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Results for “Holarctic Ecology”

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11 recordsLinked to original sources
USGS1989

Terrain, vegetation, and landscape evolution of the R4D research site, Brooks Range Foothills, Alaska

Maps of the vegetation and terrain of a 22 km2 area centered on the Department of Energy (DOE) R4D (Response, Resistance, Resilience to and Recovery from Disturbance in Arctic Ecosystems) study site in the Southern Foothills Physiographic Province of Alaska were made using integrated geobotanical mapping procedures and a geographic-information system. Typical land forms and surface f orms include hillslope water tracks, Sagavanirktok-age till deposits, nonsorted stone stripes, and colluvial-basin deposits. Thirty-two plant communities are described; the dominant vegetation (51% of the mapped area) is moist tussock-sedge, dwarf-shrub tundra dominated by Eriophorum vaginatum or Carex bigelowii. Much of the spatial variation in the mapped geobotanical characters reflects different-aged glaciated surfaces. Shannon-Wienerin dices indicate that the more mature landscapes, represented by retransported hillslope deposits and basin colluvium, are less heterogeneous than newer landscapes such as surficial till deposits and floodplains. A typical toposequence on a mid-Pleistocene-age surface is discussed with respect to evolution of the landscape. Thick Sphagnum moss layers occur on lower hillslopes, and the patterns of moss-layer development, heat flux, active layer thickness, and ground-ice are seen as keys to developing thermokarst-susceptibility maps.

Alaska↗
USGS2016

Genetic structure and viability selection in the golden eagle (Aquila chrysaetos), a vagile raptor with a Holarctic distribution

Molecular markers can reveal interesting aspects of organismal ecology and evolution, especially when surveyed in rare or elusive species. Herein, we provide a preliminary assessment of golden eagle ( Aquila chrysaetos ) population structure in North America using novel single nucleotide polymorphisms (SNPs). These SNPs included one molecular sexing marker, two mitochondrial markers, 85 putatively neutral markers that were derived from noncoding regions within large intergenic intervals, and 74 putatively nonneutral markers found in or very near protein-coding genes. We genotyped 523 eagle samples at these 162 SNPs and quantified genotyping error rates and variability at each marker. Our samples corresponded to 344 individual golden eagles as assessed by unique multilocus genotypes. Observed heterozygosity of known adults was significantly higher than of chicks, as was the number of heterozygous loci, indicating that mean zygosity measured across all 159 autosomal markers was an indicator of fitness as it is associated with eagle survival to adulthood. Finally, we used chick samples of known provenance to test for population differentiation across portions of North America and found pronounced structure among geographic sampling sites. These data indicate that cryptic genetic population structure is likely widespread in the golden eagle gene pool, and that extensive field sampling and genotyping will be required to more clearly delineate management units within North America and elsewhere.

Conservation Genetics↗
USGS2012

Temporal, spatial and ecological dynamics of speciation among amphi-Beringian small mammals

Quaternary climate cycles played an important role in promoting diversification across the Northern Hemisphere, although details of the mechanisms driving evolutionary change are still poorly resolved. In a comparative phylogeographical framework, we investigate temporal, spatial and ecological components of evolution within a suite of Holarctic small mammals. We test a hypothesis of simultaneous divergence among multiple taxon pairs, investigating time to coalescence and demographic change for each taxon in response to a combination of climate and geography.

Beringia↗
USGS2002

Preface: Proceedings of the seventh international symposium on the biology and management of corigonid fishes

This volume is the proceedings of the Seventh International Symposium on the Biology and Management of Coregonid Fishes (ISBMCF). As in all six preceding symposia, the seventh meeting of the ISBMCF provided an international forum for the scientific review and discussion of the various taxonomic, biological, ecological, and management issues that surround this important group of Holarctic fishes. The collection of presentations for this conference was addressed in the following convened sessions: Genetics, Stocking, Fisheries, and Biology, as well as special sessions on Lake Baikal, Russia and Lake Femund, Norway. The conference comprised 53 oral and 58 poster presentations by scientists from Canada, the United Kingdom, France, Switzerland, Germany, Finland, Norway, Poland, Russia, and the United States. In total, there were 162 participants, including an unprecedented 18 scientists from Russia as the result of additional, concerted support.

