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At least 343 records · Page 19Linked to original sources
USGS2002

History and environmental setting of the Grand Calumet River

The Grand Calumet River lies in an area of great ecological diversity, a result of the convergence of three biomes during glaciation. Over thousands of years the region and the river have changed ecologically due to ice retreat, lake level declines, settlement and industrialization. Settlement and industrialization have greatly accelerated the rate of change, and the Grand Calumet River and its basin are now subject to the added effects of years of direct pollution. For years, industries directly discharged into the waterway; and those contaminants remain locked in the sediment a century later. In order to preserve the remaining surrounding natural areas and to improve the Grand Calumet River, buried contaminants would have to be dredged from the river. Restoration needs to be implemented as part of the clean-up process, and recontamination should be prevented.

Proceedings of the Indiana Academy of Science↗
USGS2020

Mitochondrial genome diversity and population mitogenomics of Polar cod (Boreogadus saida) and Arctic dwelling gadoids

High-latitude fish typically exhibit a narrow thermal tolerance window, which may pose challenges when coping with temperatures that shift outside of a species’ range of tolerance. Due to its role in aerobic metabolism and energy balance, the mitochondrial genome is likely critical for the acclimation and adaptation to differing temperature regimes in marine ectotherms. As oceans continue to warm, there is growing need to understand the ability of organisms to respond to changing environmental conditions given evidence that some species, in particular cold-water species, may already be experiencing difficulties. To assess how Arctic gadids in Alaska have responded to differential thermal preferences in the past and how regions are interconnected, we sequenced complete mitochondrial genomes for four Arctic gadids to determine the distribution of mitochondrial diversity and population-level structure as well as to detect signatures of selection acting on the mitochondrial genome. We found little population-level structure within all four species with the clear exception of Gulf of Alaska saffron cod ( Eleginus gracilis ). Northern localities exhibited higher levels of genetic diversity and primarily northern lineages were observed within polar cod ( Boreogadus saida ) and saffron cod, likely reflecting asymmetrical dispersal and potentially admixture of distinct lineages via ocean currents. The main evolutionary force shaping the evolution of the mitogenome appears to be purifying selection, but we also identified potential positive selection of candidate amino acid replacements primarily in complex I (ND genes) in polar cod. The high levels of mitochondrial diversity observed in our study and large population size may provide this species with the ability to respond evolutionarily (i.e. long-term) to a changing environment.

Alaska↗
USGS2023

Widespread regeneration failure in ponderosa pine forests of the southwestern United States

As climate changes in coming decades, ponderosa pine forest persistence may be increasingly dictated by their regeneration. Sustained regeneration failure has been predicted for forests of the southwestern US (SWUS) even in absence of stand-replacing wildfire, but regeneration in undisturbed and lightly disturbed forests has been studied infrequently and at a limited number of locations. We characterized 77 ponderosa pine sites in 7 SWUS locations, documented regeneration occurring over the past ∼ "> ∼ 20 years, and utilized gridded meteorological estimates and water balance modeling to determine the climate and environmental conditions associated with regeneration failure (R0). Of these sites, 29 % "> % were R0, illuminating that regeneration failure in these forests is widespread. R0 sites were distinguished by high above- and belowground heat loading, loss of cool-season climate, and high soil moisture variation. Explanatory variables had high accuracy in identifying R0 sites, and illustrate the climate-driven pathway by which regeneration failure has occurred in the SWUS. Regeneration failure has high potential to increase in a warmer, more hydrologically variable climate, and expand regionally from lower to higher latitudes. Yet, we also found that human management interventions were associated with environmental conditions that avoided regeneration failure. To counteract regeneration-associated forest declines, interventions will need to influence climate-driven environmental change by adjusting forest characteristics at local scales. Regeneration failures are a major threat to ponderosa pine forest persistence, and they have potential to intensify and expand in a changing climate.

