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2,581 results for “amphibians”
Data from: Carotenoids and amphibians: effects on life history and susceptibility to the infectious pathogen, Batrachochytrium dendrobatidis
Carotenoids are considered beneficial nutrients because they provide increased immune capacity. Although carotenoid research has been conducted in many vertebrates, little research has been done in amphibians, a group that is experiencing global population declines from numerous causes, including disease. We raised two amphibian species through metamorphosis on three carotenoid diets to quantify the effects on life-history traits and post-metamorphic susceptibility to a fungal pathogen (Batrachochytrium dendrobatidis; Bd). Increased carotenoids had no effect on survival to metamorphosis in gray treefrogs (Hyla versicolor) but caused lower survival to metamorphosis in wood frogs [Lithobates sylvaticus (Rana sylvatica)]. Increased carotenoids caused both species to experience slower development and growth. When exposed to Bd after metamorphosis, wood frogs experienced high mortality, and the carotenoid diets had no mitigating effects. Gray treefrogs were less susceptible to Bd, which prevented an assessment of whether carotenoids could mitigate the effects of Bd. Moreover, carotenoids had no effect on pathogen load. As one of only a few studies examining the effects of carotenoids on amphibians and the first to examine potential interactions with Bd, our results suggest that carotenoids do not always serve amphibians in the many positive ways that have become the paradigm in other vertebrates.
Data from: Long-term endemism of two highly divergent lineages of the amphibian-killing fungus in the Atlantic Forest of Brazil
The recent global spread of the amphibian-killing fungus [Batrachochytrium dendrobatidis (Bd)] has been closely tied to anthropogenic activities; however, regional patterns of spread are not completely understood. Using historical samples, we can test whether Bd was a spreading or endemic pathogen in a region within a particular time frame, because those two disease states provide different predictions for the regional demographic dynamics and population genetics of Bd. Testing historical patterns of pathogen prevalence and population genetics under these predictions is key to understanding the evolution and origin of Bd. Focusing on the Atlantic Forest (AF) of Brazil, we used qPCR assays to determine the presence or absence of Bd on 2799 preserved postmetamorphic anurans collected between 1894 and 2010 and used semi-nested PCRs to determine the frequency of rRNA ITS1 haplotypes from 52 samples. Our earliest date of detection was 1894. A mean prevalence of 23.9% over time and spatiotemporal patterns of Bd clusters indicate that Bd has been enzootic in the Brazilian AF with no evidence of regional spread within the last 116 years. ITS1 haplotypes confirm the long-term presence of two divergent strains of Bd (BdGPL and Bd-Brazil) and three spatiotemporally broad genetic demes within BdGPL, indicating that Bd was not introduced into southeast Brazil by the bullfrog trade. Our data show that the evolutionary history and pathogen dynamics of Bd in Brazil is better explained by the endemic pathogen hypothesis.
Data from: Network-scale effects of invasive species on spatially-structured amphibian populations
<p>Understanding the factors affecting the dynamics of spatially-structured populations (SSP) is a central topic of conservation and landscape ecology. Invasive alien species are increasingly important drivers of the dynamics of native species. However, the impacts of invasives are often assessed at the patch scale, while their effects on SSP dynamics are rarely considered. We used long-term abundance data to test whether the impact of invasive crayfish on subpopulations can also affect the whole SSP dynamics, through their influence on source populations. From 2010 to 2018, we surveyed a network of 58 ponds and recorded the abundance of Italian agile frog clutches, the occurrence of an invasive crayfish, and environmental features. Using Bayesian hierarchical models, we assessed relationships between frog abundance in ponds and a) environmental features; b) connectivity within the SSP; c) occurrence of invasive species at both the patch- and the SSP-levels. If spatial relationships between ponds were overlooked, we did not detect effects of crayfish presence on frog abundance or trends. When we jointly considered habitat, subpopulation, and SSP features, processes acting at all these levels affected frog abundance. At the subpopulation scale, frog abundance in a year was related to habitat features, but was unrelated to crayfish occurrence at that site during the previous year. However, when we considered the SSP level, we found a strong negative relationship between frog abundance in a given site and crayfish frequency in surrounding wetlands during the previous year. Hence, SSP-level analyses can identify effects that would remain unnoticed when focussing on single patches. Invasive species can affect population dynamics even in not invaded patches, through the degradation of subpopulation networks. Patch-scale assessments of the impact of invasive species can thus be insufficient: predicting the long-term interplay between invasive and native populations requires landscape-level approaches accounting for the complexity of spatial interactions.</p>
Data from: Factors influencing detection of eDNA from a stream-dwelling amphibian
