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Results for “Ecological Complexity”

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At least 541 records · Page 30Linked to original sources
USGS2019

Revisiting the historic distribution and habitats of the Whooping Crane

The endangered Whooping Crane ( Grus americana ) historically had a wide distribution that covered diverse ecoregions across North America while retaining consistent habitat preferences within each ecoregion. We reevaluate the historic information compiled by Robert Porter Allen in 1952 and added 74 other records. Based on the ecological features of historic locations relative to crane life history, we revisit Allen’s description of the whooping crane’s niche and identify four features common to breeding and wintering areas: (1) gentle to rolling topography with an interspersion of wetland and prairie habitats, and relatively sparse cover of trees and shrubs; (2) high densities of shallow, open wetlands or wetland complexes; (3) hydrological regimes that provide reliable conditions for nesting, brood rearing, and flightless adults; and (4) high plant and animal productivity due to fertile soils, hydrological pulsing, periodic inflow of nutrients, or other periodic perturbations. Accurate determination of the ecological features that compose Whooping Crane habitats should stimulate renewed discussions about habitat requirements and can support development of improved reintroduction strategies for the long-term success of recovery efforts.

Book chapter↗
USGS2024

Origin of the Laurentian Great Lakes fish fauna through upward adaptive radiation cascade prior to the Last Glacial Maximum

The evolutionary histories of adaptive radiations can be marked by dramatic demographic fluctuations. However, the demographic histories of ecologically-linked co-diversifying lineages remain understudied. The Laurentian Great Lakes provide a unique system of two such radiations that are dispersed across depth gradients with a predator-prey relationship. We show that the North American Coregonus species complex (“ciscoes”) radiated rapidly prior to the Last Glacial Maximum (80–90 kya), a globally warm period, followed by rapid expansion in population size. Similar patterns of demographic expansion were observed in the predator species, Lake Charr ( Salvelinus namaycush ), following a brief time lag, which we hypothesize was driven by predator-prey dynamics. Diversification of prey into deep water created ecological opportunities for the predators, facilitating their demographic expansion, which is consistent with an upward adaptive radiation cascade. This study provides a new timeline and environmental context for the origin of the Laurentian Great Lakes fish fauna, and firmly establishes this system as drivers of ecological diversification and rapid speciation through cyclical glaciation.

Communications Biology↗
USGS2006

Model weights and the foundations of multimodel inference

Statistical thinking in wildlife biology and ecology has been profoundly influenced by the introduction of AIC (Akaike?s information criterion) as a tool for model selection and as a basis for model averaging. In this paper, we advocate the Bayesian paradigm as a broader framework for multimodel inference, one in which model averaging and model selection are naturally linked, and in which the performance of AIC-based tools is naturally evaluated. Prior model weights implicitly associated with the use of AIC are seen to highly favor complex models: in some cases, all but the most highly parameterized models in the model set are virtually ignored a priori. We suggest the usefulness of the weighted BIC (Bayesian information criterion) as a computationally simple alternative to AIC, based on explicit selection of prior model probabilities rather than acceptance of default priors associated with AIC. We note, however, that both procedures are only approximate to the use of exact Bayes factors. We discuss and illustrate technical difficulties associated with Bayes factors, and suggest approaches to avoiding these difficulties in the context of model selection for a logistic regression. Our example highlights the predisposition of AIC weighting to favor complex models and suggests a need for caution in using the BIC for computing approximate posterior model weights.

Ecology↗
USGS1995

Modeling and predicting intertidal variations of the salinity field in the Bay/Delta

San Francisco Bay and the Sacramento/San Joaquin Delta have challenged estuarine modelers for some years. Accurate, broad-scale models of this estuary have been in demand by those concerned with its ecological health and the development of sound management policies. A description and better understanding of the dynamics that govern the bay/delta are complicated by the system's complexity, requiring models that are sophisticated enough to capture the subtle physical processes involved. One approach to simulating daily to monthly variability in the bay is the development of intertidal model using tidally-averaged equations and a time step on the order of the day. An intertidal numerical model of the bay's physics, capable of portraying seasonal and inter-annual variability, would have several uses. Observations are limited in time and space, so simulation could help fill the gaps. Also, the ability to simulate multi-year episodes (eg, an extended drought) could provide insight into the response of the ecosystem to such events. Finally, such a model could be used in a forecast mode wherein predicted delta flow is used as model input, and predicted salinity distribution is output with estimates days and months in advance. This note briefly introduces such a tidally-averaged model (Uncles and Peterson, in press) and a corresponding predictive scheme for baywide forecasting.

