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Journal articles on the topic 'Amphibian populations'
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1
Lips, Karen R. "Overview of chytrid emergence and impacts on amphibians." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1709 (December 5, 2016): 20150465. http://dx.doi.org/10.1098/rstb.2015.0465.
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Chytridiomycosis is an emerging infectious disease of amphibians that affects over 700 species on all continents where amphibians occur. The amphibian–chytridiomycosis system is complex, and the response of any amphibian species to chytrid depends on many aspects of the ecology and evolutionary history of the amphibian, the genotype and phenotype of the fungus, and how the biological and physical environment can mediate that interaction. Impacts of chytridiomycosis on amphibians are varied; some species have been driven extinct, populations of others have declined severely, whereas still others have not obviously declined. Understanding patterns and mechanisms of amphibian responses to chytrids is critical for conservation and management. Robust estimates of population numbers are needed to identify species at risk, prioritize taxa for conservation actions, design management strategies for managing populations and species, and to develop effective measures to reduce impacts of chytrids on amphibians. This article is part of the themed issue ‘Tackling emerging fungal threats to animal health, food security and ecosystem resilience’.
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Crump, D. "The effects of UV-B radiation and endocrine-disrupting chemicals (EDCs) on the biology of amphibians." Environmental Reviews 9, no. 2 (June 1, 2001): 61–80. http://dx.doi.org/10.1139/a01-001.
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Statistical meta-analysis of large and diverse data sets has indicated that amphibians have been declining worldwide since the 1960s. Exposure to UV-B radiation (280320 nm) and endocrine-disrupting chemicals (EDCs) have been considered as possible hypotheses to explain the observed declines. Equivocal conclusions have been reached with respect to the effects of UV-B on amphibian populations. Field and laboratory studies employing both ecologically relevant and enhanced UV-B levels have been conducted using a variety of amphibian species and reports differ with respect to the most sensitive developmental stage and the ultimate implications. UV-B radiation has also been shown to interact with other stressors (e.g., pesticides, polycyclic aromatic hydrocarbons, low pH) resulting in decreased survivorship for several amphibian species. Limited evidence of reproductive toxicity of xenobiotics in amphibians exist; however, early exposure to EDCs could cause abnormal development of the amphibian reproductive system, inhibit vital hormone messages that drive metamorphosis, and ultimately contribute to the decline of some amphibian populations. The available evidence suggests that more than one agent is contributing to amphibian population declines and the following review narrows the focus to address the existing data on the effects of UV-B, alone and in combination with other stressors, and EDCs on amphibian survivorship and development. Key words: amphibians, UV-B radiation, endocrine-disrupting chemicals, declines, review.
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Whitfield, SM, G. Alvarado-Barboza, JG Abarca, H. Zumbado-Ulate, RR Jimenez, and J. Kerby. "Ranavirus is widespread in Costa Rica and co-occurs with threatened amphibians." Diseases of Aquatic Organisms 144 (April 8, 2021): 89–98. http://dx.doi.org/10.3354/dao03576.
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Amphibians are globally threatened by emerging infectious diseases, and ranaviruses are among the most concerning pathogens to threaten species in the wild. We sampled for ranaviruses in wild amphibians at 8 sites in Costa Rica, spanning broad climatic zones and taxonomic associations. Seven of these sites are inhabited by highly threatened amphibian species that persist at low global population sizes after population declines due to amphibian chytridiomycosis. One of the surveyed sites is occupied by an introduced amphibian species, which is relatively rare in Central America but may be an important pathway for long-distance transport of ranaviruses. We detected ranavirus using quantitative polymerase chain reaction in 16.3% of the 243 individuals and among 5 of our 8 sites, but not at the site with the introduced species. Infection prevalence varied among species and sites, but not with mean annual temperature or mean annual precipitation. Infection intensity did not vary with species, site, temperature, or precipitation. Our results show that ranavirus infection is spatially widespread in Costa Rica, affecting a broad range of host species, and occurs across climatic zones—though we encountered no mortality or morbidity in our sampled species. Ranaviruses are known to cause intermittent mass mortality in amphibian populations, and the threatened species sampled here are likely vulnerable to population impacts from emerging ranaviruses. Therefore, we believe the potential impacts of ranaviruses on amphibian populations in tropical regions have likely been underestimated, and that they should be viewed as a potential major stressor to threatened amphibians in tropical regions.
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Garner, Trenton W. J., Benedikt R. Schmidt, An Martel, Frank Pasmans, Erin Muths, Andrew A. Cunningham, Che Weldon, Matthew C. Fisher, and Jaime Bosch. "Mitigating amphibian chytridiomycoses in nature." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1709 (December 5, 2016): 20160207. http://dx.doi.org/10.1098/rstb.2016.0207.
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Amphibians across the planet face the threat of population decline and extirpation caused by the disease chytridiomycosis. Despite consensus that the fungal pathogens responsible for the disease are conservation issues, strategies to mitigate their impacts in the natural world are, at best, nascent. Reducing risk associated with the movement of amphibians, non-amphibian vectors and other sources of infection remains the first line of defence and a primary objective when mitigating the threat of disease in wildlife. Amphibian-associated chytridiomycete fungi and chytridiomycosis are already widespread, though, and we therefore focus on discussing options for mitigating the threats once disease emergence has occurred in wild amphibian populations. All strategies have shortcomings that need to be overcome before implementation, including stronger efforts towards understanding and addressing ethical and legal considerations. Even if these issues can be dealt with, all currently available approaches, or those under discussion, are unlikely to yield the desired conservation outcome of disease mitigation. The decision process for establishing mitigation strategies requires integrated thinking that assesses disease mitigation options critically and embeds them within more comprehensive strategies for the conservation of amphibian populations, communities and ecosystems. This article is part of the themed issue ‘Tackling emerging fungal threats to animal health, food security and ecosystem resilience’.
