Explore the vast range of titles available.

A major objective of ecology is to understand how ecological processes limit population connectivity and species' distributions. By spatially quantifying ecological components driving functional connectivity, we can understand why some locally suitable habitats are unoccupied, resulting in observed discontinuities in distribution. However, estimating connectivity may be difficult due to population stochasticity and violations of assumptions of parametric statistics. To address these issues, we present a novel application of Random Forests to landscape genetic data. We address the effects of three key ecological components on Bufo boreas connectivity in Yellowstone National Park: ecological process, scale, and hierarchical organization. Habitat permeability, topographic morphology, and temperature—moisture regime are all significant ecological processes associated with B. boreas connectivity. Connectivity was influenced by growing-season precipitation, 1988 Yellowstone fires, cover, temperature, impervious surfaces (roads and development), and topographic complexity (56% variation explained). We found that habitat permeability generally operates on fine scales, while topographic morphology and temperature—moisture regime operate across multiple scales, thus demonstrating the importance of cross-scale analysis for ecological interpretation. In a hierarchical analysis, we were able to explain more variation within genetic clusters as identified using Structure (a Bayesian algorithm) (74%; dispersal cover, growing-season precipitation, impervious surfaces) as opposed to between genetic clusters (45%; ridgelines, hot, dry slopes, length of hot season, and annual precipitation). Finally, the analytical methods we developed are powerful and can be applied to any species or system with appropriate landscape and genetic data.

Amphibian granular glands provide a wide range of compounds on the skin that defend against pathogens and predators. We identified three bufadienolides—the steroid-like compounds arenobufagin, gamabufotalin, and telocinobufagin—from the boreal toad, Anaxyrus boreas, through liquid chromatography mass spectrometry (LC/MS). Compounds were detected both after inducing skin gland secretions and in constitutive mucosal rinses from toads. We described the antimicrobial properties of each bufadienolide against Batrachochytrium dendrobatidis (Bd), an amphibian fungal pathogen linked with boreal toad population declines. All three bufadienolides were found to inhibit Bd growth at similar levels. The maximum Bd inhibition produced by arenobufagin, gamabufotalin, and telocinobufagin were approximately 50%, in contrast to the complete Bd inhibition shown by antimicrobial skin peptides produced by some amphibian species. In addition, skin mucus samples significantly reduced Bd viability, and bufadienolides were detected in 15 of 62 samples. Bufadienolides also appeared to enhance growth of the anti-Bd bacterium Janthinobacterium lividum, and thus may be involved in regulation of the skin microbiome. Here, we localized skin bacteria within the mucus layer and granular glands of toads with fluorescent in situ hybridization. Overall, our results suggest that bufadienolides can function in antifungal defense on amphibian skin and their production is a potentially convergent trait similar to antimicrobial peptide defenses found on the skin of other species. Further studies investigating bufadienolide expression across toad populations, their regulation, and interactions with other components of the skin mucosome will contribute to understanding the complexities of amphibian immune defense.

1. The need to increase our understanding of factors that regulate animal population dynamics has been catalysed by recent, observed declines in wildlife populations worldwide. Reliable estimates of demographic parameters are critical for addressing basic and applied ecological questions and understanding the response of parameters to perturbations (e.g. disease, habitat loss, climate change). However, to fully assess the impact of perturbation on population dynamics, all parameters contributing to the response of the target population must be estimated. 2. We applied the reverse-time model of Pradel in Program MARK to 6 years of capture—recapture data from two populations of Anaxyrus boreas (boreal toad) populations, one with disease and one without. We then assessed a priori hypotheses about differences in survival and recruitment relative to local environmental conditions and the presence of disease. 3. We further explored the relative contribution of survival probability and recruitment rate to population growth and investigated how shifts in these parameters can alter population dynamics when a population is perturbed. 4. High recruitment rates (0·41) are probably compensating for low survival probability (range 0·51—0·54) in the population challenged by an emerging pathogen, resulting in a relatively slow rate of decline. In contrast, the population with no evidence of disease had high survival probability (range 0·75—0·78) but lower recruitment rates (0·25). 5. Synthesis and applications. We suggest that the relationship between survival and recruitment may be compensatory, providing evidence that populations challenged with disease are not necessarily doomed to extinction. A better understanding of these interactions may help to explain, and be used to predict, population regulation and persistence for wildlife threatened with disease. Further, reliable estimates of population parameters such as recruitment and survival can guide the formulation and implementation of conservation actions such as repatriations or habitat management aimed to improve recruitment.

