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USGS2025

Insect pollinator crossing of international border barriers along the U.S.-Mexico border

Infrastructure along the U.S.-Mexico Border may not be equally permeable to all types of insect pollinators with potential implications for pollen and gene flow between plant populations. Pollinators were observed on their approach to two types of border barriers (slatted and cemented) along the U.S.-Mexico Border from March 2023 to January 2024. Near the barrier, four insect behaviors were observed including 1) flying over the barrier, 2) crossing through the slats of the barrier, 3) not crossing the barrier, or 4) flying parallel to the barrier without crossing. Overall, 90.2% of the pollinators crossed the barrier. Butterflies were most often observed flying over the barrier (86.8%) or sometimes moving through the slats in the barrier (6.8%). It was more common for moths to crawl through the slats than to fly over the barrier based on the occurrence model. On windy days, both butterflies and moths sometimes flew parallel to the barrier without crossing (1.2% and 27.3%, respectively), although moth crossing behavior was not related to the abundance model. Butterfly abundance increased in higher temperatures and decreased in higher wind speeds. Other insect pollinators were also observed (bee, skipper, wasp) but their crossing behavior was not significantly related to the model. Because pollinators support endangered plant species, strategies to facilitate their barrier crossing could support plant conservation in South Texas.

Texas↗

USGS2026

Vulnerability of different Colorado Plateau land types to drivers of change

Public lands are challenged by a range of pressures—changing climate, increasing visitation, resource extraction—and their effects can span spatial scales, often crossing land management jurisdictional boundaries. Research approaches which explicitly span jurisdictions can support strategies to contend with regional pressures. We assess management-relevant drivers of change—aridification, livestock grazing, invasive species, surface disturbance, and fire—across a patchwork of land management units and agencies on the Colorado Plateau, focusing on southeastern Utah, USA. We use vulnerability analysis, first evaluating exposure to drivers across the landscape, then quantifying sensitivity to each driver across different land types, defined by mapped Ecological Site Groups, a system for classifying landscapes according to physical factors including climate, soils, and topographic setting. We address the questions: 1) how are drivers spatially distributed across the study region; and, 2) based on exposure and sensitivity, are certain land types more vulnerable to these drivers? We find that the study region has high exposure and sensitivity—and thus high vulnerability—to aridification and grazing, but low exposure and vulnerability to other drivers. Although more sensitive land types were not generally more exposed, identifying which areas are most sensitive can guide adaptive measures, like where new uses or disturbances would be least harmful and which areas could be prioritized for restoration. The method we demonstrate is a flexible tool for assessing landscape-scale impacts, is built on nationally available datasets, and can be tailored to different datasets and sensitivity metrics.

Utah↗

USGS2017

The waterfall paradox: How knickpoints disconnect hillslope and channel processes, isolating salmonid populations in ideal habitats

Waterfalls create barriers to fish migration, yet hundreds of isolated salmonid populations exist above barriers and have persisted for thousands of years in steep mountainous terrain. Ecological theory indicates that small isolated populations in disturbance-prone landscapes are at greatest risk of extirpation because immigration and recolonization are not possible. On the contrary, many above-barrier populations are currently thriving while their downstream counterparts are dwindling. This quandary led us to explore geomorphic knickpoints as a mechanism for disconnecting hillslope and channel processes by limiting channel incision and decreasing the pace of base-level lowering. Using LiDAR from the Oregon Coast Range, we found gentler channel gradients, wider valleys, lower gradient hillslopes, and less shallow landslide potential in an above-barrier catchment compared to a neighboring catchment devoid of persistent knickpoints. Based on this unique geomorphic template, above-barrier channel networks are less prone to debris flows and other episodic sediment fluxes. These above-barrier catchments also have greater resiliency to flooding, owing to wider valleys with greater floodplain connectivity. Habitat preference models further indicate that salmonid habitat is present in greater quantity and quality in these above-barrier networks. Therefore the paradox of the persistence of small isolated fish populations may be facilitated by a geomorphic mechanism that both limits their connectivity to larger fish populations yet dampens the effect of disturbance by decreasing connections between hillslope and channel processes above geomorphic knickpoints.

