potential life history phenology differences within fish populations along a gradient from their historic to current distributional range have not been studied. In a rapidly shifting fish population, the Northern stock of black sea bass (Centropristis striata), we investigated spawning phenology and output across the US Northeast Shelf to comprise locations in their historic and more recently occupied range near their northern range boundary. Spawning started later in the northern extreme of our study but also ended earlier, leading to decreased spawning duration from south to north. Spawning phenology was mostly driven by Julian day followed by temperature and latitude. Gonadosomatic index, a proxy for reproductive output, was lower in the northern region, indicating that black sea bass did not compensate for the shorter spawning season there. Hepatosomatic index was lower in the northern regions indicating lower pre-spawning liver energy reserves, potentially leading to lower reproductive output. These results suggest a potential for lower recruitment in the recently occupied range and should be further investigated to predict the impacts of ocean warming and for proactive fisheries management as black sea bass distributional range expands poleward.

Influence of habitat availability and fire disturbance on a northern range boundary

AbstractAimNon‐climatic constraints on species northern range boundaries are often overlooked in attempts to predict climate‐induced range shifts. Here, we examined the effects of habitat availability and fire disturbance on the distribution of a species that transitions from being common to being found only in marginal populations at the northern boundary of its range.LocationNorth‐western Quebec, Canada (46–51° N and 74–79° W).Taxon : Eastern white cedar (Thuja occidentalis L.)MethodsWe used forest inventory data (n = 4,987) to characterize white‐cedar habitat based on edaphic and topographic conditions at sampled sites along a 600‐km latitudinal gradient. Non‐metric multidimensional scaling was used to assess habitat similarity of sites in the south, where white‐cedar stands are abundant, and sites in the north, where white‐cedar stands are rare. We constructed ensemble white cedar distribution models based on habitat variables in the south and compared ensemble forecast projections of white cedar in the north with observed occurrences to determine if habitat availability was limiting. We independently estimated the age of white‐cedar stands and adjacent stands without white cedar along the gradient. ANOVA was performed to test the age difference between white‐cedar and adjacent stands to determine whether the location of white‐cedar stands was influenced by disturbance, primarily stand‐replacing fire.ResultsHabitat availability was not limiting the distribution of eastern white cedar at its northern range boundary. White cedar did not occupy most sites with suitable habitat in the north, suggesting that other factors prevent white cedar from establishing more stands northward. White‐cedar stands were older than adjacent stands without white cedar all along the gradient, but the difference was more pronounced in the north. This suggests that white‐cedar stands in the north are restricted to undisturbed areas.Main conclusionsFire disturbance, more than habitat availability, limits the distribution of white cedar at its northern range boundary. Projections of white cedar distribution under climate change that ignore fire could overestimate the ability of warming temperatures to extend its northern range limit.

Substrate-dependent fish have shifted less in distribution under climate change

Analyses of the impacts of climate change on fish species have primarily considered dynamic oceanographic variables that are the output of predictive models, yet fish species distributions are determined by much more than just variables such as ocean temperature. Functionally diverse species are differentially influenced by oceanographic as well as physiographic variables such as bottom substrate, thereby influencing their ability to shift distributions. Here, we show that fish species distributions that are more associated with bottom substrate than other dynamic environmental variables have shifted significantly less over the last 30 years than species whose distributions are associated with bottom salinity. Correspondingly, species whose distributions are primarily determined by bottom temperature or ocean salinity have shifted their mean centroid and southern and northern range boundaries significantly more than species whose distributions are determined by substrate or depth. The influence of oceanographic versus static variables differs by species functional group, as benthic species distributions are more associated with substrate and they have shifted significantly less than pelagic species whose distributions are primarily associated with ocean temperatures. In conclusion, benthic fish, that are more influenced by substrate, may prove much less likely to shift distributions under future climate change.

Monitoring the influx of new species through citizen science: the first introduced ant in Denmark

Climate change and invasive species threaten biodiversity, yet rigorous monitoring of their impact can be costly. Citizen science is increasingly used as a tool for monitoring exotic species, because citizens are geographically and temporally dispersed, whereas scientists tend to cluster in museums and at universities. Here we report on the establishment of the first exotic ant taxon (Tetramorium immigrans) in Denmark, which was discovered by children participating in The Ant Hunt. The Ant Hunt is a citizen science project for children that we ran in 2017 and 2018, with a pilot study in 2015. T. immigrans was discovered in the Botanical Garden of the Natural History Museum of Denmark in 2015 and confirmed as established in 2018. This finding extends the northern range boundary of T. immigrans by almost 460 km. Using climatic niche modelling, we compared the climatic niche of T. immigrans in Europe with that of T. caespitum based on confirmed observations from 2006 to 2019. T. immigrans and T. caespitum had a 13% niche overlap, with T. immigrans showing stronger occurrence in warmer and drier areas compared to T. caespitum. Mapping the environmental niches onto geographic space identified several, currently uninhabited, areas as climatically suitable for the establishment of T. immigrans. Tetramorium immigrans was sampled almost three times as often in areas with artificial surfaces compared to T. caespitum, suggesting that T. immigrans may not be native to all of Europe and is being accidentally introduced by humans. Overall, citizen scientists collected data on ants closer to cities and harbours than scientists did and had a stronger bias towards areas of human disturbance. This increased sampling effort in areas of likely introduction of exotic species naturally increases the likelihood of discovering species sooner, making citizen science an excellent tool for exotic species monitoring, as long as trained scientists are involved in the identification process.