Arizona, Colorado, Nevada, New Mexico↗
USGS2019

Using a mechanistic model to develop management strategies to cool Apache Trout streams under the threat of climate change

User‐friendly stream temperature models populated with on‐site data may help in developing strategies to manage temperatures of individual stream reaches that are subject to climate change. We used the field‐tested Stream Segment Temperature model (U.S. Geological Survey) to simulate how altering discharge, groundwater input, channel wetted width, and shade prevents the temperatures of White Mountain, Arizona, stream reaches from exceeding the thermal tolerance of Apache Trout Oncorhynchus apache , both under existing conditions and under a climate change scenario. Simulations suggested increasing shade, either through streamside planting of specific numbers and species of plants or by other means, would be most effective and feasible for cooling the stream reaches we studied. Ponderosa pine Pinus ponderosa and Douglas fir Pseudotsuga menziesii provided the most shade followed in order by Engelman spruce Picea engelmannii , Bebb's willow Salix bebbiana , Arizona alder Alnus oblongifolia , and finally coyote willow Salix exigua . Vegetation survival depends on the appropriateness of site conditions at present and under climate change, and planting in buffer strips minimizes additional water removal from the watershed through evapotranspiration. Alternative shading options, including thick sedge growth, shade cloth, or felled woody vegetation, may be considered when environmental conditions do not support plantings. Increasing groundwater input can cool streams, but additional sources are scarce in the region. Decreasing the width‐to‐depth ratio would succeed best on reaches with widths greater than 2.0 m. Increasing discharge from upstream may lower water temperature on reaches with an initial discharge greater than 0.5 m 3 /s. Existing models provide suggestions to cool stream reaches. Further development of accessible software packages that incorporate evaporation, fragmentation, and other projected climate change effects into their routines will provide additional tools to help manage climate change effects.

Arizona↗
USGS2016

Competitive exclusion over broad spatial extents is a slow process: Evidence and implications for species distribution modeling

There is considerable debate about the role of competition in shaping species distributions over broad spatial extents. This debate has practical implications because predicting changes in species' geographic ranges in response to ongoing environmental change would be simpler if competition could be ignored. While this debate has been the subject of many reviews, recent literature has not addressed the rates of relevant processes. This omission is surprising in that ecologists hypothesized decades ago that regional competitive exclusion is a slow process. The goal of this review is to reassess the debate under the hypothesis that competitive exclusion over broad spatial extents is a slow process. Available evidence, including simulations presented for the first time here, suggests that competitive exclusion over broad spatial extents occurs slowly over temporal extents of many decades to millennia. Ecologists arguing against an important role for competition frequently study modern patterns and/or range dynamics over periods of decades, while much of the evidence for competition shaping geographic ranges at broad spatial extents comes from paleoecological studies over time scales of centuries or longer. If competition is slow, as evidence suggests, the geographic distributions of some, perhaps many species, would continue to change over time scales of decades to millennia, even if environmental conditions did not continue to change. If the distributions of competing species are at equilibrium it is possible to predict species distributions based on observed species–environment relationships. However, disequilibrium is widespread as a result of competition and many other processes. Studies whose goal is accurate predictions over intermediate time scales (decades to centuries) should focus on factors associated with range expansion (colonization) and loss (local extinction), as opposed to current patterns. In general, understanding of modern range dynamics would be enhanced by considering the rates of relevant processes.