Geomorphology↗

USGS2016

Recurrent hybridization and recent origin obscure phylogenetic relationships within the ‘white-headed’ gull (Larus sp.) complex

Species complexes that have undergone recent radiations are often characterized by extensive allele sharing due to recent ancestry and (or) introgressive hybridization. This can result in discordant evolutionary histories of genes and heterogeneous genomes, making delineating species limits difficult. Here we examine the phylogenetic relationships among a complex group of birds, the white-headed gulls (Aves: Laridae), which offer a unique window into the speciation process due to their recent evolutionary history and propensity to hybridize. Relationships were examined among 17 species (61 populations) using a multilocus approach, including mitochondrial and nuclear intron DNA sequences and microsatellite genotype information. Analyses of microsatellite and intron data resulted in some species-based groupings, although most species were not represented by a single cluster. Considerable allele and haplotype sharing among white-headed gull species was observed; no locus contained a species-specific clade. Despite this, our multilocus approach provided better resolution among some species than previous studies. Interestingly, most clades appear to correspond to geographic locality: our BEAST analysis recovered strong support for a northern European/Icelandic clade, a southern European/Russian clade, and a western North American/ canus clade, with weak evidence for a high latitude clade spanning North America and northwestern Europe. This geographical structuring is concordant with behavioral observations of pervasive hybridization in areas of secondary contact. The extent of allele and haplotype sharing indicates that ecological and sexual selection are likely not strong enough to complete reproductive isolation within several species in the white-headed gull complex. This suggests that just a few genes are driving the speciation process.

Molecular Phylogenetics and Evolution↗

USGS2001

Cost considerations for long-term ecological monitoring

For an ecological monitoring program to be successful over the long-term, the perceived benefits of the information must justify the cost. Financial limitations will always restrict the scope of a monitoring program, hence the program’s focus must be carefully prioritized. Clearly identifying the costs and benefits of a program will assist in this prioritization process, but this is easier said than done. Frequently, the true costs of monitoring are not recognized and are, therefore, underestimated. Benefits are rarely evaluated, because they are difficult to quantify. The intent of this review is to assist the designers and managers of long-term ecological monitoring programs by providing a general framework for building and operating a cost-effective program. Previous considerations of monitoring costs have focused on sampling design optimization. We present cost considerations of monitoring in a broader context. We explore monitoring costs, including both budgetary costs, what dollars are spent on, and economic costs, which include opportunity costs. Often, the largest portion of a monitoring program budget is spent on data collection, and other, critical aspects of the program, such as scientific oversight, training, data management, quality assurance, and reporting, are neglected. Recognizing and budgeting for all program costs is therefore a key factor in a program’s longevity. The close relationship between statistical issues and cost is discussed, highlighting the importance of sampling design, replication and power, and comparing the costs of alternative designs through pilot studies and simulation modeling. A monitoring program development process that includes explicit checkpoints for considering costs is presented. The first checkpoint occurs during the setting of objectives and during sampling design optimization. The last checkpoint occurs once the basic shape of the program is known, and the costs and benefits, or alternatively the cost-effectiveness, of each program element can be evaluated. Moving into the implementation phase without careful evaluation of costs and benefits is risky because if costs are later found to exceed benefits, the program will fail. The costs of development, which can be quite high, will have been largely wasted. Realistic expectations of costs and benefits will help ensure that monitoring programs survive the early, turbulent stages of development and the challenges posed by fluctuating budgets during implementation.

Ecological Indicators↗

USGS2003

Natural and anthropogenic factors affecting the structure of the benthic macroinvertebrate community in an effluent-dominated reach of the Santa Cruz River, AZ

This study provides an assessment of the ecological conditions of a 46-km effluent-dominated stream section of the Santa Cruz River in the vicinity of the International Waste Water Treatment Plant, Nogales, AZ. We associated changes in the structure of the macroinvertebrate community to natural and anthropogenic chemical and physical variables using multivariate analysis. The analysis shows that biological criteria for effluent-dominated streams can be established using macroinvertebrate community attributes only with an understanding of the contribution of three classes of variables on the community structure: (1) low flow hydrological discharge as affected by groundwater withdrawals, treatment plant discharge, and subsurface geomorphology; (2) chemical composition of the treatment plant discharge and natural dilution; and (3) naturally produced floods resulting from seasonality of precipitation. ?? 2003 Elsevier Science Ltd. All rights reserved.