Targeted environmental DNA (eDNA) studies mainly rely on quantitative real‐time polymerase chain reaction (qPCR) to amplify extremely low concentrations of DNA present in environmental samples. Understanding factors that influence targeted eDNA assay performance and detection in field samples, such as Taq DNA polymerase enzyme type and thermocycle protocol, is critical for the interpretation of qPCR results. We completed a systematic performance evaluation of five distinct targeted eDNA assays (eANFI6, eFISH1, eANBO5, eGLIN1, and eLICA3 targeting sablefish, general fish, Boreal toad, wood turtle, and the American bullfrog) by subjecting the same samples to analysis by five different Taq enzyme reagent mixes (Immolase, Environmental Master Mix (EMM), Amplitaq, QIAcuity, and QuantiNova) and the commonly used 2‐step (95°C, 60°C) and 3‐step (95°C, 64°C, 72°C) thermocycle protocols. We evaluated assay performance using a standardized dilution series of synthetic dsDNA target sequences and calculated limits of detection (LOD) and quantification (LOQ) and 95% confidence intervals for each combination of Taq enzyme and thermocycle protocol. All assays performed within acceptable performance criteria as defined by the Canadian national standard for targeted eDNA assays. Based on data generated by synthetic dsDNA fragments, the eDNA assays performed comparably regardless of the enzyme reagent mix and protocol used, except for eANFI6 and eGLIN1 using EMM and the 3‐step protocol, where no amplification was observed. On freshwater field samples, EMM and Immolase performed best. On marine field samples, Immolase, EMM, Qiacuity, and QuantiNova performed equally well, although EMM failed to amplify some samples. The work reveals that an enzyme reaction mix or thermocycle protocol can affect the result of an eDNA assay, but the appropriate choice also depends on the nature of the field sample. It is therefore imperative that these are considered when selecting appropriate reaction conditions and that they are clearly reported. Understanding factors that influence targeted eDNA assay performance and detection in field samples, such as Taq DNA polymerase enzyme type and thermocycle protocol, is critical for the interpretation of qPCR results. We completed a systematic performance evaluation of five distinct targeted eDNA assays by subjecting the same samples to analysis by five different Taq enzyme reagent mixes and commonly used 2‐step and 3‐step thermocycle protocols. The results accentuate the necessity of considering assay sensitivity and potential environmental inhibitors in selecting appropriate reaction conditions.

Understanding the demographic consequences of interactions among pathogens, hosts, and weather conditions is critical in determining how amphibian populations respond to disease and in identifying site-specific conservation actions that can be developed to bolster persistence of amphibian populations. We investigated population dynamics in Boreal Toads (Anaxyrus boreas) relative to abiotic (fall temperatures and snowpack) and biotic (the abundance of another anuran host and disease) characteristics of the local environment in Wyoming, USA. We used capture–recapture data and a multistate model where state was treated as a hidden Markov process to incorporate disease state uncertainty and assess our a priori hypotheses. Our results indicated that snowpack during the coldest week of winter is more influential to toad survival, disease transition probabilities, and the population-level prevalence of the amphibian chytrid fungus (Batrachochytrium dendrobatidis) in the spring, than temperatures in the fall or the presence of another host. As hypothesized, apparent survival at low (i.e., <25 cm) snowpack (0.22; confidence interval [CI] = 0.15–0.31) was lower than apparent survival at high snowpack (90.65; CI = 0.50–0.78). Our findings highlight the potential for local environmental factors, like snowpack, to influence disease and host persistence, and demonstrate the ecological complexity of disease effects on population demography in natural environments. This work further emphasizes the need for improved understanding of how climate change may influence the relationships among pathogens, hosts, and their environment for wild animal populations challenged by disease.