Ecography↗
USGS2012

The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing

Recent large and frequent fires above the Alaskan arctic circle have forced a reassessment of the ecological and climatological importance of fire in arctic tundra ecosystems. Here we provide a general overview of the occurrence, distribution, and ecological and climate implications of Alaskan tundra fires over the past half-century using spatially explicit climate, fire, vegetation and remote sensing datasets for Alaska. Our analyses highlight the importance of vegetation biomass and environmental conditions in regulating tundra burning, and demonstrate that most tundra ecosystems are susceptible to burn, providing the environmental conditions are right. Over the past two decades, fire perimeters above the arctic circle have increased in size and importance, especially on the North Slope, indicating that future wildfire projections should account for fire regime changes in these regions. Remote sensing data and a literature review of thaw depths indicate that tundra fires have both positive and negative implications for climatic feedbacks including a decadal increase in albedo radiative forcing immediately after a fire, a stimulation of surface greenness and a persistent long-term (>10 year) increase in thaw depth. In order to address the future impact of tundra fires on climate, a better understanding of the control of tundra fire occurrence as well as the long-term impacts on ecosystem carbon cycling will be required.

Alaska↗
USGS2010

Depth as an organizer of fish assemblages in floodplain lakes

Depth reduction is a natural process in floodplain lakes, but in many basins has been accelerated by anthropogenic disturbances. A diverse set of 42 floodplain lakes in the Yazoo River Basin (Mississippi, USA) was examined to test the hypothesis of whether depth reduction was a key determinant of water quality and fish assemblage structure. Single and multiple variable analyses were applied to 10 commonly monitored water variables and 54 fish species. Results showed strong associations between depth and water characteristics, and between depth and fish assemblages. Deep lakes provided less variable environments, clearer water, and a wider range of microhabitats than shallow lakes. The greater environmental stability was reflected by the dominant species in the assemblages, which included a broader representation of large-body species, species less tolerant of extreme water quality, and more predators. Stability in deep lakes was further reflected by reduced among-lake variability in taxa representation. Fish assemblages in shallow lakes were more variable than deep lakes, and commonly dominated by opportunistic species that have early maturity, extended breeding seasons, small adult size, and short lifespan. Depth is a causal factor that drives many physical and chemical variables that contribute to organizing fish assemblages in floodplain lakes. Thus, correlations between fish and water transparency, temperature, oxygen, trophic state, habitat structure, and other environmental descriptors may ultimately be totally or partly regulated by depth. In basins undergoing rapid anthropogenic modifications, local changes forced by depth reductions may be expected to eliminate species available from the regional pool and could have considerable ecological implications.

Mississippi↗
USGS2014

Spatial variation and low diversity in the major histocompatibility complex in walrus ( Odobenus rosmarus )

Increased global temperature and associated changes to Arctic habitats will likely result in the northward advance of species, including an influx of pathogens novel to the Arctic. How species respond to these immunological challenges will depend in part on the adaptive potential of their immune response system. We compared levels of genetic diversity at a gene associated with adaptive immune response [Class II major histocompatibility complex (MHC), DQB exon 2] between populations of walrus ( Odobenus rosmarus ), a sea ice-dependent Arctic species. Walrus was represented by only five MHC DQB alleles, with frequency differences observed between Pacific and Atlantic populations. MHC DQB alleles appear to be under balancing selection, and most (80 %; n = 4/5) of the alleles were observed in walruses from both oceans, suggesting broad scale differences in the frequency of exposure and diversity of pathogens may be influencing levels of heterozygosity at DQB in walruses. Limited genetic diversity at MHC, however, suggests that walrus may have a reduced capacity to respond to novel immunological challenges associated with shifts in ecological communities and environmental stressors predicted for changing climates. This is particularly pertinent for walrus, since reductions in summer sea ice may facilitate both northward expansion of marine species and associated pathogens from more temperate regions, and exchange of marine mammals and associated pathogens through the recently opened Northwest Passage between the Atlantic and Pacific Oceans in the Canadian high Arctic.