Ecological Indicators↗

USGS2003

A Benthic Community Index for streams in the Northern Lakes and Forests Ecoregion

Encompassing the northern glaciated section of the Midwest United States, the Northern Lakes and Forests Ecoregion is characterized by mixed conifer and deciduous forests and wetlands. Sites were randomly selected in the ecoregion using the Environmental Protection Agency's Environmental Monitoring and Assessment Program designed to develop an index of biotic integrity for wadeable streams. Macroinvertebrates were sampled during the fall of 1998 and 1999 using a multi-habitat, composite-sample method. Two hundred forty-six invertebrate taxa in 97 families were collected from 94 sites. Ten of 42 candidate metrics satisfied metric selection criteria, including six structural metrics (number of Ephemeroptera taxa, number of Diptera taxa, richness, Shannon-Wiener diversity, percent Trichoptera abundance, and percent Crustacea and Mollusca abundance), two functional metrics (number of Filterer taxa and number of Scraper taxa), and two conditional metrics (number of Ephemeroptera, Trichoptera, and Plecoptera taxa and Hilsenhoff Biotic Index). These metrics were used to develop a Benthic Community Index to assess the biological integrity of wadeable streams in the ecoregion. Index values ranged from 10 to 50, and scores from impaired sites were significantly different than non-impaired sites (P<0.001). Index values were divided into three narrative interpretations of biological integrity (poor, fair, and good). After further testing, the index may provide a useful biological assessment tool for resource managers in the ecoregion.

Ecological Indicators↗

USGS2003

Effects of two classification strategies on a Benthic Community Index for streams in the Northern Lakes and Forests Ecoregion

Ninety-four sites were used to analyze the effects of two different classification strategies on the Benthic Community Index (BCI). The first, a priori classification, reflected the wetland status of the streams; the second, a posteriori classification, used a bio-environmental analysis to select classification variables. Both classifications were examined by measuring classification strength and testing differences in metric values with respect to group membership. The a priori (wetland) classification strength (83.3%) was greater than the a posteriori (bio-environmental) classification strength (76.8%). Both classifications found one metric that had significant differences between groups. The original index was modified to reflect the wetland classification by re-calibrating the scoring criteria for percent Crustacea and Mollusca. A proposed refinement to the original Benthic Community Index is suggested. This study shows the importance of using hypothesis-driven classifications, as well as exploratory statistical analysis, to evaluate alternative ways to reveal environmental variability in biological assessment tools.

Ecological Indicators↗

USGS2006

Firm size diversity, functional richness, and resilience

This paper applies recent advances in ecology to our understanding of firm development, sustainability, and economic development. The ecological literature indicates that the greater the functional richness of species in a system, the greater its resilience - that is, its ability to persist in the face of substantial changes in the environment. This paper focuses on the effects of functional richness across firm size on the ability of industries to survive in the face of economic change. Our results indicate that industries with a richness of industrial functions are more resilient to employment volatility. ?? 2006 Cambridge University Press.

Environment and Development Economics↗

USGS2004

Differences in dissolved cadmium and zinc uptake among stream insects: Mechanistic explanations

This study examined the extent to which dissolved Cd and Zn uptake rates vary in several aquatic insect taxa commonly used as indicators of ecological health. We further attempted to explain the mechanisms underlying observed differences. By comparing dissolved Cd and Zn uptake rates in several aquatic insect species, we demonstrated that species vary widely in these processes. Dissolved uptake rates were not related to gross morphological features such as body size or gill size-features that influence water permeability and therefore have ionoregulatory importance. However, finer morphological features, specifically, the relative numbers of ionoregulatory cells (chloride cells), appeared to be related to dissolved metal uptake rates. This observation was supported by Michaelis-Menten type kinetics experiments, which showed that dissolved Cd uptake rates were driven by the numbers of Cd transporters and not by the affinities of those transporters to Cd. Calcium concentrations in exposure media similarly affected Cd and Zn uptake rates in the caddisfly Hydropsyche californica. Dissolved Cd and Zn uptake rates strongly co-varied among species, suggesting that these metals are transported by similar mechanisms.

