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Vernal pools—small seasonal wetlands—provide critical breeding habitat for many species but are under-protected in environmental regulation. Because vernal pools are not rare in the northeastern United States, regulatory emphasis is typically placed on protecting "significant" vernal pools yet scientific criteria for determining thresholds for conservation significance remain poorly developed. We used an evidence-based approach to identify thresholds of pool significance based on populations of breeding amphibians in five ecoregions and across urbanization gradients of New York State, where a recent revision to wetland law allows regulation based on amphibian productivity. We combined existing population survey data with new surveys to yield a dataset of 587 pools for estimating statistical distributions of productivity of two indicator species: spotted salamanders (Ambystoma maculatum) and wood frogs (Lithobates sylvaticus). Spotted salamander egg mass counts were significantly lower in highly developed landscapes. Larger pools were generally more productive for both species yet no single habitat feature reliably predicted high egg mass counts. Pool incidence and productivity also varied regionally: the Hudson-Mohawk region hosted the most known vernal pools and highest egg mass counts and the Lake Plain region the fewest known pools. Our dataset yielded threshold options for guiding pool protection that varied by the proportion of pools targeted. We suggest a lower standard for protecting pools in high-development areas and that presence of other pool-breeding indicator species could also qualify pools for significance. These recommendations can guide regulators in affording protection critical to small wetland habitats specific to regional and landscape contexts. [ABSTRACT FROM AUTHOR]

The Spotted Salamander (Ambystoma maculatum) is a common salamander throughout Virginia. Its embryos and larvae can withstand both low and high temperatures, but because the time from fertilization to complete metamorphosis is about 5.5 months, depending on latitude and ambient temperatures, they require long-lived vernal ponds for their development. Adults home year after year to their natal ponds by olfactory imprinting. Various stages in their development, through metamorphosis, are documented here. Some clutches of eggs contained mutualistic algae. [ABSTRACT FROM AUTHOR]

Understanding the environmental drivers of species' dispersal and migration patterns is needed to accurately predict climate change impacts on populations. For pond-breeding amphibians, adult movements associated with the breeding period are well studied but major gaps exist in our knowledge of the drivers of adult and juvenile non-breeding movements. Here, we assess environmental drivers of adult and juvenile Ambystoma maculatum (Shaw, 1802), Ambystoma jeffersonianum (Green, 1827), and their unisexual dependants' (Ambystoma laterale–jeffersonianum (Uzzell, 1964)) summer and fall non-breeding movements using data from pitfall trapping and radio telemetry tracking. We used generalized linear models to assess the influence of precipitation, minimum temperature, day of year, and days since last precipitation on salamander movements. Juvenile summer dispersal movements were related to days since last precipitation in Jefferson Salamander complex individuals and 24 h precipitation in Spotted Salamanders. Adult and juvenile fall movements were driven by minimum temperature, 24 h precipitation, and days since last precipitation, and the effect of these environmental factors varied slightly between species and between Jefferson bisexuals and unisexuals. Our work indicates that changes in both temperature and precipitation will likely impact non-breeding dispersal and migration in these species and, overall, improves our understanding of ecological patterns throughout their entire life cycle. [ABSTRACT FROM AUTHOR]

A common challenge that oviparous animals face is securing survivorship during the vulnerable embryonic stage. One of the parental investment strategies to improve survivorship is providing physical structures to protect the embryos. In amphibians, there is a notable diversity in jelly‐layer structures surrounding eggs. Previous studies show that these jelly layers provide eggs with protection against egg predators, egg pathogens, and desiccation. However, few studies examined the cost–benefit relationship of the jelly‐layer structures. By using the predator–prey interaction between wood frog (Lithobates sylvaticus) tadpoles and spotted salamander (Ambystoma maculatum) eggs as a model system, we tested three hypotheses: (1) having the outer jelly layers would be costly to the embryos, (2) the relative benefit of the structural egg defense would become apparent and increase as the intensity of egg predation increases, and (3) a certain degree of predation would increase the hatching success of salamander embryos by mechanically thinning the thick outer jelly layers and increasing oxygen diffusion throughout an egg mass. To test these hypotheses, we conducted a factorial experiment in which we crossed four egg‐predation levels with two jelly‐layer conditions, intact or removed. We found that the jelly layers were essential in protecting spotted salamander embryos from wood frog tadpoles but that the associated cost was apparent in no‐predation treatments. The differential survivorship between intact eggs and eggs without jelly layers showed that the fitness advantage of jelly layers increased as the level of predation increased. Finally, the hatching success of intact egg masses was highest under the high predation conditions. These results imply that the evolution of the jelly‐layer thickness occurred under constant egg‐predation pressure. Given this predator–prey coevolution, egg predators may play a critical role in improving the hatching success of salamander embryos under certain conditions. [ABSTRACT FROM AUTHOR]

Abstract A common challenge that oviparous animals face is securing survivorship during the vulnerable embryonic stage. One of the parental investment strategies to improve survivorship is providing physical structures to protect the embryos. In amphibians, there is a notable diversity in jelly‐layer structures surrounding eggs. Previous studies show that these jelly layers provide eggs with protection against egg predators, egg pathogens, and desiccation. However, few studies examined the cost–benefit relationship of the jelly‐layer structures. By using the predator–prey interaction between wood frog (Lithobates sylvaticus) tadpoles and spotted salamander (Ambystoma maculatum) eggs as a model system, we tested three hypotheses: (1) having the outer jelly layers would be costly to the embryos, (2) the relative benefit of the structural egg defense would become apparent and increase as the intensity of egg predation increases, and (3) a certain degree of predation would increase the hatching success of salamander embryos by mechanically thinning the thick outer jelly layers and increasing oxygen diffusion throughout an egg mass. To test these hypotheses, we conducted a factorial experiment in which we crossed four egg‐predation levels with two jelly‐layer conditions, intact or removed. We found that the jelly layers were essential in protecting spotted salamander embryos from wood frog tadpoles but that the associated cost was apparent in no‐predation treatments. The differential survivorship between intact eggs and eggs without jelly layers showed that the fitness advantage of jelly layers increased as the level of predation increased. Finally, the hatching success of intact egg masses was highest under the high predation conditions. These results imply that the evolution of the jelly‐layer thickness occurred under constant egg‐predation pressure. Given this predator–prey coevolution, egg predators may play a critical role in improving the hatching success of salamander embryos under certain conditions.

Phenotypic polymorphisms are common in nature, but the mechanism through which natural selection maintains them can be difficult to identify. Heterozygote advantage, negative frequency-dependent selection, and variation in selective environment each can explain polymorphisms in some systems. Although first observed nearly 100 years ago, the egg mass color polymorphism in the spotted salamander (Ambystoma maculatum) still is not well understood. Females of this species lay egg masses with either clear or white jelly. White egg masses are preyed upon less than clear egg masses in some environments, suggesting an advantage to white masses, whereas an advantage to clear masses has not been identified. We propose that embryos in clear masses have an advantage in some light environments, mediated by the symbiotic green alga, Oophila amblystomatis, that grows in the egg capsules. The transparent jelly of clear masses may allow for greater algal growth, which could have cascading effects on embryonic development and larval performance. We asked whether larvae from clear and white masses differ in performance or survivorship and, if so, whether this difference is mediated by differences in algal density. We paired clear and white masses in a pond during the embryonic period and quantified egg capsule algal density at hatching. A portion of the larvae were subject to swim trials and were measured for size and shape. The remaining larvae were placed in mesocosms to quantify survival in the presence and absence of newt predators. There was no difference in algal density between membranes of clear and white masses. Similarly, there were no differences in larval performance, morphology, or survivorship between morphs. Our data do not support our hypothesis that variation in predator density and light availability among microhabitats could maintain the two phenotypes within populations. [ABSTRACT FROM AUTHOR]

