Phenotypic plasticity in developmental rate is insufficient to offset high tadpole mortality in rapidly drying ponds
Authors: Amburgey SA, Murphy MA, Funk WC | Date: 2016-06 | Outlet: Ecosphere 2016, 00(00):e01386. 10.1002/ecs2.1386 | Format: .PDF
Habitat suitability is strongly regulated by seasonal conditions and stochastic processes, and
this is especially important in temporary aquatic systems that contain organisms with complex life cycles.
We investigated the potential for phenotypic plasticity in timing of and size at metamorphosis to mitigate
effects of altered habitat conditions, specifically shortened hydroperiod (duration of water in ponds)
and altered predator-prey dynamics, in the pond-breeding boreal chorus frog (Pseudacris maculata). We
simulated reduced hydroperiod and concentrated predator cue in the laboratory to understand potential
benefits and costs of plasticity. Tadpoles developed faster in response to the combined effects of reduced
hydroperiod and increased concentration of predator cue, potentially due to reduced conspecific density.
In contrast, there was no effect of reduced hydroperiod or predator cue on size at metamorphosis. Alone,
this result suggests that phenotypic plasticity may allow P. maculata to escape the negative effects of rapidly
drying ponds. However, tadpole survival was significantly lower in reduced hydroperiod treatments
relative to all other treatments, suggesting that even if plasticity acts as a buffer against reduced hydroperiod
by facilitating metamorphosis, heightened mortality may offset benefits of this rapid response. Our
results add to previous studies of plastic responses in amphibians by disentangling the costs and benefits
of plasticity in habitats with multiple, simultaneous stressors. We show that while plasticity may accelerate
metamorphosis, similar, heightened levels of mortality are experienced regardless of plasticity. This
implies that plasticity may not completely buffer populations against the effects of altered habitat conditions,
such as those that occur with climate change or urbanization.
Potential Interactions Among Disease, Pesticides, Water Quality and Adjacent Land Cover in Amphibian Habitats in the United States
Authors: Battaglin W, Smalling K, Anderson C, Calhoun D, Chestnut T, Muths E | Date: 2016-05-24 | Outlet: Science of the Total Environment 320-332
To investigate interactions among disease, pesticides, water quality and adjacent land cover we collected samples of water, sediment, and frog tissue from 21 sites in 7 States in the United States (US) representing a variety of amphibian habitats. All samples were analyzed for > 90 pesticides and pesticide degradates, and water and frogs were screened for the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) using molecular methods. Pesticides and pesticide degradates were detected frequently in frog breeding habitats (water and sediment) as well as in frog tissue. Fungicides occurred more frequently in water, sediment, and tissue than was expected based upon their limited use relative to herbicides or insecticides. Pesticide occurrence in water or sediment was not a strong predictor of occurrence in tissue, but pesticide concentrations in tissue were correlated positively to agricultural and urban land, and negatively to forested land in 2-kilometer buffers around the sites. Bd was detected in water at 45% of sites, and on 34% of swabbed frogs. Bd detections in water were not associated with differences in land use around sites, but sites with detections had colder water. Frogs that tested positive for Bd were associated with sites that had higher total fungicide concentrations in water and sediment, but lower insecticide concentrations in sediments relative to frogs that were Bd negative. Bd concentrations on frog swabs were positively correlated to dissolved organic carbon, and total nitrogen and phosphorus, and negatively correlated to pH and water temperature.
Data were collected from a range of locations and amphibian habitats and represent some of the first field-collected information aimed at understanding the interactions between pesticides, land use, and amphibian disease. These interactions are of particular interest to conservation efforts as many amphibians live in altered habitats and may depend on wetlands embedded in these landscapes to survive.
S A Amburgey
First Estimates of the Probability of Survival in a Small-bodied, High Elevation Frog or, how Historical Data Can Be Useful
Authors: Muths E, Scherer R D, Amburgey S M, Matthews T, Spencer A W, Corn P S | Date: 2016-06 | Outlet: Canadian Journal of Zoology, doi: 10.1139/cjz-2016-0024 | Format: .PDF
In an era of shrinking budgets yet increasing demands for conservation, the value of existing (i.e., historical) data is elevated. Lengthy time-series on common, or previously common, species are particularly valuable and may be available only through the use of historical information. We provide first estimates of the probability of survival and longevity (0.67-0.79
; 5-7 yr) for a subalpine population of a small-bodied, ostensibly common amphibian, the boreal chorus frog, using historical data and contemporary, hypothesis-driven information-theoretic analyses. We also test a priori hypotheses about the effects of color morph (as suggested by early reports) and of drought (as suggested by recent climate predictions on survival). Using robust mark-recapture models, we find some support for early hypotheses regarding the effect of color on survival, but we find no effect of drought. The congruence between early findings and our analyses highlights the usefulness of historical information by providing raw data for contemporary analyses and context for conservation and management decisions.