Environmental Science & Technology↗

USGS1999

Dissolved oxygen conditions in northern Gulf of Mexico estuaries

Because deficient dissolved oxygen (DO) levels may have severe detrimental effects on estuarine and marine life, DO has been widely used as an indicator of ecological conditions by environmental monitoring programs. The U.S. EPA's Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) monitored DO conditions in the estuaries of the Gulf of Mexico from 1991 to 1994. DO was measured in two ways: 1)instantaneous profiles from the surface to the bottom were taken during the day, and 2) continuous measurements were taken near the bottom at 15 min intervals for at least 12 h. This information was summarized to assess the spatial distribution and severity of DO conditions in these estuaries. Depending on the criteria used to define hypoxia (DO concentrations usually < 2 mg L-1 or 15 mg L-1) and the method by which DO is measured, we estimate that between 5.2 and 29.3% of the total estuarine area in the Louisianian Province was affected by low DO conditions.

Environmental Monitoring and Assessment↗

USGS2016

Species traits and catchment-scale habitat factors influence the occurrence of freshwater mussel populations and assemblages

Conservation of freshwater unionid mussels presents unique challenges due to their distinctive life cycle, cryptic occurrence and imperilled status. Relevant ecological information is urgently needed to guide their management and conservation. We adopted a modelling approach, which is a novel application to freshwater mussels to enhance inference on rare species, by borrowing data among species in a hierarchical framework to conduct the most comprehensive occurrence analysis for freshwater mussels to date. We incorporated imperfect detection to more accurately examine effects of biotic and abiotic factors at multiple scales on the occurrence of 14 mussel species and the entire assemblage of the Tar River Basin of North Carolina, U.S.A. The single assemblage estimate of detection probability for all species was 0.42 (95% CI, 0.36–0.47) with no species- or site-specific detection effects identified. We empirically observed 15 mussel species in the basin but estimated total species richness at 21 (95% CI, 16–24) when accounting for imperfect detection. Mean occurrence probability among species ranged from 0.04 (95% CI, 0.01–0.16) for Alasmidonta undulata, an undescribed Lampsilis sp. , and Strophitus undulatus to 0.67 (95% CI, 0.42–0.86) for Elliptio icterina . Median occurrence probability among sites was <0.30 for all species with the exception of E. icterina . Site occurrence probability generally related to mussel conservation status, with reduced occurrence for endangered and threatened species. Catchment-scale abiotic variables (stream power, agricultural land use) and species traits (brood time, host specificity, tribe) influenced the occurrence of mussel assemblages more than reach- or microhabitat-scale features. Our findings reflect the complexity of mussel ecology and indicate that habitat restoration alone may not be adequate for mussel conservation. Catchment-scale management can benefit an entire assemblage, but species-specific strategies may be necessary for successful conservation. The hierarchical multispecies modelling approach revealed findings that could not be elucidated by other means, and the approach may be applied more broadly to other river basins and regions. Accurate measures of assemblage dynamics, such as occurrence and species richness, are required to create management plans for effective conservation.

Freshwater Biology↗

USGS2007

Restoration of waterbird habitats in Chesapeake Bay: Great expectations or Sisyphus revisited?