Environmental DNA (eDNA) methods for detecting and estimating abundance of aquatic species are emerging rapidly, but little is known about how processes such as secretion rate, environmental degradation, and time since colonization or extirpation from a given site affect eDNA measurements. Using stream-dwelling salamanders and quantitative PCR (qPCR) analysis, we conducted three experiments to assess eDNA: (1) production rate, (2) persistence time under different temperature and light conditions, and (3) detectability and concentration through time following experimental introduction and removal of salamanders into previously unoccupied streams. We found that 44–50 g individuals held in aquaria produced 77 ng eDNA/hr for two hours, after which production either slowed considerably or began to equilibrate with degradation. eDNA in both full-sun and shaded treatments degraded exponentially to <1% of the original concentration after 3 days. eDNA was no longer detectable in full-sun samples after 8 days, whereas eDNA was detected in 20% of shaded samples after 11 days and 100% of refrigerated control samples after 18 days. When translocated into unoccupied streams, salamanders were detectable after 6 hours, but only when densities were relatively high (0.2481 individuals/m2) and when samples were collected within 5 m of the animals. Concentrations of eDNA detected were very low and increased steadily from 6–24 hours after introduction, reaching 0.0022 ng/L. Within 1 hour of removing salamanders from the stream, eDNA was no longer detectable. These results suggest that eDNA detectability and concentration depend on production rates of individuals, environmental conditions, density of animals, and their residence time.
Data from: Fine-grained adaptive divergence in an amphibian: genetic basis of phenotypic divergence and the role of non-random gene flow in restricting effective migration among wetlands
Adaptive ecological differentiation among sympatric populations is promoted by environmental heterogeneity, strong local selection and restricted gene flow. High gene flow, on the other hand, is expected to homogenize genetic variation among populations and therefore prevent local adaptation. Understanding how local adaptation can persist at the spatial scale at which gene flow occurs has remained an elusive goal, especially for wild vertebrate populations. Here, we explore the roles of natural selection and nonrandom gene flow (isolation by breeding time and habitat choice) in restricting effective migration among local populations and promoting generalized genetic barriers to neutral gene flow. We examined these processes in a network of 17 breeding ponds of the moor frog Rana arvalis, by combining environmental field data, a common garden experiment and data on variation in neutral microsatellite loci and in a thyroid hormone receptor (TRβ) gene putatively under selection. We illustrate the connection between genotype, phenotype and habitat variation and demonstrate that the strong differences in larval life history traits observed in the common garden experiment can result from adaptation to local pond characteristics. Remarkably, we found that haplotype variation in the TRβ gene contributes to variation in larval development time and growth rate, indicating that polymorphism in the TRβ gene is linked with the phenotypic variation among the environments. Genetic distance in neutral markers was correlated with differences in breeding time and environmental differences among the ponds, but not with geographical distance. These results demonstrate that while our study area did not exceed the scale of gene flow, ecological barriers constrained gene flow among contrasting habitats. Our results highlight the roles of strong selection and nonrandom gene flow created by phenological variation and, possibly, habitat preferences, which together maintain genetic and phenotypic divergence at a fine-grained spatial scale.
Data from: Cryptic genetic diversity is paramount in small-bodied amphibians of the genus Euparkerella (Anura: Craugastoridae) endemic to the Brazilian Atlantic Forest
Morphological similarity associated to restricted distributions and low dispersal abilities make the direct developing "Terrarana" frogs of the genus Euparkerella a good model for examining diversification processes. We here infer phylogenetic relationships within the genus Euparkerella, using DNA sequence data from one mitochondrial and four nuclear genes coupled with traditional Bayesian phylogenetic reconstruction approaches and more recent coalescent methods of species tree inference. We also used Bayesian clustering analysis and a recent Bayesian coalescent-based approach specifically to infer species delimitation. The analysis of 39 individuals from the four known Euparkerella species uncovered high levels of genetic diversity, especially within the two previously morphologically-defined E. cochranae and E. brasiliensis. Within these species, the gene trees at five independent loci and trees from combined data (concatenated dataset and the species tree) uncovered six deeply diverged and geographically coherent evolutionary units, which may have diverged between the Miocene and the Pleistocene. These six units were also uncovered in the Bayesian clustering analysis, and supported by the Bayesian coalescent-based species delimitation (BPP), and Genealogical Sorting Index (GSI), providing thus strong evidence for underestimation of the current levels of diversity within Euparkerella. The cryptic diversity now uncovered opens new opportunities to examine the origins and maintenance of microendemism in the context of spatial heterogeneity and/or human induced fragmentation of the highly threatened Brazilian Atlantic forest hotspot.
