Insect outbreaks can have important consequences for tundra ecosystems. In this study, we synthesise available information on outbreaks of larvae of the noctuid moth Eurois occulta in Greenland. ...Based on an extensive dataset from a monitoring programme in Kobbefjord, West Greenland, we demonstrate effects of a larval outbreak in 2011 on vegetation productivity and CO₂ exchange. We estimate a decreased carbon (C) sink strength in the order of 118-143 g Cm⁻², corresponding to 1210-1470 tonnes C at the Kobbefjord catchment scale. The decreased C sink was, however, counteracted the following years by increased primary production, probably facilitated by the larval outbreak increasing nutrient turnover rates. Furthermore, we demonstrate for the first time in tundra ecosystems, the potential for using remote sensing to detect and map insect outbreak events.
Predicting which species will occur together in the future, and where, remains one of the greatest challenges in ecology, and requires a sound understanding of how the abiotic and biotic environments ...interact with dispersal processes and history across scales. Biotic interactions and their dynamics influence species' relationships to climate, and this also has important implications for predicting future distributions of species. It is already well accepted that biotic interactions shape species' spatial distributions at local spatial extents, but the role of these interactions beyond local extents (e.g. 10 km2 to global extents) are usually dismissed as unimportant. In this review we consolidate evidence for how biotic interactions shape species distributions beyond local extents and review methods for integrating biotic interactions into species distribution modelling tools. Drawing upon evidence from contemporary and palaeoecological studies of individual species ranges, functional groups, and species richness patterns, we show that biotic interactions have clearly left their mark on species distributions and realised assemblages of species across all spatial extents. We demonstrate this with examples from within and across trophic groups. A range of species distribution modelling tools is available to quantify species environmental relationships and predict species occurrence, such as: (i) integrating pairwise dependencies, (ii) using integrative predictors, and (iii) hybridising species distribution models (SDMs) with dynamic models. These methods have typically only been applied to interacting pairs of species at a single time, require a priori ecological knowledge about which species interact, and due to data paucity must assume that biotic interactions are constant in space and time. To better inform the future development of these models across spatial scales, we call for accelerated collection of spatially and temporally explicit species data. Ideally, these data should be sampled to reflect variation in the underlying environment across large spatial extents, and at fine spatial resolution. Simplified ecosystems where there are relatively few interacting species and sometimes a wealth of existing ecosystem monitoring data (e.g. arctic, alpine or island habitats) offer settings where the development of modelling tools that account for biotic interactions may be less difficult than elsewhere.
The muskox (Ovibos moschatus) is the largest terrestrial herbivore in the Arctic and plays a vital role in the tundra ecosystem 1–4. Its range, abundance, and genetic diversity have declined ...dramatically over the past 30,000 years 5. Two subspecies are recognized, but little is known about the genetic structure and how this relates to the species history. One unresolved question is how and when the species dispersed into its present range, notably the present strongholds in the Canadian archipelago and Greenland. We used genotyping by sequencing (GBS) data from 116 muskox individuals and genotype likelihood-based methods to infer the genetic diversity and distribution of genetic variation in the species. We identified a basal split separating the two recognized subspecies, in agreement with isolation of the muskox into several refugia in the Nearctic around 21,000 years ago 6, near the last glacial maximum (LGM). In addition, we found evidence of strong, successive founder effects inflicting a progressive loss of genetic diversity as the muskox colonized the insular High Arctic from an unknown Nearctic origin. These have resulted in exceptionally low genetic diversity in the Greenlandic populations, as well as extremely high genetic differentiation among regional populations. Our results highlight the need for further investigations of genetic erosion in Nearctic terrestrial mammals, of which several show similar colonization histories in the High Artic.
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•Successive founder effects caused progressive loss of genetic diversity in the muskox•Evidence of strong population structure in the muskox•Extremely low genetic diversity in the Greenlandic muskox populations•Arctic mammals show striking similarities in their genetic history
Hansen et al. analyze genetic variation in the muskox, the largest herbivore in the Arctic. The muskox has experienced drastic declines in population size, leading to lower genetic diversity levels than most herbivores. The low genetic diversity and strong genetic structure holds implications for the future conservation efforts for the species.
