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Fungi and invertebrates comprise a major part of biodiversity in dead wood ecosystems and invertebrates depend on fungi to utilise the dead wood resource. Many invertebrates also visit the long-lived fruit bodies of wood-decay fungi to feed on spores, the hymenium or other invertebrates. However, as traditional sampling methods are labour-intensive, we know little of these interactions. In this study, we use time-lapse cameras to monitor invertebrates visiting the hymenium of a common wood-decay fungus, Fomitopsis pinicola, and explain their activity in terms of temporal variation, temperature and presence of Gyrophaena boleti, a highly abundant fungivorous beetle living primarily in fruit bodies of F. pinicola. The most common invertebrates on F. pinicola fruit bodies were Coleoptera, Araneae, Diptera, Gastropoda and Chilopoda. The invertebrate activity exhibited strong temporal variation with higher abundance during night and, for Coleoptera, earlier in the season. We discuss how this might correlate with the sporulation period of F. pinicola. The presence of G. boleti had a positive impact on the predatory Lordithon lunulatus and Ipidia binotata, and a negative impact on the fungivorous Thymalus limbatus and Peltis ferruginea. Chilopoda and L. lunulatus were ephemeral visitors, while the fungivorous Coleoptera and Araneae stayed the longest. We estimated the invertebrates' visitation frequency and duration, which would be time-consuming to obtain with traditional methods. We offer improvements to our method and urge future research on invertebrate–fungus interactions to quantify invertebrate visits to fungal fruit bodies.

High-resolution monitoring is fundamental to understand ecosystems dynamics in an era of global change and biodiversity declines. While real-time and automated monitoring of abiotic components has been possible for some time, monitoring biotic components—for example, individual behaviours and traits, and species abundance and distribution—is far more challenging. Recent technological advancements offer potential solutions to achieve this through: (i) increasingly affordable high-throughput recording hardware, which can collect rich multidimensional data, and (ii) increasingly accessible artificial intelligence approaches, which can extract ecological knowledge from large datasets. However, automating the monitoring of facets of ecological communities via such technologies has primarily been achieved at low spatiotemporal resolutions within limited steps of the monitoring workflow. Here, we review existing technologies for data recording and processing that enable automated monitoring of ecological communities. We then present novel frameworks that combine such technologies, forming fully automated pipelines to detect, track, classify and count multiple species, and record behavioural and morphological traits, at resolutions which have previously been impossible to achieve. Based on these rapidly developing technologies, we illustrate a solution to one of the greatest challenges in ecology: the ability to rapidly generate high-resolution, multidimensional and standardised data across complex ecologies.

The marsh fritillary (Euphydryas aurinia) is a critically endangered butterfly species in Denmark known to be particularly vulnerable to habitat fragmentation due to its poor dispersal capacity. We identified and genotyped 318 novel SNP loci across 273 individuals obtained from 10 small and fragmented populations in Denmark using a genotyping-by-sequencing (GBS) approach to investigate its population genetic structure. Our results showed clear genetic substructuring and highly significant population differentiation based on genetic divergence (FST) among the 10 populations. The populations clustered in three overall clusters, and due to further substructuring among these, it was possible to clearly distinguish six clusters in total. We found highly significant deviations from Hardy–Weinberg equilibrium due to heterozygote deficiency within every population investigated, which indicates substructuring and/or inbreeding (due to mating among closely related individuals). The stringent filtering procedure that we have applied to our genotype quality could have overestimated the heterozygote deficiency and the degree of substructuring of our clusters but is allowing relative comparisons of the genetic parameters among clusters. Genetic divergence increased significantly with geographic distance, suggesting limited gene flow at spatial scales comparable to the dispersal distance of individual butterflies and strong isolation by distance. Altogether, our results clearly indicate that the marsh fritillary populations are genetically isolated. Further, our results highlight that the relevant spatial scale for conservation of rare, low mobile species may be smaller than previously anticipated.

Observations of changes in phenology have provided some of the strongest signals of the effects of climate change on terrestrial ecosystems. The International Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to measure plant phenology in tundra study areas across the globe. Today, this valuable collection of phenology measurements depicts the responses of plants at the colder extremes of our planet to experimental and ambient changes in temperature over the past decades. The database contains 150,434 phenology observations of 278 plant species taken at 28 study areas for periods of 1 to 26 years. Here we describe the full dataset to increase the visibility and use of these data in global analyses, and to invite phenology data contributions from underrepresented tundra locations. Portions of this tundra phenology database have been used in three recent syntheses, some datasets are expanded, others are from entirely new study areas, and the entirety of these data are now available at the Polar Data Catalogue., Arctic Science, 8 (3), ISSN:2368-7460

Recent decades have seen a surge in awareness about insect pollinator declines. Social bees receive the most attention, but most flower-visiting species are lesser known, non-bee insects. Nocturnal flower visitors, e.g. moths, are especially difficult to observe and largely ignored in pollination studies. Clearly, achieving balanced monitoring of all pollinator taxa represents a major scientific challenge. Here, we use time-lapse cameras for season-wide, day-And-night pollinator surveillance of Trifolium pratense (L.; red clover) in an alpine grassland. We reveal the first evidence to suggest that moths, mainly Noctua pronuba (L.; large yellow underwing), pollinate this important wildflower and forage crop, providing 34% of visits (bumblebees: 61%). This is a remarkable finding; moths have received no recognition throughout a century of T. pratense pollinator research. We conclude that despite a non-negligible frequency and duration of nocturnal flower visits, nocturnal pollinators of T. pratense have been systematically overlooked. We further show how the relationship between visitation and seed set may only become clear after accounting for moth visits. As such, population trends in moths, as well as bees, could profoundly affect T. pratense seed yield. Ultimately, camera surveillance gives fair representation to non-bee pollinators and lays a foundation for automated monitoring of species interactions in future., Biology Letters, 18 (7), ISSN:1744-9561, ISSN:1744-957X

