Ambystoma Annulatum Research Articles

Isolation of Naegleria lustrarea n. sp. (Excavata, Discoba, Heterolobosea) from the feces of Ambystoma annulatum (Ringed Salamander) in Northwest Arkansas.

The salamander, Ambystoma annulatum, is considered a "species of special concern" in the state of Arkansas, USA, due to its limited geographic range, specialized habitat requirements and low population size. Although metazoan parasites have been documented in this salamander species, neither its native protists nor microbiome have yet been evaluated. This is likely due to the elusive nature and under-sampling of the animal. Here, we initiate the cataloguing of microbial associates with the identification of a new heterlobosean species, Naegleria lustrarea n. sp. (Excavata, Discoba, Heterolobosea), isolated from feces of an adult A. annulatum.

Predicting prey diversity with multiple predator effects

Emergent multiple predator effects can result in either risk enhancement or reduction for prey populations. However, whether emergent multiple predator effects influence survival of entire prey assemblages is unknown, which could alter community diversity. We tested whether emergent multiple predator effects would lead to changes in survival of multiple prey species that would subsequently alter prey diversity. We experimentally tested whether larval ringed (Ambystoma annulatum) and marbled salamanders (A. opacum) had additive or multiplicative effects on hatchlings of an assemblage of five amphibian prey species using outdoor mesocosms. We also examined this question using data from a previously published experiment. We extended the multiplicative risk model to estimate prey diversity based on individual prey survival probabilities from each mesocosm. We found that predators generally had additive effects on all prey species, as the expected survival of prey was not different from the observed data, indicating a lack of emergent multiple predator effects. Consistent with this result, observed diversity was not different from expected diversity based on our extension of the multiplicative risk model, further indicating predator species had additive effects. Re-analysis of previously published data showed that when emergent multiple predator effects resulted in risk reduction, diversity changed in a manner consistent that outcome. Overall, we found that additive and multiplicative effects of multiple predators contributed to structuring entire prey communities, including influencing community metrics like diversity. Future work should consider further under what conditions diversity enhancement or reduction would occur.

Multiple-Predator Effects and Functional Redundancy of Pond Predators

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

Demographic effects of phenological variation in natural populations of two pond-breeding salamanders

Phenology is a key driver of population and community dynamics. Phenological metrics (e.g., first date that an event occurred) often simplify information from the full phenological distribution, which may undermine efforts to determine the importance of life history events. Data regarding full phenological distributions are especially needed as many species are shifting phenology with climatic change which can alter life-history patterns and species dynamics. We tested whether skewness, kurtosis or maximum duration of breeding phenology affected juvenile emigration phenology and survival in natural populations of ringed (Ambystoma annulatum) and spotted salamanders (A. maculatum) spanning a 7-year period at two study locations. We evaluated the relative importance of different phenological metrics in breeding phenology and larval density dependence on emigration phenology and survival. We found that variability in emigration phenology differed by species, with ringed salamanders having a shorter duration and distributions that were more often right-skewed and leptokurtic compared to spotted salamanders. Emigration phenology was not linked to any measure of variability in breeding phenology, indicating phenological variability operates independently across life stages and may be subject to stage-specific influences. Emigration duration and skewness were partially explained by larval density, which demonstrates how phenological distributions may change with species interactions. Further tests that use the full phenological distribution to link variability in timing of life history events to demographic traits such as survival are needed to determine if and how phenological shifts will impact species persistence.

Asymmetric density‐dependent competition and predation between larval salamanders

