Pseudacris Crucifer Research Articles

LACK OF SIZE-ASSORTATIVE MATING IN A WIDESPREAD TREEFROG: PSEUDACRIS CRUCIFER IN IOWA

The Spring Peeper (Pseudacris crucifer) is a small treefrog native to much of the Central and Eastern USA. Here, we tested if Spring Peepers exhibit size-assortative mating—non-random mate pairings based on body size—from a population in eastern Iowa. We captured 75 amplecting pairs of Spring Peepers during the 2021 breeding season, measured their body sizes, and marked them for future recognition. We found that while sexual-size dimorphism exists between males and females, there was no evidence for size-assortative mating among amplectant pairs. Our study contributes to other recent work indicating that size-assortative mating is rare among most anurans, and that previous findings of this phenomenon in frogs should be interpreted with caution.

Experimental warming and drying act independently on developmental responses for two amphibian species

AbstractClimate change is affecting freshwater habitats worldwide through multiple, interacting pressures that influence the survival, distribution, and persistence of freshwater organisms. Temporary freshwater habitats, or those that dry seasonally, can exhibit wide‐ranging variability in temperature and drying regimes. Aquatic organisms with complex life cycles (e.g., aquatic and terrestrial life stages) often rely on temporary freshwaters to complete their life cycles and have specific adaptations to cope with these dynamic environments. However, climate change is altering the temperature and drying regime of many temporary freshwater habitats worldwide, often resulting in warmer habitats available for shorter durations of time. The ways in which climate‐mediated changes to temporary freshwaters affect development and life history of aquatic organisms, particularly those with complex life cycles, remains poorly understood.We investigated larval development, growth, survival, and relationships among them for two amphibian species, wood frogs (Lithobates sylvaticus) and spring peepers (Pseudacris crucifer), in response to warming and drying in a mesocosm experiment. Over 13 weeks in the spring and summer of 2019, we manipulated temperature and water levels in 48 outdoor pond mesocosms to produce four treatments: control (ambient conditions), drying alone, warming alone, and drying + warming. We predicted reduced survival, body size, and time to metamorphosis for both species in response to warming and drying, with the effect being stronger on wood frogs due to their more specialised habitat use and shorter breeding period.Warming treatments were on average 2°C higher than controls, and drying treatments decreased water depth by 2.5 cm each week. We found that warming temperature shortened larval time to metamorphosis, and drying decreased body size at metamorphosis. Surprisingly, we also found that, across all treatment groups, individuals with early metamorphosis tended to be larger in size and from mesocosms with generally higher survival.Our study indicates that warming and drying may act independently on different developmental responses for amphibians. Our results echo recent calls for a better understanding of the nuanced, often unpredictable, relationships among climate‐mediated environmental pressures and the developmental traits they influence, particularly for organisms with complex life cycles that depend upon dynamic habitat for growth and survival. Understanding these relationships and the mechanisms that drive them will be key to predicting the response of freshwater organisms to climate change.