Insects and other terrestrial invertebrates are declining in species richness and abundance. This includes the invertebrates associated with herbivore dung, which have been negatively affected by grazing abandonment and the progressive loss of large herbivores since the Late Pleistocene. Importantly, traditional monitoring of these invertebrates is time‐consuming and requires considerable taxonomic expertise, which is becoming increasingly scarce. In this study, we investigated the potential of environmental DNA (eDNA) metabarcoding of cow dung samples for biomonitoring of dung‐associated invertebrates. From eight cowpats we recovered eDNA from 12 orders, 29 families, and at least 54 species of invertebrates (mostly insects), representing several functional groups. Furthermore, species compositions differed between the three sampled habitats of dry grassland, meadow, and forest. These differences were in accordance with the species’ ecology; for instance, several species known to be associated with humid conditions or lower temperatures were found only in the forest habitat. We discuss potential caveats of the method, as well as directions for future study and perspectives for implementation in research and monitoring.

Publisher's version (útgefin grein), Climatic impacts are especially pronounced in the Arctic, which as a region is warming twice as fast as the rest of the globe. Here, we investigate how mean climatic conditions and rates of climatic change impact parasitoid insect communities in 16 localities across the Arctic. We focus on parasitoids in a widespread habitat, Dryas heathlands, and describe parasitoid community composition in terms of larval host use (i.e., parasitoid use of herbivorous Lepidoptera vs. pollinating Diptera) and functional groups differing in their closeness of host associations (koinobionts vs. idiobionts). Of the latter, we expect idiobionts—as being less fine‐tuned to host development—to be generally less tolerant to cold temperatures, since they are confined to attacking hosts pupating and overwintering in relatively exposed locations. To further test our findings, we assess whether similar climatic variables are associated with host abundances in a 22 year time series from Northeast Greenland. We find sites which have experienced a temperature rise in summer while retaining cold winters to be dominated by parasitoids of Lepidoptera, with the reverse being true for the parasitoids of Diptera. The rate of summer temperature rise is further associated with higher levels of herbivory, suggesting higher availability of lepidopteran hosts and changes in ecosystem functioning. We also detect a matching signal over time, as higher summer temperatures, coupled with cold early winter soils, are related to high herbivory by lepidopteran larvae, and to declines in the abundance of dipteran pollinators. Collectively, our results suggest that in parts of the warming Arctic, Dryas is being simultaneously exposed to increased herbivory and reduced pollination. Our findings point to potential drastic and rapid consequences of climate change on multitrophic‐level community structure and on ecosystem functioning and highlight the value of collaborative, systematic sampling effort., We are grateful for data from the Greenland Ecosystem Monitoring Programme provided by the Department of Bioscience, Aarhus University, Denmark, in collaboration with Greenland Institute of Natural Resources, Nuuk, Greenland, and the Department of Biology, University of Copenhagen, Denmark, and data from the Greenland Ecosystem Monitoring Programme provided by Asiaq—Greenland Survey, Nuuk, Greenland. We acknowledge CSC–IT Center for Science Ltd., Espoo, Finland, for the allocation of computational resources. Rósa Erlendsdóttir kindly provided access to the sampling site in Votilækur, Iceland. We thank Marie‐Andree Giroux and Kristen Peck for their assistance in Igloolik and Marjo Kilpinen, Eija Takala and Emma Hakanen for their hard work in the laboratory. We gratefully acknowledge funding from the Academy of Finland (grants 276909, 285803 to T.R., and 276671 to M.V.K.), Nessling Foundation (grants 201700420, 201600034, 201500090 to T.K.), Jane and Aatos Erkko Foundation, Societas pro Fauna et Flora Fennica, The Danish Environmental Protection Agency (N.M.S.), French Polar Institute‐IPEV (program “Interactions 1036” to O.G. and B.S.), INTERACT, Russian Foundation for Basic Research (grant 18‐05‐60261 to A.S. and N.S.), Research Council of Norway (grant 249902/F20), the Natural Sciences and Engineering Research Council of Canada (PGS‐D award to S.K.M., CGS‐D award to A.M.S., Discovery Grant to J.B.), Churchill Northern Studies Centre (Northern Research Fund Award to A.M.S. and M.P.), Canadian Polar Commission (Northern Scientific Training Program Award to D.L.B., K.H.I.D., S.K.M., A.M.S., and M.P.), ArcticNet, Polar Continental Shelf Project, Parks Canada, Fonds Québécois de Recherche ‐ Nature et Technologies, Polar Knowledge Canada, Entomological Society of Canada, University of Guelph. The Icelandic Research Fund (Rannsóknasjóður, grant nr 152468‐051 to I.C.B.). Thanks to PhyloPic contributors Gareth Monger and Melissa Broussard.

