Amphibian Presence Research Articles

A framework to identify priority wetland habitats and movement corridors for urban amphibian conservation

Abstract Cities worldwide are expanding in area and human population, posing multiple challenges to amphibian populations, including habitat loss from removal of wetlands and terrestrial upland habitat, habitat fragmentation due to roads and the built environment, and habitat degradation from pollutants, extensive human use and introduced species. We developed an eight‐step urban amphibian conservation framework based on established monitoring, analytical methods and community engagement to enable amphibian conservation in a large urban centre. The framework outlines a process used to conserve biodiversity in a complex landuse and decision‐making environment supported by a series of successive complementary modelling techniques to measure amphibian presence, priority habitat and functional connectivity. We applied the framework in Calgary, Alberta, Canada to illustrate its potential. Here, urbanization has reduced wetlands by 90% and ecological knowledge on amphibians was poor. We improved knowledge on amphibian diversity and distribution, identified core wetlands and movement pathways for amphibian species and identified barriers in the wetland network where construction or restoration measures could re‐establish amphibians or increase their densities. This knowledge was shared with ecologists and city planners for implementation through appropriate policies and plans. Our framework provides a series of stepwise products to improve an urban municipality's ability to restore or conserve priority habitat and movement pathways necessary for amphibian survival under pressure from multiple land uses. The framework provides a platform to identify city plans, policy and or programmes and to derive necessary information to support amphibian conservation.

Slight variations in coastal topography mitigate the consequence of storm-induced marine submersion on amphibian communities

The rise in sea-level and the increase in frequency and intensity of extreme weather events (i.e., storms and associated surges) are expected to strongly impact coastal areas. The gradual impacts of sea-level rise may allow species to display adaptive responses to overcome environmental changes. In contrast, the abruptness of marine submersions during extreme weather events can induce changes that may exceed the ability of species to respond to brutally changing environments. Yet, site-specific topographical features may buffer the expected detrimental effects of marine submersions on wildlife. In order to test such topographical effects, we examined the long-term consequences of a major marine submersion (storm Xynthia) on the amphibian communities of two French Atlantic coastal wetlands that slightly differ in their topography and, thus, their susceptibility to marine submersion. Amphibians were monitored on 64 ponds for up to 13 years, using acoustic and visual methods, in conjunction with environmental parameters (e.g., pond topology, vegetation, salinity). We found that the amphibian communities at the two neighboring sites displayed different responses to the marine submersion linked to storm Xynthia. As predicted, slight differences in local topography induced strong differences in local magnitude of the landward marine surge, influencing salinization dynamics and associated consequences on wildlife (amphibians). The different species responses show that amphibian richness can recover to that of pre-storm conditions, but with significant changes in the composition of the community. Our results suggest that amphibian presence post-submersion in coastal wetlands results from an interaction between species traits (e.g., tolerance to elevated salinity), site-specific topography, and environmental parameters. Finally, our study emphasizes that relatively modest landscaping management may be critical to allow wildlife to successfully recover after a marine submersion.

Correlates of Waterbody Characteristics and the Occurrence or Diversity of Larval Amphibians in Central Ontario, Canada.

Watershed acidification and poor water quality can deleteriously affect amphibian populations. Between 1990 and 2008, we sampled 333 small, permanent (inundated year round) waterbodies that drain forested areas in the Algoma, Muskoka and Sudbury regions of central Ontario, Canada to determine whether water chemistry parameters, fish presence, and waterbody area and depth predict amphibian presence or diversity. Amphibians were present in some low-pH waterbodies, contrasting earlier studies, and generally water chemistry was not a strong indicator of amphibian presence or diversity in central Ontario. We suspect that other biotic and abiotic factors have a stronger effect on amphibian presence, and that the relationships between chemical and physical attributes and amphibian presence are complex. Future research should focus on long-term habitat change in central Ontario waterbodies to determine how watershed degradation has affected amphibians.