Evaluating fence-end treatments for migratory amphibians

Migratory amphibians require movements to complete their biphasic life cycle, often across altered landscapes fragmented by roadways, which can have severe consequences on their populations. To manage this threat, transportation agencies have begun to implement exclusion fencing to separate natural areas from the roadway to prevent wildlife-vehicle collisions. Although fences are an effective conservation tool, the tendency of animals to access the road by circumventing the fence ends, known as the fence-end effect, threatens to jeopardize management efforts to reduce road associated mortality. One strategy to lessen the impacts of the fence-end effect is to construct fence-end treatments to block amphibian movement and guide the animals to safe crossing locations. By using experimental fence arenas, we examined how nine amphibian species responded to two alternative fence-end structures: horizontal v-shape and perpendicular fence-end treatments. Using a generalized linear model framework, we found both fence-end treatments to be an effective strategy to reduce the impacts of the fence-end effect, with our predictor variable, fence-end treatment, explaining most of the variation in amphibian response. Structure effectiveness also started to improve by 20% with each 7°C increase in temperature, however, this was not significant. Despite these promising findings, we also found for each additional 312 s an amphibians spent attempting to navigate around the experimental fence resulted in a 25% decline in structure effectiveness, suggesting longer fences are not an adequate protection measure to combat the fence-end effect for amphibians. In addition, Anaxyrus americanus was not found to differ in their response, performing equally well to both experimental fence-end treatments. In contrast, Rana spp., Pseudacris crucifer, and Notopthalmus viridescens showed a greater response to the horizontal v-shape fence-end treatment compared to the perpendicular fence-end treatment. Variation in response for Ambystoma spp. could not be detected due to a small sample size; however, no individuals responded positively to the perpendicular fence-end treatment. Guidelines for amphibian fences should continue to incorporate fence-end treatments into the design and implementation to mitigate for the fence-end effect, and preferably angle the fence-ends inward in the horizontal v-shape pattern with the fence ends diagonal to the road for migratory amphibians.

The morphological effects of artificial light at night on amphibian predators and prey are masked at the community level

Artificial light at night (ALAN) is a pervasive pollutant that influences wildlife at both the individual and community level. In this study, we tested the individual-level effects of ALAN on three species of tadpole prey and their newt predators by measuring prey pigmentation and predator and prey mass. Then we evaluated whether the individual-level effects of ALAN on pigmentation and mass had cascading community-level effects by assessing the outcome of predator-prey interactions. We found that spring peepers exposed to ALAN were significantly darker than those reared under control conditions. Additionally, wood frogs reared in ALAN conditions were significantly smaller than those reared in control conditions. In contrast, Eastern newts collected earlier in the spring that were exposed to ALAN were significantly larger than controls while those collected later in the spring were not affected by ALAN, suggesting phenological differences in the effect of ALAN. To understand how changes in pigmentation and size due to ALAN influence predation rates, we ran predation assays in both ALAN-polluted and ALAN-free outdoor environments. After the predation assay, the size disparity in wood frogs reared in ALAN was eliminated such that there was no longer a treatment difference in wood frog size, likely due to size-selective predation. This demonstrates the beneficial nature of predators’ selective pressure on prey populations. Lastly, despite individual-level effects of ALAN on pigmentation and mass, we did not detect cascading community-level effects on predation rates. Overall, this study highlights important species-level distinctions in the effects of ALAN. It also emphasizes the need to incorporate ecological complexity to understand the net impact of ALAN.

Multiple-Predator Effects and Functional Redundancy of Pond Predators

Functional redundancy occurs when different predator species have similar effects on the diversity, abundance, and composition of a prey community. When multiple predators coexist, their interactions can alter prey survival and ultimately diversity through emergent multiple-predator effects (MPEs). MPEs can be exacerbated by differences in predator behavior; however, little is known about the magnitude of MPEs when predators compete for the same prey or have similar behavioral traits. To understand functional redundancy and the interactions of multiple predators in similar niches, as well as their impacts on the composition of a prey community, we conducted two experiments using two ambystomatid salamander predators (Ambystoma opacum and Ambystoma annulatum). We exposed a suite of tadpole prey (Anaxyrus americanus, Rana sphenocephala, Rana sylvatica, Pseudacris feriarum, and Pseudacris crucifer) to different experimental food webs in a mesocosm experiment, and a single prey species (R. sphenocephala) in microcosm experiment with substitutive and additive designs to test for MPEs. We found no evidence for functional redundancy between the two predators: A. annulatum selectively preyed on competitively dominant prey species (A. americanus) and did not alter community diversity. Ambystoma opacum decreased prey diversity relative to the control because of natural phenological mismatch with A. americanus. Interactions between the two predators (e.g., predator inference) were lacking, indicating that predation risk from each predator was independent for the one prey species we tested. A better understanding of community and ecosystem-level effects by A. annulatum can inform future conservation efforts and management decisions regarding this endemic species.

