Widespread Exposure to Mosquitoborne California Serogroup Viruses in Caribou, Arctic Fox, Red Fox, and Polar Bears, Canada.

Northern Canada is warming at 3 times the global rate. Thus, changing diversity and distribution of vectors and pathogens is an increasing health concern. California serogroup (CSG) viruses are mosquitoborne arboviruses; wildlife reservoirs in northern ecosystems have not been identified. We detected CSG virus antibodies in 63% (95% CI 58%-67%) of caribou (n = 517), 4% (95% CI 2%-7%) of Arctic foxes (n = 297), 12% (95% CI 6%-21%) of red foxes (n = 77), and 28% (95% CI 24%-33%) of polar bears (n = 377). Sex, age, and summer temperatures were positively associated with polar bear exposure; location, year, and ecotype were associated with caribou exposure. Exposure was highest in boreal caribou and increased from baseline in polar bears after warmer summers. CSG virus exposure of wildlife is linked to climate change in northern Canada and sustained surveillance could be used to measure human health risks.

Combining deep sequencing and conventional molecular approaches reveals broad diversity and distribution of fleas and Bartonella in rodents and shrews from Arctic and Subarctic ecosystems.

BACKGROUND: Bartonella are intracellular bacteria that are transmitted via animal scratches, bites and hematophagous arthropods. Rodents and their associated fleas play a key role in the maintenance of Bartonella worldwide, with > 22 species identified in rodent hosts. No studies have addressed the occurrence and diversity of Bartonella species and vectors for small mammals in Arctic and Subarctic ecosystems, which are increasingly impacted by invasive species and climate change. METHODS: In this study, we characterized the diversity of rodent fleas using conventional PCR targeting the mitochondrial cytochrome c oxidase II gene (COII) and Bartonella species in rodents and shrews (n = 505) from northern Canada using conventional PCR targeting the ITS (intergenic transcribed spacer) region and gltA (citrate synthase) gene. Metagenomic sequencing of a portion of the gltA gene was completed on a subset of 42 rodents and four rodent flea pools. RESULTS: Year, total summer precipitation the year prior to sampling, average minimum spring temperature and small mammal species were significant factors in predicting Bartonella positivity. Occurrence based on the ITS region was more than double that of the gltA gene and was 34% (n = 349) in northern red-backed voles, 35% (n = 20) in meadow voles, 37% (n = 68) in deer mice and 31% (n = 59) in shrews. Six species of Bartonella were identified with the ITS region, including B. grahamii, B. elizabethae, B. washoensis, Candidatus B. rudakovii, B. doshiae, B. vinsonii subsp. berkhoffii and subsp. arupensis. In addition, 47% (n = 49/105) of ITS amplicons had < 97% identity to sequences in GenBank, possibly due to a limited reference library or previously unreported species. An additional Bartonella species (B. heixiaziensis) was detected during metagenomic sequencing of the gltA gene in 6/11 rodents that had ITS sequences with < 97% identity in GenBank, highlighting that a limited reference library for the ITS marker likely accounted for low sequence similarity in our specimens. In addition, one flea pool from a northern red-backed vole contained multiple species (B. grahamii and B. heixiaziensis). CONCLUSION: Our study calls attention to the usefulness of a combined approach to determine the occurrence and diversity of Bartonella communities in hosts and vectors.

Increasing fire and the decline of fire adapted black spruce in the boreal forest.