Polar Biology↗
USGS2021

Implications of historical and contemporary processes on genetic differentiation of a declining boreal songbird: The rusty blackbird

The arrangement of habitat features via historical or contemporary events can strongly influence genomic and demographic connectivity, and in turn affect levels of genetic diversity and resilience of populations to environmental perturbation. The rusty blackbird ( Euphagus carolinus ) is a forested wetland habitat specialist whose population size has declined sharply (78%) over recent decades. The species breeds across the expansive North American boreal forest region, which contains a mosaic of habitat conditions resulting from active natural disturbance regimes and glacial history. We used landscape genomics to evaluate how past and present landscape features have shaped patterns of genetic diversity and connectivity across the species’ breeding range. Based on reduced-representation genomic and mitochondrial DNA, genetic structure followed four broad patterns influenced by both historical and contemporary forces: (1) an east–west partition consistent with vicariance during the last glacial maximum; (2) a potential secondary contact zone between eastern and western lineages at James Bay, Ontario; (3) insular differentiation of birds on Newfoundland; and (4) restricted regional gene flow among locales within western and eastern North America. The presence of genomic structure and therefore restricted dispersal among populations may limit the species’ capacity to respond to rapid environmental change.

Diversity↗
USGS2009

Monitoring land use on military installations

The US Geological Survey's Land Cover Trends is a research projects aimed to understand the rates, trends, causes, and consequences of contemporary US land use and land-cover change. The project is using the EPA Level III eco-regions as a geographic framework to process geospatial data collected between 1973 and 2000 to characterize ecosystem responses to land-use changes. The results are expected to be used for collaborative environmental change consequences research with various partners including the National Science Foundation, the National Oceanic and Atmospheric Administration, and the US Fish and Wildlife Service. The Land Cover project can provide geographic understanding of the state of the nation's ecosystems. The project is scheduled to be completed by 2010 and expected to provide an unbiased, national synthesis of land-cover changes.

Military Engineer↗
USGS2026

Decadal shifts in groundwater age detected by environmental tracers across California, USA

Groundwater age offers important insight into recharge, storage, and contamination risk. Although models predict age changes can be driven by pumping and climate variability, direct observational evidence remains limited. Here, we analyzed paired environmental tracer suites (tritium, carbon-14, and tritiogenic helium-3) collected a decade apart from 268 wells across California to assess the prevalence of groundwater age transience. Travel-time distribution models and statistical tests indicated age transience at 29% of sites, occurring most often in agricultural regions, such as the San Joaquin Valley and Southern Coast Ranges, where large carbon-14 changes coincided with substantial nitrate and chloride shifts. Sites with tritiogenic helium-3 data showed more frequent age transience, underscoring the value of multi-tracer data sets. These results provide the first regional evidence of widespread groundwater age change and a method for detecting changing water balances with implications for groundwater sustainability and water quality.

California↗
USGS2007

Potential effects of climate change on ground water in Lansing, Michigan

Computer simulations involving general circulation models, a hydrologic modeling system, and a ground water flow model indicate potential impacts of selected climate change projections on ground water levels in the Lansing, Michigan, area. General circulation models developed by the Canadian Climate Centre and the Hadley Centre generated meteorology estimates for 1961 through 1990 (as a reference condition) and for the 20 years centered on 2030 (as a changed climate condition). Using these meteorology estimates, the Great Lakes Environmental Research Laboratory's hydrologic modeling system produced corresponding period streamflow simulations. Ground water recharge was estimated from the streamflow simulations and from variables derived from the general circulation models. The U.S. Geological Survey developed a numerical ground water flow model of the Saginaw and glacial aquifers in the Tri-County region surrounding Lansing, Michigan. Model simulations, using the ground water recharge estimates, indicate changes in ground water levels. Within the Lansing area, simulated ground water levels in the Saginaw aquifer declined under the Canadian predictions and increased under the Hadley.