Wetland cohesion is associated with increased probability of infection by the amphibian chytrid fungus Batrachochytrium dendrobatidis.

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) poses a substantial threat to amphibian populations. Understanding the landscape conditions that facilitate Bd transmission and persistence is crucial for predicting Bd trends in amphibian populations. Here, we investigated the interactions between land use, wetland connectivity, and Bd occurrence and infection intensity. In northeastern Massachusetts, we sampled Pseudacris crucifer, Lithobates sylvaticus, L. clamitans, and L. pipiens from 24 sites. We found an overall 30.6% Bd prevalence at our sites, with prevalence differing among species. Bd occurrence increased with wetland-patch cohesion, potentially due to microclimate shifts from decreased forest or changes in host movement. Bd infection intensity was not mediated by landscape context. Overall, our results highlight the importance of landscape structure for Bd dynamics, suggesting that certain landscapes may facilitate transmission and harbor Bd more than others. To mitigate the impacts of Bd on amphibian populations, conservation efforts should account for interactions between Bd and landscape variables.

Time in the Laboratory, but Not Exposure to a Chytrid Fungus, Results in Rapid Change in Spring Peeper (Pseudacris crucifer) Skin Bacterial Communities

Interactions between pathogens and the symbiotic microbial communities that reside in hosts can impact disease processes. Symbiotic microbial communities can act to prevent pathogen infection in some instances, while in other instances, pathogens can disrupt these symbiotic communities. We sought to address these interactions between the fungal skin pathogen Batrachochytrium dendrobatidis (Bd) and the skin bacterial communities of adult Spring Peepers (Pseudacris crucifer). In the laboratory, frogs were exposed to Bd zoospores for a 12-hour period and then monitored for five days. Bacterial community composition on the skin was assessed upon initial collection, 24 hours post-exposure, and at the conclusion of the experiment using 16S rRNA gene amplicon sequencing. Little impact on the bacterial community was observed as a result of Bd exposure, suggesting that the timeline was either too short to observe the effects of Bd, or that the skin communities are resilient in the face of such short exposure periods. In contrast, laboratory housing was associated with changes in skin bacterial community composition, in terms of both relative abundances and bacterial taxa that were present. These findings suggest that even a short time away from their natural environment can have strong effects on the composition of amphibian skin communities and that Bd exposure may not always disrupt these skin communities.

Cytonuclear discordance, reticulation and cryptic diversity in one of North America's most common frogs

Complicated phylogenetic histories benefit from diverse sources of inference. Pseudacris crucifer (spring peeper) spans most of eastern North America and comprises six mtDNA lineages that form multiple contact zones. The putative Miocene or early Pliocene origins of the oldest lineages within Pseudacris crucifer imply sufficient time for species-level divergence. To understand why this species appears unified while congeners have radiated, we analyze and compare male advertisement calls, mitochondrial, and nuclear markers and speak to the complex processes that have potentially influenced its contemporary patterns. We find extensive geographic and topological mitonuclear discordance, with three nuclear lineages containing 6 more-structured mtDNA lineages, and nuclear introgression at some contact zones. Male advertisement call differentiation is incongruent with the genetic structure as only one lineage appears differentiated. Occupying the Interior Highlands of the central United States, this Western lineage also has the most concordant mitochondrial and nuclear geographic patterns. Based on our findings we suggest that the antiquity of common ancestors was not as important as the maintenance of allopatry in the divergence in P. crucifer genetic lineages. We use multiple lines of evidence to generate hypotheses of isolation, reticulation, and discordance within this species and to expand our understanding of the early stages of speciation.