Assessing the role of habitat and species interactions in the population decline and detection bias of Neotropical leaf litter frogs in and around La Selva Biological Station, Costa Rica

Worldwide, amphibian populations have been declining rapidly. This decline can be attributed to many factors including climate change, pesticide exposure, and emerging infectious diseases, among other important factors, but few studies have examined the influence of species interactions. In this study, we examined how habitat factors and co-occurring avian and mammalian species, as well as humans, exert direct and indirect effects on Neotropical amphibian population dynamics. We further examined how these habitat and species interactions could affect our ability to reliably detect amphibian presence to robustly estimate population trends. We conducted amphibian visual encounter surveys at 26 randomly selected sites in the La Selva Biological Station, in northeastern Costa Rica, as well as 26 sites across five additional forest fragments in the region. Furthermore, we used camera traps to collect data on avian and mammalian communities and human visitation at those amphibian survey plots. From these data, we were able to estimate species occupancy probabilities for leaf litter frogs across sites and their relationships to habitat and interspecific species interaction covariates. We also conducted an experiment with plastic model frogs to estimate detection probabilities when a population is known to occur at a site with certainty. Our results suggested that strawberry poison dart frog (Oophagapumilio) occupancy was positively related to secondary forest and their detection was negatively related to increasing air temperatures at the times of the surveys. Leaf litter frog occupancy was negatively related to core La Selva sites and human detections at sites, yet their detection was positively related to human trail presence, which might be related to reduced leaf litter cover due to heavy trampling. Our experimental surveys suggested that Neotropical leaf litter frog communities are difficult to detect when present and future studies should explicitly account for this detection bias to effectively monitor population trends.

Recent Development of Aprotic Na−O2 Batteries

AbstractThe development of batteries with high energy density and low costs involves chemistry beyond lithium‐ion batteries. Rechargeable sodium‐oxygen (Na−O2) batteries make two essential steps forward: i) replacing Li by Na to remove the bottleneck in resources supply and ii) using oxygen from air to raise the theoretical energy density. A lot of progress has been made in performance and understanding of Na−O2 battery since its first report in 2012. However, there remain significant challenges, such as the instability of discharge products, dendrite growth of Na metal, and the crossover of superoxide. A timely review is given here to summarize the challenges encountered in the components of the Na−O2 battery. Insights are offered on sodium anode protection, morphology dynamics at the cathode, amphibian presence of superoxide, and the roles of electrolyte. Bright prospects in further development of aprotic Na−O2 batteries are envisioned.

Influence of Landscape Factors on Amphibian Roadkills at the National Level

Roads exert multiple effects on wildlife, from animal mortality, habitat and population fragmentation, to modification of animal reproductive behaviour. Amphibians are the most frequently road-killed animal group. Many studies have attempted to analyse the factors driving amphibian casualties on roads, but these factors are limited to the roads themselves (e.g., traffic, type of roads, roads crossing water bodies) or to structures along them (e.g., ditches, walls). Sometimes, roadkills are related to land use along the roads. We analysed the influence of landscape factors on roadkill hotspots at the national level (Slovenia). Specifically, we aimed at: (1) identifying hotspots of roadkills, (2) analysing whether records of amphibian presence on roads are related to the distribution of water bodies and (3) analysing which factors (proximity to water bodies or human factors) explain the distribution of hotspots. Hotspots were identified by Malo’s method. Roadkills were modelled with Maxent for the first time in Slovenia. The relationships between amphibian presence and hotspots with factors were analysed with GLM. A total of 237 road sections were identified as hotspots, corresponding to 8% of road sections and containing 90% of road-killed individuals. Proximity to forests, meadows and agricultural land were the most important variables in Maxent models. The number of roadkills depended on the proximity to agricultural land, forests, water bodies and wetland areas, while the number of hotspots additionally depended on the proximity to urban settlements.

