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DNA sequences offer powerful tools for describing the members and interactions of natural communities. In this study, we establish the to-date most comprehensive library of DNA barcodes for a terrestrial site, including all known macroscopic animals and vascular plants of an intensively studied area of the High Arctic, the Zackenberg Valley in Northeast Greenland. To demonstrate its utility, we apply the library to identify nearly 20 000 arthropod individuals from two Malaise traps, each operated for two summers. Drawing on this material, we estimate the coverage of previous morphology-based species inventories, derive a snapshot of faunal turnover in space and time and describe the abundance and phenology of species in the rapidly changing arctic environment. Overall, 403 terrestrial animal and 160 vascular plant species were recorded by morphology-based techniques. DNA barcodes ( CO1) offered high resolution in discriminating among the local animal taxa, with 92% of morphologically distinguishable taxa assigned to unique Barcode Index Numbers ( BINs) and 93% to monophyletic clusters. For vascular plants, resolution was lower, with 54% of species forming monophyletic clusters based on barcode regions rbcL a and ITS2. Malaise catches revealed 122 BINs not detected by previous sampling and DNA barcoding. The insect community was dominated by a few highly abundant taxa. Even closely related taxa differed in phenology, emphasizing the need for species-level resolution when describing ongoing shifts in arctic communities and ecosystems. The DNA barcode library now established for Zackenberg offers new scope for such explorations, and for the detailed dissection of interspecific interactions throughout the community. [ABSTRACT FROM AUTHOR]

Significant progress has been made in our understanding of species-level responses to climate change, but upscaling to entire ecosystems remains a challenge. This task is particularly urgent in the Arctic, where global warming is most pronounced. Here we report the results of an international collaboration on the direct and indirect effects of climate on the functioning of Arctic terrestrial ecosystems. Our data from seven terrestrial food webs spread along a wide range of latitudes (∼1,500 km) and climates (Δ mean July temperature = 8.5 °C) across the circumpolar world show the effects of climate on tundra primary production, food-web structure and species interaction strength. The intensity of predation on lower trophic levels increased significantly with temperature, at approximately 4.5% per °C. Temperature also affected trophic interactions through an indirect effect on food-web structure (that is, diversity and number of interactions). Herbivore body size was a major determinant of predator-prey interactions, as interaction strength was positively related to the predator-prey size ratio, with large herbivores mostly escaping predation. There is potential for climate warming to cause a switch from bottom-up to top-down regulation of herbivores. These results are critical to resolving the debate on the regulation of tundra and other terrestrial ecosystems exposed to global change. [ABSTRACT FROM AUTHOR]

A morphometric study was conducted on six skull traits and seven teeth traits of 282 polar bear Ursus maritimus skulls sampled in East Greenland from 1892 to 2002, the polar bear material originated from two distinct periods: one period covering 1892–1939 and the other from 1961–2002. The first period being before the introduction of organochlorines in the Arctic environment and having more extensive sea ice cover when compared with the later period. Admixture analysis, followed by multivariate analyses provided evidence for morphometric differences in both the size and the shape of individual skulls collected in the two periods. These findings are possibly a consequence of environmental factors, such as exposure of organohalogens and changed extension of sea ice, ultimately affecting the amount of prey available, a general weakening of the immune system and reduced reproductive success, factors that can affect the individual growth and the realized size at maturity. The process of reduced reproductive success due to a high concentration of organochlorine and/or changes in the amount of food resources may also have affected the polar bears' genetic composition and effective population size. Changes in the genetic composition of the population are suggested to have contributed to the observed morphometric changes with time. The fact that environmental and genetic changes produce different combinations of patterns of morphometric changes allows us to individuate the causes of the morphometrical modifications. [ABSTRACT FROM AUTHOR]