Functional Equivalence of Created Wetland Water Quality: A Comparison of Amphibian Metamorphic Success

Wetlands are often created through wetland mitigation to replace lost natural wetlands, but further evaluation is needed to determine the ability of a created wetland to replace lost wetland functions, especially providing wildlife habitat. We used a mesocosm design to compare the water quality between three created wetlands and three natural wetlands in West Virginia, USA and to evaluate how the water quality from the two wetland types were able to support metamorphosis in larval spring peepers (Pseudacris crucifer) and wood frogs (Lithobates sylvaticus) across two years (2014-2015). Responses in metamorphosis rates differed between species and between years. Spring peepers displayed similar metamorphosis rates in the created and natural wetlands in both years of the study. Wood frogs displayed similar metamorphosis rates in created and natural wetlands in 2015, but in 2014 wood frogs reached metamorphosis in less time and at a larger body size in the natural wetlands, suggesting that the wood frogs that developed in the natural wetlands may have higher fitness than those that developed in the created wetlands. Water quality was largely similar between created and natural wetlands, although dissolved oxygen, conductivity, and pH varied between mesocosms and wetlands. Our study suggests that created wetlands may be providing partial mitigation in terms of water quality for amphibian development. We recommend that future monitoring of created wetlands include measures of juvenile amphibian recruitment as well as additional habitat variables to better determine the ability of created wetlands to function as amphibian habitat.

High and dry: Trade-off in arboreal calling in a treefrog mediated by local environment

AbstractTrade-offs shaping behavioral variation are often influenced by the environment. We investigated the role that the environment plays in mediating trade-offs using a widespread frog with a conspicuous mating display, Pseudacris crucifer. We first demonstrated, using playback and desiccation experiments, that calling site selection involves a trade-off between sound transmission and desiccation. We then determined the influence of local environmental conditions on the intensity of the trade-off by examining range-wide behavioral and environmental data. We showed that the benefit of improved call transmission is positively influenced by vegetation density and ground cover. Behavioral data are consistent with this relationship: sites with a greater transmission benefit have increased prevalence of arboreally calling males. We also found that the prevalence of arboreal calling behavior increases with relative humidity and air temperature, suggesting an influence of these environmental variables on the desiccation cost of arboreal calling. This study provides a clear example of the role of the environment in mediating trade-off intensities and shaping critical behavioral traits.Local environment mediates the intensity of a trade-off associated with arboreal calling behavior in a treefrog. Combining observational and experimental approaches, we show that arboreal calling behavior increases the transmission of a mating call while potentially subjecting individuals to a rate of desiccation six times greater than terrestrial calling. Local environmental conditions influence both the benefit and the cost of this trade-off, subjecting different populations to varying trade-off intensities and shaping arboreal calling behavior.

Parasite-induced vulnerability to predation in larval anurans.

Within communities, pathogens and parasites have the potential to indirectly influence predator-prey interactions. For instance, prey that exhibit pathology or altered traits (e.g. behavioral shifts) following infection could be more prone to predation, which is known as parasite-induced vulnerability to predation (PIVP). PIVP has been frequently documented for pathogens with trophic transmission, because predators are often critical in the pathogen's life cycle. However, for pathogens without trophic transmission, PIVP can lead to a healthy herds effect, thereby reducing transmission in the system. In this study, we explored whether the pathogen ranavirus (family Iridoviridae) enhances vulnerability of 4 species of larval amphibians (spring peepers Pseudacris crucifer, gray treefrogs Hyla versicolor, American toads Anaxyrus americanus, and northern leopard frogs Lithobates pipiens) to 2 common tadpole predators (larval green darners Anax junius [hereinafter Anax] and adult water bugs Belostoma flumineum [hereinafter Belostoma]). For each anuran species, we conducted short-term microcosm experiments to assess predation rates on individuals that were or were not exposed to virus. For 3 of the 4 species, we found that exposure to ranavirus decreased survival rates with Anax between 2- and 9-fold. However, we did not see the same trend with Belostoma, which indicates that predator identity is important in this interaction. More specifically, the higher efficiency of Anax in capturing and consuming prey, relative to Belostoma, may allow Anax to capitalize on trait changes induced by virus exposure and enhance the PIVP effect. Our results indicate that trait-mediated indirect effects could play a role in creating healthy herds in amphibian communities.