International audience; The Arctic tundra is characterised by harsh conditions and environmental gradients are especially pronounced. Variation in functional traits along such gradients provide insights into the drivers of species abundance and distribution and are particularly valuable in this region currently experiencing strong climate warming. Over three consecutive years, we analysed the interacting effect of two environmental factors, habitat and elevation, on the abundance, body size, and clutch size in two common Low-Arctic invertebrate predators (Lycosidae, Araneae), Pardosa furcifera (Thorell 1875) and Pardosa hyperborea (Thorell 1872). Using generalised linear models, we firstly showed a habitat partitioning between P. furcifera, which dominated wet habitats, like fens, and P. hyperborea, which was more associated with drier habitats, like shrubs. Secondly, we found smaller body sizes at high elevation in P. hyperborea, a species that has a southern distribution in Greenland, and we identified season length as a major driver of the development in this species. In P. furcifera, a species likely more cold adapted, we found no body size difference between elevations, suggesting that local conditions (e.g. prey availability or snowmelt timing) are more important in explaining body size variations. Finally, body size and clutch size were strongly correlated in both species, but clutch size was not affected by habitat or elevation. We argue that fecundity is likely influenced by trade-offs and that considering additional complementary trait measurements would allow for a better understanding of the mechanisms underlying patterns in species life-history traits along environmental gradients.

The northernmost regions of our planet experience twice the rate of climate warming compared to the global average. Despite the currently low air temperatures, tundra shrubs are known to exhibit high leaf temperatures and are increasing in height due to warming, but it is unclear how the increase in height will affect the leaf temperature. To study how temperature, soil moisture, and changes in light availability influence the physiology and emissions of climate-relevant volatile organic compounds (VOCs), we conducted a study on two common deciduous tundra shrubs, Salix glauca (separating males and females for potential effects of plant sex) and Betula glandulosa, at two elevations in South Greenland. Low-elevation Salix shrubs were 45% taller, but had 37% lower rates of net CO2 assimilation and 63% lower rates of isoprene emission compared to high-elevation shrubs. Betula shrubs showed 40% higher stomatal conductance and 24% higher glandular trichome density, in the low-elevation valley, compared to those from the high-elevation mountain slope. Betula green leaf volatile emissions were 235% higher at high elevation compared to low elevation. Male Salix showed a distinct VOC blend and emitted 55% more oxygenated VOCs, compared to females, possibly due to plant defense mechanisms. In our light response curves, isoprene emissions increased linearly with light intensity, potentially indicating adaptation to strong light. Leaf temperature decreased with increasing Salix height, at 4 °C m−1, which can have implications for plant physiology. However, no similar relationship was observed for B. glandulosa. Our results highlight that tundra shrub traits and VOC emissions are sensitive to temperature and light, but that local variations in soil moisture strongly interact with temperature and light responses. Our results suggest that effects of climate warming, alone, poorly predict the actual plant responses in tundra vegetation.

Fungal and arthropod consumers constitute the vast majority of global terrestrial biodiversity. Yet, the link from richness and composition of producer (plant) communities to the richness of consumer communities is poorly understood. Fungal and arthropod species richness could be a simple function of producer species richness at a site. Alternatively, it could be a complex function of chemical and structural properties of the producer species making up communities. We used databases on plant–fungus and plant–arthropod trophic links to derive the richness of consumer biota per associated plant species (coined link score). We assessed how well link scores could be predicted by simple attributes of plant species. Next, we used a multi-taxon inventory of 130 sites, representing all major habitat types in a country (Denmark), to investigate whether link scores summed over plant species in communities (coined link sum) could outperform simple plant species richness as predictor of fungal and arthropod richness at the sites. We found plant species' link scores for both fungi and arthropods to be positively related to plant size, regional occupancy, nativeness and ectomycorrhizal status. Link-based indices generally improved the prediction of richness of fungal and arthropod communities. For fungal communities, both observed link sum (from databases) and predicted link sum (from plant attributes) had high predictive power, while plant richness alone had none. For arthropod communities, predictive performance varied between functional groups. For both fungi and arthropods, richness predictions were further improved by considering abiotic habitat conditions. Our results underline the importance of plants as niche space for the megadiverse groups of arthropods and fungi. The plant–attribute approach holds promise for predicting local and regional consumer richness in areas of the world lacking detailed plant–consumer databases.

International audience; Insects are the most diverse group of animals on Earth, but their small size and high diversity have always made them challenging to study. Recent technological advances have the potential to revolutionise insect ecology and monitoring. We describe the state of the art of four technologies (computer vision, acoustic monitoring, radar, and molecular methods), and assess their advantages, current limitations, and future potential. We discuss how these technologies can adhere to modern standards of data curation and transparency, their implications for citizen science, and their potential for integration among different monitoring programmes and technologies. We argue that they provide unprecedented possibilities for insect ecology and monitoring, but it will be important to foster international standards via collaboration.

Aim: Biogeographical studies on the entire ranges of widely distributed species can change our perception of species’ range dynamics. We studied the effects of Pleistocene glacial cycles on current butterfly species distributions, aiming to uncover complex biogeographic patterns in the Holarctic, a region dramatically affected by Cenozoic climate change. Location: Eurasia and North America. Taxon: Boloria chariclea, Agriades optilete, Carterocephalus palaemon, Oeneis jutta. Methods: We reconstructed the biogeographic history of four butterfly species differing in habitat preferences (B. chariclea – tundra, A. optilete – bogs, C. palaemon – temperate grasslands, O. jutta – taiga), using one mitochondrial and two nuclear DNA markers and species distribution modelling. Results: Except for B. chariclea, all species originated in Eurasia. The open habitat species A. optilete and C. palaemon formed widely distributed east-west genetic clusters in continental Asia and clusters separated from them in Europe. Genetic clusters of the taiga species O. jutta were not geographically separated in Eurasia, suggesting Pleistocene fragmentation and recent reconnection. The glaciated North America was recolonized from Beringian and southerly situated refugia by all four species. Main conclusions: The Pleistocene mammoth steppe allowed a widespread continuous distribution of open habitat butterflies, while in contrast the distribution of a taiga-specialist species was more limited. In the mostly flat and continental North Asia, the butterflies of various types of open habitats survived ice age in widely distributed east-west belts. In the mountainous and oceanic regions of Europe, Beringia and west North America, all four species persisted in contracted areas during the glacials. After deglaciation, they expanded their ranges and formed contact zones among populations. To conclude, the harsh climate of the glacials did not represent an obstacle for butterflies. Instead, different habitat specialists selected their own ways to thrive in the dynamic conditions of Quaternary glacial periods.