California↗
USGS2005

The ecological - Societal underpinnings of Everglades restoration

The biotic integrity of the Florida Everglades, a wetland of immense international importance, is threatened as a result of decades of human manipulation for drainage and development. Past management of the system only exacerbated the problems associated with nutrient enrichment and disruption of regional hydrology. The Comprehensive Everglades Restoration Plan (CERP) now being implemented by Federal and State governments is an attempt to strike a balance between the needs of the environment with the complex management of water and the seemingly unbridled economic growth of southern Florida. CERP is expected to reverse negative environmental trends by "getting the water right", but successful Everglades restoration will require both geochemical and hydrologic intervention on a massive scale. This will produce ecological trade-offs and will require new and innovative scientific measures to (1) reduce total phosphorus concentrations within the remaining marsh to 10 ??g/L or lower; (2) quantify and link ecological benefits to the restoration of depths, hydroperiods, and flow velocities; and (3) compensate for ecological, economic, and hydrologic uncertainties in the CERP through adaptive management. ?? The Ecological Society of America.

Conference Paper↗
USGS2022

Balancing model generality and specificity in management-focused habitat selection models for Gunnison sage-grouse

Identifying, protecting, and restoring habitats for declining wildlife populations is foundational to conservation and recovery planning for any species at risk of decline. Resource selection analysis is a key tool to assess habitat and prescribe management actions. Yet, it can be challenging to map suitable resource conditions across a wide range of ecological contexts and use the resulting models to identify effective and universal habitat improvement actions. We developed a management-centric modeling approach that sought to balance the need to evaluate the consistency of key habitat conditions and improvement actions across multiple, distinct populations, while allowing context-specific environmental variables and spatial scales to nuance selection responses that form the basis of location-specific management prescriptions. To demonstrate this approach, we developed a set of habitat selection models for Gunnison sage-grouse ( Centrocercus minimus ), a threatened species under the U.S. Endangered Species Act. Conservation, species recovery, and habitat management efforts are needed in six isolated satellite populations (San Miguel, Crawford, Piñon Mesa, Dove Creek, Cerro Summit-Cimarron-Sims, and Poncha Pass) where environmental conditions differ, and the already small number of birds are declining. We used multi-scale and seasonal resource selection analyses to quantify relationships between environmental conditions and sites used by animals. All models included key habitat variables often altered through management actions to assess their differential influences across models. We found important similarities and differences among satellites, indicating that, although some rules of thumb are generally well-grounded, the consideration of population-specific environmental differences could increase the efficiency of local habitat improvement actions. Sage-grouse also had diverse responses to resource conditions at different scales, indicating that regional spatial (e.g., landscape) and local patch scale can differentially influence expected habitat improvements associated with where such management actions are implemented. Although context variables such as topography cannot be manipulated, sage-grouse associations revealed information that could guide the siting of improvement actions. This approach to balancing management objectives associated with habitat assessment may benefit spatially-structured populations with different environmental contexts and species with complex habitat needs and associations.