In the past half century, many waterbird populations in Chesapeake Bay have declined or shifted ranges, indicating major ecological changes have occurred. While many studies have focused on the problems associated with environmental degradation such as the losses of coastal wetlands and submerged vegetation, a number of restoration efforts have been launched in the past few decades to reverse the "sea of despair." Most pertinent to waterbirds, restoration of submerged aquatic vegetation (SAV) beds, tidal wetland restoration, oyster reef restoration, and island creation/restoration have benefited a number of species. State and federal agencies and non-government agencies have formed partnerships to spawn many projects ranging in size from less than 0.5 ha to ca. 1,000 ha. While most SAV, wetland, and oyster reef projects have struggled to different degrees over the past ten to twenty years with inconsistent methods, irregular monitoring, and unknown reasons for failures, recent improvements in techniques and application of adaptive management have been made. The large dredge-material island projects at Hart-Miller Island near Baltimore, Poplar Island west of Tilghman Island, Maryland, and Craney Island in Portsmouth, Virginia have provided large outdoor "laboratories" for wildlife, fishery, and wetland habitat creation. All three have proven to be important for nesting waterbirds and migrant shorebirds and waterfowl; however nesting populations at all three islands have been compromised to different degrees by predators. Restoration success for waterbirds and other natural resources depends on: (1) establishing realistic, quantifiable objectives and performance criteria, (2) continued monitoring and management (e.g., predator control), (3) targeted research to determine causality, and (4) careful evaluation under an adaptive management regime.

Waterbirds↗

USGS1994

Persistence of metals in soil and selected vertebrates in the vicinity of the Palmerton zinc smelters

Concentration of Cd, Pb, Zn, and Cu in soil and wildlife at the Palmerton zinc smelter site in eastern Pennsylvania were determined 6 yr after zinc smelting was terminated in 1980. Levels of the four metals were higher in litter (01 and 02 horizon) than in soil (A1 horizon), and the metals were at or near levels when the smelters were still in operation. Levels of metals in soil were highest at sites close to the smelters and decreased as distances from the smelters increased. The relation of decreasing amounts of metals in body tissues with increasing distance from the smelters also held true for amphibians and mammals. An exception to this relation was higher level of Cu in red‐backed salamanders ( Plethodon cinereus ) captured ≈17 km downwind than those captured ≈12 km downwind. Levels of Zn, Pb, and Cu in liver, kidney, and muscle tissue of white‐footed mice ( Peromyscus leucopus ) were not different ( P > 0.05) which is reportedly considered an indication of environmental contamination. Levels of Cd in kidneys and liver of white‐tailed deer ( Odocoileus virginianus ) at Palmerton were five times higher than those for whitetailed deer collected 180 km southwest of Palmerton in southcentral Pennsylvania. The abnormal amounts of metals in the tissues of terrestrial vertebrates, and the absence or low abundance of wildlife at Palmerton indicated that ecological processes within 5 km of the smelters were markedly influenced 6 yr after zinc smelting was discontinued.

Pennsylvania↗

USGS2006

Users' manual for the Hydroecological Integrity Assessment Process software (including the New Jersey Assessment Tools)

This manual is a user’s guide to four computer software tools that have been developed for the Hydroecological Integrity Assessment Process. The Hydroecological Integrity Assessment Process recognizes that streamflow is strongly related to many critical physiochemical components of rivers, such as dissolved oxygen, channel geomorphology, and water temperature, and can be considered a “master variable” that limits the disturbance, abundance, and diversity of many aquatic plant and animal species. Applying the Hydroecological Integrity Assessment Process involves four steps: (1) a hydrologic classification of relatively unmodified streams in a geographic area using long-term gage records and 171 ecologically relevant indices; (2) the identification of statistically significant, nonredundant, hydroecologically relevant indices associated with the five major flow components for each stream class; and (3) the development of a stream-classification tool and a hydrologic assessment tool. Four computer software tools have been developed.