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.

Consumers constitute the vast majority of global terrestrial biodiversity. Yet, local consumer richness is poorly understood. Plant species richness offers a simple hypothesis to how the diversification of carbon substrates may promote the diversity of arthropods and fungi. We took this one step further and used databases on plant-consumer interaction links to derive the richness of associated biota per plant species (link score). Using a species inventory of 130 sites we investigated 1) how well the link score could be predicted by plant attributes and 2) if the sum of plant species’ observed or predicted link scores could predict site richness of arthropods and macrofungi better than plant species richness alone. We found plant link scores to be positively related to plant size, abundance, nativeness and ectomycorrhizal status. Link based indices generally improved prediction of richness, stressing the importance of plants as niche space for the megadiverse groups of insects and fungi.

Arthropods are excellent indicators for studying global change in the rapidly changing climate of the Arctic. We used the most comprehensive standardized dataset on Arctic arthropods to quantify diversity and abundance variation over 24 y in an area that is warming rapidly. Overall arthropod abundance and diversity showed opposing nonlinear trends, with a sharp increase in overall abundance in recent years. However, trends varied substantially among taxa and habitats and several groups declined in abundance. We found strong evidence of conditions outside the growing season and density-dependent feedbacks affecting abundance. Our results emphasize the need for a more integrated approach to investigating arthropod responses to environmental stressors at finer taxonomic resolution and by incorporating time-lagged effects.Time series data on arthropod populations are critical for understanding the magnitude, direction, and drivers of change. However, most arthropod monitoring programs are short-lived and restricted in taxonomic resolution. Monitoring data from the Arctic are especially underrepresented, yet critical to uncovering and understanding some of the earliest biological responses to rapid environmental change. Clear imprints of climate on the behavior and life history of some Arctic arthropods have been demonstrated, but a synthesis of population-level abundance changes across taxa is lacking. We utilized 24 y of abundance data from Zackenberg in High-Arctic Greenland to assess trends in abundance and diversity and identify potential climatic drivers of abundance changes. Unlike findings from temperate systems, we found a nonlinear pattern, with total arthropod abundance gradually declining during 1996 to 2014, followed by a sharp increase. Family-level diversity showed the opposite pattern, suggesting increasing dominance of a small number of taxa. Total abundance masked more complicated trajectories of family-level abundance, which also frequently varied among habitats. Contrary to expectation in this extreme polar environment, winter and fall conditions and positive density-dependent feedbacks were more common determinants of arthropod dynamics than summer temperature. Together, these data highlight the complexity of characterizing climate change responses even in relatively simple Arctic food webs. Our results underscore the need for data reporting beyond overall trends in biomass or abundance and for including basic research on life history and ecology to achieve a more nuanced understanding of the sensitivity of Arctic and other arthropods to global changes.Species records and climate data reported in this paper have been retrieved from the Greenland Ecosystem Monitoring Database (https://doi.org/10.17897/V285-Z265).

Soils are warming as air temperatures rise across the Arctic and Boreal region concurrent with the expansion of tall-statured shrubs and trees in the tundra. Changes in vegetation structure and function are expected to alter soil thermal regimes, thereby modifying climate feedbacks related to permafrost thaw and carbon cycling. However, current understanding of vegetation impacts on soil temperature is limited to local or regional scales and lacks the generality necessary to predict soil warming and permafrost stability on a pan-Arctic scale. Here we synthesize shallow soil and air temperature observations with broad spatial and temporal coverage collected across 106 sites representing nine different vegetation types in the permafrost region. We showed ecosystems with tall-statured shrubs and trees (>40 cm) have warmer shallow soils than those with short-statured tundra vegetation when normalized to a constant air temperature. In tree and tall shrub vegetation types, cooler temperatures in the warm season do not lead to cooler mean annual soil temperature indicating that ground thermal regimes in the cold-season rather than the warm-season are most critical for predicting soil warming in ecosystems underlain by permafrost. Our results suggest that the expansion of tall shrubs and trees into tundra regions can amplify shallow soil warming, and could increase the potential for increased seasonal thaw depth and increase soil carbon cycling rates and lead to increased carbon dioxide loss and further permafrost thaw.

International audience; Changing abiotic conditions can affect the phenology of animals and plants with implications for their reproductive output, especially in rapidly changing regions like the Arctic. For instance in arthropods, it was recently shown that females of the spider species Pardosa glacialis (Thorell 1872) (Lycosidae) are able to produce two clutches within one growing season in years when snowmelt occurs particularly early. This phenomenon could be widespread in northern latitudes, and here we investigated the voltinism of two other very abundant species of wolf spiders in the Low-Arctic, Pardosa hyperborea (Thorell 1872) and Pardosa furcifera (Thorell 1875), over the period 2015-2017. Whilst a bimodal pattern in the clutch size frequency distribution was only revealed for P. hyperborea, we were able to show that both species can produce a second clutch over the active season by using information on the embryonic stages. We also observed significantly larger first than second clutches. We argue that information about the embryonic stage can be critical for evaluating evidence of wolf spider populations producing more than one clutch in a season. Our study provides evidence that bivoltinism could be a more widespread pattern than expected in Arctic wolf spiders. It remains to be investigated what the trophic consequences of such patterns are in a global warming context. We thus highlight the need for a coordinated framework for such further studies, integrating and relating various functional traits.