For many species, the highest predation rates are on the earliest life stages, favoring the early development of predator detection mechanisms. Aquatic larvae of Spotted salamanders, Ambystoma maculatum, suffer very high mortality rates and juveniles are vulnerable to a new suite of terrestrial predators after metamorphosis. In some species, adult salamanders assess predation risk via chemical cues released by damaged conspecifics and some heterospecifics ("alarm cues"), but responses of larvae and metamorphs have not been tested. Our first experiment confirmed that field-caught, experienced larvae responded with fright to chemical cues of damaged conspecifics, but not to control cues or alarm cues from toad tadpoles. Responses of sedentary hatchlings in the next experiment indicated that the alarm cue was not present in damaged tissues of hatchlings (1-day-old), but was present by the time the larvae reached the age of 1 month. The third experiment tested responses of naïve lab-reared, free-swimming larvae to alarm cue. In contrast to the other two experiments, these larvae without experience did not distinguish between conspecific alarm cues and control stimuli, suggesting that either embryonic learning or reinforcement learning as larvae may be required to develop or maintain the alarm response. In the fourth experiment, post-metamorphic juveniles raised from field-experienced larvae significantly avoided alarm cues from conspecifics but not control stimuli, indicating that the production and recognition of alarm cues can be retained after metamorphosis. Our study provides the first evidence of chemical alarm cues produced by both larval and juvenile salamanders and indicates that alarm responses may vary according to experience. [ABSTRACT FROM AUTHOR]

Background: For 88 years (1931-present), the Mohonk Preserve's Daniel Smiley Research Center has been collecting data on occupancy and reproductive success of amphibian species, as well as associated water quality of 11 vernal pools each spring (February to May). Though sampling effort has varied over the dataset range, the size of the dataset is unprecedented within the field of amphibian ecology. With more than 2,480 individual species sampling dates and more than 151,701 recorded individual occurrences of the nine amphibian species, the described dataset represents the longest and largest time-series of herpetological sampling with paired water quality data. New information: We describe the novel publication of a paired dataset of amphibian occurrence with environmental indicators spanning nearly 90 years of data collection. As of February 2020, the dataset includes 2,480 sampling dates across eleven vernal pools and 151,701 unique occurrences of egg masses or individuals recorded across nine species of amphibian. The dataset also includes environmental conditions associated with the species occurrences with complete coverage for air temperature and precipitation records and partial coverage for a variety of other weather and water quality measures. Data collection has included species, egg mass and tadpole counts; weather conditions including precipitation, sky and wind codes; water quality measurements including water temperature and pH; and vernal pool assessment including depth and surface vegetation coverage. Collection of data was sporadic from 1931-1991, but data have been collected consistently from 1991 to present. We also began monitoring dissolved oxygen, nitrate concentrations and conductivity of the vernal pools using a YSI Sonde Professional Plus Instrument and turbidity using a turbidity tube in February 2018. The dataset (and periodic updates), as well as metadata in the EML format, are available in the Environmental Data Initiative Repository under package edi.398. [ABSTRACT FROM AUTHOR]

Roadside amphibian citizen science (CS) programmes bring together volunteers focused on collecting scientific data while working to mitigate population declines by reducing road mortality of pond‐breeding amphibians. Despite the international popularity of these movement‐based, roadside conservation efforts (i.e. "big nights," "bucket brigades" and "toad patrols"), direct benefits to conservation have rarely been quantified or evaluated.As a case study, we used a population simulation approach to evaluate how volunteer intensity, frequency and distribution influence three conservation outcomes (minimum population size, population growth rate and years to extinction) of the spotted salamander (Ambystoma maculatum), often a focal pond‐breeding amphibian of CS and conservation programmes in the United States.Sensitivity analysis supported the expectation that spotted salamander populations were primarily recruitment‐driven. Thus, conservation outcomes were highest when volunteers focused on metamorph outmigration as opposed to adult in‐migration—contrary to the typical timing of such volunteer events.Almost every volunteer strategy resulted in increased conservation outcomes compared to a no‐volunteer strategy. Specifically, volunteer frequency during metamorph migration increased outcomes more than the same increases in volunteer effort during adult migration. Small population sizes resulted in a negligible effect of volunteer intensity. Volunteers during the first adult in‐migration had a relatively small effect compared to most other strategies.Synthesis and applications. Although citizen science (CS)‐focused conservation actions could directly benefit declining populations, additional conservation measures are needed to halt or reverse local amphibian declines. This study demonstrates a need to evaluate the effectiveness of focusing CS mitigation efforts on the metamorph stage, as opposed to the adult stage. This may be challenging, compared to other management actions such as road‐crossing infrastructure. Current amphibian CS programmes will be challenged to balance implementing evidence‐based conservation measures on the most limiting life stage, while retaining social and community benefits for volunteers. Although citizen science (CS)‐focused conservation actions could directly benefit declining populations, additional conservation measures are needed to halt or reverse local amphibian declines. This study demonstrates a need to evaluate the effectiveness of focusing CS mitigation efforts on the metamorph stage, as opposed to the adult stage. This may be challenging, compared to other management actions such as road‐crossing infrastructure. Current amphibian CS programmes will be challenged to balance implementing evidence‐based conservation measures on the most limiting life stage, while retaining social and community benefits for volunteers. [ABSTRACT FROM AUTHOR]

Arsenic (As) and chromium (Cr) are two contaminants that are detected in aquatic and terrestrial habitats. Using the spotted salamander, Ambystoma maculatum, to assess impacts from these contaminants may be advantageous as adults live and breed in such environments. Adult amphibians typically exhibit elevated tissue concentrations of contaminants present in their environment, while larval stages were found to exhibit increased sensitivity to pollutants. From January through March of 2015, during the spring breeding season, 5 adults and approximately 32 egg masses were collected from a local breeding site. Field levels of As and Cr ranged from 5.99 to 8.88 µg/L and 1.45 to 2 µg/L, respectively, while mean adult As tissue concentrations were 56.74 µg/g dry weight for heart, 0.92 µg/g for liver, and 1.21 µg/g for tail tissue. Mean tissue concentrations for Cr were 87.64 µg/g for heart, 1.47 µg/g for liver, and 6.92 µg/g for tail. Developing larvae that were collected from the field and exposed in a lab setting for 12 d to 0.2 or 20 mg/L of either As or Cr displayed little DNA damage attributed to As, but marked damage due to exposure to 20 mg/L Cr when assessed using the comet assay. Exposure to a mixture of either 0.25:0.1 or 25:10 mg/L As and Cr resulted in significant DNA damage at the lower concentration of 0.25:0.1 mg/L. As adult spotted salamanders were found to possess high concentrations of these contaminants in cardiac tissue, and larvae were shown to be susceptible to DNA damage from increased exposures, assessing impacts and potential declines of amphibian populations exposed to As and Cr is needed. [ABSTRACT FROM AUTHOR]

Robust methods for estimating abundance of wetland-breeding amphibian species, such as mark--recapture, are often resource intensive. This limits our ability to study the processes that influence species abundance. Alternatively, more efficient sampling methods, such as indices based on visual encounter surveys (VES) (e.g., egg masses), may be biased by variability in detection probabilities and species biology (e.g., no. of egg masses per female). We combine data sources (i.e., VES and capture--mark--recapture) to provide an efficient technique for monitoring wetland-breeding amphibians. Our study focuses on understanding factors that determine local abundance of Spotted Salamanders, Ambystoma maculatum, in Pennsylvania.We first estimated abundance for a subset of wetlands using single-season, capture--mark--recapture data and then verified egg-mass counts collected from a wider network of wetlands as an unbiased index of abundance. We found a strong correlation between estimated adult abundance and estimated egg-mass abundance with an estimated ratio of one egg mass per adult per breeding effort. We next determined the factors that best explained variation in estimated A. maculatum egg-mass abundance and consequently, adult abundance among sites. Our "best-fit" model included effects for wetland hydroperiod and quadratic effects of mean water temperature. We also report positive, but weak, association with two cooccurring amphibian species, Jefferson Salamanders, A. jeffersonianum and Wood Frogs, Lithobates sylvaticus. We demonstrate how combining sampling approaches can provide efficient abundance estimates in wetland ecosystems. In particular, positive co-occurrence among species indicates shared habitat preferences that may enable us to predict the presence of difficult-to-detect species using only VES. [ABSTRACT FROM AUTHOR]