Factors influencing amphibian distributions in Grand Teton National Park and western Wyoming

Predicting the distribution of amphibians can be difficult because habitat suitability may depend on a variety of environmental and anthropogenic factors, including water quality of wetlands, geology of watersheds, and presence of invasive pathogens. Previous studies hypothesized that water chemistry may influence the rate of chytrid infection in amphibians where higher conductivity sites may have less infection. We sampled two watersheds in Grand Teton National Park and 3 watersheds adjacent to the park, and measured amphibian presence, chytrid infection, basic water quality, major ion concentrations and geology of the wetland. This is part of a larger project where we are comparing amphibian presence and infection rate among wetlands in the Gros Ventre, Wind River, and Teton Ranges. We sampled watersheds that were predominately limestone, granite or a mixture. Water quality varied among sites with higher conductivity and ion concentrations for limestone watersheds compared to granite watersheds. This report includes preliminary results of amphibian surveys and water quality analyses. Future analyses will relate occupancy rates of amphibians to environmental factors, including water chemistry, geology, and presence of chytrid fungus, as well as comparing detection rates of amphibians with environmental DNA (eDNA) and visual observation surveys.
 
 Featured photo by Neal Herbert on Flickr. https://flic.kr/p/2gv9PJA

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.

Increased Amphibian Presence In A Montane Lake After Fish Removal, Mount Rainier National Park, Washington

During the period 1996–2003, a population of introduced Salvelinus fontinalis was eradicated from a montane lake in Mount Rainier National Park, Washington State, USA. Using mostly gill-nets, 2185 fish were removed. Snorkel and visual encounter surveys (n = 10 and 6, respectively) were completed 1996–2001, to document the apparent abundances of amphibian species present in the lake and an adjacent shallow pond during fish presence and removal. During this period only 7 Ambystoma gracile larvae and 6 Rana cascadae adults were observed in the lake; no amphibians were observed in the pond. After fish removal, lake snorkel and visual encounter surveys (n = 9 and 10, respectively) conducted between 2004 and 2015 collectively documented the apparent increase in abundances of A. gracilie (n = 398), A. macrodactylum (n = 68), Ambystoma spp. (n = 184), Rana cascadae (n = 357), and Ascaphus truei (n = 12). Pond visual encounter surveys conducted between 2005 and 2012 documented the increased presence of Ambystoma spp. (n = 110) and Rana cascadae (n = approximately 5600 ) larvae. Although the number of amphibian species detected and their apparent abundances varied among surveys and years, the abundances of the amphibian species in Hidden Lake increased markedly after removal of the introduced fish population.

Amphibian breeding phenology and reproductive outcome: an examination using terrestrial and aquatic sampling

Worldwide amphibian declines highlight the need for programs that monitor species presence and track population trends. We sampled larval amphibians with a box trap at 3-week intervals for 23 months in eight wetlands, and concurrently trapped adults and juveniles with drift fences, to examine spatiotemporal patterns of tadpole occurrence; explore relationships between breeding effort, tadpole abundance, and recruitment; and compare the efficacy of both methods in detecting species presence and reproductive outcome. Intermittent detection of species within and among wetlands suggested high mortality, followed by deposition of new eggs and tadpole cohorts. Breeding effort, tadpole abundance, and juvenile recruitment were generally not correlated. The reasons for this may include differential bias in detecting species or life stages between methods and high incidence of egg or tadpole mortality. Drift fences detected more species than box traps, but each provided insights regarding amphibian presence and recruitment. Our results illustrate shortfalls in the ability of infrequent aquatic sampling to detect local species richness of larval amphibians, as occurrence of many species is spatially and temporally variable. We also show the importance of using different sampling methods to detect species’ presence, as well as difficulties associated with both methods in tracking breeding effort, tadpole occurrence, or reproductive outcome.

Do frogs really eat cardamom? Understanding the myth of crop damage by amphibians in the Western Ghats, India.