Current analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long-term average thermal conditions at coarse spatial resolutions only. Hence, many climate-forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold-air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free-air temperatures, microclimatic ground and near-surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near-surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes. ispartof: GLOBAL CHANGE BIOLOGY vol:26 issue:11 pages:6616-6629 ispartof: location:England status: published

The harsh climate, limited human infrastructures, and basic autecological knowledge gaps represent substantial challenges for studying arthropods in the Arctic. At the same time, rapid climate change, low species diversity, and strong collaborative networks provide unique and underexploited Arctic opportunities for understanding species responses to environmental change and testing ecological theory. Here, I provide an overview of individual, population, and ecosystem level responses to climate change in Arctic arthropods. I focus on thermal performance, life history variation, population dynamics, community composition, diversity, and biotic interactions. The species-poor Arctic represents a unique opportunity for testing novel, automated arthropod monitoring methods. The Arctic can also potentially provide insights to further understand and mitigate the effects of climate change on arthropods worldwide.

Amidst the global biodiversity crisis, identifying drivers of biodiversity variation remains a key challenge. Scientific consensus is limited to a few macroecological rules, such as species richness increasing with area, which provide limited guidance for conservation. In fact, few agreed ecological principles apply at the scale of sites or reserve management, partly because most community-level studies are restricted to single habitat types and species groups. We used the recently proposedecospaceframework and a comprehensive data set for aggregating environmental variation to predict multi-taxon diversity. We studied richness of plants, fungi, and arthropods in 130 sites representing the major terrestrial habitat types in Denmark. We found the abiotic environment (ecospace position) to be pivotal for the richness of primary producers (vascular plants, mosses, and lichens) and, more surprisingly, little support for ecospace continuity as a driver. A peak in richness at intermediate productivity adds new empirical evidence to a long-standing debate over biodiversity responses to productivity. Finally, we discovered a dominant and positive response of fungi and insect richness to organic matter accumulation and diversification (ecospace expansion). Two simple models of producer and consumer richness accounted for 77 % of the variation in multi-taxon species richness suggesting a significant potential for generalization beyond individual species responses. Our study widens the traditional conservation focus on vegetation and vertebrate populations unravelling the importance of diversification of carbon resources for diverse heterotrophs, such as fungi and insects.

Most animal species on Earth are insects, and recent reports suggest that their abundance is in drastic decline. Although these reports come from a wide range of insect taxa and regions, the evidence to assess the extent of the phenomenon is still sparse. Insect populations are challenging to study and most monitoring methods are labour intensive and inefficient. Advances in computer vision and deep learning provide potential new solutions to this global challenge. Cameras and other sensors that can effectively, continuously, and non-invasively perform entomological observations throughout diurnal and seasonal cycles. The physical appearance of specimens can also be captured by automated imaging in the lab. When trained on these data, deep learning models can provide estimates of insect abundance, biomass, and diversity. Further, deep learning models can quantify variation in phenotypic traits, behaviour, and interactions. Here, we connect recent developments in deep learning and computer vision to the urgent demand for more cost-efficient monitoring of insects and other invertebrates. We present examples of sensor-based monitoring of insects. We show how deep learning tools can be applied to the big data outputs to derive ecological information and discuss the challenges that lie ahead for the implementation of such solutions in entomology. We identify four focal areas, which will facilitate this transformation: 1) Validation of image-based taxonomic identification, 2) generation of sufficient training data, 3) development of public, curated reference databases, and 4) solutions to integrate deep learning and molecular tools.Significance statementInsect populations are challenging to study, but computer vision and deep learning provide opportunities for continuous and non-invasive monitoring of biodiversity around the clock and over entire seasons. These tools can also facilitate the processing of samples in a laboratory setting. Automated imaging in particular can provide an effective way of identifying and counting specimens to measure abundance. We present examples of sensors and devices of relevance to entomology and show how deep learning tools can convert the big data streams into ecological information. We discuss the challenges that lie ahead and identify four focal areas to make deep learning and computer vision game changers for entomology.

Spiders at southern latitudes commonly produce multiple clutches, but this has not been observed at high latitudes where activity seasons are much shorter. Yet the timing of snowmelt is advancing in the Arctic, and may allow some species to produce an additional clutch. To determine if this is already happening, we used specimens of the wolf spider Pardosa glacialis caught by pitfall traps from the long-term (1996-2014) monitoring program at Zackenberg, Northeast Greenland. We dissected individual egg sacs and counted the number of eggs and partially developed juveniles, and measured carapace width of the mothers. Upon discovery of a bimodal frequency distribution of clutch sizes, as is typical for wolf spiders at lower latitudes producing a second clutch, we assigned egg sacs to being a first or second clutch depending on clutch size. We tested whether the median capture date differed among first and second clutches, whether clutch size was correlated to female size, and whether the proportion of second clutches produced within a season was related to climate. We found that assigned second clutches appeared significantly later in the season than first clutches. In years with earlier snowmelt, first clutches occurred earlier and the proportion of second clutches produced was larger. This result, likely a result of female spiders producing first clutches earlier in those years, which allowed time for another clutch. Clutch size for first clutches was correlated to female size, while this was not the case for second clutches. Our results provide the first evidence for Arctic invertebrates producing additional clutches in response to warming. This could be a common but overlooked phenomenon due to the challenges associated with long-term collection of life history data in the Arctic. Moreover, given that wolf spiders are a widely distributed, important tundra predator, we may expect to see population and food web consequences of their increased reproductive rates.