Declining demographic performance and dispersal limitation influence the geographic distribution of the perennial forb Astragalus utahensis (Fabaceae)

Abstract A central goal of ecology is understanding the determinants of species’ distributions. “Metapopulation” models for the existence of distributional boundaries predict that species’ geographic ranges arise from the landscape‐scale deterioration of habitat suitability towards the range edge (i.e., niche mechanisms), which simultaneously hinders demographic performance and limits dispersal to suitable habitat beyond the edge (i.e., dispersal limitation). However, few studies have examined both of these mechanisms for the same species by examining abundance and comprehensive measures of demographic performance across the distribution and beyond its boundary. We tested the predictions of metapopulation models for range limits by contrasting abundance, demographic performance, and population growth (λ) of the perennial forb Astragalus utahensis in central and northern range edge populations. We tested for dispersal limitation by transplanting individuals at and beyond the northern range boundary and monitoring their demographic performance. Astragalus abundance and stochastic λ decreased from the range centre to the northern range edge, with stochastic λ falling to or below replacement in range edge populations. However, transplants at some sites beyond the northern range edge survived and reproduced at levels similar to transplants within the range. Thus, in addition to deteriorating conditions at the range edge, dispersal limitation appears to contribute to limiting A. utahensis’ northern distribution. Synthesis. Our results support metapopulation models for range limits by suggesting that decreased demographic performance constrains the viability of range edge populations while contributing to dispersal limitation of Astragalus utahensis’ distribution. Thus, the tandem action of niche and dispersal processes appears to play an important role in constraining this species’ northern latitudinal range.

The role of hybridization in the evolution of sexual system diversity in a clonal, aquatic plant.

The stable coexistence within populations of females, males, and hermaphrodites (subdioecy) is enigmatic because theoretical models indicate that maintenance of this sexual system involves highly restricted conditions. Subdioecy is more commonly interpreted as a transitory stage along the gynodioecious pathway from hermaphroditism to dioecy. The widespread, North American, aquatic plant Sagittaria latifolia is largely composed of monoecious or dioecious populations; however, subdioecious populations with high frequencies of hermaphrodites (mean frequency = 0.50) characterize the northern range boundary of dioecy in eastern North America. We investigated two hypotheses for the origin of subdioecy in this region. Using polymorphic microsatellite loci, we evaluated whether subdioecy arises through selection on standing genetic variation for male sex inconstancy in dioecious populations, or results from hybridization between monoecious and dioecious populations. We found evidence for both pathways to subdioecy, although hybridization was the more common mechanism, with genetic evidence of admixture in nine of 14 subdioecious populations examined. Hybridization has also played a role in the origin of androdioecious populations in S. latifolia, a mechanism not often considered in the evolution of this rare sexual system. Our study demonstrates how hybridization has the potential to play a role in the diversification of plant sexual systems.

Predicting species richness and distribution ranges of centipedes at the northern edge of Europe

In recent decades, interest in understanding species distributions and exploring processes that shape species diversity has increased, leading to the development of advanced methods for the exploitation of occurrence data for analytical and ecological purposes. Here, with the use of georeferenced centipede data, we explore the importance and contribution of bioclimatic variables and land cover, and predict distribution ranges and potential hotspots in Norway. We used a maximum entropy analysis (Maxent) to model species' distributions, aiming at exploring centres of distribution, latitudinal spans and northern range boundaries of centipedes in Norway. The performance of all Maxent models was better than random with average test area under the curve (AUC) values above 0.893 and True Skill Statistic (TSS) values above 0.593. Our results showed a highly significant latitudinal gradient of increased species richness in southern grid-cells. Mean temperatures of warmest and coldest quarters explained much of the potential distribution of species. Predictive modelling analyses revealed that south-eastern Norway and the Atlantic coast in the west (inclusive of the major fjord system of Sognefjord), are local biodiversity hotspots with regard to high predictive species co-occurrence. We conclude that our predicted northward shifts of centipedes' distributions in Norway are likely a result of post-glacial recolonization patterns, species' ecological requirements and dispersal abilities.