Ecological Correlates of Large-Scale Turnover in the Dominant Members of Pseudacris crucifer Skin Bacterial Communities

Animals host a wide diversity of symbiotic microorganisms that contribute important functions to host health, and our knowledge of what drives variation in the composition of these complex communities continues to grow. Microbiome studies at larger spatial scales present opportunities to evaluate the contribution of large-scale factors to variation in the microbiome. We conducted a large-scale field study to assess variation in the bacterial symbiont communities on adult frog skin (Pseudacris crucifer), characterized using 16S rRNA gene amplicon sequencing. We found that skin bacterial communities on frogs were less diverse than, and structurally distinct from, the surrounding habitat. Frog skin was typically dominated by one of two bacterial OTUs: at western sites, a Proteobacteria dominated the community, whereas eastern sites were dominated by an Actinobacteria. Using a metacommunity framework, we then sought to identify factors explaining small- and large-scale variation in community structure-that is, among hosts within a pond, and among ponds spanning the study transect. We focused on the presence of a fungal skin pathogen, Batrachochytrium dendrobatidis (Bd) as one potential driver of variation. We found no direct link between skin bacterial community structure and Bd infection status of individual frog hosts. Differences in pond-level community structure, however, were explained by Bd infection prevalence. Importantly, Bd infection prevalence itself was correlated with numerous other environmental factors; thus, skin bacterial diversity may be influenced by a complex suite of extrinsic factors. Our findings indicate that large-scale factors and processes merit consideration when seeking to understand microbiome diversity.

Spring Peeper (Pseudacris crucifer) in Labrador, Canada: an update

Spring Peeper (Pseudacris crucifer) was first confirmed in Labrador in 1998, when vocalizations were recorded near Happy Valley-Goose Bay. Prior to this, only unsubstantiated reports of Spring Peepers in Labrador existed. In 2006, we visually documented nine Spring Peepers at six locations west of Happy Valley-Goose Bay, in the lower Churchill River valley. In 2014, using auditory surveys, we further documented 1–10 Spring Peepers calling at 13 additional locations in the same general area. These new records support earlier findings and provide additional information on the species at the extreme northeastern edge of its range.

Multi-year data from satellite- and ground-based sensors show details and scale matter in assessing climate's effects on wetland surface water, amphibians, and landscape conditions.

Long-term, interdisciplinary studies of relations between climate and ecological conditions on wetland-upland landscapes have been lacking, especially studies integrated across scales meaningful for adaptive resource management. We collected data in situ at individual wetlands, and via satellite for surrounding 4-km2 landscape blocks, to assess relations between annual weather dynamics, snow duration, phenology, wetland surface-water availability, amphibian presence and calling activity, greenness, and evapotranspiration in four U.S. conservation areas from 2008 to 2012. Amid recent decades of relatively warm growing seasons, 2012 and 2010 were the first and second warmest seasons, respectively, dating back to 1895. Accordingly, we observed the earliest starts of springtime biological activity during those two years. In all years, early-season amphibians first called soon after daily mean air temperatures were ≥ 0°C and snow had mostly melted. Similarly, satellite-based indicators suggested seasonal leaf-out happened soon after snowmelt and temperature thresholds for plant growth had occurred. Daily fluctuations in weather and water levels were related to amphibian calling activity, including decoupling the timing of the onset of calling at the start of season from the onset of calling events later in the season. Within-season variation in temperature and precipitation also was related to vegetation greenness and evapotranspiration, but more at monthly and seasonal scales. Wetland water levels were moderately to strongly associated with precipitation and early or intermittent wetland drying likely reduced amphibian reproduction success in some years, even though Pseudacris crucifer occupied sites at consistently high levels. Notably, satellite-based indicators of landscape water availability did not suggest such consequential, intra-seasonal variability in wetland surface-water availability. Our cross-disciplinary data show how temperature and precipitation interacted to affect key ecological relations and outcomes on our study landscapes. These results demonstrate the value of multi-year studies and the importance of scale for understanding actual climate-related effects in these areas.

