Size-Mediated Trophic Interactions in Two Syntopic Forest Salamanders

Exploitative competition and interference competition differ in the way they affect re-source availability for competitors: in the former, organisms reduce resource availability for the competitors; in the latter, one organism actively prevents the competitor from accessing resources, independently of their availability. Our aim is to test for the presence of foraging competition in two forest-dwelling salamanders in Italy: Speleomantes strinatii and Salamandrina perspicillata. We also aim at testing for size-mediated competition. We obtained stomach contents from 191 sampled individuals by means of stomach flushing at 8 sampling sites where both species occur. We focused our analysis on the core prey taxa shared by both species: Collembola and Acarina. We found that the foraging activity of S. perspicillata is positively affected by body size and negatively affected by potential competitor's activity on the forest floor during the sampling, which also significantly weakened the positive relationship with body size. These results suggest the presence of an interference/interaction occurring between the two species and affecting the foraging activity of S. perspicillata. This competitive interaction is size mediated and configured as interference competition rather than exploitative competition.

Climate-associated decline of body condition in a fossorial salamander

Temperate ectotherms have responded to recent environmental change, likely due to the direct and indirect effects of temperature on key life cycle events. Yet, a substantial number of ectotherms are fossorial, spending the vast majority of their lives in subterranean microhabitats that are assumed to be buffered against environmental change. Here, we examine whether seasonal climatic conditions influence body condition (a measure of general health and vigor), reproductive output, and breeding phenology in a northern population of fossorial salamander (Spotted Salamander, Ambystoma maculatum). We found that breeding body condition declined over a 12-year monitoring period (2008-2019) with warmer summer and autumn temperatures at least partly responsible for the observed decline in body condition. Our findings are consistent with the hypothesis that elevated metabolism drives the negative association between temperature and condition. Population-level reproduction, assessed via egg mass counts, showed high interannual variation and was weakly influenced by autumn temperatures. Salamander breeding phenology was strongly correlated with lake ice melt but showed no long-term temporal trend (1986-2019). Climatic warming in the region, which has been and is forecasted to be strongest in the summer and autumn, is predicted to lead to a 5%-27% decline in salamander body condition under realistic near-future climate scenarios. Although the subterranean environment offers a thermal buffer, the observed decline in condition and relatively strong effect of summer temperature on body condition suggest that fossorial salamanders are sensitive to the effects of a warming climate. Given the diversity of fossorial taxa, heightened attention to the vulnerability of subterranean microhabitat refugia and their inhabitants is warranted amid global climatic change.

Salamander loss alters litter decomposition dynamics

Biodiversity loss affects ecosystem functioning. Top down effects of amphibian declines on the trophic food web of the forest floor are poorly understood. Here we quantify and explain the effects of disease-driven loss of salamanders on the dynamics of forest leaf litter. Using paired mesocosms, within a Belgian forest, we tested the effect of fire salamander (Salamandra salamandra) presence on the trophic cascade that results in the decomposition rate of good quality (maple - Acer pseudoplatanus) and poorer quality (oak - Quercus robur) leaf litter, over an 18 month period. The presence of salamanders reduced decomposition rate of Quercus litter up to 20%. This was associated with a significantly higher predation rate on detritivores, which altered the functional composition of the invertebrate community. Functional composition analysis of the litter microbiome showed less bacteria associated with leaf litter degradation on the Quercus litter in the presence of salamanders. Salamanders thus influence ecosystem functions through trophic cascades and promote the retention of the leaf litter fraction in poorer quality litter.

A Salamander tale: Relative abundance, morphometrics and microhabitat of the critically endangered Mexican salamander Pseudoeurycea robertsi (Taylor, 1939)

Roberts’ False Brook Salamander (Pseudoeurycea robertsi) is a critically endangered plethodontid salamander, endemic to the Nevado de Toluca Volcano (NTV), Mexico. Little is known about the biology and ecology of this species, including its microhabitats. Thus, this study aimed to collect basic information about P. robertsi. We sampled fourteen forested sites in the NTV; to corroborate the correct identification of the species we used genetic data, we assessed the variation in head morphometric measurements and dorsal colouration patterns amongst localities and the microhabitat features associated with P. robertsi presence. Of the four potential salamander species, P. robertsi was the most abundant (89.80%) and widely distributed (approximately within 130 km2) salamander in the NTV. We did not find significant variations in morphometry; however, we found significant differences in dorsal patterns between populations (in the number and size of segments of the dorsal stripe). The average total length for 185 adults was 89.15 mm (38.7–117.9 mm); we found seven patterns of dorsal stripe. We found 98% of P. robertsi individuals under the bark of fallen logs in Abies religiosa and A. religiosa-Pinus sp. forests, with a higher number of detected salamanders in naturally-fallen logs than in cut logs (34% vs. 10%). Thus, keeping well-preserved A. religiosa forests and retaining fallen logs is essential to P. robertsi conservation.