Quantitative evidence for the effects of multiple drivers on continental-scale amphibian declines
Authors: Grant EHC, Miller DAW, Schmidt BR, Adams MJ, Amburgey SM, Chambert TC, Cruickshank SS, Fisher RN, Green DM, Hossack BR, Johnson PTJ, Joseph MB, Rittenhouse T, Ryan M, Waddle JH, Walls SC, Bailey LL, Fellers GM, Gorman TA, Ray AM, Pilliod DS, Price SJ, Saenz D, Muths E | Outlet: Scientific Reports xx:xxx-xxx
Since amphibian declines were first proposed as a global phenomenon over a quarter century ago, the conservation community has made little progress in halting or reversing these trends. The early search for a "smoking gun" was replaced with the expectation that declines are caused by multiple drivers. While field observations and experiments have identified factors leading to increased local extinction risk, evidence for effects of these drivers is lacking at large spatial scales. Here, we use observations of 389 time-series of 83 species and complexes from 61 study areas across North America to test the effects of 4 of the major hypothesized drivers of declines. While we find that local amphibian populations are being lost from metapopulations at an average rate of 3.79% per year, these declines are not related to any particular threat at the continental scale; likewise the effect of each stressor is variable at regional scales. This result - that exposure to threats varies spatially, and populations vary in their response - provides little generality in the development of conservation strategies. Greater emphasis on local solutions to this globally shared phenomenon is needed.
Estimating abundance in the presence of species uncertainty
Authors: Chambert T, Hossack BR, Fishback L, Davenport JM | Outlet: Methods in Ecology and Evolution
Uncertainty in biological monitoring: a framework fordata collection and analysis to account for multiplesources of sampling bias
Authors: Ruiz-Gutierrez V, Hooten MB, Grant EHC | Outlet: Methods in Ecology and Evolution doi/10.1111/2041-210X.12542
eSummary(1) Biological monitoring programs are increasingly relying upon large volumes of citizenscience data to improve the scope and spatial coverage of information, ch a l l en g i n g thescienti&#64257;c commun i ty to develop design and model - b ase d approaches to improve inference.(2) Recent statistical models in ecology have be en develope d to accommodate false-negativeerrors, although recent work points to false positive errors as equally important sources ofbias. This is of particular concern for the success of any m o n i t or i n g program given rates assmall as 3% could lead to th e overestimation of the occurrence of rare events by as much as50%, and even small false positive r a t es can severely b i as estimates of occurrence dynamics.(3) We present an int eg ra t ed , comput at i o n al l y e&#64259;cient Bayesian hierar chical model tocorrect for fal se positi ve and negative error s in detection/no n -d et ec ti o n data. Our modelcombines ind ependent, a u x i l i ar y data sources with &#64257;eld observations to i m p r ove t h eestimation of false positive rate s, when a subset of &#64257;eld observatio n s cannot be validated aposteriori or assumed as per fe ct . We evaluated the performance of the model across arange of occurren ce rates, false positive and negative errors, and quantity of auxil i ar y data.(4) Th e mode l perfor m ed well under all simulated scenario s, and we were able t o identifycritical auxiliary data characteristics which resul t ed in improved infer en ce. We applied ourfalse positive m odel to a large-scale, citizen -sci e n ce monitor i n g program for anurans in theNortheastern U.S., using auxiliary data from an experiment d esi g n ed to estimate falsepositive er r o r rates. Not correcting for false positive ra t es resulted in biased estimates ofoccupancy in 4 of the 10 anu r a n species we an a l y zed , leadin g to an overestima t i on of theaverage number of occupi ed survey routes by as much as 70%.Conclusions. The framework we present for da ta collecti o n and analysis is able toe&#64259;ciently pr ovide reliable inference for occurrence patterns using data from acitizen-science monitorin g program . However, our approach is ap p l i ca b le to data generatedby any type of research and monit or i n g program , independent of skill level or scale, when e&#64256;ort i s placed on obtaining independent info rma t i on on false positive rates
Spatial variation in risk and consequence of Batrachochytrium salamanderivorans introduction in the United States
Authors: Richgels K, Russell R, Adams M, Grant E | Date: 2016-02-17 | Outlet: Royal Society Open Science 3:150616 | Format: .PDF
