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2,581 results for “amphibians”
Data from: Bottom-up and trait-mediated effects of resource quality on amphibian parasitism
Leaf litter subsidies are important resources for aquatic consumers like tadpoles and snails, causing bottom-up effects on wetland ecosystems. Recent studies have shown that variation in litter nutritional quality can be as important as litter quantity in driving these bottom-up effects. Resource subsidies likely also have indirect and trait-mediated effects on predation and parasitism, but these potential effects remain largely unexplored. We generated predictions for differential effects of litter nutrition and secondary polyphenolic compounds on tadpole (Lithobates sylvatica) exposure and susceptibility to Ribeiroia ondatrae, based on ecological stoichiometry and community-ecology theory. We predicted direct and indirect effects on key traits of the tadpole host (rates of growth, development and survival), the trematode parasite (production of the cercaria infective stages) and the parasite's snail intermediate host (growth and reproduction). To test these predictions, we conducted a large-scale mesocosm experiment using a natural gradient in the concentrations of nutrients (nitrogen) and toxic secondary compounds (polyphenolics) of nine leaf litter species. To differentiate between effects on exposure vs. susceptibility to infection, we included multiple infection experiments including one with constant per capita exposure. We found that increased litter nitrogen increased tadpole survival, and also increased cercaria production by the snail intermediate hosts, causing opposing effects on tadpole per capita exposure to trematode infection. Increased litter polyphenolics slowed tadpole development, leading to increased infection by increasing both their susceptibility to infection and the length of time they were exposed to parasites. Based on these results, recent shifts in forest composition towards more nitrogen-poor litter species should decrease trematode infection in tadpoles via density- and trait-mediated effects on the snail intermediate hosts. However, these shifts also involve increased abundance of litter species with high polyphenolic levels, which should increase trematode infection via trait-mediated effects on tadpoles. Future studies will be needed to determine the relative strength of these opposing effects in natural wetland communities.
Data from: Genetic basis of amphibian larval development along a latitudinal gradient: gene diversity, selection and links with phenotypic variation in transcription factor C/EBP-1
Ectotherm development rates often show adaptive divergence along climatic gradients, but the genetic basis for this variation is rarely studied. Here, we investigated the genetic basis for phenotypic variation in larval development in the moor frog Rana arvalis from five regions along a latitudinal gradient from Germany to northern Sweden. We focused on the C/EBP-1 gene, a transcription factor associated with larval development time. Allele frequencies at C/EBP-1 varied strongly among geographic regions. Overall, the distribution of alleles along the gradient was in concordance with the dual postglacial colonization routes into Scandinavia, with a large number of alleles exclusively present along the southern colonization route. Only three of 38 alleles were shared between the routes. Analysis of contemporary selection on C/EBP-1 showed divergent selection among the regions, likely reflecting adaptation to the local environmental conditions, although this was especially strong between southern and northern regions coinciding also with lineages from different colonization routes. Overall, the C/EBP-1 gene has historically been under purifying selection, however, two specific amino acid positions showed significant signals of positive selection. These positions showed divergence between southern and northern regions, and we suggest that they are functionally involved in the climatic adaptation of larval development. Using phenotypic data from a common garden experiment, we found evidence for specific C/EBP-1 alleles being correlated with larval development time, suggesting a functional role in adaptation of larval development to large-scale climatic variation.