Colorado↗
USGS2016

Application of effective discharge analysis to environmental flow decision-making

Well-informed river management decisions rely on an explicit statement of objectives, repeatable analyses, and a transparent system for assessing trade-offs. These components may then be applied to compare alternative operational regimes for water resource infrastructure (e.g., diversions, locks, and dams). Intra- and inter-annual hydrologic variability further complicates these already complex environmental flow decisions. Effective discharge analysis (developed in studies of geomorphology) is a powerful tool for integrating temporal variability of flow magnitude and associated ecological consequences. Here, we adapt the effectiveness framework to include multiple elements of the natural flow regime (i.e., timing, duration, and rate-of-change) as well as two flow variables. We demonstrate this analytical approach using a case study of environmental flow management based on long-term (60 years) daily discharge records in the Middle Oconee River near Athens, GA, USA. Specifically, we apply an existing model for estimating young-of-year fish recruitment based on flow-dependent metrics to an effective discharge analysis that incorporates hydrologic variability and multiple focal taxa. We then compare three alternative methods of environmental flow provision. Percentage-based withdrawal schemes outcompete other environmental flow methods across all levels of water withdrawal and ecological outcomes.

Environmental Management↗
USGS2024

High-quality, chromosome-level reference genomes of the viviparous Caribbean skinks Spondylurus nitidus and S. culebrae

New World mabuyine skinks are a diverse radiation of morphologically cryptic lizards with unique reproductive biologies. Recent studies examining population-level data (morphological, ecological, and genomic) have uncovered novel biodiversity and phenotypes, including the description of dozens of new species and insights into the evolution of their highly complex placental structures. Beyond the potential for this diverse group to serve as a model for the evolution of viviparity in lizards, much of the taxonomic diversity is concentrated in regions experiencing increasing environmental instability from climate and anthropogenic change. Consequently, a better understanding of genome structure and diversity will be an important tool in the adaptive management and conservation of this group. Skinks endemic to Caribbean islands are particularly vulnerable to global change with several species already considered likely extinct and several remaining species either endangered or threatened. Combining PacBio long-read sequencing, Hi-C, and RNAseq data, here we present the first genomic resources for this group by describing new chromosome-level reference genomes for the Puerto Rican Skink Spondylurus nitidus and the Culebra Skink S. culebrae . Results indicate two high quality genomes, both ∼1.4 Gb, assembled nearly telomere to telomere with complete mitochondrion assembly and annotation.

Genome Biology and Evolution↗
USGS2011

Proactive aquatic ecotoxicological assessment of room-temperature ionic liquids

Aquatic environments are being contaminated with a myriad of anthropogenic chemicals, a problem likely to continue due to both unintentional and intentional releases. To protect valuable natural resources, novel chemicals should be shown to be environmentally safe prior to use and potential release into the environment. Such proactive assessment is currently being applied to room-temperature ionic liquids (ILs). Because most ILs are water-soluble, their effects are likely to manifest in aquatic ecosystems. Information on the impacts of ILs on numerous aquatic organisms, focused primarily on acute LC50 and EC50 endpoints, is now available, and trends in toxicity are emerging. Cation structure tends to influence IL toxicity more so than anion structure, and within a cation class, the length of alkyl chain substituents is positively correlated with toxicity. While the effects of ILs on several aquatic organisms have been studied, the challenge for aquatic toxicology is now to predict the effects of ILs in complex natural environments that often include diverse mixtures of organisms, abiotic conditions, and additional stressors. To make robust predictions about ILs will require coupling of ecologically realistic laboratory and field experiments with standard toxicity bioassays and models. Such assessments would likely discourage the development of especially toxic ILs while shifting focus to those that are more environmentally benign. Understanding the broader ecological effects of emerging chemicals, incorporating that information into predictive models, and conveying the conclusions to those who develop, regulate, and use those chemicals, should help avoid future environmental degradation.

Current Organic Chemistry↗
USGS2015

Age, growth rates, and paleoclimate studies of deep sea corals

Deep-water corals are some of the slowest growing, longest-lived skeletal accreting marine organisms. These habitat-forming species support diverse faunal assemblages that include commercially and ecologically important organisms. Therefore, effective management and conservation strategies for deep-sea corals can be informed by precise and accurate age, growth rate, and lifespan characteristics for proper assessment of vulnerability and recovery from perturbations. This is especially true for the small number of commercially valuable, and potentially endangered, species that are part of the black and precious coral fisheries (Tsounis et al. 2010). In addition to evaluating time scales of recovery from disturbance or exploitation, accurate age and growth estimates are essential for understanding the life history and ecology of these habitat-forming corals. Given that longevity is a key factor for population maintenance and fishery sustainability, partly due to limited and complex genetic flow among coral populations separated by great distances, accurate age structure for these deep-sea coral communities is essential for proper, long-term resource management.

