Geology topics

Adrianne Brand

Publications and source records attributed to Adrianne Brand.

13 recordsLinked to original sources

USGS2025

The value of reducing uncertainties to support the management of a high‐elevation endemic salamander

Many salamander populations are declining, and methods to determine how best to allocate limited resources to slow or reverse these declines could support land managers in their decision‐making processes. Multiple types of uncertainty may delay management decisions, including when (1) knowledge of a species' ecology is incomplete, (2) climate change effects on environmental covariates are uncertain, and (3) the efficacy of management alternatives is unknown. For management decisions, a value‐of‐information analysis can identify which uncertainties are critical to reduce in order to identify an optimal strategy from a set of possible management actions. If the same management action is optimal across the full range of uncertainties, then resources for research can be redirected toward active management. Using value‐of‐information analyses, we examine the effect of uncertainty on identifying optimal management to maximize the future expected occupancy of Plethodon shenandoah , a Federally Endangered high‐elevation endemic salamander that is threatened by climate change. Out of 11 management actions proposed by National Park Service managers, those that increase environmental moisture are expected to maximize occupancy, and we find that the selection of this action is robust to all the identified uncertainties. We show that, even in systems with multiple sources of large uncertainty, value of information analyses discriminate among investments in species management.

Ecosphere↗

USGS2025

Pan-amphibia distribution of the fungal parasite Batrachochytrium dendrobatidis varies with species and temperature

Batrachochytrium dendrobatidis (Bd) is a globally distributed fungal pathogen of amphibians that has contributed to one of the largest disease-related biodiversity losses in wildlife. Bd is regularly viewed through the lens of a global wildlife epizootic because the spread of highly virulent genetic lineages has resulted in well-documented declines and extinctions of multiple amphibian species. However, the current state of Bd occurrence, host range, host impacts, and ecological drivers remains poorly understood outside of the most negatively affected amphibian species and regions. Our objective was to describe the macroecology of Bd occurrence and infection intensity on caudates (salamanders) across the United States and to compare these patterns with better-studied anurans (frogs and toads). We collected swabs from 11,183 amphibians at 609 sites from 54 species across the United States from 2015 to 2017. We analyzed the prevalence and intensity of Bd infection jointly using a Bayesian hurdle model with covariates of site-level temperature and precipitation, as well as individual characteristics and species identification. Bd was distributed widely across sites and species sampled across the spatial extent of the conterminous United States. We found that Bd prevalence and intensity were most strongly influenced by temperature in the month preceding sampling and by differences among taxon groups. We estimated that temperature had a strong and nonlinear influence on both Bd prevalence and intensity with peak infection at intermediate temperatures and lower infection at low and high temperatures. We found Caudate hosts tended to have higher prevalence than Anuran hosts and Anuran hosts tended to have higher intensity at optimal temperatures for Bd infection. Our findings suggest that Bd has an amphibian-wide host range, temperature gradients exert a strong influence on Bd, and enzootic transmission likely encompasses a much larger spatial and species distribution than previously recognized across North America.

conterminous United States↗

USGS2024

Reducing uncertainty with iterative model updating parses effects of competition and environment on salamander occupancy

Making timely management decisions is often hindered by uncertainty. Monitoring reduces two key types of uncertainty. First, it serves to reduce structural uncertainty of how the system works and provides support for expectations of how a system works. Second, it serves to reduce parametric uncertainty of the drivers of system dynamics. By combining monitoring data and quantitative models, we can reduce structural and parametric uncertainty. To demonstrate this, we focus on the Shenandoah salamander ( Plethodon shenandoah ), a United States Federally Endangered Species. Early work suggested that P. shenandoah extinction risk results from competition with a conspecific ( Plethodon cinereus ). However, more recent work has found equivocal support for this claim, instead suggesting that abiotic factors, such as moisture and temperature, drive P. shenandoah persistence. Using long-term monitoring data, we find that while competition may play a part in P. shenandoah extinction risk, measures of surface moisture are better predictors of occupancy dynamics. Further, we find decreased detection rates of P. shenandoah when P. cinereus is present, suggesting a conflation of detection probability with actual competition, which cautions against making inference from unadjusted observations of occurrence. Using multiple lines of inquiry allows for more robust understanding of system drivers in the face of high uncertainty, increasing opportunities to manage extinction risk.