Data from: Amphibian species' traits, evolutionary history, and environment predict Batrachochytrium dendrobatidis infection patterns, but not extinction risk
The fungal pathogen Batrachochytrium dendrobatidis (Bd) has emerged as a major agent of amphibian extinction, requiring conservation intervention for many susceptible species. Identifying susceptible species is challenging, but many aspects of species' biology are predicted to influence the evolution of host resistance, tolerance, or avoidance strategies towards disease. In turn, we may expect species exhibiting these distinct strategies to differ in their ability to survive epizootic disease outbreaks. Here we test for phylogenetic and trait-based patterns of Bd infection risk and infection intensity among 302 amphibian species by compiling a global dataset of Bd infection surveys across 95 sites. We then use best-fit models that associate traits, taxonomy, and environment with Bd infection risk and intensity to predict host disease mitigation strategies (tolerance, resistance, avoidance) for 122 Neotropical amphibian species that experienced epizootic Bd outbreaks, and noted species' persistence or extinction from these events. Aspects of amphibian species' life history, habitat use, and climatic niche were consistently linked to variation in Bd infection patterns across sites around the world. However, predicted Bd infection risk and intensity based on site environment and species traits did not reveal a consistent pattern between the predicted host disease mitigation strategy and extinction outcome. This suggests that either tolerant or resistant species may have no advantage in ameliorating disease during epizootic events, or that other factors drive the persistence of amphibian populations during chytridiomycosis outbreaks. These results suggest that using a trait-based approach may allow us to identify species with resistance or tolerance to endemic Bd infections, but that this approach may be insufficient to ultimately identify species at risk of extinction from epizootics.
Data from: The contribution of phenotypic plasticity to the evolution of insecticide tolerance in amphibian populations
Understanding population responses to rapid environmental changes caused by anthropogenic activities, such as pesticides, is a research frontier. Genetic assimilation (GA), a process initiated by phenotypic plasticity, is one mechanism potentially influencing evolutionary responses to novel environments. While theoretical and laboratory research suggests that GA has the potential to influence evolutionary trajectories, few studies have assessed its role in the evolution of wild populations experiencing novel environments. Using the insecticide, carbaryl, and 15 wood frog populations distributed across an agricultural gradient, we tested whether GA contributed to the evolution of pesticide tolerance. First, we investigated the evidence for evolved tolerance to carbaryl and discovered that population-level patterns of tolerance were consistent with evolutionary responses to pesticides; wood frog populations living closer to agriculture were more tolerant than populations living far from agriculture. Next, we tested the potential role of GA in the evolution of pesticide tolerance by assessing whether patterns of tolerance were consistent with theoretical predictions. We found that populations close to agriculture displayed constitutive tolerance to carbaryl whereas populations far from agriculture had low naïve tolerance but high magnitudes of induced tolerance. These results suggest GA could play a role in evolutionary responses to novel environments in nature.
Data from: Extreme climate-induced life-history plasticity in an amphibian
Age specific survival and reproduction are closely linked to fitness and therefore subject to strong selection that typically limits their variability within species. Furthermore, adult survival rate in vertebrate populations is typically less variable over time than other life history traits, such as fecundity or recruitment. Hence, adult survival is often conserved within a population over time, compared to the variation in survival found across taxa. In stark contrast to this general pattern, we report evidence of extreme short-term variation of adult survival in Rose's Mountain Toadlet (Capensibufo rosei), which is apparently climate-induced. Over seven years, annual survival rate varied between 0.04 and 0.92, and 94% of this variation was explained by variation in breeding-season rainfall. Preliminary results suggest that this variation reflects adaptive life-history plasticity to a degree thus far unrecorded for any vertebrate, rather than direct rainfall induced mortality. In wet years, these toads appeared to achieve increased reproduction at the expense of their own survival whereas in dry years, their survival increased at the expense of reproduction. Such environmentally induced plasticity may reflect a diversity of life-history strategies not previously appreciated among vertebrates.