Abstract Body size differences among consumers often lead to asymmetric interactions, with larger individuals typically being stronger competitors and/or predators on small individuals. These types of interaction are particularly exemplified in freshwater pond communities, where substantial size variation exists both within and among species of top consumers. We investigated whether density dependence can modify the outcome of size‐structured interactions between larval stages of two pond‐breeding salamanders, Ambystoma annulatum and Ambystoma opacum. Size structure exists in populations of these species due to variation in the timing of breeding, which we hypothesised would amplify predation rates and competitive asymmetries from the early‐arriving species (A. annulatum) on the later‐arriving species (A. opacum). We manipulated the relative densities of both A. annulatum and A. opacum in outdoor mesocosms. We maintained the experiment through metamorphosis, and analysed size at metamorphosis, larval period length and survival of each species. Ambystoma annulatum imparted a strong density‐dependent effect on A. opacum through a combination of predation and competition. Survival of A. opacum was negatively related to the density of A. annulatum. For the A. opacum that survived, body size was reduced and larval period lengthened at higher A. annulatum densities, indicative of interspecific competition that was partly explained by resource pre‐emption. In contrast, A. annulatum was only affected by intraspecific density‐dependent competition. Our results suggest that density‐dependent effects reinforce asymmetric interactions among larval salamanders. However, the intensity of the asymmetric interactions is mediated by the arrival time and size of conspecifics. Specifically, earlier‐arriving species can negatively affect the later‐arriving species via size‐mediated predation and competition. The interactive effects of density dependence and arrival time of community members are probably a common mechanism generating size variability in ecological communities. Yet, most studies only evaluate one mechanism or the other. By interweaving these two processes, our work displays the importance of understanding context‐dependence in species interactions.

Direct effects influence larval salamander size and density more than indirect effects.

Direct and indirect effects both influence population and community dynamics. The relative strengths of these pathways are often compared using experimental approaches, but their evaluation in situ has been less frequent. We examined how individual and aggregate impacts of direct and indirect effects of species densities, proxies for competition and predation pressure, and habitat variables influenced patterns of larval density and body size of ringed (Ambystoma annulatum) and spotted salamanders (A. maculatum). We surveyed > 150 ponds in Missouri, USA, from 2012 to 2014 to measure the density and body size of each focal species, the density of co-occurring pond food web members, and select habitat features. We used structural equation modeling to quantify the relative importance of direct and indirect pathways on both body size and larval density. Overall, both responses were explained through a combination of direct and indirect effects. However, the magnitudes of direct effects were often greater than indirect effects. Some of the direct and indirect relationships with larval salamander size and density were also consistent with results from experimental studies. Finally, total direct and indirect effects were often weaker due to habitat and density variables negating each other's impacts. Overall, our study shows that direct effects were equivalent to, or more important than, indirect effects. We also demonstrate that the effects stemming from individual relationships can sum to produce net patterns that are negligible in magnitude. Further work on direct and indirect effects with observational data are needed to examine their magnitudes in natural communities.

Inter- and intraspecific variation in juvenile metabolism and water loss among five biphasic amphibian species.

Population persistence is informed by the ability of individuals to cope with local abiotic conditions, which is commonly mediated by physiological traits. Among biphasic amphibians, juveniles-which are infrequently studied but play a key role in amphibian population dynamics-are the first life stage to experience terrestrial conditions following the aquatic larval stage. To illuminate phenotypic variation that may allow juveniles to survive the physiological challenges presented by this transition, we examined respiratory surface area water loss (RSAWL) and standard metabolic rates (SMR) among juveniles reared under common larval conditions for five salamander species (Ambystoma annulatum, A. maculatum, A. opacum, A. talpoideum, and A. texanum) collected across ~ 200km of latitude in Missouri, USA. We found that SMR described 34% of variation in RSAWL, suggesting that physiological water conservation may be limited by energetic regulation among these species, and vice versa. On average, species differed in juvenile SMR and residual values of RSAWL (corrected for body size/shape) by 0.04mL [Formula: see text] and 0.16, respectively, possibly because of distinct species ecologies. For example, A. annulatum had higher SMR and RSAWL compared to broadly distributed study species, potentially associated with a relatively narrow range of environmental conditions experienced across the small geographic distribution of A. annulatum. Latitude correlated negatively with temperature and precipitation, and positively with RSAWL, suggesting that variation in RSAWL may be adaptive to local conditions. We provide evidence that species differences likely have a genetic basis, reflecting selection favoring species divergence to effectively use distinct microhabitats.