Erythrism in Spring Peeper (<i>Pseudacris crucifer</i>) in Maritime Canada

We document three cases of erythrism in Spring Peeper (Pseudacris crucifer) in New Brunswick and Nova Scotia. Although the source of erythrism in Maritime P. crucifer remains uncertain, the occurrences reported here demonstrate this colour morph to be a widespread, although apparently rare, form in the Canadian Maritimes region.

Not just a peep: The evolution of calling in Pseudacris crucifer

Reproductive isolation is the hallmark of speciation as defined by the biological species concept. A species that is evolving towards reproductive isolation, but has not reached full isolation, is defined as an incipient species. One mechanism used by incipient species to further drive speciation is the use of mate recognition signals. The spring peeper, Pseudacris crucifer, is a North American frog that can be classified as an incipient species, as previous studies have found 6 distinct mitochondrial lineages within its range. Spring peepers use vocal signals for mate recognition and exhibit a female choice mating system where the males call to attract females. This study investigates the evolution of calling in spring peepers. Using calls from each lineage across the full range of spring peepers, I analyzed 11 different characteristics to determine whether the calls were different, and if so, which characteristics are being selected for. Preliminary evidence suggests that the calls between the lineages are distinct and that certain characteristics of the call are more heavily selected for than others. Full analysis on the data has not been completed at this time. This study will expand the understanding of the evolution of spring peepers, as well as offer insight into the role of mating systems on reproductive isolation.

The benefits of coinfection: trematodes alter disease outcomes associated with virus infection

Coinfections are increasingly recognized as important drivers of disease dynamics. Consequently, greater emphasis has been placed on integrating principles from community ecology with disease ecology to understand within-host interactions among parasites. Using larval amphibians and two amphibian parasites (ranaviruses and the trematode Echinoparyphium sp.), we examined the influence of coinfection on disease outcomes. Our first objective was to examine how priority effects (the timing and sequence of parasite exposure) influence infection and disease outcomes in the laboratory. We found that interactions between the parasites were asymmetric; prior infection with Echinoparyphium reduced ranaviral loads by 9% but there was no reciprocal effect of prior ranavirus infection on Echinoparyphium load. Additionally, survival rates of hosts (larval gray treefrogs; Hyla versicolor) infected with Echinoparyphium 10days prior to virus exposure were 25% greater compared to hosts only exposed to virus. Our second objective was to determine whether these patterns were generalizable to multiple amphibian species under more natural conditions. We conducted a semi-natural mesocosm experiment consisting of four larval amphibian hosts [gray treefrogs, American toads (Anaxyrus americanus), leopard frogs (Lithobates pipiens) and spring peepers (Pseudacris crucifer)] to examine how prior Echinoparyphium infection influenced ranavirus transmission within the community, using ranavirus-infected larval wood frogs (Lithobates sylvaticus) as source of ranavirus. Consistent with the laboratory experiment, we found that prior Echinoparyphium infection reduced ranaviral loads by 19 to 28% in three of the four species. Collectively, these results suggest that macroparasite infection can reduce microparasite replication rates across multiple amphibian species, possibly through cross-reactive immunity. Although the immunological mechanisms driving this outcome are in need of further study, trematode infections appear to benefit hosts that are exposed to ranaviruses. Additionally, these results suggest that consideration of priority effects and timing of exposure are vital for understanding parasite interactions within hosts and disease outcomes.