Data from: Ecological correlates of extinction risk in Chinese amphibians
Aim: China is one of the countries with the richest amphibian biodiversity in the world. Among the 408 Chinese amphibians, 174 species are considered threatened according to the China Biodiversity Red List in 2015. However, to date, which species traits or extrinsic factors are correlated with extinction risk in Chinese amphibians is rarely examined in previous studies. The aims of this study were thus to identify the patterns and correlates of extinction risk in Chinese amphibians and to determine whether patterns and processes were similar between species with either small or large geographic distributions. Location: China. Methods: We obtained twelve species traits and four extrinsic factors that have been commonly linked to the extinction risk of amphibians. After phylogenetic correction, these factors were tested separately and in combination to identify their correlations with extinction risk in all Chinese amphibians, and in small-ranged and large-ranged species. Results: Geographic range size and elevational range were the most important predictors of extinction risk in all Chinese amphibians. Although extinction risk in small-ranged amphibians was predominantly determined by small elevational range, in large-ranged amphibians it was driven by geographic and elevational range sizes, body size, human exploitation index and adult microhabitat. Small-ranged amphibians had a higher percentage of threatened species than large-ranged species. However, the body size distributions were not statistically different between these two amphibian subgroups. Main conclusions: Our findings suggest that conservation priority should be given to species with small geographic and elevational ranges. Small-ranged and large-ranged amphibians should be conserved with different strategies because the factors influencing extinction risk differ between these two groups. In specific, the reduction of habitat loss should be a primary focus of management efforts for small-ranged species. Conservation efforts should also focus on preventing habitat loss and human overexploitation for the effective conservation of large-ranged amphibians.
Drivers of amphibian population dynamics and asynchrony at local and regional scales
<ol> <li>Identifying the drivers of population fluctuations in spatially distinct populations remains a significant challenge for ecologists. Whereas regional climatic factors may generate population synchrony (i.e., the Moran effect), local factors including the level of density-dependence may reduce the level of synchrony. Although divergences in the scaling of population synchrony and spatial environmental variation have been observed, the regulatory factors that underlie such mismatches are poorly understood.</li> <li>Few previous studies have investigated how density-dependent processes and population-specific responses to weather variation influence spatial synchrony at both local and regional scales. We addressed this issue in a pond-breeding amphibian, the great crested newt (<i>Triturus cristatus</i>). We used capture-recapture data collected through long-term surveys in five <i>T. cristatus</i> populations in Western Europe.</li> <li>In all populations – and subpopulations within metapopulations – population size, annual survival and recruitment fluctuated over time. Likewise, there was considerable variation in these demographic rates between populations and within metapopulations. These fluctuations and variations appear to be context-dependent and more related to site-specific characteristics than local or regional climatic drivers. We found a low level of demographic synchrony at both local and regional levels. Weather has weak and spatially variable effects on survival, recruitment and population growth rate. In contrast, density-dependence was a common phenomenon (at least for population growth) in almost all populations and subpopulations.</li> <li>Our findings support the idea that the Moran effect is low in species where the population dynamics more closely depends on local factors (e.g. population density and habitat characteristics) than on large-scale environmental fluctuation (e.g. regional climatic variation). Such responses may have far-reaching consequences for the long-term viability of spatially structured populations and their ability to response to large-scale climatic anomalies.</li> </ol>
Data from: A key ecological trait drove the evolution of biparental care and monogamy in an amphibian
Linking specific ecological factors to the evolution of parental care pattern and mating system is a difficult task of key importance. We provide evidence from comparative analyses that an ecological factor (breeding pool size) is associated with the evolution of parental care across all frogs. We further show that the most intensive form of parental care (trophic egg feeding) evolved in concert with the use of small pools for tadpole deposition and that egg feeding was associated with the evolution of biparental care. Previous research on two Peruvian poison frogs (Ranitomeya imitator and Ranitomeya variabilis) revealed similar life histories, with the exception of breeding pool size. This key ecological difference led to divergence in parental care patterns and mating systems. We present ecological field experiments that demonstrate that biparental care is essential to tadpole survival in small (but not large) pools. Field observations demonstrate social monogamy in R. imitator, the species that uses small pools. Molecular analyses demonstrate genetic monogamy in R. imitator, the first example of genetic monogamy in an amphibian. In total, this evidence constitutes the most complete documentation to date that a single ecological factor drove the evolution of biparental care and genetic and social monogamy in an animal.