Structure of the leaf litter frog community in an area of Atlantic Forest in southeastern Brazil

Different spatial and temporal factors can influence the species richness and abundance of leaf anurans that are fundamental for the ecosystem functioning, as they act as predators and integrate the trophic chain as prey of other animals. There are relatively few studies that aimed to understand the spatio-temporal variation and the influence of environmental factors on leaf litter communities. We studied parameters of the anuran community living in the forest leaf litter in the Duas Bocas Biological Reserve (DBBR), Espírito Santo, Brazil. We sought to understand the extent to which richness, abundance, biomass and density varied between two locations with different stages of preservation (primary and secondary forest). In addition, we tested the effect of temperature and local humidity on abundance. We conducted the samplings monthly from October 2017 to September 2018, establishing 98 4 x 4 m plots (16 m2 each) demarcated on the DBBR forest leaf litter. We measured temperature (°C) and relative air humidity (%), and each plot was carefully surveyed by four observers. We tested for differences in anuran density between the two sampled locations and estimated the effects of environmental variables in the community. We recorded 102 individuals of anurans from 11 species belonging to eight families. The DBBR anuran community parameters significantly differed between the two studied locations, with the highest values of anuran richness and abundance occurring in the area covered by primary forest, probably due to differences in the preservation of each area. However, temperature and humidity did not affect the abundance of anurans in the sampled areas. Our results provide the first information about spatial variation and influence of environmental factors, directed to the community of leaf litter anurans in DBBR, and represents the second study on this group of anurans in the state of Espírito Santo.

Predicted alteration of surface activity as a consequence of climate change

Wildlife are faced with numerous threats to survival, none more pressing than that of climate change. Understanding how species will respond behaviorally, physiologically, and demographically to a changing climate is a cornerstone of many contemporary ecological studies, especially for organisms, such as amphibians, whose persistence is closely tied to abiotic conditions. Activity is a useful parameter for understanding the effects of climate change because activity is directly linked to fitness as it dictates foraging times, energy budgets, and mating opportunities. However, activity can be challenging to measure directly, especially for secretive organisms like plethodontid salamanders, which only become surface active when conditions are cool and moist because of their anatomical and physiological restrictions. We estimated abiotic predictors of surface activity for the seven species of the Plethodon jordani complex. Five independent data sets collected from 2004 to 2017 were used to determine the parameters driving salamander surface activity in the present day, which were then used to predict potential activity changes over the next 80 yrs. Average active seasonal temperature and vapor pressure deficit were the strongest predictors of salamander surface activity and, without physiological or behavioral modifications, salamanders were predicted to exhibit a higher probability of surface activity during peak active season under future climate conditions. Temperatures during the active season likely do not exceed salamander thermal maxima to cause activity suppression and, until physiological limits are reached, future conditions may continue to increase activity. Our model is the first comprehensive field-based study to assess current and future surface activity probability. Our study provides insights into how a key behavior driving fitness may be affected by climate change.

Differences in Fungal Disease Dynamics in Co-occurring Terrestrial and Aquatic Amphibians

The fungal pathogen, Batrachochytrium dendrobatidis (Bd), has devastated biodiversity and ecosystem health and is implicated as a driver of mass amphibian extinctions. This 100-year study investigates which environmental factors contribute to Bd prevalence in a fully terrestrial species, and determines whether infection patterns differ between a fully terrestrial amphibian and more aquatic host species. We performed a historical survey to quantify Bd prevalence in 1127 Batrachoseps gregarius museum specimens collected from 1920 to 2000, and recent data from 16 contemporary (live-caught) B. gregarius populations from the southwestern slopes of the Sierra Nevada mountains in California, USA. We compared these results to Bd detection rates in 1395 historical and 1033 contemporary specimens from 10 species of anurans and 427 historical Taricha salamander specimens collected throughout the Sierra Nevada mountains. Our results indicate that Bd dynamics in the entirely terrestrial species, B. gregarius, differ from aquatic species in the same region in terms of both seasonal patterns of Bd abundance and in the possible timing of Bd epizootics.