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Eijkelkamp, Michaël A., Mirjam J. Borger, Ruben Kluit, and Jan Komdeur. "Extremely low amphibian roadkill probability on busy bicycle paths." Herpetological Journal 33, no. 1 (January 1, 2023): 1–5. http://dx.doi.org/10.33256/33.1.115.
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Road mortality can have a significant negative impact on amphibian population survival. Amphibian roadkill and how to avoid it are therefore widely studied, mostly on car roads but limitedly on bicycle paths. We investigated whether amphibian mortality on bicycle paths in Bargerveen, a Dutch Natura 2000 site, was affected by the number of passing cyclists and crossing amphibians. We investigated four transects on a daily basis during most of the amphibian spring migration in 2021. We counted and identified (to species level) all killed amphibians; further, we used cyclist counters and toad fences to assess the number of passing bicycles and crossing amphibians, respectively. We found 11 killed smooth newts Lissotriton vulgaris, out of 5,037 that crossed the bicycle paths. Although 11,453 anurans crossed, we found no killed anurans. The occurrence of killed smooth newts was not affected by the number of passing bicycles or crossing newts. The probability of being killed was extremely low for crossing smooth newts (0.22 %) and anurans (0 %), possibly because cyclists successfully avoid cycling over amphibians. Future monitoring should occur from early February to late November to include the complete active period of amphibians including juvenile dispersal, and across multiple successive years because amphibian numbers can vary largely between years. During our study period, however, amphibian mortality on bicycle paths in Bargerveen seems no threat to populations, despite the high numbers of cyclists. Keywords: road ecology, animal-cyclist collisions, smooth newts, anurans, conservation
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Wynne, Felicity J. "Detection of ranavirus in endemic and threatened amphibian populations of the Australian Wet Tropics Region." Pacific Conservation Biology 26, no. 1 (2020): 93. http://dx.doi.org/10.1071/pc19009.
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The amphibian chytrid fungus (Batrachochytrium dendrobatidis) has driven severe amphibian declines in the Australian tropics. These declines have resulted in species extirpations and extinctions, with many surviving in small, highly threatened populations. Despite the fragility of remaining populations, another group of lethal pathogens, ranaviruses, have rarely been investigated among native amphibians. Ranaviruses have previously been associated with fish, reptile and amphibian mortality events in Australia, yet remain poorly understood here, especially among amphibian hosts. Here, quantitative polymerase chain reaction assays were used to detect ranavirus presence from eight of 17 tested sites containing populations of endangered and critically endangered Australian frog species. Although present in these populations, ranavirus seems to be at the lower bounds of detectability of the assay, which makes firm diagnosis at the individual level unreliable. Repeated (n=14) detections of this pathogen, however, are highly indicative of its presence at each area where it was detected. Therefore, these populations are likely often exposed to ranavirus. The results of this study are not characteristic of populations experiencing rapid disease-associated die-offs or declines, but further investigations should be undertaken to examine the potential drivers of these pathogens to predict future emergence and potential threats to endangered Australian amphibians.
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Velo-Antón, Guillermo, David Alvarez, and Lucía Alarcón-Ríos. "Monsters in the city: multiple deformities increase in terrestrial-breeding urban salamanders." Amphibia-Reptilia 42, no. 3 (April 20, 2021): 391–98. http://dx.doi.org/10.1163/15685381-bja10057.
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Abstract Amphibians are subjected to an assortment of environmental stressors responsible for their population declines and malformations. Deciphering the underlying causes of amphibian deformities is challenging due to the complex nature and interplay among factors. We evaluated morphological deformities in 9 urban and 9 woodland populations of terrestrial-breeding fire salamanders. We report several types of malformations and higher incidences among urban populations. This model system allowed us to tease apart some of the common factors responsible for amphibian deformations, suggesting airborne/terrestrial pollutants, predation, and/or inbreeding as potential environmental stressors. Yet, the putative underlying factors of fire salamander deformities need to be properly addressed in thorough studies linking habitat quality and the prevalence of morphological abnormalities, as well as predator-prey interactions. Reporting deformation rates among amphibians is key to identify warning signals of population declines and preventing local extinctions.
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Burrow, Angela K., and Stacey Lance. "Restoration of Geographically Isolated Wetlands: An Amphibian-Centric Review of Methods and Effectiveness." Diversity 14, no. 10 (October 18, 2022): 879. http://dx.doi.org/10.3390/d14100879.
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Geographically isolated wetlands provide a critical habitat for pond-breeding amphibians, a taxa of broad conservation concern. Global wetland loss and degradation has made restoration essential for amphibian conservation. Restoration goals typically include recovering the wetlands’ physiochemical, hydrological, and ecological functions. However, for pond-breeding amphibians, successful restoration should also result in sustained populations, which is difficult to assess and infrequently reported. In this paper, we review the available evidence that restoration of geographically isolated wetlands promotes pond-breeding amphibian occupancy and population persistence. We provide an overview of restoration practices addressing hydrology, vegetation, and ecological processes within these unique environments and across spatial scales. We then summarize the evidence, and discuss the limitations, for evaluating successful restoration within the context of amphibian conservation across these categories. Finally, we provide recommendations for researchers and practitioners to leverage prior successes and establish systematic data collection and dissemination. Moving restoration of wetlands for amphibian conservation forward will require more robust data collection and reporting.
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deMaynadier, Phillip G., and Malcolm L. Hunter Jr. "The relationship between forest management and amphibian ecology: a review of the North American literature." Environmental Reviews 3, no. 3-4 (July 1, 1995): 230–61. http://dx.doi.org/10.1139/a95-012.