Data from: Determinants and co-expression of anti-predator responses in amphibian tadpoles: a meta-analysis
A wide range of taxa respond to perceived predation risk (PPR) through inducible defenses, and many prey are capable of responding both behaviorally and morphologically to the same risk event. In cases where multiple defenses confer protection by independent means (i.e., they are mechanistically independent) responses will either be co-expressed, or the expression of one defense will limit the capacity (or need) to respond along another axis. Our ability to generate a broad understanding of these patters has been limited, in part, by difficulties in comparing results across studies that employ distinct experimental protocols. Using the extensive literature on tadpole responses to PPR, we conducted a meta-analysis to identify the ecological and experimental determinants of inducible defence expression. We then assessed whether the magnitude of response to PPR along behavioural versus morphological response axes was positively, or negatively, correlated. The most commonly quantified responses to perceived risk in tadpoles included reductions in movement and swimming behaviour, and altered tail morphology. Our analyses reveal that tadpole behavioural responses are strongly influenced by prey family, predator taxon, evolutionary history with the predator (native vs. non-native), amount of prey consumed by the predator, and how perceived risk was manipulated (e.g., presence vs. absence of alarm cues). Tail morphology was similarly influenced by these factors, but also whether the target prey was palatable to predators. Thus, our results identify ecological and experimental features that critically influence the observed effect size in tadpole responses to PPR. A positive correlation between behavioural and morphological responses in studies where both were measured indicates that trait co-specialization is the predominant pattern of defense deployment in larval amphibians. This positive relationship suggests that survival tends to be maximized in tadpoles through equivalent coactivation of multiple independent axes of protection, opposed to maximal expression along any single axis.
Data from: Susceptibility of amphibians to chytridiomycosis is associated with MHC class II conformation
The pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd) can cause precipitous population declines in its amphibian hosts. Responses of individuals to infection vary greatly with the capacity of their immune system to respond to the pathogen. We used a combination of comparative and experimental approaches to identify major histocompatibility complex class II (MHC-II) alleles encoding molecules that foster the survival of Bd-infected amphibians. We found that Bd-resistant amphibians across four continents share common amino acids in three binding pockets of the MHC-II antigen-binding groove. Moreover, strong signals of selection acting on these specific sites were evident among all species co-existing with the pathogen. In the laboratory, we experimentally inoculated Australian tree frogs with Bd to test how each binding pocket conformation influences disease resistance. Only the conformation of MHC-II pocket 9 of surviving subjects matched those of Bd-resistant species. This MHC-II conformation thus may determine amphibian resistance to Bd, although other MHC-II binding pockets also may contribute to resistance. Rescuing amphibian biodiversity will depend on our understanding of amphibian immune defence mechanisms against Bd. The identification of adaptive genetic markers for Bd resistance represents an important step forward towards that goal.
Data from: Skin sloughing rate increases with chytrid fungus infection load in a susceptible amphibian
1. Amphibian chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is responsible for the greatest disease-driven loss of vertebrate biodiversity in recorded history. Understanding drivers of host susceptibility to this cutaneous disease is hindered by gaps in our knowledge of the host–pathogen relationship. One such overlooked aspect of susceptibility is variation in skin maintenance processes, particularly skin turnover via routine sloughing. It has been suggested that sloughing plays a role in immune defence, by removing skin-associated microbes. Thus, skin sloughing may play an important role in the pathogenesis of chytridiomycosis. 2. To determine the relationship between skin sloughing and disease progression, we exposed adult Australian green tree frogs (Litoria caerulea) to a local Bd strain and monitored sloughing rates and individual infection loads on a naturalistic cycling temperature regime (15–23 °C). 3. We determined sloughing rates in real-time by using an array of infrared video cameras to film frog behaviour and monitored infection load before and after sloughing by swabbing and analysis with quantitative PCR. 4. We found that sloughing rate increased with Bd infection load in infected frogs, but sloughing itself did not affect Bd load on the ventral skin surface. Furthermore, Bd infection did not affect the duration of characteristic sloughing behaviour, and sloughing retained rhythmicity even at high infection loads. 5. Although an increased sloughing rate might be considered advantageous for Bd-infected animals, it does not appear to curb the progression of disease and may actually contribute to the loss of physiological homoeostasis seen in terminally ill frogs by further inhibiting water and electrolyte transport across the skin. 6. By measuring sloughing rates directly for the first time, our results shed light on how Bd interacts with the physiological processes of the skin and indicate that variation in skin sloughing frequency may play a role in the observed inter- and intraspecific variation in susceptibility to disease.