Intensifying wildfire activity and climate change can drive rapid forest compositional shifts. In boreal North America, black spruce shapes forest flammability and depends on fire for regeneration. This relationship has helped black spruce maintain its dominance through much of the Holocene. However, with climate change and more frequent and severe fires, shifts away from black spruce dominance to broadleaf or pine species are emerging, with implications for ecosystem functions including carbon sequestration, water and energy fluxes, and wildlife habitat. Here, we predict that such reductions in black spruce after fire may already be widespread given current trends in climate and fire. To test this, we synthesize data from 1,538 field sites across boreal North America to evaluate compositional changes in tree species following 58 recent fires (1989 to 2014). While black spruce was resilient following most fires (62%), loss of resilience was common, and spruce regeneration failed completely in 18% of 1,140 black spruce sites. In contrast, postfire regeneration never failed in forests dominated by jack pine, which also possesses an aerial seed bank, or broad-leaved trees. More complete combustion of the soil organic layer, which often occurs in better-drained landscape positions and in dryer duff, promoted compositional changes throughout boreal North America. Forests in western North America, however, were more vulnerable to change due to greater long-term climate moisture deficits. While we find considerable remaining resilience in black spruce forests, predicted increases in climate moisture deficits and fire activity will erode this resilience, pushing the system toward a tipping point that has not been crossed in several thousand years.

Correction to: Status and trends of circumpolar peregrine falcon and gyrfalcon populations.

While collating contributions and comments from 36 researchers, the coordinating authors accidentally omitted Dr. Suzanne Carrière from the list of contributing co-authors. Dr. Carrière's data are described in Tables 1 and 3, Figure 2 and several places in the narrative.The new author list is thus updated in this article.

Amphibian chytrid fungus and ranaviruses in the Northwest Territories, Canada.

Pathogens can cause serious declines in host species, and knowing where pathogens associated with host declines occur facilitates understanding host-pathogen ecology. Suspected drivers of global amphibian declines include infectious diseases, with 2 pathogens in particular, Batrachochytrium dendrobatidis (Bd) and ranaviruses, causing concern. We explored the host range and geographic distribution of Bd and ranaviruses in the Taiga Plains ecoregion of the Northwest Territories, Canada, in 2007 and 2008. Both pathogens were detected, greatly extending their known geographic distributions. Ranaviruses were widespread geographically, but found only in wood frogs. In contrast, Bd was found at a single site, but was detected in all 3 species of amphibians in the survey area (wood frogs, boreal chorus frogs, western toads). The presence of Bd in the Northwest Territories is not congruent with predicted distributions based on niche models, even though findings from other studies at northern latitudes are consistent with those same models. Unexpectedly, we also found evidence that swabs routinely used to collect samples for Bd screening detected fewer infections than toe clips. Our use and handling of the swabs was consistent with other studies, and the cause of the apparent lack of integrity of swabs is unknown. The ranaviruses detected in our study were confirmed to be Frog Virus 3 by sequence analysis of a diagnostic 500 bp region of the major capsid protein gene. It is unknown whether Bd or ranaviruses are recent arrivals to the Canadian north. However, the genetic analyses required to answer that question can inform larger debates about the origin of Bd in North America as well as the potential effects of climate change and industrial development on the distributions of these important amphibian pathogens.

Fire drives transcontinental variation in tree birch defense against browsing by snowshoe hares.

Fire has been the dominant disturbance in boreal America since the Pleistocene, resulting in a spatial mosaic in which the most fire occurs in the continental northwest. Spatial variation in snowshoe hare (Lepus americanus) density reflects the fire mosaic. Because fire initiates secondary forest succession, a fire mosaic creates variation in the abundance of early successional plants that snowshoe hares eat in winter, leading to geographic variation in hare density. We hypothesize that fire is the template for a geographic mosaic of natural selection: where fire is greatest and hares are most abundant, hare browsing has most strongly selected juvenile-phase woody plants for defense. We tested the hypothesis at multiple spatial scales using Alaska birch (Betula neoalaskana) and white birch (Betula papyrifera). We also examined five alternative hypotheses for geographic variation in antibrowsing defense. The fire-hare-defense hypothesis was supported at transcontinental, regional, and local scales; alternative hypotheses were rejected. Our results link transcontinental variation in species interactions to an abiotic environmental driver, fire. Intakes of defense toxins by Alaskan hares exceed those by Wisconsin hares, suggesting that the proposed selection mosaic may coincide with a geographic mosaic of coevolution.