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Questions about the compatibility of forest harvesting practices and conservation of biological diversity are largely driven by concerns that habitat quality for many species may be degraded in intensively managed forest landscapes. We review the literature on relationships between common forest harvesting practices and the distribution and abundance of amphibians, a group that has attracted considerable attention in recent years because of their potential ecological importance in forest ecosystems and because of reports of widespread population declines. Clear-cut harvesting generally has negative short-term impacts on local amphibian populations, especially salamanders. An analysis of the results of 18 studies that examined the effects of clear-cutting on amphibians yielded a 3.5-fold median difference in abundance of amphibians on controls over clear-cuts. However, research on the influence of forest age suggests that the long-term effects of forest harvesting on amphibians are variable, and for many species these effects can be mitigated if regeneration practices leave adequate microhabitat structure intact. In contrast, long-term effects can be significant in forest plantations, which are often associated with intensive site preparations and stand management practices that modify levels of coarse woody debris and other microhabitats. Other forest practices reviewed for their effect on amphibians include prescribed fire, logging roads, and streamside harvesting. We discuss problems commonly encountered in the experimental design and measurement of forest amphibian populations, including a notable lack of pretreatment data, and outline several aspects of amphibian–forestry relationships in need of further research. Management recommendations relevant to conserving upland and riparian zone amphibian habitat during forest harvesting are offered.Key words: amphibians, clear-cutting, coarse woody debris, forest management, logging roads, plantations, prescribed fire, riparian, succession.
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Peterson, Charles, Edward Koch, and Paul Corn. "Monitoring Amphibian Populations in Yellowstone and Grand Teton National Parks." UW National Parks Service Research Station Annual Reports 15 (January 1, 1991): 39–47. http://dx.doi.org/10.13001/uwnpsrc.1991.2961.
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Many amphibian populations appear to be declining throughout much of the world (Corn and Fogleman 1984, Beiswenger 1986, McAllister and Leonard 1990, Wake and Morowitz 1990, Wake 1991). Declines appear to be particularly noticeable in the western United States in the true frogs and toads (families Ranidae and Bufonidae, respectively). For example, leopard frogs (Rana pipiens) and western toads (Bufo boreas) have disappeared from the majority of their historic ranges in Colorado (Corn et al. 1989) and populations of spotted frogs (Rana pretiosa) have gone extinct or declined on the periphery of their range in Washington, Oregon, California, Nevada, and Utah (McAllister and Leonard 1990). Monitoring amphibian populations is important for several reasons. First and most obvious, we need to know if and why amphibian populations are fluctuating so we can effectively manage and preserve them. Second, amphibians are important components of many ecosystems, both as predators and prey, often making up a significant amount of a system's biomass (Pough 1983). Finally, amphibians are potentially sensitive indicators of environmental change because of a unique combination of biological characteristics such as their permeable skins, biphasic life cycles, and aquatic reproduction and development (Wake and Morowitz 1990). For these reasons, the monitoring of amphibians populations has been recommended as an "early warning system" of environmental change (Beiswenger 1986, 1988, Wake 1991).
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WAKE, D. B. "Declining Amphibian Populations." Science 253, no. 5022 (August 23, 1991): 860. http://dx.doi.org/10.1126/science.253.5022.860.
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St-Hilaire, Sophie, Sarah Bruner, Peter Murphy, Debra Patla, and Charles Peterson. "Investigation of Batrachochytrium Dendrobatidis in Four Boreal Toad (Bufo Boreas Boreas) Populations in Wyoming." UW National Parks Service Research Station Annual Reports 29 (January 1, 2005): 3–8. http://dx.doi.org/10.13001/uwnpsrc.2005.3591.
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Batrachochytrium dendrobatidis (Figure 1) is a newly described chytridiomycete fungus that infects amphibian keratin (Berger et al. 1998). It is reported to cause disease and mortality in metamorphosed amphibians around the world (Lips 1998: Young et al. 2001; Bradley et al. 2002; Muths et al. 2003). In several cases, this pathogen is believed to be the primary cause of extinction for amphibian species (Daszak et al. 1999).
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Campbell, Lewis J., Alice H. Pawlik, and Xavier A. Harrison. "Amphibian ranaviruses in Europe: important directions for future research." FACETS 5, no. 1 (January 1, 2020): 598–614. http://dx.doi.org/10.1139/facets-2020-0007.
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Ranaviruses are an emerging group of pathogens capable of infecting all cold-blooded vertebrates. In Europe, ranaviruses pose a particularly potent threat to wild amphibian populations. Since the 1980s research on amphibian-infecting ranaviruses in Europe has been growing. The wide distribution of amphibian populations in Europe, the ease with which many are monitored, and the tractable nature of counterpart ex situ experimental systems have provided researchers with a unique opportunity to study many aspects of host–ranavirus interactions in the wild. These characteristics of European amphibian populations will also enable researchers to lead the way as the field of host–ranavirus interactions progresses. In this review, we provide a summary of the current key knowledge regarding amphibian infecting ranaviruses throughout Europe. We then outline important areas of further research and suggest practical ways each could be pursued. We address the study of potential interactions between the amphibian microbiome and ranaviruses, how pollution may exacerbate ranaviral disease either as direct stressors of amphibians or indirect modification of the amphibian microbiome. Finally, we discuss the need for continued surveillance of ranaviral emergence in the face of climate change.
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Martino, Giuseppe, Andrea Chiocchio, Antonino Siclari, and Daniele Canestrelli. "Distribution and conservation status of threatened endemic amphibians within the Aspromonte mountain region, a hotspot of Mediterranean biodiversity." Nature Conservation 50 (September 12, 2022): 1–22. http://dx.doi.org/10.3897/natureconservation.50.86002.
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Amphibian biodiversity loss in recent years has exceeded that of all other groups of vertebrates. In this context, biodiversity hotspots represent priority targets for conservation in amphibian populations. However, little information is available on the distribution and conservation status of amphibian species within most biodiversity hotspots. Here, we characterized the distribution and conservation status of four threatened endemic amphibians (Bombina pachypus, Salamandra salamandra gigliolii, Salamandrina terdigitata, and Rana italica) in the Aspromonte Mountain region, a biodiversity hotspot in southern Italy where the conservation status of amphibians is almost unexplored. We conducted an intensive field survey of 507 potential breeding sites spanning over 2,326 km2. We found that all four species were widespread in the study area. We observed 337 species occurrences: 63 for S. s. gigliolii, 29 for S. terdigitata, 84 for B. pachypus, and 161 for R. italica. Species distribution analysis revealed that S. s. gigliolii and R. italica populations had an extended and homogenous distribution. Conversely, S. terdigitata showed a dispersed pattern, with long distances among breeding sites, and B. pachypus an aggregated pattern, associated with the availability of suitable artificial habitats. On the other hand, we reported a decrease in B. pachypus occurrence in its natural habitats, which reflects a negative trend of its populations. Overall, our results provide an encouraging framework for the conservation of amphibian populations in this area, but highlight the low coverage of threatened amphibian populations in protected areas, highlighting the need for a reassessment of conservation policies and spatial conservation planning for the Aspromonte region.