Environmental Factors and Host Microbiomes Shape Host-Pathogen Dynamics

Microorganisms are increasingly recognized as ecosystem-relevant components because they affect the population dynamics of hosts. Functioning at the interface of the host and pathogen, skin and gut microbiomes are vital components of immunity. Recent work reveals a strong influence of biotic and abiotic environmental factors (including the environmental microbiome) on disease dynamics, yet the importance of the host-host microbiome-pathogen-environment interaction has been poorly reflected in theory. We use amphibians and the disease chytridiomycosis caused by the fungal pathogen Batrachochytrium dendrobatidis to show how interactions between host, host microbiome, pathogen, and the environment all affect disease outcome. Our review provides new perspectives that improve our understanding of disease dynamics and ecology by incorporating environmental factors and microbiomes into disease theory.

Reciprocal Role of Salamanders in Aquatic Energy Flow Pathways

Many species of salamanders (newts and salamanders per se) have a pivotal role in energy flow pathways as they include individuals functioning as prey, competitors, and predators. Here, I synthesize historic and contemporary research on the reciprocal ecological role of salamanders as predators and prey in aquatic systems. Salamanders are a keystone in ecosystem functioning through a combination of top–down control, energy transfer, nutrient cycling processes, and carbon retention. The aquatic developmental stages of salamanders are able to feed on a wide variety of invertebrate prey captured close to the bottom as well as on small conspecifics (cannibalism) or other sympatric species, but can also consume terrestrial invertebrates on the water surface. This capacity to consume allochthonous resources (terrestrial invertebrates) highlights the key role of salamanders as couplers of terrestrial and aquatic ecosystems (i.e., aquatic–terrestrial linkages). Salamanders are also an important food resource for other vertebrates such as fish, snakes, and mammals, covering the energy demands of these species at higher trophic levels. This study emphasizes the ecological significance of salamanders in aquatic systems as central players in energy flow pathways, enabling energy mobility among trophic levels (i.e., vertical energy flow) and between freshwater and terrestrial habitats (i.e., lateral energy flow).

Preliminary Analysis of the Diet of Triturus carnifex and Pollution in Mountain Karst Ponds in Central Apennines

Mountain karst ponds are sensitive environments, hosting complex trophic networks where amphibians play a major role, often as top predators. The diet of the Italian crested newt (Triturus carnifex) is still poorly known for populations occupying mountain karst ponds. These are traditionally used as livestock’s watering points, leading to water pollution due to excreta and wading behavior. The aim of this paper is to understand the relationship between T. carnifex diet composition, assessed through the stomach flushing technique, and physical and chemical characteristics in mountain ponds, focusing on parameters altered by livestock pressure, such as ammonium concentration and dissolved oxygen. The high diversity of prey items found within the newts’ gut contents confirms the generalist diet even in mountain ponds. The number of prey taxa, their relative abundance and Shannon–Wiener diversity index show variations among the sampled sites, related to livestock organic pollution. Moreover, we report the very first European records of microplastic items in amphibians’ stomach content, which also represent the first evidence for Caudata worldwide. Our findings suggest that livestock pressure directly influences T. carnifex diet and highlight that the emerging issue of plastics is a threat even in remote high-altitude environments.

Amphibian Monitoring in Hardwood Forests: Optimizing Methods for Contaminant-Based Compensatory Restorations

Amphibians such as frogs, toads, and salamanders provide important services in aquatic and terrestrial ecosystems and have been proposed as useful indicators of progress and success for ecological restoration projects. Limited guidance is available, however, on the costs and benefits of different amphibian monitoring techniques that might be applied to sites restored in compensation for contaminant injury. We used a variety of methods to document the amphibian communities present at 4 restored bottomland hardwood sites in Indiana, USA, and to compare the information return and cost of each method. For 1 method-automated recording units-we also modeled the effect of varying levels of sampling effort on the number of species detected, using sample-based rarefaction and Bayesian nonlinear (Michaelis-Menten) mixed effects models. We detected 13 amphibian species across the restored sites, including 2 species of conservation concern in Indiana-northern leopard frogs (Lithobates pipiens) and Blanchard's cricket frogs (Acris blanchardi). Sites across a range of restoration ages demonstrated encouraging returns of amphibian communities. Although more mature sites showed greater species richness, recently restored sites still provided important habitat for amphibians, including species of conservation concern. Among the 4 methods compared, amphibian rapid assessment yielded the highest number of species detected and the greatest catch per unit effort, with the lowest per-site cost. Our analysis of level-of-effort effects in the rarefied acoustic data found that number of nights sampled was a better predictor of observed species richness than the number of hours sampled within a night or minutes sampled within an hour. These data will assist restoration practitioners in selecting amphibian monitoring methods appropriate for their site characteristics and budget. Integr Environ Assess Manag 2019;00:1-15. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