In the Western Ghats of India, amphibians are culled at cardamom plantations since they are perceived to consume cardamom. To better understand the relationship between amphibians and cardamom, a study was undertaken at these plantations, which harbor numerous threatened and range-restricted amphibians. We undertook questionnaire surveys with 298 respondents at 148 plantations across southern India. Time-activity budget and diet analysis surveys were undertaken to determine whether amphibians really consumed cardamom. The conception that amphibians eat cardamom was found to be widespread especially among small-sized plantations, leading to negative perceptions and a lack of interest in amphibian conservation. The plantation community perceives a substantial economic loss due to amphibians, even though this is non-existent as revealed by our field surveys. These perceptions would lead to a continued intolerance of amphibian presence in plantations. A suitable outreach initiative re-affirming facts and spreading awareness on the positive role of amphibians would need to be conducted to negate this age-old myth.

Spontaneous succession on spoil banks supports amphibian diversity and abundance

The ecological value and conservation potential of post-mining areas have been increasingly recognized by scientists and conservationists during recent decades. Especially valuable are sites left to spontaneous succession, which constitute habitats with high species diversity, or habitats that serve as refuges for threatened species. In contrast to several other taxa, there is a lack of such evidence for amphibians, despite the assumption that primary succession leads to a more suitable environment for amphibians than does technical reclamation. Therefore, we compared the effects of technical reclamation and spontaneous succession on amphibian presence, species richness, and abundance of the model species Rana dalmatina in technically reclaimed and unreclaimed sections of spoil banks in the Czech Republic's North Bohemian brown coal basin. We found that most recorded amphibian species, and R. dalmatina in particular, occurred predominantly within successional spoil bank sections. Apart from reclamation status, amphibians preferred partially vegetated ponds (5–75% vegetation cover) having gently sloping shores (<30°) and lower water conductivity. Mean species richness per pond (1.95 vs. 1.20), the proportion of ponds occupied by amphibians (88.5% vs. 69.4%), and the mean numbers of R. dalmatina clutches per pond (9.05 vs. 1.65) were significantly higher at unreclaimed sites compared to technically reclaimed sites. This study confirms the conservation value of post-mining sites for amphibians and evidences that sites left to spontaneous succession provide more suitable habitats for amphibians compared to technically reclaimed sites. Key habitat characteristics driving amphibian assemblages within post-mining sites are identified and guidelines for effective protection of amphibians in post-mining areas are proposed.

Terrestrial exposure and effects of Headline AMP(®) Fungicide on amphibians.

Recent studies have demonstrated that a pyraclostrobin-containing fungicide (Headline(®) Fungicide--Headline(®) Fungicide and Headline AMP(®) Fungicide are registered trademarks of BASF) is toxic to amphibians at environmentally relevant concentrations. However, these studies were performed in a laboratory setting of a worst-case direct exposure in clean media. Interception of spray by the crop canopy and ground cover used by animals for security cover will influence exposure. Thus, risk to amphibians is unclear in an environmentally realistic field environment. We tested exposure and toxicity of Headline AMP(®) Fungicide to amphibians in multiple agricultural habitat scenarios (e.g., within treated crop vs. grassy areas adjacent to crop) and at two rates during routine aerial application. Specifically, we placed Woodhouse's toads (Bufo woodhousii) and Blanchard's cricket frogs (Acris blanchardi) in enclosures located within treated and untreated corn (VT stage, approximate height = 3 m), and in the potential drift area (adjacent to treated corn) during aerial application of Headline AMP Fungicide at either 731 or 1052 ml/ha (70 and 100 % the maximum application rate in corn, respectively). Mean concentrations of pyraclostrobin measured at ground level were ≤19 % of nominal application rate in all areas. Overall, mean mortality of recovered individuals of both species was ≤15 %, and mortality within Headline AMP Fungicide-treated corn (where risk was anticipated to be highest) was <10 %. It is important to understand that application timing, interception by the crop canopy (which varies both within and between crop systems), and timing of amphibian presence in the crop field influences risk of exposure and effects; however, our results demonstrate that amphibians inhabiting VT stage corn during routine aerial application of Headline AMP Fungicide are at low risk for acute mortality, matching existing laboratory results from acute toxicity studies of Headline Fungicide.