Michigan↗
USGS2018

Northeast

The distinct seasonality of the Northeast’s climate supports a diverse natural landscape adapted to the extremes of cold, snowy winters and warm to hot, humid summers. This natural landscape provides the economic and cultural foundation for many rural communities, which are largely supported by a diverse range of agricultural, tourism, and natural resource-dependent industries (see Ch. 10: Ag & Rural, Key Message 4) . The recent dominant trend in precipitation throughout the Northeast has been towards increases in rainfall intensity, with increases in intensity exceeding those in other regions of the contiguous United States. Further increases in rainfall intensity are expected, with increases in total precipitation expected during the winter and spring but with little change in the summer. Monthly precipitation in the Northeast is projected to be about 1 inch greater for December through April by end of century (2070–2100) under the higher scenario (RCP8.5). Ocean and coastal ecosystems are being affected by large changes in a variety of climate-related environmental conditions. These ecosystems support fishing and aquaculture, tourism and recreation, and coastal communities. Observed and projected increases in temperature, acidification, storm frequency and intensity, and sea levels are of particular concern for coastal and ocean ecosystems, as well as local communities and their interconnected social and economic systems. Increasing temperatures and changing seasonality on the Northeast Continental Shelf have affected marine organisms and the ecosystem in various ways. The warming trend experienced in the Northeast Continental Shelf has been associated with many fish and invertebrate species moving northward and to greater depths. Because of the diversity of the Northeast’s coastal landscape, the impacts from storms and sea level rise will vary at different locations along the coast. Northeastern cities, with their abundance of concrete and asphalt and relative lack of vegetation, tend to have higher temperatures than surrounding regions due to the urban heat island effect. During extreme heat events, nighttime temperatures in the region’s big cities are generally several degrees higher than surrounding regions, leading to higher risk of heat-related death. Urban areas are at risk for large numbers of evacuated and displaced populations and damaged infrastructure due to both extreme precipitation events and recurrent flooding, potentially requiring significant emergency response efforts and consideration of a long-term commitment to rebuilding and adaptation, and/or support for relocation where needed. Much of the infrastructure in the Northeast, including drainage and sewer systems, flood and storm protection assets, transportation systems, and power supply, is nearing the end of its planned life expectancy. Climate-related disruptions will only exacerbate existing issues with aging infrastructure. Sea level rise has amplified storm impacts in the Northeast (Key Message 2), contributing to higher surges that extend farther inland, as demonstrated in New York City in the aftermath of Superstorm Sandy in 2012. Service and resource supply infrastructure in the Northeast is at increasing risk of disruption, resulting in lower quality of life, economic declines, and increased social inequality. Loss of public services affects the capacity of communities to function as administrative and economic centers and triggers disruptions of interconnected supply chains (Ch. 16: International, Key Message 1) . Increases in annual average temperatures across the Northeast range from less than 1°F (0.6°C) in West Virginia to about 3°F (1.7°C) or more in New England since 1901. Although the relative risk of death on very hot days is lower today than it was a few decades ago, heat-related illness and death remain significant public health problems in the Northeast. For example, a study in New York City estimated that in 2013 there were 133 excess deaths due to extreme heat. These projected increases in temperature are expected to lead to substantially more premature deaths, hospital admissions, and emergency department visits across the Northeast. For example, in the Northeast we can expect approximately 650 additional premature deaths per year from extreme heat by the year 2050 under either a lower (RCP4.5) or higher (RCP8.5) scenario and from 960 (under RCP4.5) to 2,300 (under RCP8.5) more premature deaths per year by 2090. Communities, towns, cities, counties, states, and tribes across the Northeast are engaged in efforts to build resilience to environmental challenges and adapt to a changing climate. Developing and implementing climate adaptation strategies in daily practice often occur in collaboration with state and federal agencies (e.g., New Jersey Climate Adaptation Alliance 2017, New York Climate Clearinghouse 2017, Rhode Island STORMTOOLS 2017, EPA 2017, CDC 2015 ). Advances in rural towns, cities, and suburban areas include low-cost adjustments of existing building codes and standards. In coastal areas, partnerships among local communities and federal and state agencies leverage federal adaptation tools and decision support frameworks (for example, NOAA’s Digital Coast, USGS’s Coastal Change Hazards Portal, and New Jersey’s Getting to Resilience). Increasingly, cities and towns across the Northeast are developing or implementing plans for adaptation and resilience in the face of changing climate (e.g., EPA 2017 ). The approaches are designed to maintain and enhance the everyday lives of residents and promote economic development. In some cities, adaptation planning has been used to respond to present and future challenges in the built environment. Regional efforts have recommended changes in design standards when building, replacing, or retrofitting infrastructure to account for a changing climate.