Polymorphisms play critical roles in allowing organisms to adapt to novel environments while enabling ecological speciation under divergent selection. Ambystoma maculatum, the spotted salamander, exhibits a unique polymorphism in the structure and appearance of its egg masses with two common morphs, white and clear. Amphibian egg jelly layers mediate interactions between embryos and the environment and are more responsive to ecological pressures of natural selection than other egg coat components. The A. maculatum egg mass polymorphism was hypothesized to be adaptive with regard to varying dissolved nutrient levels in ponds. We conducted two mesocosm experiments, collected field data, and constructed a population projection model to determine how dissolved nutrient levels affect embryonic and larval development and relate to the distribution of the morphs in natural ponds. We found that upon hatching there was an interaction between nutrient level and egg mass morph wherein individuals from white morphs were larger in low nutrient habitats. This interaction persisted throughout the larval stage, and along with the higher abundance of white morphs in ponds with low conductivity, we demonstrate that the white morph is advantageous in low nutrient environments. Our findings provide evidence for the role of environmental heterogeneity in enabling the persistence of a structural egg mass polymorphism, with maintenance occurring across multiple scales and persistence across its range. This indicates that polymorphisms can maximize performance in heterogeneous environments, while persisting over long timescales without leading to sympatric speciation. [ABSTRACT FROM AUTHOR]

An individual's home range, or how much space it requires to obtain resources and meet its needs for survival and reproduction, affects the scale of many fundamental processes in ecology and can inform the management of species. Although home range size has been described for many taxa in two dimensions (2D), for species that also have a strong vertical component to their movement, such representations can miss core components of their ecology, including the size of their home ranges and the amount of overlap, and thus competition, between individuals. Measuring three-dimensional (3D) home ranges for small-bodied life history stages and species can be particularly difficult, as they cannot tolerate high resolution tracking technologies like GPS collars. In this study, we used Passive Integrated Transponder (PIT) tags to measure the 2D and 3D home ranges of two species of fossorial juvenile salamander: the ringed salamander ( Ambystoma annulatum) and the spotted salamander ( A. maculatum). We also tested whether individuals modified their habitat selection or movement behavior in response to environmental variation. Salamanders in our study frequently used subterranean habitats. However, we rarely detected them more than 5 cm below ground. Additionally, the overlap among 2D and 3D home ranges, respectively, were similar. These findings indicate that these salamanders may move vertically through their habitat less than previously thought. Alternatively, salamanders may have moved into soil strata beyond the detection range of PIT telemetry. We conclude that PIT telemetry can be a suitable technique for determining the 3D home range of fossorial life-stages or species for which other tracking technologies are unsuitable. Significance statement: When animal behavior includes movements with a vertical component, simplifying assumptions of 2D home ranges can affect ecological inferences by overestimating competition between individuals and underestimating home range size. We used Passive Integrated Transponder (PIT) tags to describe the home range of fossorial juvenile salamanders in 3D. The juvenile salamanders in this study modulated their habitat selection in response to weather, but in general remained close to the soil surface. As a result, juveniles may be more susceptible than previously thought to habitat management practices that alter the local microclimate. Because individuals moved vertically less than predicted, 2D and 3D home ranges had similar patterns. We demonstrate that PIT telemetry can facilitate subterranean tracking of a cryptic life stage. However, this technology is limited in its subterranean detection depth, and until antenna strength is improved, the resolution of 3D home ranges may be limited. [ABSTRACT FROM AUTHOR]

ABSTRACT Ecological relationships and processes vary across species' geographic distributions, life stages and spatial, and temporal scales. Montane landscapes are characterized by low wetland densities, rugged topographies, and cold climates. Consequently, aquatic-dependent and low-vagility ectothermic species (e.g., pool-breeding amphibians) may exhibit unique ecological associations in montane landscapes. We evaluated the relative importance of breeding- and landscape-scale features associated with spotted salamander ( Ambystoma maculatum) and wood frog ( Lithobates sylvaticus) wetland occupancy in Maine's Upper Montane-Alpine Zone ecoregion, and we determined whether models performed better when the inclusive landscape-scale covariates were estimated with topography-weighted or circular buffers. We surveyed 135 potential breeding sites during May 2013-June 2014 and evaluated environmental relationships with multi-season implicit dynamics occupancy models. Breeding site occupancy by both species was influenced solely by breeding-scale habitat features. Spotted salamander occupancy probabilities increased with previous or current beaver ( Castor canadensis) presence, and models generally were better supported when the inclusive landscape-scale covariates were estimated with topography-weighted rather than circular buffers. Wood frog occupancy probabilities increased with site area and percent shallows, but neither buffer type was better supported than the other. Model rank order and support varied between buffer types, but model inferences did not. Our results suggest pool-breeding amphibian conservation in montane Maine include measures to maintain beaver populations and large wetlands with proportionally large areas of shallows ≤1-m deep. Inconsistencies between our study and previous studies substantiate the value of region-specific research for augmenting species' conservation management plans and suggest the application of out-of-region inferences may promote ineffective conservation. © 2016 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Natural resource extraction and wildlife conservation are often perceived as incompatible. For wetland-dependent amphibians, forested buffers may mitigate timber-harvest impacts, but little empirical research has focused on buffers around lentic habitats. We conducted a landscape experiment to examine how spotted salamander and wood frog reproductive output (i.e., eggmass and metamorph production) respond to clearcutting mediated by buffers of different widths (i.e., uncut, 30 m buffer, 100 m buffer) at ephemeral pools in an industrial forest. We found complex interactions between buffer treatment and reproductive output, which were strongly mediated by hydroperiod. Overall, reproductive output was most sensitive at 30 m-buffer pools and for salamanders, but responses diverged across productivity metrics even within these categories. Notably, for both cut treatments over time, while salamander eggmass abundance decreased, metamorph productivity (i.e., snout-vent length [SVL] and abundance) tended to increase. For example, average metamorph SVLs were predicted to lengthen between 0.2 and 0.4 mm per year post-cut. Additionally, typical relationships between reproductive output and hydroperiod (as indicated by the reference treatment) were disrupted for both species in both cut treatments. For example, long-hydroperiod pools produced more salamander metamorphs than short-hydroperiod pools in both the reference and 30 m-buffer treatments, but the rate of increase was lower in the 30 m-buffer treatment such that a long-hydroperiod pool in the reference treatment was predicted to produce, on average, 24 more metamorphs than a similar pool in the 30 m-buffer treatment. From a conservation perspective, our results highlight the importance of evaluating both terrestrial and aquatic responses to terrestrial habitat disturbance, since responses may be reinforcing (i.e., exert similarly positive or negative effects, with the potential for amplification in the aquatic habitat) or decoupled (i.e., operate independently or be negatively correlated, with responses in the aquatic habitat potentially dampening or counteracting responses in the terrestrial habitat). [ABSTRACT FROM AUTHOR]

Spotted salamanders ( Ambystoma maculatum) are pond-breeding amphibians that disperse into terrestrial habitat from natal wetlands after undergoing metamorphosis, relying on small-mammal burrows and coarse woody debris for refugia. The effect of conspecifics on burrow use in juvenile salamanders is poorly understood. Determining how the presence of conspecifics influences the settlement decisions of juvenile salamanders can increase our understanding of amphibian dispersal and our ability to predict population dynamics. We conducted behavioral laboratory trials using 58 recently metamorphosed salamanders to examine how salamanders selected burrows in the presence of conspecifics. Salamanders were more likely to settle in a burrow that was occupied by a conspecific versus an unoccupied burrow. Our results indicate that juvenile salamanders may show conspecific attraction and/or trailing behavior during the dispersal phase. [ABSTRACT FROM AUTHOR]

Comparisons of spatial and temporal variation in demographic rates are crucial to understanding population dynamics. Yet, even well-studied species are often lacking in comparisons of such variability in demographic data, making these contrasts imperative to conduct in population ecology research. We conducted a long-term monitoring study of Spotted Salamanders ( Ambystoma maculatum) at five ponds in Missouri, USA. We sampled populations using drift fences, and monitored breeding immigration dates, adult population sizes, sex ratio, juvenile recruitment, metamorph sizes, and metamorph emigration dates. Generally, we found that our study populations exhibited characteristics similar to other populations across their distribution. We also found spatial and temporal variation among populations in nearly all demographic parameters, however, indicating that multipopulation and multiyear studies will likely improve our inferential abilities in understanding population dynamics. We observed an overall positive relationship between metamorph size and date of metamorphosis, but this pattern was not consistent across ponds or years, indicating that different environmental pressures might influence selection on these traits. Finally, we identified rainfall amounts and frequency as the primary factors that influenced adult and metamorph movement patterns to and from ponds. Overall, the spatial and temporal variation in demographic data we provided can be useful for population modeling or conservation planning, in addition to furthering our understanding of population ecology of Spotted Salamanders. [ABSTRACT FROM AUTHOR]