Fish Influences on Amphibian Presence and Abundance in Prairie and Parkland Landscapes of Minnesota, USA

Many amphibian populations are declining, and increased understanding of the drivers of amphibian presence and abundance will help in their conservation. In 2005 and 2006 we estimated relative abundance of larvae of two common amphibian taxa, Tiger Salamanders (Ambystoma tigrinum) and ranid tadpoles (Northern Leopard Frog Lithobates pipiens and Wood Frog Lithobates sylvaticus), in 75 shallow lakes in prairie and parkland areas in Minnesota. We used a two-step procedure in which we first modeled presence-absence with data from all lakes and then modeled abundance only in lakes where the amphibian taxa were present. For the two amphibian taxa, a generalized linear mixed effects model was used to examine the effects of dynamic factors like fish abundance and static (timeframe of study) variables like fish community type, depth, and adjacent land cover. Fish variables had the greatest influence but differed for the presence and abundance models. Salamander and tadpole presence was inversely correlated to the abundance of benthivorous fish, while salamander abundance was best explained by total fish abundance and tadpole abundance by fish community type. We did not detect influences of land cover types on the amphibian taxa we surveyed. Our findings are important because they complement previous studies documenting that negative correlations with fish extend beyond piscivores to include both planktivores and benthivores. Hydrological changes in our study landscape (e.g., installation of drainage networks, wetland consolidation) associated with agriculture and other land uses have likely increased the distribution and abundance of fish populations, thus dampening amphibian breeding success.

Matrix and habitat quality in a montane cloud-forest landscape: amphibians in coffee plantations in central Veracruz, Mexico

Context The processes of fragmentation, habitat loss, degradation and their combined effects are formidable threats to amphibian populations. Aims We evaluate the effect of three land use-type variables and nine landscape matrix quality factors on amphibian presence in four coffee agro-ecosystems and two cloud-forest fragments in central Veracruz, Mexico. Methods Each site was thoroughly searched using the visual-encounter survey technique along different trails in the most feasible microhabitats for detecting amphibians during four rainy seasons (2005, 2006, 2008 and 2009). Centred on the location where each amphibian species was first recorded, we established what we refer to as a buffer area within a radius of 1.5 km. A Co-Inertia mathematical model was used to determine which of the explanatory variables contributed to maintaining amphibian diversity. The landscape variables were landscape-quality index, open areas, canopy cover (low, intermediate, dense) at the matrix level, river, road and human population density and site size. Local variables were elevation, plant-structure and biological-impact indices. Key results During the study we recorded 1078 amphibians belonging to 26 species, 17 genera and 10 families. The variables explaining the composition of amphibian diversity were river and human population density, low canopy cover at the matrix level, elevation, site size and plant-structure index. Amphibian diversity increased as the structural complexity of the habitat increased, and the former was positively correlated with fragment size. Conclusion The present study indicated that coffee agro-ecosystems and the cloud-forest fragments in the region form a gradient in habitat quality and landscape variables that exert a differential influence on amphibian assemblages, and that each species responds uniquely to different variables. Implications Coffee agro-ecosystems and forest fragments cannot be seen as homogenous patches with a certain habitat quality, separate from the landscape matrix in which they are immersed. Stakeholders are not advised to rely on a single strategy to conserve the amphibian community, but rather should aim to maintain a heterogeneous landscape with forest fragments and coffee agro-ecosystems that have a complex vertical plant structure at the habitat level, especially in highly river-dense landscapes.