The role of feeding strategy in the tolerance of a terrestrial salamander (Plethodon cinereus) to biogeochemical changes in northern hardwood forests

We investigated whether the trophic ecology of an apex predator is influenced by ecosystem-level nutrient depletion. The feeding behavior and nutrient assimilation of a terrestrial salamander, Eastern Red-backed Salamander (Plethodon cinereus (Green, 1818)), was surveyed along a gradient of forest biogeochemistry. Recent studies have documented populations of these salamanders in forests with low-pH soils that were long thought to be fatal. One mechanism that may enable P. cinereus to tolerate acid-impaired habitats is its generalist life history. We sampled diet, invertebrate prey abundance, and tissue composition of P. cinereus from sites that range in calcium availability and soil pH in northern forests of North America. We found that P. cinereus consistently exhibited a generalist feeding strategy, having diverse diets closely representing resource availability. Prey abundances were unrelated to the biogeochemical gradient (excluding gastropods), indicating relatively intact food webs. Although P. cinereus at the two most acid-impaired sites consumed more prey, overall trophic strategies were consistent across the gradient. Salamander tissue composition was unrelated to variation in forest biogeochemistry, although manganese levels were elevated in the most acid-impaired forests. We suggest that a generalist feeding strategy, combined with diverse and compositionally stable food webs, facilitates tolerance by this abundant predator of the challenges imposed by acid-impaired habitats.

Do Terrestrial Salamanders Indicate Ecosystem Changes in New England Forests?

Long-term ecological research (LTER) and monitoring programs accrue invaluable ecological data that inform policy and improve decisions that enable adaptation to and mitigation of environmental changes. There is great interest in identifying ecological indicators that can be monitored easily and effectively to yield reliable data about environmental changes in forested ecosystems. However, the selection, use, and validity of ecological indicators to monitor in LTER programs remain challenging tasks for ecologists and conservation biologists. Across the eastern United States of America, the foundation tree species eastern hemlock (Tsuga canadensis (L.) Carrière) is declining and dying from irruptions of a non-native insect, the hemlock woolly adelgid (Adelges tsugae Annand). We use data from the Harvard Forest LTER site’s Hemlock Removal Experiment together with information from other eastern US LTER sites to show that plethodontid salamanders can be reliable indicators of ongoing ecological changes in forested ecosystems in the eastern USA. These salamanders are abundant, they have a history of demographic stability, are both predators and prey, and can be sampled and monitored simply and cost-effectively. At the Harvard Forest LTER, red-backed salamanders (Plethodon cinereus Green) were strong indicators of intact forests dominated by eastern hemlock (Tsuga canadensis); their high site fidelity and habitat specificity yielded an indicator value (robust Dufrêne and Legendre’s “IndVal”) for this species of 0.99. Eastern red-spotted newts (Notopthalmus viridescens viridescens Rafinesque) were better indicators of nearby stands made up of young, mixed hardwood species, such as those which replace hemlock stands following adelgid infestation. At the Hubbard Brook and Coweeta LTER sites, plethodontid salamanders were associated with intact riparian habitats, which may also be dominated by eastern hemlock. We conclude that plethodontid salamanders satisfy most criteria for reliable ecological indicators of environmental changes in eastern US forests.

Environmental gradients in old-growth Appalachian forest predict fine-scale distribution, co-occurrence, and density of woodland salamanders