Virginia↗

USGS2024

Range-wide salamander densities reveal a key component of terrestrial vertebrate biomass in eastern North American forests

Characterizing the population density of species is a central interest in ecology. Eastern North America is the global hotspot for biodiversity of plethodontid salamanders, an inconspicuous component of terrestrial vertebrate communities, and among the most widespread is the eastern red-backed salamander, Plethodon cinereus . Previous work suggests population densities are high with significant geographic variation, but comparisons among locations are challenged by lack of standardization of methods and failure to accommodate imperfect detection. We present results from a large-scale research network that accounts for detection uncertainty using systematic survey protocols and robust statistical models. We analysed mark–recapture data from 18 study areas across much of the species range. Estimated salamander densities ranged from 1950 to 34 300 salamanders ha −1 , with a median of 9965 salamanders ha −1 . We compared these results to previous estimates for P. cinereus and other abundant terrestrial vertebrates. We demonstrate that overall the biomass of P. cinereus , a secondary consumer, is of similar or greater magnitude to widespread primary consumers such as white-tailed deer ( Odocoileus virginianus ) and Peromyscus mice, and two to three orders of magnitude greater than common secondary consumer species. Our results add empirical evidence that P. cinereus , and amphibians in general, are an outsized component of terrestrial vertebrate communities in temperate ecosystems.

Biology Letters↗

USGS2024

Updated range map of an endangered salamander and congeneric competitor reveals different niche preferences

Estimating distributions for cryptic and highly range-restricted species induces unique challenges for species distribution modeling. In particular, bioclimatic covariates that are typically used to model species ranges at regional and continental scales may not show strong variation at scales of 100s and 10s of meters. This limits both the likelihood and usefulness of correlated occurrence to data typically used in distribution models. Here, we present analyses of species distributions, at 100 × 100 m resolution, for a highly range restricted salamander species (Shenandoah salamander, Plethodon shenandoah ) and a closely related congener (red-backed salamander, Plethodon cinereus ). We combined data across multiple survey types, account for seasonal variation in availability of our target species, and control for repeated surveys at locations– all typical challenges in range-scale monitoring datasets. We fit distribution models using generalized additive models that account for spatial covariates as well as unexplained spatial variation and spatial uncertainty. Our model accommodates different survey protocols using offsets and incorporates temporal variation in detection and availability resulting from survey-specific variation in temperature and precipitation. Our spatial random effect was crucial in identifying small-scale differences in the occurrence of each species and provides cell-specific estimates of uncertainty in the density of salamanders across the range. Counts of both species were seen to increase in the 3 days following a precipitation event. However, P. cinereus were observed even in extremely wet conditions, while surface activity of P. shenandoah was associated with a more narrow range. Our results demonstrate how a flexible analytical approach improves estimates of both distribution and uncertainty, and identify key abiotic relationships, even at small spatial scales and when scales of empirical data are mismatched. While our approach is especially valuable for species with small ranges, controlling for spatial autocorrelation, estimating spatial uncertainty, and incorporating survey-specific information in estimates can improve the reliability of distribution models in general.

Ecology and Evolution↗

USGS2023

Broad-scale assessment of methylmercury in adult amphibians

Mercury (Hg) is a toxic contaminant that has been mobilized and distributed worldwide and is a threat to many wildlife species. Amphibians are facing unprecedented global declines due to many threats including contaminants. While the biphasic life history of many amphibians creates a potential nexus for methylmercury (MeHg) exposure in aquatic habitats and subsequent health effects, the broad-scale distribution of MeHg exposure in amphibians remains unknown. We used nonlethal sampling to assess MeHg bioaccumulation in 3,241 juvenile and adult amphibians during 2017–2021. We sampled 26 populations (14 species) across 11 states in the United States, including several imperiled species that could not have been sampled by traditional lethal methods. We examined whether life history traits of species and whether the concentration of total mercury in sediment or dragonflies could be used as indicators of MeHg bioaccumulation in amphibians. Methylmercury contamination was widespread, with a 33-fold difference in concentrations across sites. Variation among years and clustered subsites was less than variation across sites. Life history characteristics such as size, sex, and whether the amphibian was a frog, toad, newt, or other salamander were the factors most strongly associated with bioaccumulation. Total Hg in dragonflies was a reliable indicator of bioaccumulation of MeHg in amphibians (R 2 ≥ 0.67), whereas total Hg in sediment was not (R 2 ≤ 0.04). Our study, the largest broad-scale assessment of MeHg bioaccumulation in amphibians, highlights methodological advances that allow for nonlethal sampling of rare species and reveals immense variation among species, life histories, and sites. Our findings can help identify sensitive populations and provide environmentally relevant concentrations for future studies to better quantify the potential threats of MeHg to amphibians.