Learning is crucial to the survival of organisms across their life span, including during embryonic development. We set out to determine when learning becomes possible in amphibian development by exposing spotted salamander ( Ambystoma maculatum) embryos to chemical stimuli from a predator ( Ambystoma opacum), nonpredator ( Lithobates clamitans), or control at developmental stages 16-21 or 36-38 (Harrison ). Once exposures were completed and embryos hatched, we recorded the number of movements and time spent moving of individuals in both groups and all treatments. There was no significant difference in number of movements or time spent moving among any of the treatments. The groups that were exposed to predator stimuli and a blank control at stages 36-38 were also tested to determine whether there was a difference in refuge preference or difference in survivorship when exposed to a predator (marbled salamander). There was no difference in survival or refuge preference between individuals; however, all individuals preferred vegetated over open areas regardless of treatment type. We discuss hypotheses for the absence of embryonic learning in this species and suggest it may be the result of the intensity of the predator-prey interaction between the predator, large marbled salamander larvae, and the prey, spotted salamander larvae. [ABSTRACT FROM AUTHOR]

Exposure to stressors typically suppresses reproductive processes, including the expression of sexual behaviour. However, many animal species breed in extreme conditions where opportunities to mate in a given season are limited. In such species, stress-induced suppression of reproduction would be maladaptive, especially if they also have short lifespans. Species with longer lifespans, but still limited mating opportunities in a given season, may be able to withstand a few missed breeding opportunities. We tested whether capture and handling would suppress male sexual behaviour in spotted salamanders ( Ambystoma maculatum), a species with an explosive mating strategy but a relatively long lifespan. Males were captured as they migrated to breeding sites and were handled in a manner known to induce an increase in plasma corticosterone, a component of the stress response. Thirty min later, each male was paired with a freshly captured female for 60 min. Handled males deposited significantly more spermatophores than did control males. The mechanism for the increased sexual behaviour is unknown but may involve handling-induced changes in stress hormones or reproductive hormones. Regardless of the mechanism whereby handling increased male sexual behaviour, our results support the hypothesis that stressors do not suppress male mating behaviour in a long-lived species with limited opportunities to mate. [ABSTRACT FROM AUTHOR]

Predator species and body size represent critical factors that have differential effects on prey populations, as well as overall community structure. However, investigations of how morphologically-similar predator species, simultaneous to variation in predator body size, influence lower trophic levels are infrequently performed. We tested whether predator species and body size influenced the functional response curve of three larval ambystomatid salamanders (Ringed Salamander, Ambystoma annulatum Cope, 1886; Spotted Salamander, Ambystoma maculatum (Shaw, 1802); Marbled Salamander, Ambystoma opacum (Gravenhorst, 1807)) while eating congeneric prey. We combined larval salamanders of varying body sizes with up to six prey densities within experimental microcosms. We tested for the shape of the functional response curve and obtained parameter estimates for attack rate and handling time for each predator size - species combination. We found variability among both species and size classes, with a combination of type I and type II functional response curves. Large size classes of predators had higher attack rates than smaller size classes, but equivalently-sized larvae of different species exhibited differences in attack rates and handling time. Our study shows that predation risk varies depending on the size structure and diversity of predators present in a food web, and that grouping predators by either species or size class may reduce the ability to predict changes in community structure resulting from such interactions. [ABSTRACT FROM AUTHOR]

Forest loss is a primary cause of worldwide amphibian decline. Timber harvesting in the United States has caused dramatic changes in quality and extent of forest ecosystems, and intensive forest management still occurs. Although numerous studies have documented substantial reductions in amphibian densities related to timber harvest, subsequent extinctions are rare. To better understand the population dynamics that have allowed so many amphibian species to persist in the face of widespread forest disturbance, we developed spatially explicit metapopulation models for four forest-dependent amphibian species (Lithobates sylvaticus, Ambystoma opacum, A. talpoideum, and A. maculatum) that incorporated demographic and habitat selection data derived from experiments conducted as part of the Land Use Effects on Amphibian Populations Project (LEAP). We projected local and landscape-scale population persistence under 108 different forestry practice scenarios, varying treatment (partial cut, clear-cut with coarse woody debris [CWD] removed, and clearcut with CWD retained), cut patch size (1, 10, or 50 ha), total area cut (10, 20, or 30%), and initial amphibian population size (5, 50, or 500 adult females per local breeding population). Under these scenarios, landscape-scale extinction was highly unlikely, occurring in <1% of model runs and for only 2 of the 4 species, because landscape-scale populations were able to persist via dispersal even despite frequent local extinctions. Yet for all species, population sizes were reduced to ~50% in all clear-cut scenarios, regardless of the size of harvested patches. These findings suggest that debate over timber harvesting on pool-breeding amphibian populations in the United States should focus not on questions of landscape-scale extinction but on the ecological consequences of dramatic reductions in amphibian biomass, including changes in trophic interactions, nutrient cycling, and energy transfer. Additionally, we conclude that amphibian declines and extinctions are far more likely to occur as a result of permanent habitat loss resulting from development than from the temporary degradation of habitat caused by current forestry practices. [ABSTRACT FROM AUTHOR]

Regional monitoring strategies frequently employ a nested sampling design where a finite set of study areas from throughout a region are selected and intensive sampling occurs within a subset of sites within the individual study areas. This sampling protocol naturally lends itself to a hierarchical analysis to account for dependence among subsamples. Implementing such an analysis using a classic likelihood framework is computationally challenging when accounting for detection errors in species occurrence models. Bayesian methods offer an alternative approach for fitting models that readily allows for spatial structure to be incorporated. We demonstrate a general approach for estimating occupancy when data come from a nested sampling design. We analyzed data from a regional monitoring program of wood frogs ( Lithobates sylvaticus) and spotted salamanders ( Ambystoma maculatum) in vernal pools using static and dynamic occupancy models. We analyzed observations from 2004 to 2013 that were collected within 14 protected areas located throughout the northeast United States. We use the data set to estimate trends in occupancy at both the regional and individual protected area levels. We show that occupancy at the regional level was relatively stable for both species. However, substantial variation occurred among study areas, with some populations declining and some increasing for both species. In addition, When the hierarchical study design is not accounted for, one would conclude stronger support for latitudinal gradient in trends than when using our approach that accounts for the nested design. In contrast to the model that does not account for nesting, the nested model did not include an effect of latitude in the 95% credible interval. These results shed light on the range-level population status of these pond-breeding amphibians, and our approach provides a framework that can be used to examine drivers of local and regional occurrence dynamics. [ABSTRACT FROM AUTHOR]

Embryonic growth of the yellow-spotted salamander ( Ambystoma maculatum ) is enhanced by the presence of the green alga Oophila amblystomatis , in the egg capsule. To further assess potential impacts of herbicides on this relationship, A. maculatum egg masses were exposed to atrazine (0–338 μg/L) until hatching (up to 66 days). Exposure to atrazine reduced PSII yield of the symbiotic algae in a concentration-dependent manner, but did not significantly affect visible algal growth or any metrics associated with salamander development. Algal cells were also cultured in the laboratory for toxicity testing. In the 96-h growth inhibition test (0–680 μg/L), ECx values were generally greater than those reported for standard algal test species. Complete recovery of growth rates occurred within 96-h of transferring cells to untreated media. Overall, development of A. maculatum embryos was not affected by exposure to atrazine at concentrations and durations exceeding those found in the environment. [ABSTRACT FROM AUTHOR]