Assessing Capture Probabilities of Larval Pond-Breeding Anurans in New Brunswick, Canada

Abstract We used removal sampling (RS) and neutral red dye capture–mark–recapture (CMR) methods to estimate capture probabilities for larval Wood Frogs (Lithobates sylvaticus), Spring Peepers (Pseudacris crucifer), and first-year Green Frogs (Lithobates clamitans) in ponds in southern New Brunswick, Canada. We modeled capture probability as a function of environmental variables and tested whether marks were retained between surveys. We also performed simulations to understand the effect of survey effort, capture probability, and abundance on detection probabilities and the number of surveys needed to be confident of absence. Capture probabilities (P ± SD) were low and variable: Wood Frogs, P = 0.262 ± 0.128; Spring Peepers, P = 0.323 ± 0.241; and first-year Green Frogs, P = 0.159 ± 0.106. With the use of AICc, we determined a model with the proportion of non-Typha emergent vegetation to have a positive effect, whereas pond depth had a negative effort on capture probabilities in first-year Green Frog larva...

Amphibian reproductive success as a gauge of functional equivalency of created wetlands in the Central Appalachians

Context Evaluating the adequacy of created wetlands to replace the functions of lost natural wetlands is important because wetland mitigation is a major tool used to offset wetland losses. However, measurements such as vegetative cover and presence of wildlife may not provide sufficient evidence that created wetlands are functioning properly. Thus, examining the ecology of wetland biota such as that of amphibians may be a more useful surrogate for function. Aims The objectives of this study were to compare the abundance of amphibian metamorphs and survival and growth of larval amphibians in created wetlands, relative to natural wetlands. Methods Amphibian metamorphs were trapped in created and natural wetlands during the spring (April–May) and summer (June–August) of 2009 and 2010, and 165 green frog (Lithobates clamitans) larvae were raised during the spring of 2010 in laboratory aquaria containing water from created or natural wetlands. Key results Abundance of spring peeper (Pseudacris crucifer) metamorphs decreased significantly from 2009 to 2010 and abundance of green frog metamorphs increased with habitat complexity, but both were unaffected by wetland type. Detection probability of metamorphs of both species was low, increased with water temperature and declined with month of observation. Survival, growth curves and mass were similar among green frog larvae raised in created and natural wetland aquaria. Conclusions Our results suggest that the created and natural wetlands we examined function similarly with respect to providing adequate breeding habitat for green frogs and spring peepers. Implications Wetlands created to offset the loss of natural wetlands, although generally not designed for the purpose of wildlife habitat, can function as adequate breeding habitat for generalist amphibians such as green frogs and spring peepers.

Effect of Simultaneous Amphibian Exposure to Pesticides and an Emerging Fungal Pathogen, Batrachochytrium dendrobatidis.

Amphibian declines have been linked to numerous factors, including pesticide use and the fungal pathogen Batrachochytrium dendrobatidis (Bd). Moreover, research has suggested a link between amphibian sensitivity to Bd and pesticide exposure. We simultaneously exposed postmetamorphic American toads (Anaxyrus americanus), western toads (A. boreas), spring peepers (Pseudacris crucifer), Pacific treefrogs (P. regilla), leopard frogs (Lithobates pipiens), and Cascades frogs (Rana cascadae) to a factorial combination of two pathogen treatments (Bd+, Bd-) and four pesticide treatments (control, ethanol vehicle, herbicide mixture, and insecticide mixture) for 14 d to quantify survival and infection load. We found no interactive effects of pesticides and Bd on anuran survival and no effects of pesticides on infection load. Mortality following Bd exposure increased in spring peepers and American toads and was dependent upon snout-vent length in western toads, American toads, and Pacific treefrogs. Previous studies reported effects of early sublethal pesticide exposure on amphibian Bd sensitivity and infection load at later life stages, but we found simultaneous exposure to sublethal pesticide concentrations and Bd had no such effect on postmetamorphic juvenile anurans. Future research investigating complex interactions between pesticides and Bd should employ a variety of pesticide formulations and Bd strains and follow the effects of exposure throughout ontogeny.