Development and validation of four environmental DNA assays for species of conservation concern in the South-Central United States

We describe the development and testing of qPCR assays to detect four species of amphibians and reptiles of conservation concern in the South Central United States through environmental DNA (eDNA) samples. The target species include the Ringed Salamander (Ambystoma annulatum), Three-toed Amphiuma (Amphiuma tridactylum), Crawfish Frog (Rana areolata), and Chicken Turtle (Deirochelys reticularia). A set of primers and probes amplifying a 64–72 bp target regions were designed for each species from DNA sequence data for either the mitochondrial Cytochrome Oxidase I or Cytochrome B gene. All assays were assessed for target specificity, with no evidence of amplification in closely related or sympatrically-distributed non-target species. In vitro tests indicate that all assays consistently detect focal species down to concentrations of 2 × 10− 9 pg/µL. We evaluated the utility of qPCR assays on the eDNA samples collected during field surveys across Eastern Oklahoma, focusing on counties with vouchered historical records for the target species. Although detection rates were low for field applications of the assays, positive detection of Ambystoma annulatum, Rana areolata, and Deirochelys reticularia, but not Amphiuma tridactylum, were recorded. These assays can provide a practical tool for a non-invasive, genetic monitoring program that allows for both rapid detection and tracking of native aquatic and semi-aquatic amphibian and reptile species of conservation concern.

Estimating Survival for Elusive Juvenile Pond‐Breeding Salamanders

ABSTRACTJuvenile vital rates have important effects on population dynamics for many species, but this demographic is often difficult to locate and track. As such, we frequently lack reliable estimates of juvenile survival, which are necessary for accurately assessing population stability and potential management approaches to conserve biodiversity. We estimated survival rates for elusive juveniles of 3 species, the ringed salamander (Ambystoma annulatum), spotted salamander (A. maculatum), and small‐mouthed salamander (A. texanum), using 2 approaches. First, we conducted an 11‐month (2016–2017) mark‐recapture study within semi‐natural enclosures and used Bayesian Cormack‐Jolly‐Seber models to estimate survival and recapture probabilities. Second, we inferred the expected annual juvenile survival rate given published vital rates for pre‐metamorphic and adult ambystomatids assuming stable population growth. For all 3 species, juvenile survival probabilities were constant across recapture occasions, whereas recapture probability estimates were time‐dependent. Further, survival and recapture probabilities among study species were similar. Post‐study sampling revealed that the initial study period median estimate of annual survival probability (0.39) underestimated the number of salamanders known alive at 11 months. We therefore appended approximately 1 year of opportunistic data, which produced a median annual survival probability of 0.50, encompassing salamanders that we knew to have been alive. Calculation from literature values suggested a mean annual terrestrial juvenile ambystomatid survival probability of 0.49. Similar results among our approaches indicated that juvenile survival estimates for the study species were robust and likely comparable to rates in nature. These estimates can now be confidently applied to research, monitoring, and management efforts for the study species and ecologically similar taxa. Our findings indicated that similarly robust vital rate estimates for subsets of ecologically and phylogenetically similar species can provide reasonable surrogate demographic information that can be used to reveal key factors influencing population viability for data‐deficient species. © 2020 The Wildlife Society.

Impacts of phenological variability in a predatory larval salamander on pond food webs

AbstractPhenological shifts are expected to affect species interactions, in part by influencing which size classes, life stages or species occur simultaneously in a community. Yet, changes in phenology beyond shifts to the first, mean or median date of an ontogenetic event are underexplored in their importance to community dynamics. Using outdoor mesocosms, we experimentally mimicked increasing variability in breeding phenology of a top predatory salamander in pond food webs (Ambystoma annulatum) to assess its impacts on its own demographic traits and survival. We also tested whether variability in predator breeding would cascade to impact survival and diversity of lower trophic levels (intermediate salamander predators, anuran tadpoles, zooplankton and periphyton). We found that only variability in body size at metamorphosis of A. annulatum was impacted by phenological manipulations, with size variability being greater at higher levels of phenological variability. Because size at metamorphosis is often correlated with adult fitness, covarying variability in body size and phenology may lead to altered population dynamics. We also found that the density and size of A. annulatum were better predictors of overall survival and diversity of amphibian prey compared to phenological variability. We speculate that overwintering mortality of A. annulatum due to pond freezing modulated the impacts of phenological variability, such that changes in demographic traits and cascading effects throughout the food web were mollified.