Climate projections over the next century include disproportionately warmer nighttime temperatures (“asymmetrical warming”). Cool nighttime temperatures lower metabolic rates of aquatic ectotherms. In contaminated waters, areas with cool nights may provide thermal refugia from high rates of daytime contaminant uptake. We exposed Cope's gray tree frogs ( Hyla chrysoscelis ), southern leopard frogs ( Lithobates sphenocephalus ), and spotted salamanders ( Ambystoma maculatum ) to five concentrations of a mixture of cadmium, copper, and lead under three to four temperature regimes, representing asymmetrical warming. At concentrations with intermediate toxicosis at test termination (96 h), temperature effects on acute toxicity or escape distance were evident in all study species. Asymmetrical warming (day:night, 22:20 °C; 22:22 °C) doubled or tripled mortality relative to overall cooler temperatures (20:20 °C) or cool nights (22:18 °C). Escape distances were 40–70% shorter under asymmetrical warming. Results suggest potentially grave ecological impacts from unexpected toxicosis under climate change. [ABSTRACT FROM AUTHOR]

I have been studying amphibians in Canaan Valley and its surrounding region since 1976. Most of my studies inventoried populations of Plethodon nettingi (Cheat Mountain Salamander). I sampled 29 upland sites on the mountains around Canaan Valley: (1) twelve sites on Canaan Mountain, which forms Canaan Valley's western rim, were distributed from Chimney Rock, at the southern end of Canaan Mountain, northwards to the Blackwater River at Camp 70; (2) on the eastern rim of Canaan Valley, 17 sites were on Cabin Mountain, from Snowy Point in the north to Weiss Knob in the south. At the montane sites, I observed 11 salamander species and 1 toad species. Salamanders found included Ambystoma maculatum (Spotted Salamander), Notophthalmus v. viridescens (Red-spotted Newt), Desmognathus monticola (Seal Salamander), Desmognathus ochrophaeus (Allegheny Mountain Dusky Salamander); Gyrinophilus p. porphyriticus (Northern Spring Salamander), Hemidactylium scutatum (Four-toed Salamander), Eurycea bislineata (Northern Two-lined Salamander), Plethodon cinereus (Eastern Red-backed Salamander), Cheat Mountain Salamander; P. glutinosus (Northern Slimy Salamander), and P. wehrlei (Wehrle's Salamander). The only toad observed was Anaxyrus americanus (Eastern American Toad). I have monitored one population of the Cheat Mountain Salamander at the headwaters of Yoakum Run on Cabin Mountain since 1986, making this the longest continuously running study of a salamander in West Virginia. I also studied 10 sites in Canaan Valley, where I found 1 toad, 7 frog, and 8 salamander species. Anurans observed included the Eastern American Toad, Pseudacris brachyphona (Mountain Chorus Frog), P. crucifer (Spring Peeper), Hyla chrysoscelis (Cope's Gray Treefrog), Lithobates catesbeianus (American Bullfrog); L. clamitans melanota (Northern Green Frog), L. palustris (Pickerel Frog), and L. sylvaticus (Wood Frog). Urodeles found included the Spotted Salamander, Red-spotted Newt, Desmognathus fuscus (Northern Dusky Salamander), Seal Salamander, Allegheny Mountain Dusky Salamander, Northern Spring Salamander, Four-toed Salamander, and Northern Two-lined Salamander. Amphibians that may occur in Canaan Valley, but which I have not recorded, include Ambystoma jeffersonianum (Jefferson Salamander); Eurycea l. longicauda (Longtailed Salamander); and Pseudotriton r. ruber (Northern Red Salamander). [ABSTRACT FROM AUTHOR]

Before the establishment of reproductive isolation, deeply diverged intraspecific lineages can experience complex genetic and behavioral interactions as they come into secondary contact. Divergent selective and demographic processes mediate gene flow among lineages, resulting in hybrid zones with complex biogeographic structure. Discordance in the biogeographic patterns of autosomal and maternally inherited loci provides a useful window to infer the processes mediating admixture and introgression across hybrid zones. Here, we sampled 489 genotypes across a hybrid zone between 2 phylogeographic lineages of the spotted salamander, Ambystoma maculatum, and characterize discordant patterns of nuclear and mitochondrial introgression across the contact boundary. Our results indicate asymmetric introgression of nuclear DNA beyond the contact boundary from the western to eastern lineage, with introgression of eastern mitochondrial DNA into the western lineage. We discuss alternative mechanisms for this pattern and attribute this result to neutral patterns of population expansion of the western lineage into the east in combination with female mate choice for larger-bodied western males. Our results underscore the complexity of interacting mechanisms that give rise to reproductive asymmetries in the earliest stages of the speciation process. [ABSTRACT FROM AUTHOR]

In recent studies, habitat traits have emerged as stronger predictors of species occupancy, abundance, richness and diversity than competition. However, in many cases, it remains unclear whether habitat also mediates processes more subtle than competitive exclusion, such as growth, or whether intra- and interspecific interactions among individuals of different species may be better predictors of size., To test whether habitat traits are a stronger predictor of abundance and body size than intra- and interspecific interactions, we measured the density and body size of three species of larval salamanders in 192 ponds across a landscape., We found that the density of larvae was best predicted by models that included habitat features, while models incorporating interactions among individuals of different species best explained the body size of larvae. Additionally, we found a positive relationship between focal species density and congener density, while focal species body size was negatively related to congener density., We posit that salamander larvae may not experience competitive exclusion and thus reduced densities, but instead compensate for increased competition behaviourally (e.g. reduced foraging), resulting in decreased growth. The discrepancy between larval density and body size, a strong predictor of fitness in this system, also highlights a potential shortcoming in using density or abundance as a metric of habitat quality or population health. [ABSTRACT FROM AUTHOR]

Glyphosate-based herbicides are the number one pesticide in the United States and are used commonly around the world. Understanding the affects of glyphosate-based herbicides on non-target wildlife, for example amphibians, is critical for evaluation of regulations pertaining to the use of such herbicides. Additionally, it is important to understand how variation in biotic and abiotic environmental conditions, such as UV-B light regime, could potentially affect how glyphosate-based herbicides interact with non-target species. This study used artificial pond mesocosms to identify the effects of generic glyphosate-based herbicide (GLY-4 Plus) on mortality, cellular immune response, body size, and morphological plasticity of larvae of the spotted salamander ( Ambystoma maculatum) under conditions that reflect moderate (UV) and low (UV) UV-B light regimes. Survival within a given UV-B level was unaffected by herbicide presence or absence. However, when herbicide was present, survival varied between UV-B levels with higher survival in UV conditions. Herbicide presence in the UV treatments also decreased body size and reduced cellular immune response. In the UV treatments, the presence of herbicide increased body size and affected tail morphology. Finally, in the absence of herbicide, body size and cellular immune response were higher in UV treatments compared to UV treatments. Thus, the effects of herbicide on salamander fitness were dependent on UV-B level. As anthropogenic habitat modifications continue to alter landscapes that contain amphibian breeding ponds, salamanders may increasingly find themselves in locations with reduced canopy cover and increased levels of UV light. Our findings suggest that the probability of surviving exposure to the glyphosate-based herbicide used in this study may be elevated in more open canopy ponds, but the effects on other components of fitness may be varied and unexpected. [ABSTRACT FROM AUTHOR]

A fundamental goal of evolutionary ecology is to understand how asymmetric competition influences phenotype expression, yet few studies have quantified the relative effects of intra- and interspecific competition on phenotypes. We examined the effects of intra- and interspecific larval competition on both discrete and continuous phenotype expression of the facultatively paedomorphic mole salamander (Ambystoma talpoideum). We manipulated the density and frequency of larval A. talpoideum and a common competitor, the spotted salamander (A. maculatum), in experimental mesocosms within a response surface design. The production of discrete ontogenetic morphs (metamorphs, paedomorphs, and overwintering larvae) was affected more by intraspecific than interspecific competition, but the effect varied between morphs. Paedomorph and metamorph production were more strongly affected by intraspecific than interspecific competition, while the production of overwintering larvae was affected by each type of competition approximately equally. Paedomorphs largely occurred only at low conspecific densities, overwintering larvae primarily occurred at high overall densities, and metamorph production peaked at intermediate densities of con- and heterospecifics. Density-dependent intraspecific competition had stronger effects on body size and growth rates than interspecific competition for both metamorphs and overwintering larvae, whereas interspecific competition more strongly affected paedomorph size. Overall, these results support the hypothesis that intraspecific competition influences both continuous and discrete phenotypic expression more strongly than interspecific competition. Fluctuating strengths of each type of competition can affect variation in life history strategies by influencing discrete ontogenetic pathways via individual body sizes, leading to differential morph production and fitness within and among morphs. [ABSTRACT FROM AUTHOR]

The article reports on evaluation of identification techniques for Spotted Salamanders. It states that as an identification method pattern recognition reduces need for tagging methods by using natural color patterns as main identifier for individual and goal for this study was to assess feasibility of using the pattern recognition methods. It mentions that spot code technique is accurate and requires no use of anesthesia and computer software is used in assigning identities based on patterns.