Report↗
USGS2002

Development of oak plantations established for wildlife

Extensive areas that are currently in agricultural production within the Mississippi Alluvial Valley are being restored to bottomland hardwood forests. Oaks (Quercus sp.), sown as seeds (acorns) or planted as seedlings, are the predominant trees established on most afforested sites. To compare stand development and natural invasion on sites afforested by planting seedlings or by sowing acorns, we sampled woody vegetation on ten 14- to 18-year-old oak plantations established to provide wildlife habitat. Stem densities of about 900 oaks/ha were comparable between stands established by sowing 4000 acorns/ha and stands established by planting 900 seedlings/ha. Densities of oaks in stands established from seedlings increased 38% from densities detected when these stands were 4- to 8-year-old. Densities of oaks established from field-sown acorns increased >100% during this same 10-year span. Oaks that were planted as seedlings were larger than those established from acorns, but trees resulting from either afforestation method were larger than trees naturally colonizing these sites. Natural invasion of woody species varied greatly among afforested sites, but was greater and more diverse on sites sown with acorns. Afforested stands were dominated by planted species, whereas naturally invading species were rare among dominant canopy trees. When afforestation objectives are primarily to provide wildlife habitat, we recommend, sowing acorns rather than planting seedlings. Additionally, planting fewer seeds or seedlings, diversifying the species planted, and leaving non-planted gaps will increase diversity of woody species and promote a more complex forest structure that enhances the suitability of afforested sites for wildlife.

Forest Ecology and Management↗
USGS2013

Response of walleye and yellow perch to water-level fluctuations in glacial lakes

The influence of water levels on population characteristics of yellow perch, Perca flavescens (Mitchill), and walleye, Sander vitreus (Mitchill), was evaluated across a range of glacial lakes in north-eastern South Dakota, USA. Results showed that natural variation in water levels had an important influence on frequently measured fish population characteristics. Yellow perch abundance was significantly ( P < 0.10) greater during elevated water levels. Yellow perch size structure, as indexed by the proportional size distribution of quality- and preferred-length fish (PSD and PSD-P), was significantly greater during low-water years, as was walleye PSD. Mean relative weight of walleye increased significantly during high-water periods. The dynamic and unpredictable nature of water-level fluctuations in glacial lakes ultimately adds complexity to management of these systems.

South Dakota↗
USGS1998

The role of introduced species in the degradation of island ecosystems: A case history of Guam

The accidental introduction of the brown treesnake ( Boiga irregularis ) on Guam around 1950 induced a cascade of extirpations that may be unprecedented among historical extinction events in taxonomic scope and severity. Birds, bats, and reptiles were affected, and by 1990 most forested areas on Guam retained only three native vertebrates, all of which were small lizards. Of the hypotheses to account for the severity of this extinction event, we find some support for the importance of lack of coevolution between introduced predator and prey, availability of alternate prey, extraordinary predatory capabilities of the snake, and vulnerabilities of the Guam ecosystem. In addition, there were important interactions among these factors, especially the presence of introduced prey (possessing coevolutionary experience) that were thus able to maintain their populations and provide alternate prey to the introduced predator while it was driving the native prey species to extinction. This complex of vulnerabilities is common on oceanic islands.

Annual Review of Ecology and Systematics↗
USGS2016

Bayesian cross-validation for model evaluation and selection, with application to the North American Breeding Bird Survey

The analysis of ecological data has changed in two important ways over the last 15 years. The development and easy availability of Bayesian computational methods has allowed and encouraged the fitting of complex hierarchical models. At the same time, there has been increasing emphasis on acknowledging and accounting for model uncertainty. Unfortunately, the ability to fit complex models has outstripped the development of tools for model selection and model evaluation: familiar model selection tools such as Akaike's information criterion and the deviance information criterion are widely known to be inadequate for hierarchical models. In addition, little attention has been paid to the evaluation of model adequacy in context of hierarchical modeling, i.e., to the evaluation of fit for a single model. In this paper, we describe Bayesian cross-validation, which provides tools for model selection and evaluation. We describe the Bayesian predictive information criterion and a Bayesian approximation to the BPIC known as the Watanabe-Akaike information criterion. We illustrate the use of these tools for model selection, and the use of Bayesian cross-validation as a tool for model evaluation, using three large data sets from the North American Breeding Bird Survey.