Report↗
USGS2012

Threats and stressors to the health of the ecosystems of Lakes Mead and Mohave: Chapter 6 in A synthesis of aquatic science for management of Lakes Mead and Mohave

Ecosystem impacts from visitor activities or natural environmental change are important concerns in all units of the National Park system. Possible impacts to aquatic ecosystems at Lake Mead National Recreation Area (LMNRA) are of particular concern because of the designation of Lakes Mead and Mohave as critical habitat for the federally listed endangered razorback sucker (Xyrauchen texanus), the significance of the sport fishery, and the regional importance of its habitats to more than 90 documented species of waterbirds. Potential threats to shoreline habitats are of concern not only for their ecosystem values but also for maintaining the recreational setting. Many areas adjacent to the shorelines of Lakes Mead and Mohave are designated wilderness areas. For purposes of this document, stressors are any chemical, biological, or physical agent that has a detrimental effect on aquatic ecosystems at the organism, population, or community level. Human-made stressors at Lakes Mead and Mohave include direct effects of recreation on the lakes, like boating and fishing, as well as indirect effects of activities away from the lakes, such as growing population and increasing urbanization. Common natural environmental stressors include extended changes in climate (precipitation or temperature), or the erosion, transport, and loading of chemical constituents in rocks and sediments to aquatic environments. Human activity also can exacerbate natural stressors in a variety of ways.

Circular↗
USGS2021

Re-examination of population structure in Arctic ringed seals using DArTseq genotyping

Although Arctic ringed seals Phoca hispida hispida are currently abundant and broadly distributed, their numbers are projected to decline substantially by the year 2100 due to climate warming. While understanding population structure could provide insight into the impact of environmental changes on this subspecies, detecting demographically important levels of exchange can be difficult in taxa with high abundance. We used a next-generation sequencing approach (DArTseq) to genotype ~5700 single nucleotide polymorphisms in 79 seals from 4 Pacific Arctic regions. Comparison of the 2 most geographically separated strata (eastern Bering vs. northeastern Chukchi-Beaufort Seas) revealed a statistically significant level of genetic differentiation ( F ST = 0.001, p = 0.005) that, while small, was 1 to 2 orders of magnitude greater than expected based on divergence estimated for similarly sized populations connected by low (1% yr -1 ) dispersal. A relatively high proportion (72 to 88%) of individuals within these strata could be genetically assigned to their stratum of origin. These results indicate that demographically important structure may be present among Arctic ringed seals breeding in different areas, increasing the risk that declines in the number of seals breeding in areas most negatively affected by environmental warming could occur.

Alaska↗
USGS2010

Great Basin Integrated Landscape Monitoring Pilot Summary Report

The Great Basin Integrated Landscape Monitoring Pilot project (GBILM) was one of four regional pilots to implement the U.S. Geological Survey (USGS) Science Thrust on Integrated Landscape Monitoring (ILM) whose goal was to observe, understand, and predict landscape change and its implications on natural resources at multiple spatial and temporal scales and address priority natural resource management and policy issues. The Great Basin is undergoing rapid environmental change stemming from interactions among global climate trends, increasing human populations, expanding and accelerating land and water uses, invasive species, and altered fire regimes. GBLIM tested concepts and developed tools to store and analyze monitoring data, understand change at multiple scales, and forecast landscape change. The GBILM endeavored to develop and test a landscape-level monitoring approach in the Great Basin that integrates USGS disciplines, addresses priority management questions, catalogs and uses existing monitoring data, evaluates change at multiple scales, and contributes to development of regional monitoring strategies. GBILM functioned as an integrative team from 2005 to 2010, producing more than 35 science and data management products that addressed pressing ecosystem drivers and resource management agency needs in the region. This report summarizes the approaches and methods of this interdisciplinary effort, identifies and describes the products generated, and provides lessons learned during the project.