Movement of individuals has been described as one of the best studied, but least understood concepts in ecology. The magnitude of movements, routes, and probability of movement have significant application to conservation. Information about movement can inform efforts to model species persistence and is particularly applicable in situations where specific threats (e.g., disease) may depend on the movement of hosts and potential vectors. We estimated the probability of movement (breeding dispersal and permanent emigration) in a metapopulation of 16 breeding sites for boreal toads (Anaxyrus boreasboreas). We used a multi‐state mark–recapture approach unique in its complexity (16 sites over 18 yr) to address questions related to these movements and variation in resident survival. We found that individuals had a 1–2% probability of dispersing in a particular year and that approximately 10–20% of marked individuals were transient and observed in the metapopulation only once. Resident survival probabilities differed by season, with 71–90% survival from emergence from hibernation through early post‐breeding and >97% survival from mid‐/late active season through hibernation. Movement‐related probabilities are needed to predict species range expansions and contractions, estimate population and metapopulation dynamics, understand host–pathogen and native–invasive species interactions, and to evaluate the relative effects of proposed management actions.

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 ). Using the model, we explored the management implications of major uncertainties in this system, including whether there is a genetic basis for resistance to pathogenic infection by Bd , how translocation can best be implemented, and the effectiveness of efforts to reduce the spread of Bd . Our modeling exercise suggested that while selection for resistance to pathogenic infection by Bd could increase numbers of sites occupied by toads, and translocations could increase the rate of toad recovery, efforts to reduce the spread of Bd may have little effect. We emphasize the need to continue developing and parameterizing models necessary to assess management actions for combating chytridiomycosis-associated declines.

Two populations of boreal toads (Bufo boreas) experienced drastic declines in abundance in the late 1990s. Evidence supported the hypothesis of disease (the chytrid fungus, Batrachochytrium dendrobatidis) as the cause of these declines, but other hypotheses had not been evaluated. We used an 11-year capture-recapture data set to evaluate weather and disease as causes of these declines. We developed sets of mathematical models that reflected hypothesized relationships between several weather variables and annual survival rates of adult males in these populations. In addition, models that reflected the possibility that the declines were caused by an introduced fungus were developed. All models were fit to the data and were evaluated using a model selection criterion (QAICc). Our analysis provided strong support for the hypothesis of an introduced fungus and little support for the hypothesis that weather conditions caused the declines. Our results also suggest a strong, negative \"marking effect\" on survival rates of boreal toads. Model-averaged estimates of survival rate are presented.

Male boreal toads (Bufo boreas) are thought to return to the breeding site every year but, if absent in a particular year, will be more likely to return the following year. Using Pollock's robust design we estimated temporary emigration (the probability a male toad is absent from a breeding site in a given year) at three locations in Colorado, USA: two in Rocky Mountain National Park and one in Chaffee County. We present data that suggest that not all male toads return to the breeding site every year. Our analyses indicate that temporary emigration varies by site and time (for example, from 1992 to 1998, the probability of temporary emigration ranged from 10% to 29% and from 3% to 95% at Lost Lake and Kettle Tarn, respectively). Although the results provide weak evidence that males are more likely to return after a year's hiatus, a general pattern of state-dependent temporary emigration was not supported. We also hypothesized relationships between temporary emigration and a number of weather variables. While some competitive models included weather covariates, imprecise and variable estimates of the effects of these covariates precluded fully defining their impact on temporary emigration.

The pathogen Batrachochytrium dendrobatidis (Bd), which causes the skin disease chytridiomycosis, has been linked to amphibian population declines and extinctions worldwide. Bd has been implicated in recent declines of boreal toads, Bufo boreas boreas , in Colorado but populations of boreal toads in western Wyoming have high prevalence of Bd without suffering catastrophic mortality. In a field and laboratory study, we investigated the prevalence of Bd in boreal toads from the Grand Teton ecosystem (GRTE) in Wyoming and tested the pathogenicity of Bd to these toads in several environments. The pathogen was present in breeding adults at all 10 sites sampled, with a mean prevalence of 67%. In an experiment with juvenile toadlets housed individually in wet environments, 10 6 zoospores of Bd isolated from GRTE caused lethal disease in all Wyoming and Colorado animals within 35 days. Survival time was longer in toadlets from Wyoming than Colorado and in toadlets spending more time in dry sites. In a second trial involving Colorado toadlets exposed to 35% fewer Bd zoospores, infection peaked and subsided over 68 days with no lethal chytridiomycosis in any treatment. However, compared with drier aquaria with dry refuges, Bd infection intensity was 41% higher in more humid aquaria and 81% higher without dry refuges available. Our findings suggest that although widely infected in nature, Wyoming toads may escape chytridiomycosis due to a slight advantage in innate resistance or because their native habitat hinders Bd growth or provides more opportunities to reduce pathogen loads behaviorally than in Colorado.