Ecology↗
USGS2014

Mercury in fishes from 21 national parks in the Western United States: inter- and intra-park variation in concentrations and ecological risk

Mercury (Hg) is a global contaminant and human activities have increased atmospheric Hg concentrations 3- to 5-fold during the past 150 years. This increased release into the atmosphere has resulted in elevated loadings to aquatic habitats where biogeochemical processes promote the microbial conversion of inorganic Hg to methylmercury, the bioavailable form of Hg. The physicochemical properties of Hg and its complex environmental cycle have resulted in some of the most remote and protected areas of the world becoming contaminated with Hg concentrations that threaten ecosystem and human health. The national park network in the United States is comprised of some of the most pristine and sensitive wilderness in North America. There is concern that via global distribution, Hg contamination could threaten the ecological integrity of aquatic communities in the parks and the wildlife that depends on them. In this study, we examined Hg concentrations in non-migratory freshwater fish in 86 sites across 21 national parks in the Western United States. We report Hg concentrations of more than 1,400 fish collected in waters extending over a 4,000 kilometer distance, from Alaska to the arid Southwest. Across all parks, sites, and species, fish total Hg (THg) concentrations ranged from 9.9 to 1,109 nanograms per gram wet weight (ng/g ww) with a mean of 77.7 ng/g ww. We found substantial variation in fish THg concentrations among and within parks, suggesting that patterns of Hg risk are driven by processes occurring at a combination of scales. Additionally, variation (up to 20-fold) in site-specific fish THg concentrations within individual parks suggests that more intensive sampling in some parks will be required to effectively characterize Hg contamination in western national parks. Across all fish sampled, only 5 percent had THg concentrations exceeding a benchmark (200 ng/g ww) associated with toxic responses within the fish themselves. However, Hg concentrations in 35 percent of fish sampled were above a benchmark for risk to highly sensitive avian consumers (90 ng/g ww), and THg concentrations in 68 percent of fish sampled were above exposure levels recommended by the Great Lakes Advisory Group (50 ng/g ww) for unlimited consumption by humans. Of the fish assessed for risk to human consumers (that is, species that are large enough to be consumed by recreational or subsistence anglers), only one individual fish from Yosemite National Park had a muscle Hg concentration exceeding the benchmark (950 ng/g ww) at which no human consumption is advised. Zion, Capital Reef, Wrangell-St. Elias, and Lake Clark National Parks all contained sites in which most fish exceeded benchmarks for the protection of human and wildlife health. This finding is particularly concerning in Zion and Capitol Reef National Parks because the fish from these parks were speckled dace, a small, invertebrate-feeding species, yet their Hg concentrations were as high or higher than those in the largest, long-lived predatory species, such as lake trout. Future targeted research and monitoring across park habitats would help identify patterns of Hg distribution across the landscape and facilitate management decisions aimed at reducing the ecological risk posed by Hg contamination in sensitive ecosystems protected by the National Park Service.