Post-Pleistocene differentiation in a Central Interior Highlands endemic salamander.

AimFor many endemic species with limited dispersal capacities, the relationship between landscape changes and species distributions is still unclear. We characterized the population structure of the endemic ringed salamander (Ambystoma annulatum) across its distribution in the Central Interior Highlands (CIH) of North America, an area of high species endemism, to infer the ecological and evolutionary history of the species.MethodsWe sampled 498 individuals across the species distribution and characterized the population genetic structure using nuclear microsatellite and mitochondrial DNA (mtDNA) markers.Results Ambystoma annulatum exist in two strongly supported nuclear genetic clusters across the CIH that correspond to a northern cluster that includes the Missouri Ozark populations and a southern cluster that includes the Arkansas and Oklahoma Ozarks and the Ouachita Mountains. Our demographic models estimated that these populations diverged approximately 2,700 years ago. Pairwise estimates of genetic differentiation at microsatellite and mtDNA markers indicated limited contemporary gene flow and suggest that genetic differentiation was primarily influenced by changes in the post‐Pleistocene landscape of the CIH.Main ConclusionsBoth the geologic history and post‐European settlement history of the CIH have influenced the population genetic structure of A. annulatum. The low mtDNA diversity suggests a retraction into and expansion out of refugial areas in the south‐central Ozarks, during temperature fluctuations of the Pleistocene and Holocene epochs. Similarly, the estimated divergence time for the two nuclear clusters corresponds to changes in the post‐Pleistocene landscape. More recently, decreased A. annulatum gene flow may be a result of increased habitat fragmentation and alteration post‐European settlement.

Learning to find food: evidence for embryonic sensitization and juvenile social learning in a salamander

For many species, learning is an essential mechanism for dealing with the environment correctly and efficiently. Animals that quickly learn important information, and learn at a young age, can gain a competitive advantage in exploiting resources. Moreover, animals that learn indirectly through social observations can avoid the fitness costs of directly learning about potential dangers. Here we tested such learning capabilities in ringed salamanders, Ambystoma annulatum , a species where adults are primarily solitary and do not provide parental care. Adults lay eggs in ponds where embryos have the opportunity to learn from chemical cues in their environment before hatching, whereupon the high density of larvae provides an opportunity to learn from social information. In this study, we found that these salamanders can learn an attraction to novel food stimuli as embryos and that naive observer larvae can learn from conspecifics that show attraction to stimuli. Embryonic exposure to a novel food stimulus (shrimp odour) caused attraction to that stimulus posthatching, and this response appeared to be generalized to another potential prey stimulus (mussel odour) but not to a novel plant stimulus. In a test of social learning, only observers that were paired with models corralled near a novel food stimulus were subsequently attracted to the stimulus. This study is the first to report embryonic learning of food or social learning by salamanders, providing more evidence for generalized learning by embryos and social learning by species lacking more complex social behaviours.

Effects of conditionally expressed phenotypes and environment on amphibian dispersal in nature

Individuals vary greatly in the distance they disperse, and in doing so, strongly affect ecological and evolutionary processes. Dispersal, when viewed as a component of phenotype, can be affected independently or jointly by environment. However, among taxa with complex life cycles that occupy different habitats over ontogeny, the effects of environment on dispersal and the interaction between environment and phenotype remains poorly understood. Here, we conducted a field experiment to measure how dispersal distance was affected by phenotype, environment experienced before and after metamorphosis, and their interaction. We manipulated the environment encountered by a pond‐breeding salamander Ambystoma annulatum during the aquatic larval stage and again as dispersing terrestrial juveniles. After assaying juvenile phenotype (exploration behavior, body condition, and morphology), we then measured the initial distance dispersed by juveniles. The distance moved by dispersing salamanders was affected by attributes of both larval and juvenile habitat, with salamanders that encountered low quality habitat in either life stage moving the farthest. However, we did not find support for an interactive effect of phenotype and environment affecting the distance moved by dispersers. Interestingly, exploration behavior explained the distance moved by philopatric animals but not dispersing ones. Our findings indicate that the environment experienced before metamorphosis can affect juvenile dispersal behavior, and demonstrates the need to consider dispersal in species with complex life cycles to understand the coupling between local and regional population dynamics.