Time-series data on arthropod populations are critical for understanding the magnitude, direction, and drivers of abundance changes. However, most arthropod monitoring programs are short-lived and limited in taxonomic resolution and spatial extent. Consequently, variation in population dynamics among taxa and habitats remains poorly understood. Monitoring data from the Arctic are particularly underrepresented, yet important to assessments of species abundance changes because many anthropogenic drivers of change that are present in other regions are absent in polar regions. Here, we utilise 24 years of abundance data from Zackenberg in High-Arctic Greenland, which is the longest running Arctic arthropod monitoring program, to study temporal trends in abundance. Despite a strong warming signal in air temperature, we only find evidence of weak temporal trends in arthropod abundances across most taxa. These trends are more pronounced in the most recent decade, with change point analyses suggesting distinct non-linear dynamics within some functional groups such as predators and detritivores. Although the abundances of many taxa were correlated, we detected both positive and negative correlations, suggesting that multiple processes are affecting arthropod populations even in this relatively simple Arctic food web. Finally, we found clear differences among species within single families of arthropods, indicating that an apparent lack of change in abundance at broader taxonomic or functional levels could mask substantial species-specific trends. Our results reiterate the need for more basic research into the life-history, ecology, and adaptation of arthropod species to better understand their sensitivity to global changes.Significance statementTerrestrial arthropods, including insects and spiders, serve critical ecosystem functions and are excellent indicators of environmental change due to their physiology, short generation time, and abundance. The Arctic, with its rapid climate change and limited direct anthropogenic impact, is ideal for examining arthropod population dynamics. We use the most comprehensive, standardized dataset available on Arctic arthropods to evaluate the variability in population dynamics for the most common arthropod groups at various taxonomic levels across 24 years. Our results highlight that temporal trends of arthropod populations seem less directional in the Arctic than in temperate regions. Although abundances of some arthropod taxa are declining, particularly in recent decades, population trends still display high variation among time periods, taxa, and habitats.

The emission and spread of global contaminants such as Pb, Cd, Hg, U and rare earth elements (REE) are of high global concern as they pose a serious health risk to humans and wildlife alike. Although the Arctic is a known hot-spot for deposition of globally transported organic and inorganic contaminants, Greenland is often viewed as pristine with little influence of local emission sources. This perception is, however, flawed as Greenland hosts numerous former, active and prospected mining activities, many of which have a profound adverse impact on the surrounding environment. Detailed monitoring before, during, and after mining activities is thus essential to evaluate the environmental health status of a mining area and to minimize the potential spread of mining derived contaminants.Arthropods constitute the majority of the terrestrial Arctic species diversity, which facilitates sampling for environmental assessment. With documented abilities to accumulate contaminant metals (e.g. Cd, Ag, Hg), we show that spiders play a key role in bioaccumulation and biomagnification processes. Acting as both predator and prey, and by linking food webs in the aquatic to the terrestrial environment, spiders can enable a continued transfer of contaminants up the food chain. Moreover, and because arthropods are an important food source for migrating birds, there is a strong potential for a further geographical spread of contaminants. However, the extent to which contaminant bioaccumulation occurs in Arctic spiders, and their role in global contaminant cycles, remain unclear.The aim of this project and presentation is to examine the use of wolf spiders (e.g. P. glacialis, P. furcifera and P. hyperborea) as biomonitors of metal and radiogenic contamination near Arctic mine sites. Particular focus will be given to the globally prioritized elements Pb and Hg (incl. isotopic signatures), as well as contaminants of local concern such as U (incl. decay series) and REEs. Further, we discuss the role of spiders in local- to global contaminant cycles by linking the contamination transfer through onsite food webs to location data from migrating birds (e.g. GPS-trackers). Combining contamination- and location-data will allow us to model movement of biota, and inherent mining derived contamination, to and from arctic ecosystems on an annual basis.

Insect monitoring methods are typically very time-consuming and involve substantial investment in species identification following manual trapping in the field. Insect traps are often only serviced weekly, resulting in low temporal resolution of the monitoring data, which hampers the ecological interpretation. This paper presents a portable computer vision system capable of attracting and detecting live insects. More specifically, the paper proposes detection and classification of species by recording images of live individuals attracted to a light trap. An Automated Moth Trap (AMT) with multiple light sources and a camera was designed to attract and monitor live insects during twilight and night hours. A computer vision algorithm referred to as Moth Classification and Counting (MCC), based on deep learning analysis of the captured images, tracked and counted the number of insects and identified moth species. Observations over 48 nights resulted in the capture of more than 250,000 images with an average of 5675 images per night. A customized convolutional neural network was trained on 2000 labeled images of live moths represented by eight different classes, achieving a high validation F1-score of 0.93. The algorithm measured an average classification and tracking F1-score of 0.71 and a tracking detection rate of 0.79. Overall, the proposed computer vision system and algorithm showed promising results as a low-cost solution for non-destructive and automatic monitoring of moths.

The terrestrial chapter of the Circumpolar Biodiversity Monitoring Programme (CBMP) has the potential to bring international multi-taxon, long-term monitoring together, but detailed fundamental species information for Arctic arthropods lags far behind that for vertebrates and plants. In this paper, we demonstrate this major challenge to the CBMP by focussing on spiders (Order: Araneae) as an example group. We collate available circumpolar data on the distribution of spiders and highlight the current monitoring opportunities and identify the key knowledge gaps to address before monitoring can become efficient. We found spider data to be more complete than data for other taxa, but still variable in quality and availability between Arctic regions, highlighting the need for greater international co-operation for baseline studies and data sharing. There is also a dearth of long-term datasets for spiders and other arthropod groups from which to assess status and trends of biodiversity. Therefore, baseline studies should be conducted at all monitoring stations and we make recommendations for the development of the CBMP in relation to terrestrial arthropods more generally. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13280-019-01185-y) contains supplementary material, which is available to authorised users.