Alaska;Arizona;California;Colorado;Idaho;Montana;N↗
USGS2024

Evidence on the ecological and physical effects of built structures in shallow, tropical coral reefs: A systematic map

Shallow, tropical coral reefs face compounding threats from climate change, habitat degradation due to coastal development and pollution, impacts from storms and sea-level rise, and pulse disturbances like blast fishing, mining, dredging, and ship groundings that reduce reef height and complexity. One approach toward restoring coral reef physical structure from such impacts is deploying built structures of artificial, natural, or hybrid (both artificial and natural) origin. Built structures range from designed modules and repurposed materials to underwater sculptures and intentionally placed natural rocks. Restoration practitioners and coastal managers increasingly consider incorporating – and in many cases have already begun to incorporate – built structures into coral reef-related applications, yet synthesized evidence on the ecological (coral-related; e.g., coral growth, coral survival) and physical performance of built structures in coral ecosystems across a variety of contexts (e.g., restoration, coastal protection, mitigation, tourism) is not readily available to guide decisions. To help fill this gap and inform management decisions, we systematically mapped the global distribution and abundance of published evidence on the ecological (coral-related) and physical performance of built structure interventions in shallow (≤ 30 m), tropical (35°N to 35°S) coral ecosystems.

Environmental Evidence↗
USGS1999

Assessing biological effects from highway-runoff constituents

Increased emphasis on evaluation of nonpoint-source pollution has intensified the need for techniques that can be used to discern the toxicological effects of complex chemical mixtures. In response, the use of biological assessment techniques is receiving increased regulatory emphasis. When applied with documented habitat assessment and chemical analysis, these techniques can increase our understanding of the influence of environmental contaminants on the biological integrity and ecological function of aquatic communities. The contaminants of greatest potential concern in highway runoff are those that arise from highway construction, maintenance, and use. The major contaminants of interest are deicers; nutrients; metals; petroleum-related organic compounds, such as polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethylbenzene, and xylene (BTEX), and methyl tert -butyl ether (MTBE); sediment washed off the road surface; and agricultural chemicals used in highway maintenance. Hundreds, if not thousands, of biological endpoints (measurable responses of living organisms) may be either directly or associatively affected by contaminant exposure. Measurable effects can occur throughout ecosystem processes across the wide range of biological complexity, ranging from responses at the biochemical level to the community level. The challenge to the environmental scientist is to develop an understanding of the relationship of effects at various levels of biological organization in order to determine whether a causal relationship exists between chemical exposure and substantial ecological impairment. This report provides a brief history of the evolution of biological assessment techniques, a description of the major classes of contaminants that are of particular interest in highway runoff, an overview of representative biological assessment techniques, and a discussion of data-quality considerations. Published reports with a focus on the effects of highway runoff on the local ecosystem were reviewed to provide information on (1) the suitability of the existing data for a quantitative national synthesis, (2) the methods available to study the effects of highway runoff on local ecosystems, and (3) the potential for adverse effects on the roadside environment and receiving waters. Although many biological studies have been done, the use of different methods and a general lack of sufficient documentation precludes a quantitative national synthesis on the basis of the existing data. The Federal Highway Administration, the U.S. Environmental Protection Agency, the U.S. Geological Survey, the Intergovernmental Task Force on Monitoring Water Quality, and the National Resources Conservation Service all have developed and documented methods for assessing the effects of contaminants on ecosystems in receiving waters. These published methods can be used to formulate a set of protocols to provide consistent information from highway-runoff studies. Review of the literature indicates (qualitatively) that highway runoff (even from highways with high traffic volume) may not usually be acutely toxic. Tissue analysis and community assessments, however, indicate effects from highway- runoff sediments near discharge points (even from sites near highways with relatively low traffic volumes). At many sites, elevated concentrations of highway-runoff constituents were measured in tissues of species associated with aquatic sediments. Community assessments also indicate decreases in the diversity and productivity of aquatic ecosystems at some sites receiving highway runoff. These results are not definitive, however, and depend on many site-specific criteria that were not sufficiently documented in most of the studies reviewed.

Open-File Report↗
USGS2003

Amphibian decline: An integrated analysis of multiple stressor effects

Capturing the attention and imagination of the public and the scientific community alike, the mysterious decline in amphibian populations drew scientists and resource managers from ecotoxicology and chemistry, ecology and field biology, conservation biology, and natural resource policy to a SETAC–Johnson Foundation workshop. Facilitating environmental stewardship, increasing capacity of the sciences to explain complex stressors, and educating the public on relationships among communities of all types motivated these experts to address amphibian decline and the role of various stressors in these losses.

Book↗