Book chapter↗
USGS2021

Diverse patterns of migratory timing, site use, and site fidelity by Alaska-breeding Whimbrels

Birds that conduct long-distance migrations exhibit varied patterns of consistency in migratory timing and site use. Understanding variation in these traits among populations can help uncover mechanisms driving migratory behaviors and identify potential population threats. Whimbrels ( Numenius phaeopus ) are long-distance migratory shorebirds with a Holarctic breeding distribution, and recent studies have documented population-specific migrations that vary in duration (short to long) and frequency of stops (none/few to multiple). Factors driving these population-specific differences are unclear. We studied the migration ecology of Whimbrels breeding in Alaska, USA, using satellite transmitters deployed from 2006 to 2010 and tracked through 2015. Whimbrels moved entirely within the Pacific Americas Flyway, and some conducted nonstop flights that exceeded seven days across ~ 8700 km. Birds dispersed across numerous sites throughout the flyway, often using agriculture or aquaculture habitats. Whimbrels generally exhibited fidelity to breeding and non-breeding sites, but typically only exhibited fidelity to staging sites used prior to long, nonstop migratory flights. The duration of migration for Whimbrels at more southern non-breeding locations was longer than for those at more northern non-breeding sites, and birds at more southern sites also terminated southbound migration later and initiated northbound migration earlier than birds at more northern sites. Alaska-breeding Whimbrels exhibited greater variation in migratory behaviors than those in other populations in the species’ range. We attribute this within-population diversity to the extensive breadth of non-breeding distributions (~ 70° latitude across ~ 8600 km), a range that naturally shaped individual responses to unequal migratory demands.

Alaska↗
USGS2011

Persistence and diversification of the Holarctic shrew, Sorex tundrensis (Family Soricidae), in response to climate change

Environmental processes govern demography, species movements, community turnover and diversification and yet in many respects these dynamics are still poorly understood at high latitudes. We investigate the combined effects of climate change and geography through time for a widespread Holarctic shrew, Sorex tundrensis . We include a comprehensive suite of closely related outgroup taxa and three independent loci to explore phylogeographic structure and historical demography. We then explore the implications of these findings for other members of boreal communities. The tundra shrew and its sister species, the Tien Shan shrew ( Sorex asper ), exhibit strong geographic population structure across Siberia and into Beringia illustrating local centres of endemism that correspond to Late Pleistocene refugia. Ecological niche predictions for both current and historical distributions indicate a model of persistence through time despite dramatic climate change. Species tree estimation under a coalescent process suggests that isolation between populations has been maintained across timeframes deeper than the periodicity of Pleistocene glacial cycling. That some species such as the tundra shrew have a history of persistence largely independent of changing climate, whereas other boreal species shifted their ranges in response to climate change, highlights the dynamic processes of community assembly at high latitudes.

Molecular Ecology↗
USGS2025

Burbot population dynamics in northern Lake Michigan, 2001–2023, and predation on newly stocked lake trout by burbot

Although the worldwide status of burbot ( Lota lota ) across its Holarctic distribution has recently been assessed, adverse effects of dreissenid mussels on burbot abundance in waters invaded by mussels have not been investigated. We analyzed data from an annual spring gillnet survey to characterize burbot population dynamics in northern Lake Michigan during 2001–2023. Adult burbot abundance in northern Lake Michigan trended neither significantly upward nor downward during 2001–2023. Thus, expansion of the quagga mussel ( Dreissena rostriformis bugensis ) population into deeper waters of Lake Michigan during 2003–2008 had no detectable negative effects on burbot abundance. Burbot continued to feed on lake trout ( Salvelinus namaycush ) stocked in the Northern Refuge of Lake Michigan through 2023, which supported a hypothesis that the burbot population potentially impeded lake trout restoration in the refuge.

Michigan↗
USGS2012

Behavioral vs. molecular sources of conflict between nuclear and mitochondrial DNA: The role of male-biased dispersal in a Holarctic sea duck

Genetic studies of waterfowl (Anatidae) have observed the full spectrum of mitochondrial (mt) DNA population divergence, from apparent panmixia to deep, reciprocally monophyletic lineages. Yet, these studies often found weak or no nuclear (nu) DNA structure, which was often attributed to male-biased gene flow, a common behaviour within this family. An alternative explanation for this ‘conflict’ is that the smaller effective population size and faster sorting rate of mtDNA relative to nuDNA lead to different signals of population structure. We tested these alternatives by sequencing 12 nuDNA introns for a Holarctic pair of waterfowl subspecies, the European goosander ( Mergus merganser merganser ) and the North American common merganser ( M. m. americanus ), which exhibit strong population structure in mtDNA. We inferred effective population sizes, gene flow and divergence times from published mtDNA sequences and simulated expected differentiation for nuDNA based on those histories. Between Europe and North America, nuDNA Ф ST was 3.4-fold lower than mtDNA Ф ST , a result consistent with differences in sorting rates. However, despite geographically structured and monophyletic mtDNA lineages within continents, nuDNA Ф ST values were generally zero and significantly lower than predicted. This between- and within-continent contrast held when comparing mtDNA and nuDNA among published studies of ducks. Thus, male-mediated gene flow is a better explanation than slower sorting rates for limited nuDNA differentiation within continents, which is also supported by nonmolecular data. This study illustrates the value of quantitatively testing discrepancies between mtDNA and nuDNA to reject the null hypothesis that conflict simply reflects different sorting rates.