Urban Amphibians of the Texas Panhandle

&#x0D; &#x0D; &#x0D; &#x0D; Habitat loss, degradation, and fragmentation due to urbanization are implicated in amphibian declines worldwide. Conservation efforts require information on resident species and their habitat interactions, but amphibian ecology is largely unstudied in urban centers of the Southern High Plains. Here, we gathered baseline data on amphibian presence, species richness, and habitat preferences at site-specific and landscape scales during a severe drought year in the city of Lubbock, in northwestern Texas. Ephemeral playa wetlands are characteristic of this landscape. During urbanization, these have been extensively modifiied for stormwater drainage, agriculture, and construction of roads, buildings and neighborhoods. A semi-arid climate with frequent droughts, together with urbanization, could have an adverse effect on resident amphibians. In 2011, we sampled 23 urban lakes for amphibian presence, using a combination of audio, visual, and larval surveys. We detected five amphibian species at seven lakes; Texas Toads (Anaxyrus speciosus) and Spotted Chorus Frogs (Pseudacris clarkii) were the most frequently encountered species. We found significant negative effects of nearby road density on amphibian species presence and richness. We also detected significant negative effects of basic pH on amphibian species richness. These data can be used for prioritizing lakes for amphibian conservation strategies, to monitor ecosystem function in urban wetlands, and to guide future development and restoration efforts.&#x0D; &#x0D; &#x0D; &#x0D;

Influence of Landscape Elements in Riparian Buffers on the Conservation of Semiaquatic Amphibians

Studies on riparian buffers have usually focused on the amount of land needed as habitat for the terrestrial life stages of semiaquatic species. Nevertheless, the landscape surrounding wetlands is also important for other key processes, such as dispersal and the dynamics of metapopulations. Multiple elements that influence these processes should therefore be considered in the delineation of buffers. We analyzed landscape elements (forest cover, density of roads, and hydrographic network) in concentric buffers to evaluate the scale at which they influence stream amphibians in 77 distinct landscapes. To evaluate whether our results could be generalized to other contexts, we determined whether they were consistent across the study areas. Amphibians required buffers of 100-400 m of suitable terrestrial habitat, but interspecific differences in the amount of habitat were large. The presence of amphibians was related to roads and the hydrographic network at larger spatial scales (300-1500 m), which suggests that wider buffers are needed with these elements. This pattern probably arose because these elements influence dispersal and metapopulation persistence, processes that occur at large spatial scales. Furthermore, in some cases, analyses performed on different sets of landscapes provided different results, which suggests caution should be used when conservation recommendations are applied to disparate areas. Establishment of riparian buffers should not be focused only on riparian habitat, but should take a landscape perspective because semiaquatic species use multiple elements for different functions. This approach can be complex because different landscape elements require different spatial extents. Nevertheless, a shift of attention toward the management of different elements at multiple spatial scales is necessary for the long-term persistence of populations.

Biodiversity in southern Wisconsin storm-water retention ponds: Correlations with watershed cover and productivity

This research is based on the management principle that watershed land cover is a better predictor of pond biodiversity than primary productivity. Ponds in watersheds with more than 30% lawn cover have few zooplankton species, no macrophytes, no snails, and no amphibians. A recent meta-analysis generated the hypothesis that watershed (catchment basin) land cover is a better predictor of lake biodiversity than traditional predictors (such as in-lake primary productivity) if the watershed includes human development (agriculture, residential, or urban). This hypothesis was tested via a field survey of 23 similar-sized artificial ponds in southern Wisconsin. The ponds had similar climate and geology, but differed in the relative proportions of land cover in the watershed. Twelve environmental variables (including pond area, depth, and primary productivity surrogates) and seven watershed land cover variables were correlated with biodiversity measures of seven major aquatic communities. Percent lawn cover was negatively correlated with zooplankton richness (r2 = 0.41), macrophyte abundance (r2 = 61), molluscan presence (r2 = 0.48), and amphibian presence (r2 = 0.55 for spring species and r2 = 0.78 for summer species). Fish presence was negatively correlated with percent watershed covered by meadow (r2 = 0.16). Chlorophyll a (a primary productivity surrogate) was negatively correlated with three groups: zooplankton richness (r2 = 0.18), macrophyte abundance (r2 = 0.23), and molluscan presence/absence (r2 = 0.31). Total phosphorus and nitrogen (surrogates of in-lake primary productivity) were weakly correlated with biodiversity.