Using spatial demographic network models to optimize habitat management decisions

ABSTRACTConservation and management activities are always constrained by finite resources. Therefore, decisions such as which sites to protect, whether existing habitat should be restored or whether new habitat should be created, and where on the landscape management efforts should be focused present difficult challenges. An overarching goal of many conservation or management plans is the long‐term persistence of populations, which is often dependent on functional connectivity and the maintenance of metapopulation dynamics. Graph theory and network approaches are frequently used tools for modeling functional connections between populations and between habitats. Less often, graph models are used to guide conservation or management decisions. We used spatial networks derived for an amphibian population to determine optimal locations to create new habitat, prioritize existing habitat for restoration, and determine the habitat most critical for maintaining connectivity within the existing metapopulation within Fort Leonard Wood, Missouri, USA, 2012–2014. Using data collected at 206 breeding ponds over 3 years, we constructed demographic networks representing the functional connectivity between ponds by dispersing ringed salamanders (Ambystoma annulatum). We incorporated uncertainty in key model parameters through Monte Carlo simulation, and used a graph‐theoretical parameterization of the metapopulation mean lifetime model to assess how changes in network structure affect persistence of the network. We conducted addition and removal experiments within our Monte Carlo simulations to rank and prioritize locations for pond creation, ponds for restoration, and ponds for preservation. Salamanders bred in 106 ponds in ≥1 year; 2.4% of ponds functioned predominantly as sources and 51% of occupied ponds functioned predominantly as sinks. The importance of a pond to the network was correlated with the number of emigrants dispersing from a pond, the number of ponds reached by these dispersers, and the frequency a pond functioned as a source. Creating new ponds at optimal locations increased the persistence of the network an average of 15.4% compared to randomly selected locations, whereas selective restoration of currently unoccupied ponds resulted in an average increase of 31.4% in network persistence, as compared to randomly selected unoccupied ponds. Through Monte Carlo simulation, we constructed biologically informed demographic connectivity networks for use as a spatial conservation or management planning tool. Although our approach was implemented with an amphibian and a breeding pond network, it is generalizable to any species occupying discrete habitat patches. © 2017 The Wildlife Society.

Variation in phenology and density differentially affects predator-prey interactions between salamanders.

Variation in the timing of breeding (i.e., phenological variation) can affect species interactions and community structure, in part by shifting body size differences between species. Body size differences can be further altered by density-dependent competition, though synergistic effects of density and phenology on species interactions are rarely evaluated. We tested how field-realistic variation in phenology and density affected ringed salamander (Ambystoma annulatum) predation on spotted salamanders (Ambystoma maculatum), and whether these altered salamander dynamics resulted in trophic cascades. In outdoor mesocosms, we experimentally manipulated ringed salamander density (low/high) and breeding phenology (early/late) of both species. Ringed salamander body size at metamorphosis, development, and growth were reduced at higher densities, while delayed phenology increased hatchling size and larval development, but reduced relative growth rates. Survival of ringed salamanders was affected by the interactive effects of phenology and density. In contrast, spotted salamander growth, size at metamorphosis, and survival, as well as the biomass of lower trophic levels, were negatively affected primarily by ringed salamander density. In an additional mesocosm experiment, we isolated whether ringed salamanders could deplete shared resources prior to their interactions with spotted salamanders, but instead found direct interactions (e.g., predation) were the more likely mechanism by which ringed salamanders limited spotted salamanders. Overall, our results indicate the effects of phenological variability on fitness-related traits can be modified or superseded by differences in density dependence. Identifying such context dependencies will lead to greater insight into when phenological variation will likely alter species interactions.

Breeding Pond Occupancy of the Ringed Salamander (Ambystoma annulatum) in East-central Missouri

Abstract Ringed Salamanders are wetland-dependent amphibians that are regionally endemic to the Ozark Highlands and Ouachita Mountains. To assess the most important variables influencing breeding wetland use by Ringed Salamanders in east-central Missouri, we sampled a total of 38 wetlands during the fall 2010 breeding season. We found the presence of predatory fish was the most important variable determining whether Ringed Salamanders used a breeding wetland and that breeding wetlands were significantly associated with increased areas of continuous forest. These breeding habitat requirements can be used to aid in conservation efforts for this species as well as other fall-breeding ambystomatid salamanders.