Environmental Science and Technology↗

USGS2023

Abiotic and biotic factors reduce the viability of a high-elevation salamander in its native range

Amphibian populations are undergoing worldwide declines, and high-elevation, range-restricted amphibian species may be particularly vulnerable to environmental stressors. In particular, future climate change may have disproportional impacts to these ecosystems. Evaluating the combined effects of abiotic changes and biotic interactions simultaneously is important for forecasting the range of future outcomes. This information is necessary to aid conservation decision-making. We use field data to estimate population demographic parameters for an exemplary high-elevation amphibian species, the federally endangered Shenandoah salamander Plethodon shenandoah . These parameters were entered into a Markov projection model which we used to forecast the future population status of the Shenandoah salamander. We found that if the population maintains its current site colonization and persistence rates, it is at the risk of extinction that could be exacerbated by both climate and interspecific competition. Synthesis and applications. Managers have a fundamental objective directed by official policy of maintaining the species ‘for the foreseeable future’. Our evaluation of multiple hypotheses about population drivers reveals that extinction is projected for this species. Our analysis suggests that considering active management need not depend on resolving the uncertainty.

Virginia↗

USGS2023

Long-term effects of timber harvest on ephemeral pool and occupancy of Spotted Salamanders (Ambystoma maculatum) and Wood Frogs (Lithobates sylvaticus)

The effects of timber harvest on amphibians can be complex and persist for years postharvest, but overall they are poorly understood. We examined how timber harvest has impacted two pool-breeding species, Spotted Salamander ( Ambystoma maculatum ) and Wood Frog ( Lithobates sylvaticus ), across the Canaan Valley National Wildlife Refuge, West Virginia, USA. We surveyed Spotted Salamanders and Wood Frogs at 49 pools from 2004 to 2016. Pools in recently harvested tracts tended to be smaller and less likely to hold water than pools in unharvested tracts for the duration of the breeding period. For both species, mean egg mass abundance was lower in harvested tracts than in the unharvested tracts, and over time declined substantially for Wood Frogs. Similarly, occupancy rates were lower in harvested sites for the duration of the study for both species. Occupancy rates declined over time for both species across all sites; this decline was steeper for Wood Frogs in harvested sites. Our results show the importance of long-term landscape-level studies when evaluating the effects of habitat disturbance. Understanding how forest loss and degradation impact pool-breeding amphibians will help to develop better management targets and mitigate compounding factors of decline to promote survival of these species.

West Virginia↗

USGS2022

Testing assumptions in the use of PIT tags to study movement of Plethodon salamanders

Studying the movements of organisms that live underground for at least a portion of their life history is challenging, given the state of current technology. Passive integrated transponders (PIT tags) provide a way to individually identify and, more recently, study the movement of smaller animals, including those that make subterranean movements. However, there are widespread assumptions of the use of PIT tags that remain problematic. We tested the effects of PIT-tag implantation on growth and survival, along with the effects of electromagnetic fields for reading PIT tags on behavior, of the smallest salamander that has been PIT-tagged: the Red-Backed Salamander. We found no effect of PIT tags on growth or survival. Using a mesocosm experiment, we also found that electromagnetic effects associated with reading PIT tags, had no effect on salamander behavior. Further, we describe a novel PIT antenna and soil mesocosm experimental arena for studying belowground movements of woodland salamanders. Collectively, these studies suggest that the use of PIT tags do not influence the growth, survival, or behavior of Red-Backed Salamanders. Given the challenges of studying salamanders that live underground and the impending changes in climate and landscapes, this research suggests that PIT tags remain a viable tool for studying the movement ecology of salamanders under global change.

Journal of Herpetology↗

USGS2022

Summary and synthesis of 15 years of the Amphibian Vital Sign monitoring in the National Capital Region Inventory and Monitoring Network

The amphibian monitoring program, designed and conducted by the U.S. Geological Survey’s Amphibian Research and Monitoring Initiative program, is designed to estimate the status and trends of amphibian populations to assist management decisions in individual parks and across the National Capital Region Network. Detection/non-detection data for stream and wetland habitats has been collected in 2 parks annually since 2005, and recently expanded to 11 units in the network following habitat mapping efforts. Data for all parks were incorporated into an analysis of site-occupancy for each habitat type (e.g. streams, wetlands) to estimate the occupancy rates for each species. This report summarizes the monitoring efforts, changes in the program over time, and findings based on data from 2005-2018. Fifteen species or species complexes within wetland sites and 5 species of salamander in stream sites were encountered during surveys. Across the network, more than half of wetland populations (65%) are estimated to be stable, 2% are increasing, and 33% indicate a negative trend. Stream salamander populations appear to be relatively stable, with observed population fluctuations likely related to availability of surface water in a given year. Although there were among-park differences in baseline occupancy and dynamics, overall factors promoting occupancy and persistence from year to year included sites that are large, well-connected to other breeding habitats, forested, and with low conductivity.

Report↗

USGS2021

Monitoring the status and trends of the Shenandoah salamander in Shenandoah National Park

The Shenandoah salamander ( Plethodon shenandoah ) is a federally endangered salamander whose distribution is restricted to high-elevation habitats in Shenandoah National Park (SHEN). During the ranking of vital signs monitoring priorities for this park, “Federal Threatened and Endangered Species” received the 2nd highest ranking for terrestrial vital signs because of ecological, management, and policy criteria. The following protocol narrative describes the objectives and methods for monitoring the Shenandoah salamander. Because the range size and habitat occupancy are of principle interest, this protocol generates data suitable for estimating the annual proportion of occupied habitat across the species range. Objectives focus on describing the status and trends of the species distribution (i.e., spatial extent) and the proportion of the range that is occupied (i.e., density of occupied sites). To do so, monitoring sites in the core and the edge of the known range are surveyed for salamanders multiple times during both the spring and fall. The resulting data not only allow for an assessment of the status and trends of the species but also provide supporting data to assist in understanding causal drivers of population change. This monitoring protocol consists of a protocol narrative and eight standard operating procedures (SOPs) which are listed below in the Background and Objectives and are available as separate documents at irma.nps.gov.

Natural Resource Report↗

USGS2019

Proactive management of amphibians: Challenges and opportunities

Delaying species management reduces the chance of successful recovery, increases the risk of extinction, and can be expensive. Acting before major declines are realized affords access to a greater suite of cost-effective management actions to sustain populations, reducing the likelihood of declines warranting protected status. It is clear that reactive management approaches are not sufficient for amphibian conservation and a successful path forward will require novel proactive approaches and strong leadership. We describe how conservation timelines and structured decision making can help explicitly evaluate management options available to species given current, and often limited, knowledge about populations or distributions. We illustrate this framework using common and widespread amphibians, as many species are in decline, including those found in protected conservation areas. We promote the development of explicit management objectives, management triggers and advocate for evaluating the cost-effectiveness of actions before species declines are observed.

Biological Conservation↗

USGS2019

Estimating occurrence, prevalence, and detection of amphibian pathogens: Insights from occupancy models

Understanding the distribution of pathogens across landscapes and their prevalence within host populations is a common aim of wildlife managers. Despite the need for unbiased estimates of pathogen occurrence and prevalence for planning effective management interventions, many researchers fail to account for imperfect pathogen detection. Instead raw data are often reported, which may lead to ineffective, or even detrimental, management actions. We illustrate the utility of occupancy models for generating unbiased estimates of disease parameters by 1) providing a written tutorial describing how to fit these models in Program PRESENCE and 2) presenting a case study with the pathogen ranavirus. We analyzed ranavirus detection data from a wildlife refuge (Maryland, US) using occupancy modeling, which yields unbiased estimates of pathogen occurrence and prevalence. We found ranavirus prevalence was underestimated by up to 30% if imperfect pathogen detection was ignored. The unbiased estimate of ranavirus prevalence in larval wood frog ( Lithobates sylvaticus ; 0.73) populations was higher than in larval spotted salamander ( Ambystoma maculatum ; 0.56) populations. In addition, the odds of detecting ranavirus in tail samples were 6.7 times higher than detecting ranavirus in liver samples. Therefore, tail samples presented a nonlethal sampling method for ranavirus that may be able to detect early (nonsystemic) infections.

Maryland↗