Open-File Report↗
USGS2002

Sociocultural and institutional drivers and constraints to mineral supply; the meaning of scarcity in the 21st century: drivers and constraints to the supply of minerals using regional, national and global perspectives

The sociocultural dimensions of mineral supply at the outset of the 21st century are making the supply process increasingly complex. The dimensions encompass legal, financial, environmental, cultural, and global implications of mining, and are driving unprecedented change in the way minerals supply will be accomplished in the future. Minerals scarcity on a global scale is subordinate to other societal issues about mineral resources and reserves estimated to meet society's demands for decades to centuries in the future. This report reviews historical and present-day sociocultural drivers of change, and reactions of the minerals industry to these drivers. It is reflective primarily of conditions in the United States, but also uses examples from other countries. It expresses viewpoints on sociocultural drivers as seen by constituents of the minerals industry and several other communities of interest including Aboriginal peoples, non-government organizations; labor; mining-dependent communities; mining-affected communities; researchers; and government (federal, state/provincial, and local). It provides overviews of the demand for minerals in the United States, and the status of land available for mining. The report uses a case study of a metals mining project in Wisconsin to illustrate specific sociocultural drivers and constraints to minerals supply, and how these influence the minerals industry. Over the past 150 years, a progression of sociocultural movements under the headings of conservationism, environmentalism, and sustainable development have nurtured societal values that have come to influence the mineral supply process in important ways. These movements reflect a continuing tension between the demand for minerals and other resources, and the simultaneous demand for aesthetic, spiritual, ecological, cultural, and other attributes of the land. The tension is an important element in current international debates about the meaning and future of sustainable development. This report focuses on some of the social challenges to the minerals industry to supply minerals, while at the same time providing environmental protection, economic growth, and sociocultural acceptance. All these issues fall under the rubric of sustainable development. It also describes current industry responses to sustainability, including the Global Mining Initiative (2001a), an attempt to introduce major changes in global industry practices to begin the 21st century. This report complements other documents in the series on physical supply, technological advancement, and economic and policy drivers (Wilburn and others, 2001).

Open-File Report↗
USGS2012

A climate for speciation: rapid spatial diversification within the Sorex cinereus complex of shrews

The cyclic climate regime of the late Quaternary caused dramatic environmental change at high latitudes. Although these events may have been brief in periodicity from an evolutionary standpoint, multiple episodes of allopatry and divergence have been implicated in rapid radiations of a number of organisms. Shrews of the Sorex cinereus complex have long challenged taxonomists due to similar morphology and parapatric geographic ranges. Here, multi-locus phylogenetic and demographic assessments using a coalescent framework were combined to investigate spatiotemporal evolution of 13 nominal species with a widespread distribution throughout North America and across Beringia into Siberia. For these species, we first test a hypothesis of recent differentiation in response to Pleistocene climate versus more ancient divergence that would coincide with pre-Pleistocene perturbations. We then investigate the processes driving diversification over multiple continents. Our genetic analyses highlight novel diversity within these morphologically conserved mammals and clarify relationships between geographic distribution and evolutionary history. Demography within and among species indicates both regional stability and rapid expansion. Ancestral ecological differentiation coincident with early cladogenesis within the complex enabled alternating and repeated episodes of allopatry and expansion where successive glacial and interglacial phases each promoted divergence. The Sorex cinereus complex constitutes a valuable model for future comparative assessments of evolution in response to cyclic environmental change.

Molecular Phylogenetics and Evolution↗