The influence of breeding phenology on the genetic structure of four pond-breeding salamanders.

Understanding metapopulation dynamics requires knowledge about local population dynamics and movement in both space and time. Most genetic metapopulation studies use one or two study species across the same landscape to infer population dynamics; however, using multiple co‐occurring species allows for testing of hypotheses related to different life history strategies. We used genetic data to study dispersal, as measured by gene flow, in three ambystomatid salamanders (Ambystoma annulatum, A. maculatum, and A. opacum) and the Central Newt (Notophthalmus viridescens louisianensis) on the same landscape in Missouri, USA. While all four salamander species are forest dependent organisms that require fishless ponds to reproduce, they differ in breeding phenology and spatial distribution on the landscape. We use these differences in life history and distribution to address the following questions: (1) Are there species‐level differences in the observed patterns of genetic diversity and genetic structure? and (2) Is dispersal influenced by landscape resistance? We detected two genetic clusters in A. annulatum and A. opacum on our landscape; both species breed in the fall and larvae overwinter in ponds. In contrast, no structure was evident in A. maculatum and N. v. louisianensis, species that breed during the spring. Tests for isolation by distance were significant for the three ambystomatids but not for N. v. louisianensis. Landscape resistance also contributed to genetic differentiation for all four species. Our results suggest species‐level differences in dispersal ability and breeding phenology are driving observed patterns of genetic differentiation. From an evolutionary standpoint, the observed differences in dispersal distances and genetic structure between fall breeding and spring breeding species may be a result of the trade‐off between larval period length and size at metamorphosis which in turn may influence the long‐term viability of the metapopulation. Thus, it is important to consider life history differences among closely related and ecologically similar species when making management decisions.

Moving beyond the plane: measuring 3D home ranges of juvenile salamanders with passive integrated transponder (PIT) tags

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. 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.

Effects of diet quality and stress on interference behaviour of larval ringed salamanders

Interference behaviour (aggression and cannibalism) can be influenced by both intrinsic factors, such as animal physiology, size, or motivation, and extrinsic factors, such as presence of competitors, predators, or prey. Our experiment examined the effects of differences in diet quality of focal salamanders and their opponents, and levels of handling on biting by pairs of larval ringed salamanders,Ambystoma annulatum, before and after presentation of prey. Diet quality and handling affect the intrinsic qualities of body size/condition and stress, respectively. Presence of prey and diet quality of opponents are extrinsic factors. Unstressed larvae on high-quality diets bit their high-condition opponents more frequently than those that had been on low-quality diets in both the presence and absence of food. Stressed larvae (all on high quality diets) showed low levels of biting when food was absent. However, when food was present, the level of biting depended on the diet quality of their opponents: stressed larvae bit opponents on low-quality diets more than opponents on high-quality diets. Overall, both intrinsic and extrinsic factors influenced interference behaviour, with larvae on high-quality diets exhibiting relatively high levels of biting unless they had experienced handling stress, and the effect of handling stress depending on the condition of the opponent in paired interactions.

Differences in Larval Allometry among Three Ambystomatid Salamanders

Abstract Ecological and evolutionary processes commonly result in morphological variation among larval amphibians. Variation in head shape plays a critical role in both food capture and predation risk in gape-limited salamanders, yet in situ studies of head shape variability are rare outside of cannibal morph assessments. We examined allometry differences in larval head width (HW) and snout–vent length (SVL) among three sympatric species of ambystomatid salamanders from 166 ponds in Missouri, USA: Ringed Salamander (Ambystoma annulatum), Marbled Salamander (A. opacum), and Spotted Salamander (A. maculatum). We also tested whether several abiotic and biotic factors would predict HW after accounting for SVL. We found that larval HW and SVL were strongly correlated for all species but that the strength of this relationship varied among species. For early-stage larvae, Marbled Salamanders showed isometric scaling relationships, whereas both Spotted Salamanders and Ringed Salamanders were allometric. For late-...