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Blaustein, Andrew, Jenny Urbina, Paul Snyder, Emily Reynolds, Trang Dang, Jason Hoverman, Barbara Han, Deanna Olson, Catherine Searle, and Natalie Hambalek. "Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies." Diversity 10, no. 3 (August 4, 2018): 81. http://dx.doi.org/10.3390/d10030081.
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Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease.
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Basanta, M. Delia, Victor Avila-Akerberg, Allison Q. Byrne, Gabriela Castellanos-Morales, Tanya M. González Martínez, Yurixhi Maldonado-López, Erica Bree Rosenblum, Ireri Suazo-Ortuño, Gabriela Parra Olea, and Eria A. Rebollar. "The fungal pathogen Batrachochytrium salamandrivorans is not detected in wild and captive amphibians from Mexico." PeerJ 10 (October 3, 2022): e14117. http://dx.doi.org/10.7717/peerj.14117.
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The recent emergence of the pathogen Batrachochytrium salamandrivorans (Bsal) is associated with rapid population declines of salamanders in Europe and its arrival to new areas could cause dramatic negative effects on other amphibian populations and species. Amphibian species, present in areas with high amphibian diversity such as Mexico, could be highly threatened due to the arrival of Bsal, particularly salamander species which are more vulnerable to chytridiomycosis caused by this pathogen. Thus, immediate surveillance is needed as a strategy to efficiently contend with this emerging infectious disease. In this study, we analyzed 490 wild and captive amphibians from 48 species across 76 sites in the North, Central, and South of Mexico to evaluate the presence of Bsal. Amphibians were sampled in sites with variable degrees of amphibian richness and suitability for Bsal according to previous studies. From the 76 sampling sites, 10 of them were located in areas with high amphibian richness and potential moderate to high Bsal habitat suitability. We did not detect Bsal in any of the samples, and no signs of the disease were observed in any individual at the time of sampling. Our results suggest that Bsal has not yet arrived at the sampled sites or could be at low prevalence within populations with low occurrence probability. This is the first study that evaluates the presence of Bsal in different regions and amphibian species in Mexico, which is the second most diverse country in salamander species in the world. We highlight the risk and the importance of continuing surveillance of Bsal in Mexico and discuss control strategies to avoid the introduction and spread of Bsal in the country.
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Murphy, Peter, Sophie St-Hilaire, and Charles Peterson. "The Effect of Aquatic and Terrestrial Environmental Factors on the Interaction Between Grand Teton Boreal Toads and a Lethal Fungal Pathogen." UW National Parks Service Research Station Annual Reports 31 (January 1, 2008): 125–31. http://dx.doi.org/10.13001/uwnpsrc.2008.3723.
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Batrachochytrium dendrobatidis (Bd), the chytrid fungus which infects keratinized amphibian skin and causes the lethal disease chytridiomycosis, has been linked to population declines and extinctions worldwide (Lips et al. 2006). Amphibians infected with Bd may suffer a variety of outcomes. Individuals of some species have been killed by :S 100 Bd zoospores, while other species, such as the North American bullfrog Rana catesbiana, are highly resistant (Daszak et al. 2004). Within an amphibian species, populations may also respond differently to Bd, with some declining et al. remaining stable (Kriger and Hero 2006). Divergent outcomes among species and populations with respect to Bd may arise from at least three factors, or their interaction.
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Cunningham, A. A. "Infectious disease threats to amphibian conservation." Glasgow Naturalist 27, Supplement (2018): 81–90. http://dx.doi.org/10.37208/tgn27s14.
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The unexplained decline of amphibian populations across the world was first recognised in the late 20th century. When investigated, most of these “enigmatic” declines have been shown to be due to one of two types of infectious disease: ranavirosis caused by infection with FV3-like ranavirus or with common midwife toad virus, or chytridiomycosis caused by infection with Batrachochytrium dendrobatidis or B. salamandrivorans. In all cases examined, infection has been via the human-mediated introduction of the pathogen to a species or population in which it has not naturally co-evolved. While ranaviruses and B. salamandrivorans have caused regionally localised amphibian population declines in Europe, the chytrid fungus, B. dendrobatidis, has caused catastrophic multi-species amphibian population declines and species extinctions globally. These diseases have already caused the loss of amphibian biodiversity, and over 40% of known amphibian species are threatened with extinction. If this biodiversity loss is to be halted, it is imperative that regulations are put in place – and enforced – to prevent the spread of known and yet-to-be discovered amphibian pathogens. Also, it is incumbent on those who keep or study amphibians to take measures to minimise the risk of disease spread, including from captive animals to those in the wild.
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C. Nias, Raymond. "Recent trends in amphibian conservation: a report from the Third World Congress of Herpetology." Pacific Conservation Biology 4, no. 3 (1998): 179. http://dx.doi.org/10.1071/pc980179.
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The Third World Congress of Herpetology was held in Prague, capital of the Czech Republic from 2nd to 10th August, 1997. Some 40 papers and posters about the conservation of amphibians were presented, including a full day symposium on declining amphibian populations. The Declining Amphibian Task Force (an IUCN Species Survival Commission Specialist Group) held an open meeting on Tuesday, August 5.