Advancing phenology is one of the most visible effects of climate change on plant communities, and has been especially pronounced in temperature-limited tundra ecosystems. However, phenological responses have been shown to differ greatly between species, with some species shifting phenology more than others. We analysed a database of 42,689 tundra plant phenological observations to show that warmer temperatures are leading to a contraction of community-level flowering seasons in tundra ecosystems due to a greater advancement in the flowering times of late-flowering species than early-flowering species. Shorter flowering seasons with a changing climate have the potential to alter trophic interactions in tundra ecosystems. Interestingly, these findings differ from those of warmer ecosystems, where early-flowering species have been found to be more sensitive to temperature change, suggesting that community-level phenological responses to warming can vary greatly between biomes.

1. Species richness is unrivalled as the most reported biodiversity metric in ecological and conservation research. Unfortunately, species richness ignores the scale-dependency of biodiversity. 2. We propose the metric uniquity, a quantitative and spatially scalable measure of uniqueness of a site based on a species-by-site matrix and a site-by-habitat type classification with area weights for habitat types correcting for sampling biases. 3. An example of uniquity is presented using vascular plant data from 130 sites representing a larger region (Denmark). We demonstrate the importance of the scale parameter of uniquity for the prediction of independent uniqueness indices calculated from species distribution data and the number of recorded red listed species. 4. We compare the performance of uniquity with the performance of the indices Local Contribution to Beta Diversity (LCBD) and Range Rarity Richness (RRR), and we investigate its sensitivity to small sample size and poorly resolved habitat classification. 5. We assess the performance of the uniquity metric applied to DNA metabarcoding data for plants, fungi and eukaryotes from the same set of study sites. 6. Uniquity is a strong predictor of site uniqueness based on national distribution data and also correlates neatly with the observed number of red listed species. Uniquity based on DNA metabarcoding corresponds well with the number of red listed species observed. 7. Perspective: Uniquity is generally applicable to biotas sampled with comparable effort, including field inventories, trap sampling, and DNA metabarcoding data. To our knowledge uniquity is the first index of uniqueness that explicitly considers spatial scale and sampling biases, while simultaneously accepting non-annotated DNA-data as input. Based on our study we offer general recommendations for further use and testing of uniquity as conservation value metric.

Arthropods perform critically important functions in food webs and ecosystems and are highly sensitive to the effects of environmental change. Despite their importance, the knowledge gaps in arthropod ecology are substantial. This is particularly problematic in Earth's polar and alpine regions, where tundra ecosystems are responding rapidly to climate change. Species diversity is lower in these regions versus temperate and tropical regions, but (1) we lack baseline and long-term data about the distributions and abundances of arthropods and their relationships to abiotic variation and (2) the roles of arthropods in these ecosystems are far from fully described. In recognition of the need for increased tundra arthropod research activity, a group of international scientists formed the Network for Arthropods of the Tundra (NeAT). In the past 3 years, this academic network has brought together entomologists from research institutions around the world to revitalize and coordinate the study of tundra arthropods. This special issue on the ecology of tundra arthropods represents a tangible example of this increased momentum. The papers in the special issue highlight recent advances in understanding the relationships between arthropod communities and abiotic variation in tundra ecosystems and clarify the roles that arthropods play in ecosystems. They collectively demonstrate the utility of tundra arthropods as a model system for testing general ecological theory about how species respond to environmental variation. We hope this special issue with the insights it provides and the new frontiers it outlines, together with NeAT, will leverage further momentum to the interest in, and study of the ecology of tundra arthropods in the years to come.

Invasive alien plant species (IAPS) pose a threat to biodiversity as they propagate and outcompete natural vegetation. In this study, a system for monitoring IAPS on the roadside is presented. The system consists of a camera that acquires images at high speed mounted on a vehicle that follows the traffic. Images of seven IAPS (Cytisus scoparius, Heracleum, Lupinus polyphyllus, Pastinaca sativa, Reynoutria, Rosa rugosa, and Solidago) were collected on Danish motorways. Three deep convolutional neural networks for classification (ResNet50V2 and MobileNetV2) and object detection (YOLOv3) were trained and evaluated at different image sizes. The results showed that the performance of the networks varied with the input image size and also the size of the IAPS in the images. Binary classification of IAPS vs. non-IAPS showed an increased performance, compared to the classification of individual IAPS. This study shows that automatic detection and mapping of invasive plants along the roadside is possible at high speeds.

The organization of ecological communities along local environmental gradients provides important information about how such communities may respond to environmental change. In the Arctic, the importance of gradients in shrub cover and soil moisture for non-marine arthropod communities has been clearly demonstrated. By replicating studies along shrub and moisture gradients at multiple elevations and using space-for-time substitution, it is possible to examine how arthropod communities may respond to future environmental change. We collected and identified 4640 adult specimens of spiders and beetles near Narsarsuaq, South Greenland between 8 July and 25 August, 2014 from 112 pitfall traps. The traps were arranged in eight plots covering local gradients in either soil moisture or tall shrub dominance at both low and high elevation. Multivariate generalized linear models revealed that community composition was significantly related to shrub height and soil moisture, and that this relationship varied between low and high elevation. Among the 46 species we found, more species were unique to the high elevation plots than to the low elevation plots, a finding that was most pronounced for spiders in plots along soil moisture gradients. Indicator species analysis corroborated earlier findings of the indicator value of specific species in Greenland and suggested that beetles may serve as better indicators of specific habitats than spiders. The location of plots along local environmental gradients allowed us to detect fine-scale variation in arthropod communities. Together, our results suggest that Arctic arthropod community responses to environmental change may differ among low and high elevation sites.