At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem ...scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These rapid changes may be a bellwether of changes to come at lower latitudes and have the potential to affect ecosystem services related to natural resources, food production, climate regulation, and cultural integrity. We highlight areas of ecological research that deserve priority as the Arctic continues to warm.
Genomic studies of species threatened by extinction are providing crucial information about evolutionary mechanisms and genetic consequences of population declines and bottlenecks. However, to ...understand how species avoid the extinction vortex, insights can be drawn by studying species that thrive despite past declines. Here, we studied the population genomics of the muskox (Ovibos moschatus), an Ice Age relict that was at the brink of extinction for thousands of years at the end of the Pleistocene yet appears to be thriving today. We analysed 108 whole genomes, including present‐day individuals representing the current native range of both muskox subspecies, the white‐faced and the barren‐ground muskox (O. moschatus wardi and O. moschatus moschatus) and a ~21,000‐year‐old ancient individual from Siberia. We found that the muskox' demographic history was profoundly shaped by past climate changes and post‐glacial re‐colonizations. In particular, the white‐faced muskox has the lowest genome‐wide heterozygosity recorded in an ungulate. Yet, there is no evidence of inbreeding depression in native muskox populations. We hypothesize that this can be explained by the effect of long‐term gradual population declines that allowed for purging of strongly deleterious mutations. This study provides insights into how species with a history of population bottlenecks, small population sizes and low genetic diversity survive against all odds.
Fourhorn sculpins (Myoxocephalus quadricornis) and shorthorn sculpins (Myoxocephalus scorpius) have been considered suitable local bioindicators for environmental monitoring studies in the Arctic. ...Because these species share many characteristics, data from the two species have previously been pooled when assessing marine metal contamination. A chemical and histological study was conducted on fourhorn and shorthorn sculpins collected around a contaminated lead-zinc mine at East Greenland to investigate whether there were any differences in the residues of metals, histopathology and parasites in liver and gills between the two sculpin species. The results demonstrated that concentrations of copper (Cu), zinc (Zn), mercury (Hg) and lead (Pb) were significantly higher in the fourhorn sculpins (p<0.001) while there were no significant differences for arsenic (As) or cadmium (Cd). Furthermore, density of blood vessel fibrosis (p=0.028), prevalence and density of chondroplasia (p=0.002 and p=0.005, respectively), number of mucin-containing mucous cells (p<0.001) and chloride cells (p<0.001) and mean intensity of colonial Peritricha (p<0.001) were significantly higher in fourhorn sculpin. Based on these results we suggest that pooling the two species when conducting environmental assessments is not recommended as it can lead to incorrect conclusions. We propose that a larger study investigating the biological effects of zinc-lead mining in Greenland is needed.
•Fourhorn sculpins (Myoxocephalus quadricornis) more sensitive to pollution than shorthorn sculpins (Myoxocephalus scorpius).•Metal residues, histological changes and presence of parasites were species-specific.•Different sculpin species should not be pooled together as pollution biomarkers.
Insect outbreaks can have important consequences for tundra ecosystems. In this study, we synthesise available information on outbreaks of larvae of the noctuid moth Eurois occulta in Greenland. ...Based on an extensive dataset from a monitoring programme in Kobbefjord, West Greenland, we demonstrate effects of a larval outbreak in 2011 on vegetation productivity and CO sub(2) exchange. We estimate a decreased carbon (C) sink strength in the order of 118-143 g C m super(-2), corresponding to 1210-1470 tonnes C at the Kobbefjord catchment scale. The decreased C sink was, however, counteracted the following years by increased primary production, probably facilitated by the larval outbreak increasing nutrient turnover rates. Furthermore, we demonstrate for the first time in tundra ecosystems, the potential for using remote sensing to detect and map insect outbreak events.