A newly identified fungal pathogen, <i>Batrachochytrium salamandrivorans</i> (<i>Bsal</i>), is responsible for mass mortality events and severe population declines in European salamanders. The eastern USA has the highest diversity of salamanders in the world and the introduction of this pathogen is likely to be devastating. Although data is inevitably limited for new pathogens, disease risk assessments utilize best available data to inform management decisions. Using characteristics of <i>Bsal</i> ecology, spatial data on imports and pet trade establishments, and salamander species diversity, we identify high risk areas with both a high likelihood of introduction and severe consequences for local salamanders. We predict that the Pacific coast, southern Appalachian Mountains, and mid-Atlantic regions will have the highest relative risk from <i>Bsal</i>. Management of invasive pathogens becomes difficult once they are established in wildlife populations; therefore, import restrictions to limit pathogen introduction and early detection through surveillance of high risk areas are priorities for preventing the next crisis for North American salamanders
Integrating biology, field logistics, and simulations to optimize parameter estimation for imperiled species
Authors: Lanier WE, Bailey LL, Muths E | Date: 2016 | Outlet: Ecological Modeling | Format: .PDF
Conservation of imperiled species often requires knowledge of vital rates and population dynamics. However, these can be difficult to estimate for rare species and small populations. This problem is further exacerbated when individuals are not available for detection during some surveys due to limited access, delaying surveys and creating mismatches between the breeding behavior and survey timing. Here we use simulations to explore the impacts of this issue using four separate boreal toad (Anaxyrus boreas boreas) populations, representing combinations of logistical access (accessible, inaccessible) and breeding behavior (synchronous, asynchronous). We examine the bias and precision of survival and breeding probability estimates generated by survey designs that differ in effort and timing for these populations.
A Model to Inform Management Actions as a Response to Chytridiomycosis-Associated Decline
Authors: Converse SJ, Bailey LL, Mosher BA, Funk WC, Gerber BD, Muths E | Date: 2016-02-15 | Outlet: Ecohealth | Format: .PDF
Decision-analytic models provide forecasts of how systems of interest will respond to management. These models can be parameterized using empirical data, but sometimes require information elicited from experts. When evaluating the effects of disease in species translocation programs, expert judgment is likely to play a role because complete empirical information will rarely be available. We illustrate development of a decision-analytic model built to inform decision-making regarding translocations and other management actions for the boreal toad (Anaxyrus boreas boreas), a species with declines linked to chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd).
Non-native and native organisms moving into high elevation and high latitude ecosystems in an era of climate change: new challenges for ecology and conservation
Authors: Albihn A, Alexander J, Burgess T, Daehler C, Englund G, Essl F, Evengård B, Greenwood G, Haider S, Lenoir J, McDougall K, Muths E, Nuñez M, Olofsson J, Pellissier L, Rabitsch W, Rew L, Robertson M, Sanders N, Kueffer C, Milbau A, Pauchard A | Date: 2016 | Outlet: Biological Invasions | Format: .PDF
Cold environments at high elevation and high latitude are often viewed as resistant to biological invasions. However, climate warming, land use change and associated increased connectivity all increase the risk of biological invasions in these environments. Here we present a summary of the key discussions of the workshop ‘Biosecurity in Mountains and Northern Ecosystems: Current Status and Future Challenges’ (Flen, Sweden, 1-3 June 2015). The aims of the workshop were to (i) increase awareness about the growing importance of species expansion – both non-native and native – at high elevation and high latitude with climate change, (ii) review existing knowledge about invasion risks in these areas, and (iii) encourage more research on how species will move and interact in cold environments, and the consequences for animal and human health and wellbeing. The diversity of potential and actual invaders reported at the workshop and the likely interactions between them create major challenges for managers of cold environments. However, since these cold environments have experienced fewer invasions when compared with many warmer, more populated environments, prevention has a real chance of success, especially if it is coupled with prioritisation schemes for targeting invaders likely to have greatest impact. Communication and co-operation between cold environment regions will facilitate rapid response and maximise use of limited research and management resources.