Molecular Ecology↗
USGS2011

Ecoregional-scale monitoring within conservation areas, in a rapidly changing climate

Long-term monitoring of ecological systems can prove invaluable for resource management and conservation. Such monitoring can: (1) detect instances of long-term trend (either improvement or deterioration) in monitored resources, thus providing an early-warning indication of system change to resource managers; (2) inform management decisions and help assess the effects of management actions, as well as anthropogenic and natural disturbances; and (3) provide the grist for supplemental research on mechanisms of system dynamics and cause-effect relationships (Fancy et al., 2009). Such monitoring additionally provides a snapshot of the status of monitored resources during each sampling cycle, and helps assess whether legal standards and regulations are being met. Until the last 1-2 decades, tracking and understanding changes in condition of natural resources across broad spatial extents have been infrequently attempted. Several factors, however, are facilitating the achievement of such broad-scale investigation and monitoring. These include increasing awareness of the importance of landscape context, greater prevalence of regional and global environmental stressors, and the rise of landscape-scale programs designed to manage and monitor biological systems. Such programs include the US Forest Service's Forest Inventory and Analysis (FIA) Program (Moser et al., 2008), Canada's National Forest Inventory, the 3Q Programme for monitoring agricultural landscapes of Norway (Dramstad et al., 2002), and the emerging (US) Landscape Conservation Cooperatives (USDOI Secretarial Order 3289, 2009; Anonymous, 2011). This Special Section explores the underlying design considerations, as well as many pragmatic aspects associated with program implementation and interpretation of results from broad-scale monitoring systems, particularly within the constraints of high-latitude contexts (e.g., low road density, short field season, dramatic fluctuations in temperature). Although Alaska is the focus of most papers in this Special Section, we posit that many of the issues that characterize the remote, relatively undisturbed ecosystems of high northern latitudes are widespread and thus applicable to natural-resource management and conservation across northern portions of the Holarctic ecozone and indeed anywhere broad-scale monitoring is contemplated.

Biological Conservation↗
USGS2012

Hybridization among Arctic white-headed gulls (Larus spp.) obscures the genetic legacy of the Pleistocene

We studied the influence of glacial oscillations on the genetic structure of seven species of white-headed gull that breed at high latitudes ( Larus argentatus, L. canus, L. glaucescens, L. glaucoides, L. hyperboreus, L. schistisagus, and L. thayeri ). We evaluated localities hypothesized as ice-free areas or glacial refugia in other Arctic vertebrates using molecular data from 11 microsatellite loci, mitochondrial DNA (mtDNA) control region, and six nuclear introns for 32 populations across the Holarctic. Moderate levels of genetic structure were observed for microsatellites ( F ST = 0.129), introns ( Φ ST = 0.185), and mtDNA control region ( Φ ST = 0.461), with among-group variation maximized when populations were grouped based on subspecific classification. Two haplotype and at least two allele groups were observed across all loci. However, no haplotype/allele group was composed solely of individuals of a single species, a pattern consistent with recent divergence. Furthermore, northernmost populations were not well differentiated and among-group variation was maximized when L. argentatus and L. hyberboreus populations were grouped by locality rather than species, indicating recent hybridization. Four populations are located in putative Pleistocene glacial refugia and had larger t estimates than the other 28 populations. However, we were unable to substantiate these putative refugia using coalescent theory, as all populations had genetic signatures of stability based on mtDNA. The extent of haplotype and allele sharing among Arctic white-headed gull species is noteworthy. Studies of other Arctic taxa have generally revealed species-specific clusters as well as genetic structure within species, usually correlated with geography. Aspects of white-headed gull behavioral biology, such as colonization ability and propensity to hybridize, as well as their recent evolutionary history, have likely played a large role in the limited genetic structure observed.

Ecology and Evolution↗
USGS2021

Investigating the morphological and genetic divergence of arctic char (Salvelinus alpinus) populations in lakes of arctic Alaska

Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char ( Salvelinus sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length-frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus was likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present-day char populations. Although some lakes exhibit bimodal size distributions, using model-based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping by sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha -1 ), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food-limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation.

Alaska↗