Open-File Report↗

USGS2016

Hydrothermal vents and methane seeps: Rethinking the sphere of influence

Although initially viewed as oases within a barren deep ocean, hydrothermal vent and methane seep communities are now recognized to interact with surrounding ecosystems on the sea floor and in the water column, and to affect global geochemical cycles. The importance of understanding these interactions is growing as the potential rises for disturbance from oil and gas extraction, seabed mining and bottom trawling. Here we synthesize current knowledge of the nature, extent and time and space scales of vent and seep interactions with background systems. We document an expanded footprint beyond the site of local venting or seepage with respect to elemental cycling and energy flux, habitat use, trophic interactions, and connectivity. Heat and energy are released, global biogeochemical and elemental cycles are modified, and particulates are transported widely in plumes. Hard and biotic substrates produced at vents and seeps are used by “benthic background” fauna for attachment substrata, shelter, and access to food via grazing or through position in the current, while particulates and fluid fluxes modify planktonic microbial communities. Chemosynthetic production provides nutrition to a host of benthic and planktonic heterotrophic background species through multiple horizontal and vertical transfer pathways assisted by flow, gamete release, animal movements, and succession, but these pathways remain poorly known. Shared species, genera and families indicate that ecological and evolutionary connectivity exists among vents, seeps, organic falls and background communities in the deep sea; the genetic linkages with inactive vents and seeps and background assemblages however, are practically unstudied. The waning of venting or seepage activity generates major transitions in space and time that create links to surrounding ecosystems, often with identifiable ecotones or successional stages. The nature of all these interactions is dependent on water depth, as well as regional oceanography and biodiversity. Many ecosystem services are associated with the interactions and transitions between chemosynthetic and background ecosystems, for example carbon cycling and sequestration, fisheries production, and a host of non-market and cultural services. The quantification of the sphere of influence of vents and seeps could be beneficial to better management of deep-sea environments in the face of growing industrialization.

Frontiers in Marine Science↗

USGS2021

Establishment and survival of subalpine fir (Abies lasiocarpa) in meadows of Olympic National Park, Washington

Establishment of trees in subalpine meadows is a potential indicator of ecological effects of climate change. Tree establishment is a multi-year process including cone and seed production, germination, establishment, and growth, with each demographic step possibly sensitive to different climate limitations. While most studies have focused on one or a few steps, this study follows a cohort of individually marked saplings for 27 years beginning as seeds in two meadows on Hurricane Ridge, Olympic National Park. These meadows are examples of a south-facing tall sedge community type rather than the north-facing heath-shrub type where establishment has usually been observed. Results showed that mortality was high for the first few years, but number of saplings stabilized after the first decade. Seedling mortality during germination and establishment was directly related to weather that resulted in high air and soil temperatures and drought, while mortality of established saplings was indirectly related to weather through effects on growth. Growth was enhanced by longer growing season and warmer minimum temperatures; growth over three years and sapling height were predictive of mortality. Most sapling survival occurred in lichen (primarily Trapeliopsis granulosa ) and Vaccinium deliciosum plant communities. Many saplings are growing at very low rates compared with the rate predicted from adult trees. It is also apparent that while microsite within meadow (e.g., relative snow depth) is important in determining sapling success, the landscape position of meadows (e.g., north versus south aspect) exerts a higher-level control over whether a subalpine meadow is likely to disappear with warming climate.

Washington↗

USGS1992

A review of differentiation in Great Lakes ciscoes

Seven species of ciscoes (Coregonus, subgenus Leucichthys) were found in the Great Lakes as recently as the early 1950's. Variation within and among species of Great Lakes ciscoes indicates that much of the divergence occurred within lakes. Following postglacial colonization by perhaps two or three species, population differentiation began with homing and reproduction at different localities and times. Physiological interaction between temperature (depth) and maturation time, as well as behavioral tendencies to home to spawning grounds and mate with related individuals, are the basis of premating reproductive separation. Phenotypic differences between populations indicate that ecological character displacement has been an important mechanism in the divergence. Introgression has obscured morphological species boundaries at the same time as intralacustrine speciation has created local subgroups, providing an unresolvable conflict between species definitions based on morphological and other characters and definitions dominated by inferred reproductive isolation. Species should be considered as the smallest diagnosable units within a phylogenetic framework, in which diagnoses are strictly by derived characters. Ecological and seasonal species could be recognized by application of a trinomial, equivalent to the subspecies trinomial.

Polskie Archiwum Hydrobiologii↗