Data from: Biotic resistance to an alien amphibian: larval competition between Japanese frogs and invasive cane toads
Understanding negative effects of native species on introduced taxa may suggest novel ways to control the invasive species by enhancing such effects. Previous studies have reported that the larvae of invasive cane toads (Rhinella marina) are suppressed by competition with the larvae of native anurans in Australia, but not in North America. We conducted laboratory trials to measure the effect of exposure to the larvae of Japanese frogs (Microhyla ornata, Fejervarya sakishimensis, Rhacophorus owstoni) on rates of survival, growth and development of cane toad tadpoles in Ishigaki Island, in southern Japan. Survival rates were not affected by native species, but competition with Dicroglossids and Rhacophorids (but not Microhylids) strongly reduced rates of growth and development in the tadpoles of cane toads. Dicroglossid tadpoles also reduced the body condition to toad tadpoles in addition to effects on SVL and mass. Encouraging populations of native frogs in toad-invaded areas of Japan thus may help to reduce the numbers of invasive cane toads.
Data from: Quantification of mesocosm fish and amphibian species diversity via eDNA metabarcoding
Freshwater fauna are particularly sensitive to environmental change and disturbance. Management agencies frequently use fish and amphibian biodiversity as indicators of ecosystem health and a way to prioritize and assess management strategies. Traditional aquatic bioassessment that relies on capture of organisms via nets, traps and electrofishing gear typically has low detection probabilities for rare species and can injure individuals of protected species. Our objective was to determine whether environmental DNA (eDNA) sampling and metabarcoding analysis can be used to accurately measure species diversity in aquatic assemblages with differing structures. We manipulated the density and relative abundance of eight fish and one amphibian species in replicated 206-L mesocosms. Environmental DNA was filtered from water samples, and six mitochondrial gene fragments were Illumina-sequenced to measure species diversity in each mesocosm. Metabarcoding detected all nine species in all treatment replicates. Additionally, we found a modest, but positive relationship between species abundance and sequencing read abundance. Our results illustrate the potential for eDNA sampling and metabarcoding approaches to improve quantification of aquatic species diversity in natural environments and point the way towards using eDNA metabarcoding as an index of macrofaunal species abundance.
FIGURE 8 in Note on a collection of Amphibians and Reptiles from Western Sumatra (Indonesia), with the description of a new species of the genus Bufo
FIGURE 8. Naja sumatrana (Müller, 1887). Specimen not preserved.
FIGURE 14 in Taxonomy and distribution of caecilian amphibians (Gymnophiona) of Brazilian Amazonia, with a key to their identification
FIGURE 14. Scatterplot graphs showing variation in scale inception in Microcaecilia taylori.
FIGURE 7 in Lost and found: One of the world's most elusive amphibians, Pseudophilautus stellatus (Kelaart 1853) rediscovered
FIGURE 7. Forest die back in the Peak Wilderness area, habitat of Pseudophilautus stellatus.
FIGURE 2 in Lost and found: One of the world's most elusive amphibians, Pseudophilautus stellatus (Kelaart 1853) rediscovered
FIGURE 2. Dorsolateral view of neotype.
FIGURE 3 in Lost and found: One of the world's most elusive amphibians, Pseudophilautus stellatus (Kelaart 1853) rediscovered
FIGURE 3. Front view of neotype.
FIGURE 9 in Type specimens in the Port Elizabeth Museum, South Africa, including the historically important Albany Museum collection. Part 1: Amphibians
FIGURE 9. Family Pipidae: Holotype of Xenopus gilli (PEM A1523).
FIGURE 2. A, B, C, D in Alfredo Dugès' type specimens of amphibians and reptiles revisited
FIGURE 2. A, B, C, D, Syntypes of Ambystoma altamirani (HE 316, 317, 318, 319).
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.