Local enhancement is an underexplored social learning mechanism that is often observed in organisms that live in groups. This mechanism occurs when individuals are attracted to areas where conspecifics have previously been, but which are not present when the animal actually moves into the area. We tested for local enhancement in wood frog tadpoles ( Lithobates sylvatica) and spotted salamander larvae ( Ambystoma maculatum) in three experiments that exposed individuals to one side of a test chamber which was empty and another that contained a group of three conspecifics. Side preference of the focal individual was recorded once the conspecifics were removed. Tadpoles showed a clear preference for moving to areas where a group of tadpoles had previously been located. Conversely, this preference was not observed in salamander larvae. In addition, salamander larvae took significantly more time to initially choose a side. These results indicate that tadpoles exhibit local enhancement, whereas aquatic salamander larvae do not. This difference in social learning could be largely due to differences in aquatic ecology between tadpoles and salamander larvae. [ABSTRACT FROM AUTHOR]

Dispersal and gene flow within animal populations are influenced by the composition and configuration of the landscape. In this study, we evaluated hypotheses about the impact of natural and anthropogenic factors on genetic differentiation in two amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Lithobates sylvaticus) in a commercial forest in central Maine. We conducted this analysis at two scales: a local level, focused on factors measured at each breeding pond, and a landscape level, focused on factors measured between ponds. We investigated the effects of a number of environmental factors in six categories including Productivity, Physical, Land Composition, Land Configuration, Isolation and Location. Embryos were sampled from 56 spotted salamander breeding ponds and 39 wood frog breeding ponds. We used a hierarchical Bayesian approach in the program GESTE at each breeding pond and a random forest algorithm in conjunction with a network analysis between the ponds. We found overall high genetic connectivity across distances up to 17 km for both species and a limited effect of natural and anthropogenic factors on gene flow. We found the null models best explained patterns of genetic differentiation at a local level and found several factors at the landscape level that weakly influenced gene flow. This research indicates multiscale investigations that incorporate local and landscape factors are valuable for understanding patterns of gene flow. Our findings suggest that dispersal rates in this system are high enough to minimize genetic structuring and that current forestry practices do not significantly impede dispersal. [ABSTRACT FROM AUTHOR]

The article focuses on the spotted turtle Clemmys guttata. Topics discussed include the shortage of suitable habitat for the turtles, several salamander species in Connecticut such as Ambystoma maculatum, Ambystoma opacum, and Ambystoma laterale, and the law for the protection of Clemmys guttata in the state.

Learning to use a landmark as a beacon to locate resources is one of the simplest forms of spatial learning. We tested whether landmark learning occurs in a semifossorial salamander that migrates annually to breeding ponds as adults. Juvenile spotted salamanders ( Ambystoma maculatum ) were tested in square containers with a plastic feeding dish in each corner, and a piece of earthworm was placed in one randomly-chosen dish. For landmark-trained salamanders, a rock was placed beside the dish containing the prey. For control salamanders, the rock was placed beside a randomly selected feeding dish. Each salamander was trained once every 2 days for 30 days. Significantly more landmark-trained salamanders than control salamanders entered the landmark area first, and landmark-trained individuals had faster latencies to enter the landmark area and longer stay-times. These results suggest that spotted salamanders are able to locate resources by associating their positions with landmarks. [ABSTRACT FROM AUTHOR]

A better understanding of how individuals respond to variation in habitat quality while moving through heterogeneous habitats is needed to predict ecological phenomena at larger scales, such as local population and metapopulation dynamics. We sought to identify how fine-scale habitat quality affects the decisions of juvenile pond-breeding salamanders (Ambystoma maculatum and A. annulatum) to cease dispersive movements away from their natal pond, select a refuge, and settle. Because of the acute susceptibility of juvenile amphibians to evaporative water loss in terrestrial habitats, we predicted that they possess mechanisms for adjusting their behavior in response to variations in fine-scale habitat quality. We used experimental field enclosures to isolate the effects of habitat quality on settling behavior and employed generalized linear mixed models to examine how manipulations in canopy cover (closed or open) and microhabitat (control, compacted soils, high coarse woody debris, high burrow density), along with environmental variables (rainfall and air temperature), affect the individual's probability of settling. Our results indicated that A. maculatum and A. annulatum had a 10% and 30% decreased probability of settling in opencanopy clearcut habitat, respectively, compared to closed-canopy forest habitat. In addition, A. annulatum were 24% less likely to settle in compacted soil treatments. Although the settlement probability of A. annulatum did not depend on refuge availability, A. maculatum were 18% and 25% more likely to settle under conditions of high burrow density and high coarse woody debris, respectively. These findings make a unique contribution to our understanding of amphibian movement ecology by demonstrating how the interplay of external factors and individual behavior produce observed patterns of movement and habitat selection. [ABSTRACT FROM AUTHOR]

Habitat linkages can help maintain connectivity of animal populations in developed landscapes. However, the lack of empirical data on the width of lateral movements (i.e., the zigzagging of individuals as they move from one point to point another) makes determining the width of such linkages challenging. We used radiotracking data from wood frogs (Lithobates sylvaticus) and spotted salamanders (Ambystoma maculatum) in a managed forest in Maine (U.S.A.) to characterize movement patterns of populations and thus inform planning for the width of wildlife corridors. For each individual, we calculated the polar coordinates of all locations, estimated the vector sum of the polar coordinates, and measured the distance from each location to the vector sum. By fitting a Gaussian distribution over a histogram of these distances, we created a population-level probability density function and estimated the 50th and 95th percentiles to determine the width of lateral movement as individuals progressed from the pond to upland habitat. For spotted salamanders 50% of lateral movements were ≤13 m wide and 95% of movements were ≤39 m wide. For wood frogs, 50% of lateral movements were ≤17 m wide and 95% of movements were ≤ 51 m wide. For both species, those individuals that traveled the farthest from the pond also displayed the greatest lateral movement. Our results serve as a foundation for spatially explicit conservation planning for pond-breeding amphibians in areas undergoing development. Our technique can also be applied to movement data from other taxa to aid in designing habitat linkages. Caracterización de la Amplitud de Movimiento de Anfibios durante la Migración Pos-Reproducción [ABSTRACT FROM AUTHOR]

Brilliant and conspicuous coloration in animals is often thought to signal quality to conspecifics (sexual selection) or to signal unpalatability to predators (aposematic selection). Ambystoma maculatum (spotted salamanders) have bilateral rows of conspicuous bright yellow dorsal spots against dark skin. Although this coloration has been long thought a classic example of warning coloration, to date, there are no quantitative measures of spot coloration. We captured adult male and female A. maculatum as they entered breeding ponds and measured body condition, spectral reflectance of the yellow spots, spot size, and coverage of the dorsal area in spots. We found evidence of sexual dichromatism; males had a larger area of their dorsum covered in spots, and tended to have more chromatic, but less bright yellow color. Moreover, our data suggest a tradeoff between coloration and body condition. Animals in better body condition expressed lower chroma and those with greater spot coverage expressed brighter spots and lower yellow chroma. Although these data are not entirely consistent with the predictions of sexual selection, they suggest a physiological tradeoff associated with coloration that has not been documented in salamanders. [ABSTRACT FROM AUTHOR]