Woodland salamanders are among the most abundant vertebrate animals in temperate deciduous forests of eastern North America. Because of their abundance, woodland salamanders are responsible for the transformation of nutrients and translocation of energy between highly disparate levels of trophic organization: detrital food webs and high-order predators. However, the spatial extent of woodland salamanders' role in the ecosystem is likely contingent upon the distribution of their biomass throughout the forest. We sought to determine if natural environmental gradients influence the fine-scale distribution and density of Southern Ravine Salamanders (Plethodon richmondi) and Cumberland Plateau Salamanders (P. kentucki). We addressed this objective by constructing occupancy, co-occurrence, and abundance models from temporally replicated surveys within an old-growth forest in the Cumberland Plateau region of Kentucky. We found that Plethodon richmondi had a more restricted fine-scale distribution than P. kentucki (mean occupancy probability [ψ ¯ ^ ] = 0.737) and exhibited variable density, from <250 to >1000 individuals per hectare, associated with increased soil moisture and reduced solar exposure due to slope face. While more ubiquitously distributed (ψ ¯ ^  = 0.95), P. kentucki density varied from <400 to >1,000 individuals per hectare and was inversely related to increased solar exposure from canopy disturbance and landscape convexity. Our data suggest co-occurrence patterns of P. richmondi and P. kentucki are influenced primarily by abiotic conditions within the forest, and that populations likely occur independently and without evidence of biotic interaction. Given the critical role that woodland salamanders play in the maintenance of forest health, regions that support large populations of woodland salamanders, such as those highlighted in this study-mesic forest stands on north-to-east facing slopes with dense canopy and abundant natural cover, may provide enhanced ecosystem services and support the stability of the total forest.

Batrachochytrium salamandrivorans and the Risk of a Second Amphibian Pandemic

Amphibians are experiencing devastating population declines globally. A major driver is chytridiomycosis, an emerging infectious disease caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). Bd was described in 1999 and has been linked with declines since the 1970s, while Bsal is a more recently discovered pathogen that was described in 2013. It is hypothesized that Bsal originated in Asia and spread via international trade to Europe, where it has been linked to salamander die-offs. Trade in live amphibians thus represents a significant threat to global biodiversity in amphibians. We review the current state of knowledge regarding Bsal and describe the risk of Bsal spread. We discuss regional responses to Bsal and barriers that impede a rapid, coordinated global effort. The discovery of a second deadly emerging chytrid fungal pathogen in amphibians poses an opportunity for scientists, conservationists, and governments to improve global biosecurity and further protect humans and wildlife from a growing number of emerging infectious diseases.

Methodological considerations for detection of terrestrial small-body salamander eDNA and implications for biodiversity conservation

Environmental DNA (eDNA) can be used as an assessment tool to detect populations of threatened species and provide fine-scale data required to make management decisions. The objectives of this project were to use quantitative PCR (qPCR) to: (i) detect spiked salamander DNA in soil, (ii) quantify eDNA degradation over time, (iii) determine detectability of salamander eDNA in a terrestrial environment using soil, faeces, and skin swabs, (iv) detect salamander eDNA in a mesocosm experiment. Salamander eDNA was positively detected in 100% of skin swabs and 66% of faecal samples and concentrations did not differ between the two sources. However, eDNA was not detected in soil samples collected from directly underneath wild-caught living salamanders. Salamander genomic DNA (gDNA) was detected in all qPCR reactions when spiked into soil at 10.0, 5.0, and 1.0 ng/g soil and spike concentration had a significant effect on detected concentrations. Only 33% of samples showed recoverable eDNA when spiked with 0.25 ng/g soil, which was the low end of eDNA detection. To determine the rate of eDNA degradation, gDNA (1 ng/g soil) was spiked into soil and quantified over seven days. Salamander eDNA concentrations decreased across days, but eDNA was still amplifiable at day 7. Salamander eDNA was detected in two of 182 mesocosm soil samples over 12 weeks (n = 52 control samples; n = 65 presence samples; n = 65 eviction samples). The discrepancy in detection success between experiments indicates the potential challenges for this method to be used as a monitoring technique for small-bodied wild terrestrial salamander populations.

Evaluating Multi-Level Models to Test Occupancy State Responses of Plethodontid Salamanders

Plethodontid salamanders are diverse and widely distributed taxa and play critical roles in ecosystem processes. Due to salamander use of structurally complex habitats, and because only a portion of a population is available for sampling, evaluation of sampling designs and estimators is critical to provide strong inference about Plethodontid ecology and responses to conservation and management activities. We conducted a simulation study to evaluate the effectiveness of multi-scale and hierarchical single-scale occupancy models in the context of a Before-After Control-Impact (BACI) experimental design with multiple levels of sampling. Also, we fit the hierarchical single-scale model to empirical data collected for Oregon slender and Ensatina salamanders across two years on 66 forest stands in the Cascade Range, Oregon, USA. All models were fit within a Bayesian framework. Estimator precision in both models improved with increasing numbers of primary and secondary sampling units, underscoring the potential gains accrued when adding secondary sampling units. Both models showed evidence of estimator bias at low detection probabilities and low sample sizes; this problem was particularly acute for the multi-scale model. Our results suggested that sufficient sample sizes at both the primary and secondary sampling levels could ameliorate this issue. Empirical data indicated Oregon slender salamander occupancy was associated strongly with the amount of coarse woody debris (posterior mean = 0.74; SD = 0.24); Ensatina occupancy was not associated with amount of coarse woody debris (posterior mean = -0.01; SD = 0.29). Our simulation results indicate that either model is suitable for use in an experimental study of Plethodontid salamanders provided that sample sizes are sufficiently large. However, hierarchical single-scale and multi-scale models describe different processes and estimate different parameters. As a result, we recommend careful consideration of study questions and objectives prior to sampling data and fitting models.