Data from: Patterns and biases in climate change research on amphibians and reptiles: a systematic review
Climate change probably has severe impacts on animal populations, but demonstrating a causal link can be difficult because of potential influences by additional factors. Assessing global impacts of climate change effects may also be hampered by narrow taxonomic and geographical research foci. We review studies on the effects of climate change on populations of amphibians and reptiles to assess climate change effects and potential biases associated with the body of work that has been conducted within the last decade. We use data from 104 studies regarding the effect of climate on 313 species, from 464 species–study combinations. Climate change effects were reported in 65% of studies. Climate change was identified as causing population declines or range restrictions in half of the cases. The probability of identifying an effect of climate change varied among regions, taxa and research methods. Climatic effects were equally prevalent in studies exclusively investigating climate factors (more than 50% of studies) and in studies including additional factors, thus bolstering confidence in the results of studies exclusively examining effects of climate change. Our analyses reveal biases with respect to geography, taxonomy and research question, making global conclusions impossible. Additional research should focus on under-represented regions, taxa and questions. Conservation and climate policy should consider the documented harm climate change causes reptiles and amphibians.
Data from: The response of amphibian larvae to environmental change is both consistent and variable
Many environments are undergoing rapid environmental change and there is a need to understand the mechanisms by which species can persist in altered environments. Model systems, such as amphibian metamorphosis, which can be generalized across many types of environmental change and across many species, are a powerful tool for understanding mechanisms that facilitate persistence in altered and disturbed environments. Amphibian larvae respond to environmental change by varying age at metamorphosis, or size at metamorphosis. Differential selection pressures on age or size at metamorphosis may result in a differential response among taxa to environmental change. Using a meta-analysis, we investigated whether age at metamorphosis, size at metamorphosis, and larval growth rate vary within and among taxonomic families of amphibians in experiments that modified the environmental temperature, density of individuals, food, hydroperiod and the presence of predators. For all environmental factors except predators, the direction of the response was consistent across most of the studied taxa. However, there was considerable variation in effect size both within and among families. Results demonstrate that amphibian metamorphosis is a valuable model system for studying the effects of environmental change. Yet, we stress the need for caution in making generalizations about how individuals respond to environmental factors that have an indirect effect on physiology and require the perception of an environmental cue, such as the presence of predators.
Anthropogenic disturbance drives dispersal syndromes, demography, and gene flow in amphibian populations
<p>There is growing evidence that anthropogenic landscapes can strongly influence the evolution of dispersal, particularly through fragmentation, and may drive organisms into an evolutionary trap by suppressing dispersal. However, the influence on dispersal evolution of anthropogenic variation in habitat patch turnover has so far been largely overlooked. In this study, we examined how human-driven variation in patch persistence affects dispersal rates and distances, determines dispersal-related phenotypic specialization, and drives neutral genetic structure in spatially structured populations. We addressed this issue in an amphibian, Bombina variegata, using an integrative approach combining capture-recapture modeling, demographic simulation, common garden experiments, and population genetics. B. variegata reproduces in small ponds that occur either in habitat patches that are persistent (i.e. several decades or more), located in riverine environments with negligible human activity, or in patches that are highly temporary (i.e. a few years), created by logging operations in intensively harvested woodland. Our capture-recapture models revealed that natal and breeding dispersal rates and distances were drastically higher in spatially structured populations (SSPs) in logging environments than in riverine SSPs. Population simulations additionally showed that dispersal costs and benefits drive the fate of logging SSPs, which cannot persist without dispersal. The common garden experiments revealed that toadlets reared in laboratory conditions have morphological and behavioral specialization that depends on their habitat of origin. Toadlets from logging SSPs were found to have higher boldness and exploration propensity than those from riverine SSPs, indicating transgenerationally transmitted dispersal syndromes. We also found contrasting patterns of neutral genetic diversity and gene flow in riverine and logging SSPs, with genetic diversity and effective population size considerably higher in logging than in riverine SSPs. In parallel, intra-patch inbreeding and relatedness levels were lower in logging SSPs. Controlling for the effect of genetic drift and landscape connectivity, gene flow was found to be higher in logging than in riverine SSPs. Taken together, these results indicate that anthropogenic variation in habitat patch turnover may have an effect at least as important as landscape fragmentation on dispersal evolution and the long-term viability and genetic structure of wild populations.</p>