ABSTRACT Egg size is a key life history trait affecting fitness, and it varies abundantly. The value of egg size to a mother and her offspring is often determined by a trade-off between investing more yolk in a few large eggs or less yolk into many more, smaller eggs. Smaller eggs are generally expected to be phenotypically inferior or females could increase their fitness by making more smaller eggs. However, many females produce a mix of egg sizes and natural yolk variation induces normal developmental responses which may persist into subsequent stages of a complex life history. Since sources of phenotypic variation are easily confounded, I surgically removed yolk from embryonic spotted salamanders ( Ambystoma maculatum) using a sham surgery as a control and a split-clutch design to isolate the effects of yolk reserve variation from genetic sources of variation. Yolk removal induced early hatching, reduced developmental stage and hatchling body size. Small hatchlings stayed relatively small through the early larval period, but 17 weeks later the correlation with early larval body size was lost. When the experiment ended, larger individuals were further along in metamorphic development but mortality was independent of early larval body size. Variation in spotted salamander yolk reserves affects a suite of hatchling life history traits that persists into the larval period. Outside the laboratory, egg size effects may cascade throughout complex amphibian life histories. Applied experimentally and comparatively, this simple yolk removal technique may help identify how traits increase or decrease their response to maternal yolk investment. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 45-53, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The article focuses on a study on detection of ranavirus among amphibians in Ohio in the U.S. Topics discussed include signs ranavirus detected among Ambystoma maculatum (A. maculatum), Lithobates clamitans (L. clamitans), and Lithobates sylvaticus (L. sylvaticus), extraction of DNA from the animals to screen the virus and virus titer level in L. clamitans in comparison to others.

Secondary compounds leached from plant litter can negatively affect aquatic amphibian larvae. Non-native plants and their potentially distinct secondary compounds may constitute cryptic threats to native amphibians. We used the availability of both native and introduced Phragmites australis (common reed) populations in North America to assess the importance of origin, intraspecific variation, and two purified classes of compounds (tannins and saponins; gradients 0-25 mg L) on two common and widespread amphibians ( Ambystoma maculatum, spotted salamander, and Lithobates palustris, pickerel frog). In experiments with purified compounds, high tannin concentrations reduced A. maculatum survival and developmental rate while high saponin concentrations reduced survival, developmental rate, and size of L. palustris and reduced A. maculatum developmental rate. In experiments using leaf litter extracts of 14 different P. australis populations, A. maculatum larval survival varied among populations but plant origin (native or introduced) did not explain this variation. In contrast to the lack of effects of purified saponins, increases in saponin concentrations in P. australis leachates significantly decreased A. maculatum survival. Our results suggest: (1) secondary compounds can impact larval amphibian survival and development in species-specific ways; (2) impacts of P. australis on A. maculatum vary among P. australis populations, reflecting intraspecific variation in secondary chemistry; and (3) origin (whether the plant is native or introduced) is a poor predictor of P. australis effects on A. maculatum. Scientists and managers may need to move beyond considering origin as a predictive variable when managing plant communities to benefit amphibians. [ABSTRACT FROM AUTHOR]

Behavioral strategies of natal dispersers in response to human-altered habitat have far-reaching implications for functional connectivity and local population dynamics. Spotted salamanders Ambystoma maculatum are forest-dependent, pond-breeding amphibians which metamorphose and disperse out of aquatic habitat with limited knowledge of the terrestrial habitat. We quantified the fine-scale movement behavior and search strategies of recently metamorphosed spotted salamanders in three different habitat types (field, early successional forest and forest) and at varying distances from both hard (field and forest) and soft (early successional forest and forest) edges using fluorescent powder tracking. We found that salamanders moved straighter and with fewer turns through field habitat compared with both forest and early successional habitat. Salamanders significantly oriented movement toward forest when released in the field and when released on the edge between the forest and field. We found that salamander movement in the forest and early successional forest was approximated by a correlated random walk. Based on these results, dispersing spotted salamanders exhibit strong edge-mediated behavior when differences between habitats are stark (forest and field) and can perceive forest habitat from distances of at least 10 m. These results indicate that dispersing juvenile salamanders exhibit reasonable behavioral rules when moving through habitat types of differing quality. Knowledge of these behavioral rules will improve predictions of the effects of habitat type and configuration on amphibian survival and dispersion in altered landscapes. [ABSTRACT FROM AUTHOR]

Despite having relatively little dimorphism in external morphology, male and female Ambystoma maculatum have substantial differences in both short-term (e.g., resting metabolic rate) and long term (e.g., growth rate) physiological processes. In this study, I investigated differences in themass of reproductive (gonads and proximal reproductive tract) and somatic (liver and heart) organs, and in hematological parameters related to oxygen carrying capacity (erythrocyte count, hematocrit, and hemoglobin concentration) and osmotic balance (plasma osmolality) between males and females before and after breeding. Pre-breeding females had substantially larger ovaries and oviducts compared to post-breeding females, whereas males had similar reproductive organ masses before and after breeding. Females had smaller livers than males, but similar heart masses. Males had similar erythrocyte counts to females, but higher hematocrits, hemoglobin concentrations, and plasma osmolalities. The internal anatomical and physiological differences between males and females suggest greater investment in gametogenesis in females and higher performance in aquatic environments in males. These findings highlight the importance of physiological dimorphisms in organisms where there is little apparent difference in external morphology between the sexes. [ABSTRACT FROM AUTHOR]

Predation risk is an important contributor to community structure that varies in response to abiotic and biotic factors. In aquatic habitats, predation risk is often linked to hydroperiod as the latter directly influences predator identity within these ecosystems. For pond-breeding salamanders, intraguild predation (IGP) and cannibalism are prevalent interactions in larval communities, but the frequency of each type of agonistic interaction, as well as changes in their pervasiveness along hydroperiod gradients are not well understood. Size-structured populations of aquatic life stages (paedomorphic adults and overwintered larvae) of mole salamanders (Ambystoma talpoideum) have the potential to be dominant IG predators and cannibals in permanent ponds because of large size advantages over successive cohorts, but the species exists as only a single larval cohort in temporary ponds with reduced predatory abilities on guild members. Thus, both the potential for and intensity of predation by this species is linked to hydroperiod; yet, the predatory abilities of aquatic life stages of mole salamanders have not been evaluated. This study examined the extent to which larger size classes (paedomorphs and overwintered larvae) of mole salamanders preyed upon conspecifics and a congeneric competitor, the spotted salamander (Ambystoma maculatum). Predation trials occurred in indoor microcosms and were executed under two habitat treatments that included pseudo-natural conditions containing alternate prey and refugia, as well as simplified environments (no alternative food or cover). Embryos or hatchlings of mole and spotted salamanders were exposed either separately or concurrently to paedomorphic and overwintered larval mole salamanders in each habitat treatment. Additionally, overwintered larvae were offered as prey to paedomorphic adults. No significant differences in mortality were observed between habitat treatments (complex versus simple) for either embryo or hatchling predation experiments. Mortality of mole and spotted embryos did not differ when they were offered separately or together, but paedomorphs caused significantly higher mortality among mole embryos compared to spotted embryos. Hatchlings of both species were heavily preyed upon (nearly 100% in all trials), but overwintered larvae exhibited 100% survival with paedomorph predators, indicating size-thresholds of predation risk that were not species specific. Paedomorphs and overwintered larvae therefore are most likely generalist predators that feed equally and effectively on hatchlings of co-occurring species, but are more likely to consume egg masses that do not incur significant handling costs. When present, paedomorphs or overwintered larvae have the potential to alter population dynamics of both guild members and conspecifics by being dominant predators on early life stages. As the prevalence of overwintering and paedomorphosis varies along hydroperiod gradients, predation risk from this species is likely to occur discontinuously and thereby may be an important, yet variable, structuring force. [ABSTRACT FROM AUTHOR]