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Collins, James P., and Tim Halliday. "Forecasting changes in amphibian biodiversity: aiming at a moving target." Philosophical Transactions of the Royal Society B: Biological Sciences 360, no. 1454 (February 28, 2005): 309–14. http://dx.doi.org/10.1098/rstb.2004.1588.
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Amphibian population declines and sudden species' extinctions began to be noted at the beginning of the 1980s. Understanding the causes of the losses is hampered by our poor knowledge of the amphibian fauna in many parts of the world. Amphibian taxa are still being described at a high rate, especially in the tropics, which means that even quantifying species lost as a percentage of the current fauna can be a misleading statistic in some parts of the globe. The number of species that have gone missing is only one measure of the loss of biodiversity. Long-term studies of single-species populations are needed, but this approach has its limits. Amphibian populations often show great annual variation in population size making it difficult, if not impossible, to use short-term studies as a basis for deciding if a population is increasing or decreasing in the long term. Aggregating single studies into databases and searching for patterns of variation is a way of overcoming this limitation. Several databases on species and population time series are available or in development. These records show that declines are continuing worldwide with some species and populations, especially in the tropics and at higher elevations, at greater risk of extinction than others. Unfortunately, amphibian databases with population time series have much less information for the tropics compared to the temperate zone, and less for Africa and Asia compared with Europe and North America. Focusing limited resources using comprehensive statistical designs is a way to maximize the efficiency and effectiveness of monitoring efforts. It is clear that, in the first decades of the twenty-first century, the regions of the globe with the highest diversity of amphibian species will experience the greatest rates of decrease of forests and increase in human population size, fertilizer use, agricultural production, creation of new croplands and irrigation. Many of these changes are likely negatively to affect amphibian species diversity, and their influence must be understood before concluding, at least for amphibians, that the 2010 millennium assessment goal of significantly reversing the rate of loss of Earth's biodiversity can be met.
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Costa, Sara, and Isabel Lopes. "Saprolegniosis in Amphibians: An Integrated Overview of a Fluffy Killer Disease." Journal of Fungi 8, no. 5 (May 22, 2022): 537. http://dx.doi.org/10.3390/jof8050537.
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Amphibians constitute the class of vertebrates with the highest proportion of threatened species, with infectious diseases being considered among the greatest causes for their worldwide decline. Aquatic oomycetes, known as “water molds”, are fungus-like microorganisms that are ubiquitous in freshwater ecosystems and are capable of causing disease in a broad range of amphibian hosts. Various species of Achlya sp., Leptolegnia sp., Aphanomyces sp., and mainly, Saprolegnia sp., are responsible for mass die-offs in the early developmental stages of a wide range of amphibian populations through a disease known as saprolegniosis, aka, molding or a “Saprolegnia-like infection”. In this context, the main objective of the present review was to bring together updated information about saprolegniosis in amphibians to integrate existing knowledge, identify current knowledge gaps, and suggest future directions within the saprolegniosis–amphibian research field. Based on the available literature and data, an integrated and critical interpretation of the results is discussed. Furthermore, the occurrence of saprolegniosis in natural and laboratory contexts and the factors that influence both pathogen incidence and host susceptibility are also addressed. The focus of this work was the species Saprolegnia sp., due to its ecological importance on amphibian population dynamics and due to the fact that this is the most reported genera to be associated with saprolegniosis in amphibians. In addition, integrated emerging therapies, and their potential application to treat saprolegniosis in amphibians, were evaluated, and future actions are suggested.
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Lenhardt, Patrick P., Carsten A. Brühl, Christoph Leeb, and Kathrin Theissinger. "Amphibian population genetics in agricultural landscapes: does viniculture drive the population structuring of the European common frog (Rana temporaria)?" PeerJ 5 (July 11, 2017): e3520. http://dx.doi.org/10.7717/peerj.3520.
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Amphibian populations have been declining globally over the past decades. The intensification of agriculture, habitat loss, fragmentation of populations and toxic substances in the environment are considered as driving factors for this decline. Today, about 50% of the area of Germany is used for agriculture and is inhabited by a diverse variety of 20 amphibian species. Of these, 19 are exhibiting declining populations. Due to the protection status of native amphibian species, it is important to evaluate the effect of land use and associated stressors (such as road mortality and pesticide toxicity) on the genetic population structure of amphibians in agricultural landscapes. We investigated the effects of viniculture on the genetic differentiation of European common frog (Rana temporaria) populations in Southern Palatinate (Germany). We analyzed microsatellite data of ten loci from ten breeding pond populations located within viniculture landscape and in the adjacent forest block and compared these results with a previously developed landscape permeability model. We tested for significant correlation of genetic population differentiation and landscape elements, including land use as well as roads and their associated traffic intensity, to explain the genetic structure in the study area. Genetic differentiation among forest populations was significantly lower (median pairwiseFST = 0.0041 at 5.39 km to 0.0159 at 9.40 km distance) than between viniculture populations (median pairwiseFST = 0.0215 at 2.34 km to 0.0987 at 2.39 km distance). Our analyses rejected isolation by distance based on roads and associated traffic intensity as the sole explanation of the genetic differentiation and suggest that the viniculture landscape has to be considered as a limiting barrier forR. temporariamigration, partially confirming the isolation of breeding ponds predicted by the landscape permeability model. Therefore, arable land may act as a sink habitat, inhibiting genetic exchange and causing genetic differentiation of pond populations in agricultural areas. In viniculture, pesticides could be a driving factor for the observed genetic impoverishment, since pesticides are more frequently applied than any other management measure and can be highly toxic for terrestrial life stages of amphibians.
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Sánchez-Domene, David, Alba Navarro-Lozano, Raphael Acayaba, Katiuce Picheli, Cassiana Montagner, Denise de Cerqueira Rossa-Feres, Fernando Rodrigues da Silva, and Eduardo Alves de Almeida. "Eye malformation baseline in Scinax fuscovarius larvae populations that inhabit agroecosystem ponds in southern Brazil." Amphibia-Reptilia 39, no. 3 (2018): 325–34. http://dx.doi.org/10.1163/15685381-20181038.