Sub‐alpine amphibian distributions related to species palatability to non‐native salmonids in the Klamath mountains of northern California

ABSTRACTThe goal of this study was to examine how introduced trout influence the distributions and abundances of a sub‐alpine amphibian assemblage whose members display a variety of different life‐history and defence strategies. Our study was conducted in the sub‐alpine lentic habitats of three wilderness areas that form the core of the Klamath‐Siskiyou Bioregion of northern California, a biodiversity ‘hotspot’ that supports the highest diversity of sub‐alpine, lentic‐breeding amphibians in the western USA. These wilderness areas contain no native fishes, but all have been populated with non‐native trout for recreational fishing. Five of the eight amphibian species that occur in this region were sufficiently common to use in our study; these included one that breeds in both temporary and permanent waters and is palatable to fish (Pacific treefrog, Pseudacris regilla), two that breed primarily in permanent waters and are unpalatable to fish (western toad, Bufo boreas, and rough‐skinned newt, Taricha granulosa), and two that breed primarily in permanent waters and are palatable to fish (Cascades frog, Rana cascadae, and long‐toed salamander, Ambystoma macrodactylum). Based on life histories and predator defence strategies (i.e. palatable or not), we predicted that the three palatable species would likely be negatively correlated with introduced trout, but with P. regilla less impacted because of its use of both temporary and permanent waters. We predicted that B. boreas and T. granulosa would not be significantly correlated with introduced trout due to the lack of any predator/prey interactions between them. We surveyed 728 pond, lake, or wet meadow sites during the summers of 1999–2002, using timed gill‐net sets to measure trout occurrence and relative density, and visual encounter surveys to determine amphibian presence and abundance. We used semiparametric logistic regression models to quantify the effect of trout presence/absence and density on the probability of finding amphibian species in a water body while accounting for variation within and among the various lentic habitats sampled. The distributions of P. regilla, A. macrodactylum and R. cascadae were strongly negatively correlated with trout presence across all three wilderness areas. Ambystoma macrodactylum was 44 times more likely to be found in lakes without fish than in lakes with fish. Rana cascadae and P. regilla were 3.7 and 3.0 times more likely, respectively, to be found in fishless than fish‐containing waters. In contrast, the two unpalatable species were either uncorrelated (T. granulosa) or positively correlated (B. boreas) with fish presence. We found that the relative density of fish (catch per unit effort) was negatively correlated with the combined abundances of the three palatable amphibians, and also with both the length and the condition of the fish themselves. Our results are consistent with a compelling body of evidence that introduced fishes greatly alter the aquatic community structure of mountain lakes, ponds, and wet meadows.

Distribution Patterns of Lentic-Breeding Amphibians in Relation to Ultraviolet Radiation Exposure in Western North America

An increase in ultraviolet-B (UV-B) radiation has been posited to be a potential factor in the decline of some amphibian population. This hypothesis has received support from laboratory and field experiments showing that current levels of UV-B can cause embryo mortality in some species, but little research has addressed whether UV-B is influencing the distribution of amphibian populations. We compared patterns of amphibian presence to sitespecific estimates of UV-B dose at 683 ponds and lakes in Glacier, Olympic, and Sequoia‐Kings Canyon National Parks. All three parks are located in western North America, a region with a concentration of documented amphibian declines. Sitespecific daily UV-B dose was estimated using modeled and field-collected data to incorporate the effects of elevation, landscape, and water-column dissolved organic carbon. Of the eight species we examined (Ambystoma gracile, Ambystoma macrodactylum, Bufo boreas, Pseudacris regilla, Rana cascadae, Rana leuteiventris, Rana muscosa, Taricha granulosa), two species (T. granulosa and A. macrodactylum) had quadratic relationships with UV-B that could have resulted from negative UV-B effects. Both species were most likely to occur at moderate UV-B levels. Ambystoma macrodactylum showed this pattern only in Glacier National Park. Occurrence of A. macrodactylum increased as UV-B increased in Olympic National Park despite UV-B levels similar to those recorded in Glacier. We also found marginal support for a negative association with UV-B for P. regilla in one of the two parks where it occurred. We did not find evidence of a negative UV-B effect for any other species. Much more work is still needed to determine whether UV-B, either alone or in concert with other factors, is causing widespread population losses in amphibians.