The former lead-zinc mine at Mestersvig, Greenland, continues to contaminate the surrounding environment despite its operations ceasing over 50 years ago. Elevated concentrations of heavy metals are ...found in water, sediment and biota in the terrestrial, freshwater and marine environments. To shed light on the present contamination and its potential effects on local fish we investigated gill and liver histology of sculpins (Myoxocephalus spp.) around the former mining area. Two species of sculpins were caught; shorthorn sculpins (M. scorpius; n = 16) and fourhorn sculpins (M. quadricornis; n = 17) at a contaminated site, Nyhavn, and shorthorn sculpins (M. scorpius; n = 25) at the reference site. In a previous study we found histopathological changes in the tissues of the sculpins, and we suspected this to be related to elevated heavy metal tissue concentrations. Concentrations of Fe, Hg, Mn, Pb, Se and Zn were significantly higher in sculpins at Nyhavn compared to the reference site. Reference NOED and LOEC thresholds for biochemistry, tissue lesions, growth, survival and reproduction for hepatic Hg, As, Cd and Pb from the ERED database were exceeded in both sculpin species. Histopathological investigations of the sculpins gills revealed significant increases in the prevalence of hyperplastic epithelium, inflammation, intensity of neutral and total mucus cells and chloride cells along with an increased infection of colonial Peritricha. At the contaminated Nyhavn site, fourhorn sculpins had a significantly higher prevalence of chondroplastic tissue and intensity of neutral, mixed and total mucus cells in the gills compared to the shorthorn sculpins. The data indicate that both sculpin species could be useful indicator species for environmental monitoring of metal pollution in Arctic areas. However, confounding effects of gender and species should be investigated further. Effects on other biomarkers as well as baseline measurements should be included in future environmental monitoring efforts around mining activities in Greenland.
•Mestersvig mine Pb-Zn mine in East Greenland has led to significant metal pollution.•Gill and liver morphology of fourhorn and shorthorn sculpins was evaluated as bio-indicators.•Significant pathologies were found and were related to metal concentrations.•Sculpin pathology may be suitable health indicators mining activity effects.•These should be enrolled in EIAs of raw material industrialisation in the Arctic.
Recent studies suggest that climate changes may have a strong impact on the vegetation composition in Arctic ecosystems, causing increasing dominance of woody species. Evidence from short-term ...studies on the effects of herbivory indicates that this effect may be counteracted by grazing, but it has not yet been studied whether the effect is persistent and general. Here, we present the results from a large-scale, long-term study of the effects of sheep grazing and climate on the relative dominance of woody plants, graminoids, and forbs. The study is based on exclosures established from 1984 onward across a climatic gradient in South Greenland. The relative cover of the three plant functional types was modeled in a state-space model. There was no significant overall change in the relative cover of the three groups, although such changes occurred intermittently on some sites. This suggests that the relative dominance of the plant functional types is resilient to the impacts of grazing and climate changes in the tundra of South Greenland in line with other studies from sites where summer temperatures have not increased.
Aim Although habitat suitability maps derived from species distribution models (SDMs) are often assumed to highlight locations that can sustain healthy populations over time, the relationship between ...suitability scores and fitness parameters has rarely been tested thoroughly. Location Zackenberg Valley, north-east Greenland. Methods Using 14 years of data (1997–2010) representing three wader species (dunlin Calidris alpina, sanderling Calidris alba and ruddy turnstone Arenaria interpres), we tested the relationships between modelled suitability and fitness parameters at nesting locations. Results Among the three species examined, only the ruddy turnstone exhibited significant relationships between suitability and nest success, but over time rather than space. During years with extensive snow cover in the landscape, the nesting sites of ruddy turnstone occurred in different habitats than were typically used across years. Moreover, in years with extensive snow cover, the ruddy turnstone initiated nests later and suffered from higher egg predation rates. Main conclusion Our results suggest that SDMs derived from species occurrences that include years of low reproductive success may over-estimate the potential suitable habitat in the landscape. Whenever possible, variation in reproductive success should be considered when building models to inform species' response to environmental change.
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