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Abstract Events of mass malformations in amphibian populations that have exceeded historical records have been reported over the past thirty years. Many of these events have been linked to human activities that occurred near amphibian breeding habitats. The rise in biofuels has promoted, and continues to promote, the growth of sugarcane plantations in Brazil, with the northwest region of São Paulo State having experienced the largest sugarcane expansion over the past few decades. In this region, we sampled temporary ponds located in agroecosystems dominated to different degrees by sugarcane. We found several larvae of Scinax fuscovarius with eye malformations (anophthalmia, aphakia, microphthalmia and sub-development). In this study, we assessed whether the distance from the ponds to the nearest sugarcane crop, the proportion of sugarcane surrounding the ponds, the presence of pesticides in the ponds, or the proportion of land uses with potential teratogens that surround the ponds were related to the frequencies of amphibian eye malformations. We found pesticides present in 11 of the 18 ponds, but none of the predictor variables was associated with the frequencies of amphibian eye malformations. Thus, our results suggest that the observed frequencies of amphibian eye malformations could be a consequence of natural mutation rates, and these data could be used as a malformation baseline for the region. This malformation baseline is the first reported for amphibians in South America and may be useful in future surveys on amphibian populations in tropical agroecosystems.
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Walston, Leroy J., and Stephen J. Mullin. "Variation in amount of surrounding forest habitat influences the initial orientation of juvenile amphibians emigrating from breeding ponds." Canadian Journal of Zoology 86, no. 2 (February 2008): 141–46. http://dx.doi.org/10.1139/z07-117.
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Juvenile dispersal is important for the persistence of amphibian populations. Previous studies have observed nonrandom orientation in juvenile amphibians emigrating from breeding ponds; however, the environmental cues associated with these movements are not well understood. We examined the emigration behavior of recently metamorphosed juveniles of three pond-breeding amphibian species from three woodland ponds. We found that juvenile small-mouthed salamanders ( Ambystoma texanum (Matthes, 1855)), American toads ( Bufo americanus Holbrook, 1836), and wood frogs ( Rana sylvatica LeConte, 1825) exhibited nonrandom orientation upon exiting the breeding ponds. Furthermore, we found a positive relationship between captures of juvenile small-mouthed salamanders and wood frogs and width of the surrounding forest habitat, indicating that these species are selecting areas with broader forested habitat upon exiting the breeding ponds. Our results indicate that migrating juvenile amphibians may rely on direct environmental cues because the orientation of small-mouthed salamanders and wood frogs was influenced by width of the surrounding forested habitat. These observations support previous studies suggesting that maintaining forest habitat, along at least a portion of breeding ponds, is important for the persistence of amphibian populations.
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Matos, Cátia, Neftalí Sillero, and Elena Argaña. "Spatial analysis of amphibian road mortality levels in northern Portugal country roads." Amphibia-Reptilia 33, no. 3-4 (2012): 469–83. http://dx.doi.org/10.1163/15685381-00002850.
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Animal mortality caused by vehicle collisions is one of the main ecological impacts of roads. Amphibians are the most affected group and road fatalities have a significant impact on population dynamics and viability. Several studies on Iberian amphibians have shown the importance of country roads on amphibian road mortality, but still, little is known about the situation in northern Portugal. By being more permeable to amphibian passage, country roads represent a greater source of mortality than highways, which act as barriers. Thus, mitigation measures should be applied, but due to the extensive road network, the identification of precise locations (hotspots) and variables related to animal-vehicle collision is needed to plan these measures successfully. The aim of the study was to analyse the spatial occurrence and related factors linked to amphibian mortality on a number of country roads in northern Portugal, using spatial statistics implemented in GIS and applying a binary logistical regression. We surveyed 631 km of road corresponding to seven transects, and observed 404 individual amphibians: 74 (18.3%) alive and 330 (81.7%) road-killed. Bufo bufo represented 80% of the mortality records. Three transects showed clustered distribution of road-kills, and broadleaved forests and road ditches were the most important factors associated with hotspots of road-kill. Logistic regression models showed that habitat quality, Bufo bufo’s habitat preferences, and road ditches are positively associated with amphibians’ road mortality in northern Portugal, whereas average altitude and length of walls were negatively associated. This study is a useful tool to understand spatial occurrence of amphibian road-kills in the face of applying mitigation measures on country roads from northern Portugal. This study also considers the necessity of assessing the condition of amphibian local populations to understand their road-kills spatial patterns and the urgency to apply mitigation measures on country roads.
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Kuzmin, Sergius L. "Threatened amphibians in the former Soviet Union: the current situation and the main threats." Oryx 30, no. 1 (January 1996): 24–30. http://dx.doi.org/10.1017/s0030605300021359.
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Before the dissolution of the USSR in 1991, research and conservation of the region's amphibian fauna was co-ordsinated by a network of scientists. The use of similar survey methods made it possible to obtain comparable estimates of amphibian populations in different parts of the territory. Since 1991 the system of research and conservation has broken down as a result of political changes and economic crisis. The scientific community has become fragmented and there is a scarcity of funds available for essential research and conservation. There is an urgent need for the adoption and implementation of conservation measures, both within the territory of the former USSR and elsewhere, in order to prevent further declines in threatened amphibian populations. This paper presents a summary of the status of amphibians in the former USSR, the threats they face and recommended measures to protect them.
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Fu, Minjie, and Bruce Waldman. "Ancestral chytrid pathogen remains hypervirulent following its long coevolution with amphibian hosts." Proceedings of the Royal Society B: Biological Sciences 286, no. 1904 (June 5, 2019): 20190833. http://dx.doi.org/10.1098/rspb.2019.0833.