Monophagous butterflies often have smaller ranges than their host plants, which could relate to host plant abundance. Many specialist butterflies have already gone regionally extinct and studies of the role of host plant and habitat abundance at resolutions sufficiently detailed to cover host plant abundance are urgently needed for conservation management. Here, we investigate the link between a predominantly monophagous butterfly – the critically endangered Euphydryas aurinia and its host – Succissa pratensis in Denmark using high resolution (1 × 1 km) butterfly distribution data and an extensive national host plant frequency data set. More specifically, we assessed whether patterns in the present day distribution of S. pratensis and its habitat can explain the current distribution of E. aurinia and which ecological factors determine habitat suitability for S. pratensis. We used logistic regression to model the occurrence of E. aurinia as a function of habitat and host plant abundance as well as connectivity among habitats. We also modelled the occurrence of S. pratensis from habitat type, soil type, precipitation and indicators of soil moisture, nutrient level, and pH using generalized additive models. The remaining E. aurinia populations are confined to small regions in northern Jutland and this pattern was well predicted by our model. High modelled probabilities of E. aurinia coincided with habitat abundance exceeding 6–7% of land area and host plant frequency within habitat exceeding 40% at plot scale. Habitat connectivity was not included in the most parsimonious model. S. pratensis occurrence probability increased with pH, decreased with nutrient status and showed a unimodal response to soil moisture. The geographic partitioning of pH and nutrient effects indicated host plant scarcity due to eutrophication in Eastern Denmark and acidification in Western Denmark. Our findings highlight the importance of identifying empirical thresholds for habitat and host plant abundance in future conservation of herbivorous insects while also taking host plant habitat requirements into account.

This review provides a synopsis of the main findings of individual papers in the special issue Terrestrial Biodiversity in a Rapidly Changing Arctic. The special issue was developed to inform the State of the Arctic Terrestrial Biodiversity Report developed by the Circumpolar Biodiversity Monitoring Program (CBMP) of the Conservation of Arctic Flora and Fauna (CAFF), Arctic Council working group. Salient points about the status and trends of Arctic biodiversity and biodiversity monitoring are organized by taxonomic groups: (1) vegetation, (2) invertebrates, (3) mammals, and (4) birds. This is followed by a discussion about commonalities across the collection of papers, for example, that heterogeneity was a predominant pattern of change particularly when assessing global trends for Arctic terrestrial biodiversity. Finally, the need for a comprehensive, integrated, ecosystem-based monitoring program, coupled with targeted research projects deciphering causal patterns, is discussed.

This is the third in a planned series of data papers presenting modelled vector distributions produced during the ECDC and EFSA funded VectorNet project. The data package presented here includes those 'Culicoides' vectors species first modelled in 2015 as part of the VectorNet gap analysis work namely 'C. imicola, C. obsoletus, C. scoticus, C. dewulfi, C. chiopterus, C. pulicaris, C. lupicaris, C. punctatus, and C. newsteadi'. The known distributions of these species within the Project area (Europe, the Mediterranean Basin, North Africa, and Eurasia) are currently incomplete to a greater or lesser degree. The models are designed to fill the gaps with predicted distributions, to provide a) first indication of vector species distributions across the project geographical extent, and b) assistance in targeting surveys to collect distribution data for those areas with no field validated information. The models are based on input data from light trap surveillance of adult 'Culicoides' across continental Europe and surrounding regions (71.8°N –33.5°S, – 11.2°W – 62°E), concentrated in Western countries, supplemented by transect samples in eastern and northern Europe. Data from central EU are relatively sparse. Funding statement: This work was carried out with support from the VectorNet framework contract OC/EFSA/AHAW/2013/02-FWC1 funded by the European Centre for Disease prevention and Control (ECDC) and the European Food Safety Agency (EFSA) and the PALE-Blu H2020 Project ID: 727393.

Arctic and sub-Arctic terrestrial ectotherms contend with large daily and seasonal temperature ranges. However, there are few data available on the thermal biology of these high-latitude species, especially arachnids. We determined the lower and upper thermal limits of seven species of wolf spider from the genus Pardosa (Araneae: Lycosidae) collected in summer from the Yukon Territory (Canada) and Southern Greenland. None of these species survived freezing, and while spiderlings appeared freeze-avoidant, surviving to their supercooling point (SCP, the temperature at which they spontaneously freeze), chill-susceptible adults and juveniles died at temperatures above their SCP. The critical thermal minimum (CTmin, the lower temperature of activity) and SCP were very close (spiders continued moving until they freeze), and at − 5.4 to − 8.4 °C, are not substantially lower than those of lower-latitude species. The SCP of spiderlings was significantly lower than that of overwintering juveniles or adults, likely because of their small size. There was no systematic variation in SCP among collection sites, latitude, or species. Critical thermal maxima (CTmax) ranged from + 42.3 to + 46.8 °C, showed no systematic patterns of variation, and were also similar to those of lower-latitude relatives. Overall, heat tolerances of the Pardosa spp. were likely sufficient to tolerate even very warm Arctic summer temperatures, but cold tolerance is probably inadequate to survive winter conditions. We expect that seasonal thermal plasticity is necessary for overwintering in these species.

In the version of this Article originally published, the following sentence was missing from the Acknowledgements: “This work was supported by the Norwegian Research Council SnoEco project, grant number 230970”. This text has now been added.