Microgeographic adaptation occurs when populations evolve divergent fitness advantages across the spatial scales at which focal organisms regularly disperse. Although an increasing number of studies find evidence for microgeographic adaptation, the underlying causes often remain unknown. Adaptive divergence requires some combination of limited gene flow and strong divergent natural selection among populations. In this study, we estimated the relative influence of selection, gene flow, and the spatial arrangement of populations in shaping patterns of adaptive divergence in natural populations of the spotted salamander ( Ambystoma maculatum). Within the study region, A. maculatum co-occur with the predatory marbled salamander ( Ambystoma opacum) in some ponds, and past studies have established a link between predation risk and adaptive trait variation in A. maculatum. Using 14 microsatellite loci, we found a significant pattern of genetic divergence among A. maculatum populations corresponding to levels of A. opacum predation risk. Additionally, A. maculatum foraging rate was strongly associated with predation risk, genetic divergence, and the spatial relationship of ponds on the landscape. Our results indicate the sorting of adaptive genotypes by selection regime and strongly suggest that substantial selective barriers operate against gene flow. This outcome suggests that microgeographic adaptation in A. maculatum is possible because strong antagonistic selection quickly eliminates maladapted phenotypes despite ongoing and substantial immigration. Increasing evidence for microgeographic adaptation suggests a strong role for selective barriers in counteracting the homogenizing influence of gene flow. [ABSTRACT FROM AUTHOR]

Herpetofauna have declined globally, and monitoring is a useful approach to document local and long-term changes. However, monitoring efforts often fail to account for detectability or follow standardized protocols. We performed a case study at Hemlock Bluffs Nature Preserve in Cary, NC to model occupancy of focal species and demonstrate a replicable long-term protocol useful to parks and nature preserves. From March 2010 to 2011, we documented occupancy of Ambystoma opacum (Marbled Salamander), Plethod-on cinereus (Red-backed Salamander), Carphophis amoenus (Eastern Worm Snake), and Diadophis punctatus (Ringneck Snake) at coverboard sites and estimated breeding female Ambystoma maculatum (Spotted Salamander) abundance via dependent double-observer egg-mass counts in ephemeral pools. Temperature influenced detection of both Marbled and Red-backed Salamanders. Based on egg-mass data, we estimated Spotted Salamander abundance to be between 21 and 44 breeding females. We detected 43 of 53 previously documented herpetofauna species. Our approach demonstrates a monitoring protocol that accounts for factors that influence species detection and is replicable by parks or nature preserves with limited resources. [ABSTRACT FROM AUTHOR]

The physical and environmental attributes of landscapes often shape patterns of population connectivity by influencing dispersal and gene flow. Landscape effects on movement are typically evaluated for single species. However, inferences from multiple species are required for multi-species management strategies increasingly being applied in conservation. In this study, I compared the spatial genetic patterns of two amphibian species across the northeastern United States and estimated the influence of specific landscape features on the observed genetic structure. The spotted salamander ( Ambystoma maculatum) and wood frog ( Rana sylvatica) share many ecological attributes related to habitat use, phenology and site fidelity. However, I hypothesized that important differences in their movement patterns and life history would create distinct genetic patterns for each species. Using 14 microsatellite loci, I tested for differences in the level of genetic differentiation between the two species across 22 breeding ponds. The effects of eight landscape features were also estimated by evaluating 32 landscape resistance models. Spotted salamanders exhibited significantly higher genetic differentiation than wood frogs. Different landscape features were also identified as potential drivers of the genetic patterns in each species, with little overlap in model support between species. Collectively, these results provide strong evidence that these two amphibian species interact with the landscape in measurably different ways. The distinct genetic patterns observed are consistent with key differences in movement ability and life history between A. maculatum and R. sylvatica. These results highlight the importance of considering more than one species when assessing the impacts of the landscape matrix on population connectivity, even for ecologically similar species within the same habitats. [ABSTRACT FROM AUTHOR]

The inner egg capsule of embryos of the yellow-spotted salamander (Ambystoma maculatum) are routinely colonized by green algae, such as Oophila amblystomatis, that supply O2 in the presence of light and may consume nitrogenous wastes, forming what has been proposed to be a mutualistic relationship. Given that A. maculatum have been reported to breed in acidic (pH <5.0) and neutral lakes, we hypothesized that low water pH would negatively affect these symbiotic organisms and alter the gradients within the jelly mass. Oxygen gradients were detected within jelly masses measured directly in a natural breeding pond (pH 4.5--4.8) at midday in full sunlight. In the lab, embryo jelly masses reared continuously at pH 4.5 had lower and higher ammonia levels relative to jelly masses PO2 held at pH 8.0 (control). Ammonia and lactate concentrations in embryonic tissues were approximately 37%--93% higher, respectively, in embryos reared at water pH 4.5 compared with pH 8.0. Mass was also reduced in embryos reared at pH 4.5 versus pH 8.0. In addition, light conditions (24 h light, 12L : 12D, or 24 h dark) and embryonic position (periphery vs. center) in the jelly mass affected but not ammonia PO2 gradients, suggesting that algal symbionts generate O2 but do not significantly impact local ammonia concentrations, regardless of the pH of the water. We conclude that chronic exposure to acidic breeding ponds had a profound effect on the microenvironment of developing A. maculatum embryos, which in turn resulted in an elevation of potentially harmful metabolic end products and inhibited growth. Under acidic conditions, the expected benefit provided by the algae to the salamander embryo (i.e., high O2 and low ammonia microenvironment) is compromised, suggesting that the A. maculatum--algal mutualism is beneficial to salamanders only at higher water pH values. [ABSTRACT FROM AUTHOR]

The distribution and abundance of species are shaped by local and landscape processes, but the dominant processes may differ with scale and increasing human disturbance. We investigated population responses of two pool-breeding amphibian species to differences in local and landscape characteristics in suburbanizing, southeastern New Hampshire, USA. In 2003 and 2004, we sampled 49 vernal pools for spotted salamander ( Ambystoma maculatum) and wood frog ( Lithobates sylvaticus) egg masses. Using egg masses as a proxy for breeding-female population size, we examined the relative influence of five land-use and three isolation variables at two scales (300 and 1000 m) and five wetland variables on egg-mass abundance. For both species, road density at the landscape scale (1000 m) and hydroperiod most strongly predicted egg-mass abundance, with abundance decreasing as roads became denser and hydroperiods shortened. Wetland isolation was also an important predictor, with abundance greatest at more isolated pools, suggesting that both species concentrate at isolated pools when alternative breeding sites are scarce. Surprisingly, no 300-m parameters were strongly associated with salamander egg-mass abundance, whereas several landscape parameters were. In suburbanizing areas, it is at least as important to consider landscape-scale road density as to consider hydroperiod when designing conservation plans for these species. Furthermore, both isolated and clustered pools provide these species important habitat and may require protection. Finally, the conceptual framework for spotted-salamander management must be expanded so that spatial configuration at the landscape scale becomes a regular, integrated component of conservation planning for this species. [ABSTRACT FROM AUTHOR]

1. The life stage suffering the highest predation rate is expected to have the highest escape performance unless developmental or functional constraints interfere. Peak aquatic escape performance in ephemeral pond-breeding amphibians is expected to develop early in the larval period, and metamorphosis is expected to reduce or completely disrupt aquatic escape performance. In anurans, exceptionally low escape performance during metamorphosis creates selection favouring rapid metamorphosis – which minimizes the time individuals spend in the vulnerable transition between tadpole and frog. 2. We investigated the development of aquatic escape performance in the spotted salamander, Ambystoma maculatum (Shaw, 1802), from embryonic development through metamorphosis. We expected performance to peak early in the larval period as hatchlings face high rates of predation but embryos must first develop escape behaviours. We also tested whether escape performance during metamorphosis was intermediate, as predicted by tail fin resorption, or lower than larvae and adults indicating a major physiological disruption. 3. Escape performance shows a complex ontogeny that is first positively influenced by embryonic and early larval development and then negatively correlated with tail resorption and body size. Escape distance was the only performance metric not affected by life stage. In contrast, both escape velocity and duration showed ontogenetic peaks early in the larval period with the lowest performance found in early embryos and adults and intermediate performance during metamorphosis. 4. This pattern suggests that metamorphosis does not impose a major physiological disruption on escape performance. Because spotted salamanders do not pass through a frog-like ‘ontogenetic performance valley’ during metamorphosis, they may be less subject than anurans to selection favouring rapid metamorphosis. 5. Functional implications of phenotypic variation should be considered in an ontogenetic framework because the relationship between body size and escape performance can be reversed on either side of an ontogenetic performance peak. The assumption that metamorphosis radically disrupts basic functions such as predator evasion does not seem universally warranted and suggests examination of ontogenetic performance trajectories in a diversity of animals with complex life cycles. [ABSTRACT FROM AUTHOR]