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Many amphibian species around the world, except in Asia, suffer morbidity and mortality when infected by the emerging infectious pathogen Batrachochytrium dendrobatidis (Bd). A lineage of the amphibian chytrid fungus isolated from South Korean amphibians (BdAsia-1) is evolutionarily basal to recombinant global pandemic lineages (BdGPL) associated with worldwide amphibian population declines. In Asia, the Bd pathogen and its amphibian hosts have coevolved over 100 years or more. Thus, resilience of Asian amphibian populations to infection might result from attenuated virulence of endemic Bd lineages, evolved immunity to the pathogen or both. We compared susceptibilities of an Australasian amphibian, Litoria caerulea , known to lack resistance to BdGPL, with those of three Korean species, Bufo gargarizans , Bombina orientalis and Hyla japonica , after inoculation with BdAsia-1, BdGPL or a blank solution. Subjects became infected in all experimental treatments but Korean species rapidly cleared themselves of infection, regardless of Bd lineage. They survived with no apparent secondary effects. By contrast, L. caerulea , after infection by either BdAsia-1 or BdGPL, suffered deteriorating body condition and carried progressively higher Bd loads over time. Subsequently, most subjects died. Comparing their effects on L. caerulea , BdAsia-1 induced more rapid disease progression than BdGPL. The results suggest that genomic recombination with other lineages was not necessary for the ancestral Bd lineage to evolve hypervirulence over its long period of coevolution with amphibian hosts. The pathogen's virulence may have driven strong selection for immune responses in endemic Asian amphibian host species.
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Kaczmarski, Mikołaj, and Krzysztof Kolenda. "Non-native Amphibian Pet Trade via Internet in Poland." European Journal of Ecology 4, no. 1 (August 28, 2018): 30–40. http://dx.doi.org/10.2478/eje-2018-0004.
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Abstract Overharvesting and trade in amphibian populations is one of the causes of their global decline. Online trade not only encourages the exploitation of an increasing number of rare and endangered amphibian species from all over the world but also influences the spread of invasive species. The aim of our research was to investigate the amphibian pet trade conducted in online stores and portals in Poland and determine its potential impact on native species. Between November 2013 and October 2014, we regularly (on a monthly basis) checked sale offers on the websites of the 18 biggest pet shops in the country specialised in exotic animals, on a nationwide auction portal and on three exotic pet fan portals. During the study, we reported 486 offers of 112 amphibian species in online stores and on portals. Most of the offers involved one of the four families of amphibians: poison dart frogs (Dendrobatidae), tree frogs (Hylidae), true toads (Bufonidae) and true salamanders (Salamandridae). Our data show increased interest in amphibians as pets in Poland. At least half of the offered species are possible hosts for the chytrid fungus Batrachochytrium dendrobatidis. However, only one species, the American bullfrog Lithobates catesbeianus (Shaw, 1802), appears to be a potential invasive species. To summarise, the species offered in Poland that are characterised as threatened are predominantly those that are relatively easy to breed and that are popular as pets. Further studies are required to investigate the real threat to wild amphibian populations caused by the pet trade
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Peterson, Charles, and Stephen Spear. "Status, Appropriate Sampling Scheme, and Movement in the Tiger Salamander (Ambystoma tigrinum) in Yellowstone National Park." UW National Parks Service Research Station Annual Reports 26 (January 1, 2002): 80–81. http://dx.doi.org/10.13001/uwnpsrc.2002.3511.
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Due to the current trend of amphibian declines (Wake 1998, Alford and Richards 1999, Semlitsch 2000), the monitoring and study of amphibian populations has become increasingly necessary. To properly do such studies, we must consider several issues. Some of these include the detectability of the species at a site, current status of the population, and the spatial scale for sampling of a population. Determining the detectability of a species is important to consider because some amphibian species may have different difficulties of detection. Therefore, if a species is difficult to observe, it may occupy a greater number of sites than a survey indicates (MacKenzie et al. 2002). The appropriate spatial scale is also important for monitoring studies. For example, in a pond breeding amphibian, do one or two breeding ponds with the appropriate terrestrial habitat constitute the correct sampling area for a population, or does a population utilize multiple ponds within a larger terrestrial area? If the sampling scale is not appropriate, then any conclusions made may be inaccurate (Wiens 1989). In addition, understanding the terrestrial habitat use of pond breeding amphibians is important for both monitoring and conservation reasons. Many pond-breeding amphibians use the ponds for breeding and then utilize terrestrial zones around the pond for the rest of the year. The total area that is encompassed by these terrestrial zones is known as the terrestrial "buffer zone" or core habitat area for that population (Semlitsch 1998). To identify these core habitat areas, we must know not only the distance that the amphibians physically move from the breeding pond, but also the type of habitat that they will use. For example, short, steep slopes or rivers can serve as a barrier to amphibian movement (Laan and Verboom 1990, Storfer 1999), even if they are within the movement range of a population. Understanding individual movement may also give insights into the spatial population structure of the species. If we can identify the average distance of movement, we can then extrapolate if a breeding pond is likely to have an isolated subpopulation based on its distance from other ponds.
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Murrieta-Galindo, Rene, Fabiola López-Barrera, Alberto González-Romero, and Gabriela Parra-Olea. "Matrix and habitat quality in a montane cloud-forest landscape: amphibians in coffee plantations in central Veracruz, Mexico." Wildlife Research 40, no. 1 (2013): 25. http://dx.doi.org/10.1071/wr12076.