A New Latitudinal Record for the Ant GenusLeptogenys(Hymenoptera: Formicidae) in North America

Abstract. We report the first record of the ant genus Leptogenys in Oklahoma. Two species have been recorded from the United States, but northern range boundaries for both have been primarily limited to Gulf Coast states. This collection increases the known distribution northward into the central United States for one of those species, Leptogenys elongata (Buckley 1866).

Dispersal limitation and population differentiation in performance beyond a northern range limit in an asexually reproducing fern

Aim A species’ distribution reflects its ecological niche when all of the habitats that support population growth are occupied. However, organisms with limited dispersal potential may not colonize all suitable habitats and may consist of differentially adapted populations that have different niche requirements. Here, we evaluate the factors determining the northern range limit in a fern species that is endemic to a patchily distributed habitat throughout its geographic range. Location Non-calcareous rock shelters that provide habitat for six separate populations spanning the geographic range of Vittaria appalachiana, an asexual, gametophytic fern species, in the Appalachian Mountains and Appalachian Plateau of eastern North America. Methods We transplanted V. appalachiana gametophytes from six different populations to a rock shelter habitat 19 km north of the contemporary northern range boundary and 48 km away from the most northern population and back into their home locations as experimental controls. We compared the fitness of transplants at ‘home’ versus ‘beyond the northern range limit’ to test whether the northern range boundary is defined by physiological limits or dispersal limitation. Furthermore, we tested whether transplant success beyond the northern range boundary varied among individuals collected from different populations in the species’ range. Results Overall, transplant performance was similar between the home locations and the site beyond the northern range limit. However, populations differed in their response to transplantation beyond the northern range boundary, with individuals from the northernmost population having higher fitness beyond the range limit than all other populations. Main Conclusions We conclude that the northern range limit of V. appalachiana is heavily influenced by dispersal limitation because transplant performance was, on average, similar between home sites and beyond the northern range limit. However, because populations varied in their relative performance beyond the range limit, we also conclude that the ecological niches of these populations are not equivalent.

The abiotic and biotic factors limiting establishment of predatory fishes at their expanding northern range boundaries in Ontario, Canada.

There is a poor understanding of the importance of biotic interactions in determining species distributions with climate change. Theory from invasion biology suggests that the success of species introductions outside of their historical ranges may be either positively (biotic acceptance) or negatively (biotic resistance) related to native biodiversity. Using data on fish community composition from two survey periods separated by approximately 28years during which climate was warming, we examined the factors influencing the establishment of three predatory centrarchids: Smallmouth Bass (Micropterus dolomieu), Largemouth Bass (M. salmoides), and Rock Bass (Ambloplites rupestris) in lakes at their expanding northern range boundaries in Ontario. Variance partitioning demonstrated that, at a regional scale, abiotic factors play a stronger role in determining the establishment of these species than biotic factors. Pairing lakes within watersheds where each species had established with lakes sharing similar abiotic conditions where the species had not established revealed both positive and negative relationships between the establishment of centrarchids and the historical presence of other predatory species. The establishment of these species near their northern range boundaries is primarily determined by abiotic factors at a regional scale; however, biotic factors become important at the lake-to-lake scale. Studies of exotic species invasions have previously highlighted how spatial scale mediates the importance of abiotic vs. biotic factors on species establishment. Our study demonstrates how concepts from invasion biology can inform our understanding of the factors controlling species distributions with changing climate.

Cold hardiness and deacclimation of overwintering Papilio zelicaon pupae

Seasonally-acquired cold tolerance can be reversed at warm temperatures, leaving temperate ectotherms vulnerable to cold snaps. However, deacclimation, and its underlying mechanisms, has not been well-explored in insects. Swallowtail butterflies are widely distributed but in some cases their range is limited by low temperature and their cold tolerance is seasonally acquired, implying that they experience mortality resulting from deacclimation. We investigated cold tolerance and hemolymph composition of Anise swallowtail (Papilio zelicaon) pupae during overwintering in the laboratory, and after four days exposure to warm temperatures in spring. Overwintering pupae had supercooling points around −20.5°C and survived brief exposures to −30°C, suggesting partial freeze tolerance. Overwintering pupae had hemolymph osmolality of approximately 920mOsm, imparted by high concentrations of glycerol, K+ and Na+. After exposure to spring warming, supercooling points increased to approximately −17°C, and survival of a 1h exposure to −20°C decreased from 100% to 0%. This deacclimation was associated with decreased hemolymph osmolality and reduced glycerol, trehalose, Na+ and Ca2+ concentrations. We compared cold tolerance of pupae to weather conditions at and beyond the species' northern range boundary. Minimum temperatures at the range boundary approached the lower lethal temperature of pupae, and were colder north of the range, suggesting that cold hardiness may set northern range limits. Minimum temperatures following warm snaps were likely to cause mortality in at least one of the past three years. Cold snaps in the spring are increasing in frequency as a result of global climate change, so are likely to be a significant source of mortality for this species, and other temperate ectotherms.