Data from: Biogeographic analysis reveals ancient continental vicariance and recent oceanic dispersal in amphibians
Amphibians comprise over 7000 extant species distributed in almost every ecosystem on every continent except Antarctica. Most species also show high specificity for particular habitats, biomes, or climatic niches, seemingly rendering long-distance dispersal unlikely. Indeed, many lineages still seem to show the signature of their Pangaean origin, ~300Ma later. To date, no study has attempted a large-scale historical-biogeographic analysis of the group to understand the distribution of extant lineages. Here, I use an updated chronogram containing 3309 species (~45% of extant diversity) to reconstruct their movement between 12 global ecoregions. I find that a Pangaean origin and subsequent Laurasian and Gondwanan fragmentation explains a large proportion of patterns in the distribution of extant species. However, dispersal during the Cenozoic, likely across land bridges or short distances across oceans, has also exerted a strong influence. Finally, there are at least three strongly supported instances of long-distance oceanic dispersal between former Gondwanan landmasses during the Cenozoic. Intermediate extinction from intervening areas seems to be a strong factor in shaping present-day distributions. Both dispersal and intermediate extinction are apparently tied to the evolution of extraordinarily adaptive expansion-oriented phenotypes (allowing lineages to easily colonize new areas and speciate), or conversely, to extremely specialized phenotypes or heavily relictual climatic niches that result in strong geographic localization and limited diversification.
Data from: Pros and cons of external swabbing of amphibians for genetic analyses
Non-invasive DNA sampling is an important tool in amphibian conservation. Buccal swabs are nowadays replacing the wounding toe-clipping method. Skin and cloaca swabbing are even less invasive and easier to handle than buccal swabbing, but could result in contaminations of genetic material. Therefore, we test if external skin and cloaca swabs are as reliable as buccal swabs for genetic analysis of amphibians. We analysed eight microsatellite loci for the common frog (Rana temporaria, Linnaeus 1758) and compared genotyping results for buccal, skin and cloaca swabs regarding allelic dropouts and false alleles. Furthermore, we compared two DNA extraction methods regarding efficiency and cost. DNA quality and quantity (amplification success, genotyping error rate, in nanogram per microlitre) were comparable among DNA sources and extraction methods. However, skin and cloaca samples exhibited high degrees of contamination with foreign individuals, which was due to sample collection during mating season. Here, we established a simple low budget procedure to receive DNA of amphibians avoiding stressful buccal swabbing or harmful toe clipping. However, the possibility of contaminations of external swabs has to be considered.
Data from: Variation in age, body size, and reproductive traits among urban and rural amphibian populations
Although amphibians use human-created habitats in urban landscapes, few studies have investigated the quality of these habitats. To assess habitat quality of stormwater management ponds and adjacent urban uplands forwood frogs (Lithobates sylvaticus) and American toads (Anaxyrus americanus), we compared life history characteristics between populations breeding across an urbanization gradient. Specifically, we compared body size, ages of breeding adults, and female reproductive investment among urban, suburban, and rural populations in Baltimore County, Maryland, USA. Although there was variation in age at maturity among populations, ages of breeding adults did not differ among urban, suburban, and rural areas. Maternal body size strongly influenced reproductive investment in both species, but relationships did not vary among urban, suburban, and rural populations. Adult wood frogs and American toads from more urbanized landscapes were significantly smaller at age than conspecifics from rural landscapes; the magnitude of differences was similar across adult age classes. Our results suggest that in the urban and rural landscapes that we studied, adult habitats are similar in quality, but either larval or juvenile habitats may be of lower quality in urban areas.