Invasive Asian earthworms of the genus Amynthas alter microhabitat use by terrestrial salamanders

Invasive earthworms are rapidly transforming detrital communities in North America. Recent studies have investigated the effects of European earthworms, whereas Asian earthworms, such as species of the genus Amynthas Kinberg, 1867, remain understudied. Amynthas is a surface-dwelling earthworm that voraciously consumes the litter layer of temperate forest floor habitats. The accumulation of detritus is important for the terrestrial Eastern Red-backed Salamanders (Plethodon cinereus (Green, 1818)) because this microhabitat provides the matrix through which salamanders travel when foraging, searching for mates, and dispersing. We examined the effect of Amynthas on the activity of “naïve” (no history of co-occurrence with Amynthas) and “experienced” (recent co-occurrence with Amynthas) salamanders in laboratory microcosms. We hypothesized that earthworms would disturb normal salamander activity through the reduction of leaf litter and physical impediment, with greater negative effects on naïve salamanders encountering this “novel” invasive species. Consistent with published studies, earthworm presence significantly decreased leaf-litter mass over time. Prior experience with earthworms did not appear to influence salamander response. However, earthworm presence had a significant effect on salamander activity, with salamanders exhibiting increased movement, cover-object use, and co-occurrence under cover objects with earthworms as the study progressed. Unnecessary movement has the potential to incur fitness costs to salamanders in the form of energetic expenditure and increased exposure to predators.

Higher Trophic Levels Overwhelm Climate Change Impacts on Terrestrial Ecosystem Functioning

Forest floor food webs play pivotal roles in carbon cycling, but they are rarely considered in models of carbon fluxes, including soil carbon dioxide emissions (respiration), under climatic warming. The indirect effects of invertebrates on heterotrophic (microbial and invertebrate) respiration through interactions with microbial communities are significant and will be altered by warming. However, the interactive effects of invertebrates and warming on heterotrophic respiration in the field are poorly understood. In this study we combined field and common garden laboratory approaches to examine relationships between warming, forest floor food web structure, and heterotrophic respiration. We found that soil animals can overwhelm the effects of warming (to 5 degrees Celsius above ambient) on heterotrophic respiration. In particular, the presence of higher trophic levels and burrowing detritivores strongly determined heterotrophic respiration rates in temperate forest soils. These effects were, however, context-dependent, with greater effects in a lower-latitude site. Without isolating and including the significant impact of invertebrates, climate models will be incomplete, hindering well-informed policy decisions.

Generalisation within specialization: inter-individual diet variation in the only specialized salamander in the world

Specialization is typically inferred at population and species level but in the last decade many authors highlighted this trait at the individual level, finding that generalist populations can be composed by both generalist and specialist individual. Despite hundreds of reported cases of individual specialization there is a complete lack of information on inter-individual diet variation in specialist species. We studied the diet of the Italian endemic Spectacled Salamander (Salamandrina perspicillata), in a temperate forest ecosystem, to disclose the realised trophic niche, prey selection strategy in function of phenotypic variation and inter-individual diet variation. Our results showed that Salamandrina is highly specialized on Collembola and the more specialized individuals are the better performing ones. Analyses of inter-individual diet variation showed that a subset of animals exhibited a broader trophic niche, adopting different foraging strategies. Our findings reflects the optimal foraging theory both at population and individual level, since animals in better physiological conditions are able to exploit the most profitable prey, suggesting that the two coexisting strategies are not equivalent. At last this species, feeding on decomposers of litter detritus, could play a key role determining litter retention rate, nutrient cycle and carbon sequestration.

Spider foraging strategy affects trophic cascades under natural and drought conditions

Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests.