In situ effects of pesticides on amphibians in the Sierra Nevada
Authors: Sparling DW, Bickham J, Cowman D, Fellers GM, Lacher L, Matson CW, McConnell L | Date: 2015-03 | Outlet: Ecotoxicology 24:262-278 | Format: URL
For more than 20 years, conservationists have agreed that amphibian populations around the world are declining. Results obtained through laboratory or mesocosm studies and measurement of contaminant concentrations in areas experiencing declines have supported a role of contaminants in these declines. The current study examines the effects of contaminant exposure to amphibians in situ in areas actually experiencing declines. Early larval Pseudacris regilla were translocated among Lassen Volcanic, Yosemite and Sequoia National Parks, California, USA and caged in wetlands in 2001 and 2002 until metamorphosis. Twenty contaminants were identified in tadpoles with an average of 1.3–5.9 (maximum = 10) contaminants per animal. Sequoia National Park, which had the greatest variety and concentrations of contaminants in 2001, also had tadpoles that experienced the greatest mortality, slowest developmental rates and lowest cholinesterase activities. Yosemite and Sequoia tadpoles and metamorphs had greater genotoxicity than those in Lassen during 2001, as determined by flow cytometry. In 2001 tadpoles at Yosemite had a significantly higher rate of malformations, characterized as hemimelia (shortened femurs), than those at the other two parks but no significant differences were observed in 2002. Fewer differences in contaminant types and concentrations existed among parks during 2002 compared to 2001. In 2002 Sequoia tadpoles had higher mortality and slower developmental rates but there was no difference among parks in cholinesterase activities. Although concentrations of most contaminants were below known lethal concentrations, simultaneous exposure to multiple chemicals and other stressors may have resulted in lethal and sublethal effects.
Environmental DNA: Can it improve our understanding of biodiversity on NPS lands?
Authors: Ray A, Sepulveda A, Hossack BR, Patla D, Legg K | Date: 2014 | Outlet: Park Science 31:118 | Format: .PDF
Modeling false positive detections in species occurrence data under different study designs
Author: Chambert T, Miller DAW, Nichols JD | Outlet: Ecology | Format: URL
The occurrence of false positive detections in presence-absence data, even when they occur infrequently, can lead to severe bias when estimating species occupancy patterns. Building upon previous efforts to account for this source of observational error (Royle & Link 2006; Miller et al. 2011, 2013), we establish a general framework to model false positives in occupancy studies and extend existing modeling approaches to encompass a broader range of sampling designs. Specifically, we identified three common sampling designs that are likely to cover most scenarios encountered by researchers. The different designs all include ambiguous detections, as well as some known-truth data, but their modeling differs in the level of the model hierarchy at which the known-truth information is incorporated (site-level or observation-level). For each model, we provide the likelihood, as well as R and BUGS code needed for implementation. We also establish a clear terminology and provide guidance to help choosing the most appropriate design and modeling approach.
Glyphosate and its degradation product AMPA occur frequently and widely in U.S. soils, surface water, groundwater, and precipitation
Author: Battaglin W, Meyer M, Kuivila K, Dietze J | Date: 2014 | Outlet: Journal of the American Water Resources Association 50(2): 275-290. | Format: URL
Glyphosate use in the US increased from less than 5,000 to more than 80,000 metric tons per year between 1987 and 2007. Glyphosate is popular due to its ease of use on soybean, cotton and corn crops that are genetically modified to tolerate it, utility in no-till farming practices, utility in urban areas, and the perception that it has low toxicity and little mobility in the environment. This compilation is the largest and most comprehensive assessment of the environmental occurrence of glyphosate and AMPA in the US conducted to date, summarizing the results of 3,732 water and sediment and 1,018 quality-assurance samples collected between 2001 and 2010 from 38 States. Results indicate that glyphosate and AMPA are usually detected together, mobile, and occur widely in the environment. Glyphosate was detected without AMPA in only 2.3% of samples, whereas AMPA was detected without glyphosate in 17.9% of samples. Glyphosate and AMPA were detected frequently in soils and sediment, ditches and drains, precipitation, rivers, and streams; and less frequently in lakes, ponds, and wetlands; soil water; and groundwater. Concentrations of glyphosate were below levels of concern for humans or wildlife; however, pesticides are often detected in mixtures. Ecosystem effects of chronic low-level exposures to pesticide mixtures are uncertain. The environmental health risk of low-level detections of glyphosate, AMPA, and associated adjuvants and mixtures remain to be determined.
The effects of hydropattern and predator communities on amphibian occupancy
Authors: Amburgey S, Bailey L, Murphy M, Muths E, Funk W | Date: 2014-09-23 | Outlet: Canadian Journal of Zoology | Format: URL
Complex, interactive ecological constraints regulate species distributions, and understanding these factors is crucial for predicting species persistence. We used occupancy analysis, which corrects for imperfect detection, to test the importance of abiotic and biotic habitat and landscape factors on probability of occupancy by boreal chorus frog (Pseudacris maculata; Agassiz 1850) tadpoles. We hypothesized that hydropattern and predators are primarily important as they affect desiccation and predation risk and can interact in ways difficult to predict. We surveyed 62 wetland sites across an elevational gradient in Colorado, USA and modeled patterns in P. maculata occupancy. Tadpoles were most frequently present in intermediate hydropattern systems with lower desiccation risk and no predatory fish due to occasional drying. P. maculata occupancy had a strong negative relationship with fish presence while tadpoles, odonate larvae and tiger salamanders (Ambystoma mavortium; Baird 1850) frequently co-occurred. Dry seasonal conditions will likely result in fewer intermediate hydropattern ponds available for amphibian breeding. We hypothesize that this will force P. maculata to breed in habitats with fish. As habitats shrink, predators that co-occur with P. maculata are expected to concentrate in the remaining habitat and increase predation risk for developing tadpoles (assuming predators are similarly constricted in their habitat use as amphibians are).
Potential reduction in terrestrial salamander ranges associated with Marcellus shale development
Authors: Brand, Adrianne B, Wiewel, Amber NM, Grant, Evan H Campbell | Outlet: Biological Conservation
Natural gas production from the Marcellus shale is rapidly increasing in the northeastern United States. Most of the endemic terrestrial salamander species in the region are classified as ‘globally secure’ by the IUCN, primarily because much of their ranges include state- and federally protected lands, which have been presumed to be free from habitat loss. However, the proposed and ongoing development of the Marcellus gas resources may result in significant range restrictions for these and other terrestrial forest salamanders. To begin to address the gaps in our knowledge of the direct impacts of shale gas development, we developed occurrence models for five species of terrestrial plethodontid salamanders found largely within the Marcellus shale play. We predicted future Marcellus shale development under several scenarios. Under scenarios of 10000, 20000, and 50000 new gas wells, we predict 4%, 8%, and 20% forest loss, respectively, within the play. Predictions of habitat loss vary among species, but in general, Plethodon electromorphus and P. wehrlei are predicted to lose the greatest proportion of forested habitat within their ranges if future Marcellus predictions are based on characteristics of the shale play. If predictions are based on current well locations, P. richmondi is predicted to lose the greatest proportion of habitat. Models showed high uncertainty in species’ ranges and emphasize the need for distribution data collected by widespread and repeated, randomized surveys.
Short-term occupancy and abundance dynamics of the Oregon Spotted Frog (Rana pretiosa) across its core range
Authors: Adams MJ, Pearl CA, McCreary B, Galvan SK | Date: 2014-11-03 | Outlet: U.S. Geological Survey Open-File Report 2014-1230 | Format: .PDF
The Oregon spotted frog (Rana pretiosa) occupies only a fraction of its original range and is listed as Threatened under the Endangered Species Act. We surveyed 93 sites in a rotating panel frame design (2010–13) in the Klamath and Deschutes Basins, Oregon, which encompass most of the species’ core extant range. Oregon spotted frogs are decreasing in probability of both site occupancy and abundance. We did not find an association between the probability that Oregon spotted frogs disappear from a site (local extinction) and any of the variables hypothesized to affect Oregon spotted frog occupancy. This 4-year study provides baseline data, but the 4-year period was too short to draw firm conclusions about current (2014) trends. Further study is essential to understand how habitat changes and management practices relate to the status and trends of this species.
Using monitoring data to map amphibian breeding hotspots and describe wetland vulnerability in Yellowstone and Grand Teton National Parks
Authors: Ray A, Sepulveda A, Hossack B, Patla D, Legg K | Date: 2014 | Outlet: Park Science 31:112-119 | Format: .PDF
Amphibians have been selected as a “vital sign” by several
National Park Service (NPS) Inventory and Monitoring (I&M)
networks. An eight-year amphibian monitoring data set provided
opportunities to examine spatial and temporal patterns in
amphibian breeding richness and wetland desiccation across
Yellowstone and Grand Teton National Parks. Amphibian
breeding richness was variable across both parks, and only 4 of
31 permanent monitoring catchments contained all four widely
distributed species. Annual breeding richness was also variable
through time and fl uctuated by as much as 75% in some years and
catchments. Wetland desiccation was also documented across the
region, but alone did not explain variations in amphibian richness.
High annual variability across the region emphasizes the need for
multiple years of monitoring to accurately describe amphibian
richness and wetland desiccation dynamics.
Indicators of the Statuses of Amphibian Populations and Their Potential for Exposure to Atrazine in Four Midwestern U.S. Conservation Areas
Authors: Sadinski W, Roth M, Hayes T, Jones P, Gallant A | Date: 2014-09-12 | Outlet: PLoS ONE 9(9): e107018. doi:10.1371/journal.pone.0107018 | Format: .PDF
Extensive corn production in the midwestern United States has physically eliminated or fragmented vast areas of historical amphibian habitat. Midwestern corn farmers also apply large quantities of fertilizers and herbicides, which can cause direct and indirect effects on amphibians. Limited field research regarding the statuses of midwestern amphibian populations near areas of corn production has left resource managers, conservation planners, and other stakeholders needing more information to improve conservation strategies and management plans. We repeatedly sampled amphibians in wetlands in four conservation areas along a gradient of proximity to corn production in Illinois, Iowa, Minnesota, and Wisconsin from 2002 to 2005 and estimated site occupancy. We measured frequencies of gross physical deformities in recent metamorphs and triazine concentrations in the water at breeding sites. We also measured trematode infection rates in kidneys of recently metamorphosed Lithobates pipiens collected from nine wetlands in 2003 and 2004. We detected all possible amphibian species in each study area. The amount of nearby row crops was limited in importance as a covariate for estimating site occupancy. We observed deformities in <5% of metamorphs sampled and proportions were not associated with triazine concentrations. Trematode infections were high in metamorphs from all sites we sampled, but not associated with site triazine concentrations, except perhaps for a subset of sites sampled in both years. We detected triazines more often and in higher concentrations in breeding wetlands closer to corn production. Triazine concentrations increased in floodplain wetlands as water levels rose after rainfall and were similar among lotic and lentic sites. Overall, our results suggest amphibian populations were not faring differently among these four conservation areas, regardless of their proximity to corn production, and that the ecological dynamics of atrazine exposure were complex.
Detecting Emergence, Growth, and Senescence of Wetland Vegetation with Polarimetric Synthetic Aperture Radar (SAR) Data.
Authors: Gallant AL, Kaya SG, White L, Brisco B, Roth MF, Sadinski W, Rover J | Date: 2014-03-24 | Outlet: Water. 2014; 6(3):694-722 | Format: .PDF
Wetlands provide ecosystem goods and services vitally important to humans. Land managers and policymakers working to conserve wetlands require regularly updated information on the statuses of wetlands across the landscape. However, wetlands are challenging to map remotely with high accuracy and consistency. We investigated the use of multitemporal polarimetric synthetic aperture radar (SAR) data acquired with Canada’s Radarsat-2 system to track within-season changes in wetland vegetation and surface water. We speculated, a priori, how temporal and morphological traits of different types of wetland vegetation should respond over a growing season with respect to four energy-scattering mechanisms. We used ground-based monitoring data and other ancillary information to assess the limits and consistency of the SAR data for tracking seasonal changes in wetlands. We found the traits of different types of vertical emergent wetland vegetation were detected well with the SAR data and corresponded with our anticipated backscatter responses. We also found using data from Landsat’s optical/infrared sensors in conjunction with SAR data helped remove confusion of wetland features with upland grasslands. These results suggest SAR data can provide useful monitoring information on the statuses of wetlands over time.