Figure 3 in Amphibian taxonomy: early 21st century case studies
Figure 3. (a) Bar plot depicting number of new species of Amphibia described during 2015–2019 from global biodiversity hotspots. (b) Map depicting the distribution of hotspots that new amphibians were described from during 2015–2019. (c) Bar plot depicting number of new species of Amphibia described from broad geographical regions during 2015–2019. Europe and Central Asia have been combined due to geographic proximity and small sample sizes from Central Asia (N = 1).
Figure 2 in Amphibian taxonomy: early 21st century case studies
Figure 2. (a) Bar plot depicting number of new species of Amphibia described from each family across three extant orders (Anura, Caudata, and Gymnophiona) during 2015–2019. (b) Relationship between the number of new species described from each family and the overall number of species known from each family according to Frost (2020). Data have been fitted with a linear smoother using the 'lm' function from ggplot2 (Wickham 2016).
Figure 1 in Amphibian taxonomy: early 21st century case studies
Figure 1. (a) Description of new species of Amphibia from 2004 to 2019. Note that the number of species described has been similar during this timeframe and that there is no clear trend of increase or decrease. Data obtained amphibiaweb.org. (b) Types of data used to describe new species of Amphibia from 2015 to 2019. See text for definitions of data types. Proportion is out of 732 new species surveyed for our study. (c) Proportion of integrative studies (using two or more lines of evidence) to describe species of Amphibia from 2015 to 2019. Proportion is out of 732 new species surveyed for our study. Note general increase over the survey period. (d) Approximate DNA sequence alignment lengths used to describe species of Amphibia from 2015 to 2019 for mitochondrial (mtDNA) and nuclear DNA (nDNA). Alignment lengths have been Log10-transformed. Note increase in size of nDNA datasets in 2019.
FIGURES 4–7 in Acanthocephalans of Amphibians and Reptiles (Anura and Squamata) from Ecuador, with the description of Pandosentis napoensis n. sp. (Neoechinorhynchidae) from Hyla fasciata
FIGURES 4–7. Micrographs of Pandosentis napoensis n. sp. 4. Proboscis, specimen 1. 5. Proboscis, specimen 2. 6. Specimen 1 ventral view. &. Lacuna system showing irregular diagonal lacunae connecting with circular canals. Scale bars: 4 = 20Μm; 5 & 7 = 40µm; 6 = 200Μm.
FIGURES 1–3. Pandosentis napoensis n in Acanthocephalans of Amphibians and Reptiles (Anura and Squamata) from Ecuador, with the description of Pandosentis napoensis n. sp. (Neoechinorhynchidae) from Hyla fasciata
FIGURES 1–3. Pandosentis napoensis n. sp. 1. Adult male, ventral view. 2. Proboscis armature, lateral view. 3. Longitudinal row of hooks, lateral view. Scale bars: 1 = 60µm; 2 = 25µm; 3 = 10µm.
FIGURE 5. Left side shows a in The amphibian community at Yanayacu Biological Station, Ecuador, with a comparison of vertical microhabitat use among Pristimantis species and the description of a new species of the Pristimantis myersi group
FIGURE 5. Left side shows a power spectrum (top), sonogram (middle), and oscillogram (bottom) of a series of advertisement calls of Pristimantis bicantus (QCAZ 18983). Right side shows a sonogram (middle) and oscillogram (bottom) of a single long call (the eighth of the 11 long calls shown on the left, marked with an asterisk). This is an example of a call series consisting of three short calls (each with two pulses) and 11 long calls (each with 17–23 more rapid pulses). The power spectrum was measured along the entire duration of the call series.
FIGURE 2 in The amphibian community at Yanayacu Biological Station, Ecuador, with a comparison of vertical microhabitat use among Pristimantis species and the description of a new species of the Pristimantis myersi group
FIGURE 2. Dorsal and ventral color variation of Pristimantis bicantus in ethanol. (A, E) QCAZ 19024 (female holotype); (B) QCAZ 16186, adult female; (C) QCAZ 18988, adult female; (D, F) QCAZ 16201, adult female.
FIGURE 1 in The amphibian community at Yanayacu Biological Station, Ecuador, with a comparison of vertical microhabitat use among Pristimantis species and the description of a new species of the Pristimantis myersi group
FIGURE 1. (A) Head, (B) hand, and (C) foot of Pristimantis bicantus, holotype, adult female, QCAZ 19024.
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OpenNeuro
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