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Context The processes of fragmentation, habitat loss, degradation and their combined effects are formidable threats to amphibian populations. Aims We evaluate the effect of three land use-type variables and nine landscape matrix quality factors on amphibian presence in four coffee agro-ecosystems and two cloud-forest fragments in central Veracruz, Mexico. Methods Each site was thoroughly searched using the visual-encounter survey technique along different trails in the most feasible microhabitats for detecting amphibians during four rainy seasons (2005, 2006, 2008 and 2009). Centred on the location where each amphibian species was first recorded, we established what we refer to as a buffer area within a radius of 1.5 km. A Co-Inertia mathematical model was used to determine which of the explanatory variables contributed to maintaining amphibian diversity. The landscape variables were landscape-quality index, open areas, canopy cover (low, intermediate, dense) at the matrix level, river, road and human population density and site size. Local variables were elevation, plant-structure and biological-impact indices. Key results During the study we recorded 1078 amphibians belonging to 26 species, 17 genera and 10 families. The variables explaining the composition of amphibian diversity were river and human population density, low canopy cover at the matrix level, elevation, site size and plant-structure index. Amphibian diversity increased as the structural complexity of the habitat increased, and the former was positively correlated with fragment size. Conclusion The present study indicated that coffee agro-ecosystems and the cloud-forest fragments in the region form a gradient in habitat quality and landscape variables that exert a differential influence on amphibian assemblages, and that each species responds uniquely to different variables. Implications Coffee agro-ecosystems and forest fragments cannot be seen as homogenous patches with a certain habitat quality, separate from the landscape matrix in which they are immersed. Stakeholders are not advised to rely on a single strategy to conserve the amphibian community, but rather should aim to maintain a heterogeneous landscape with forest fragments and coffee agro-ecosystems that have a complex vertical plant structure at the habitat level, especially in highly river-dense landscapes.
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D'Amen, Manuela, Biancamaria Pietrangeli, and Marco A. Bologna. "Human-provoked amphibian decline in central Italy and the efficacy of protected areas." Wildlife Research 37, no. 7 (2010): 547. http://dx.doi.org/10.1071/wr09167.
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Context Today, more than 32% of amphibian species are threatened and more than 43% face a steep decline in numbers. Most species are being affected simultaneously by multiple stressors and habitat protection is often inadequate to prevent declines. Aims The main goal of the present research was to understand the consequences of alternative human land use in producing landscape disturbance for amphibians. At the same time, we also evaluated the effect of changing climatic conditions as additional potential drivers of population decline. Another goal was to determine whether and to what extent the existing nature reserves have been effective in protecting species in recent decades. Methods We used generalised additive models (GAMs) to investigate the association between the state (stable/decline) of amphibian populations in 5 × 5 km cells in central Italy and proxies of different typology of anthropogenic stressors, climatic variables and protection measures. Key results We found a significant association between anthropogenic landscape modifications and species decline. This negative relationship was revealed with agricultural predictors for the majority of the species, whereas urban fabrics had a slightly smaller impact. We found significant associations between amphibian declines and climatic variation, particularly the increasing number of dry days. Protected areas protected declines of two species only. Conclusions Our results showed that the status of amphibians in this region warrants greater attention than has been given previously. The detrimental effect of agricultural practices, combined with increasing aridity, makes amphibian populations particularly susceptible to extinction, and the conservation measures applied till now are inadequate for species protection in this region. Implications Our results should stimulate the implementation of environmental policies that focus not only on the protection of single habitats, but also on ensuring the environmental quality of the surrounding landscapes. Moreover, an adaptive management approach should be applied to take into account future modification of hydrology and climate.
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Lastra González, D., V. Baláž, P. Chajma, and J. Vojar. "Surveying for Batrachochytrium salamandrivorans presence in Spanish captive collections of amphibians." Diseases of Aquatic Organisms 142 (December 3, 2020): 99–103. http://dx.doi.org/10.3354/dao03535.
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Batrachochytrium salamandrivorans (Bsal), a pathogenic fungus causing the fatal disease chytridiomycosis in amphibians, was likely introduced to Europe through the trade in pet salamanders from Asia and then escaped into wild populations. Among European countries, Spain has a large number of private breeders and keepers of pet salamanders, and cases of Bsal in wild and captive populations already have been confirmed there. However, surveillance for the pathogen in Spanish collections of amphibians is sparse. Therefore, assisted by private owners and breeders, we surveyed 10 amphibian collections and analysed a total of 317 samples for presence of Bsal. All of our analyses yielded negative results. However, this apparent lack of Bsal cases in captivity should not encourage relaxation of vigilance, quarantine efforts or good practices. Because amphibian collections represent highly dynamic environments (animals are coming in and out), the pathogen could easily be introduced into a collection by new individuals. Any case of Bsal infection in captive animals could lead to its further spread to wild populations of susceptible species, potentially decimating them, and thus should be prevented.
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Knutson, Melinda G., William B. Richardson, David M. Reineke, Brian R. Gray, Jeffrey R. Parmelee, and Shawn E. Weick. "AGRICULTURAL PONDS SUPPORT AMPHIBIAN POPULATIONS." Ecological Applications 14, no. 3 (June 2004): 669–84. http://dx.doi.org/10.1890/02-5305.
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Patla, Debra, and Charles Peterson. "The Effects of Habitat Modification on a Spotted Frog Population in Yellowstone National Park." UW National Parks Service Research Station Annual Reports 18 (January 1, 1994): 135–44. http://dx.doi.org/10.13001/uwnpsrc.1994.3215.
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Declines and extinctions of many populations of amphibians have been noted worldwide in recent years (Corn and Fogelman 1984, Beiswenger 1986, McAllister and Leonard 1990, Wake and Morowitz 1990, Wake 1991, Adler 1992). Habitat modifications due to human activities may contribute to many of these declines. Habitat may be destroyed overtly, or it may be fragmented. Fragmentation results in reduced area, a differential loss of important habitat components, and increased isolation of populations (Wyman 1990). The persistence of amphibians in areas where modifications short of total habitat destruction depends on the preservation of essential habitat components and landscape connectivity that allows individual animals access to breeding, foraging, and wintering sites (Sinsch 1989). Long-term persistence also may rely on the immigration of individuals from other populations (Pechmann et al. 1991, Sjogren 1991). Although our efforts to conserve amphibian species depend on our understanding of habitat fragmentation and knowledge of the behavioral and population responses to different types of habitat modifications (Gibbons 1988, Groom and Schumaker 1993), few studies have addressed these types of questions for amphibians. Notable exceptions include some studies on the effects of logging (Corn and Bury 1989) and acidification (Wyman and Hawksley-Lescault 1988, Harte and Hoffman 1989, Corn and Vertucci 1992). In Europe, researchers and wildlife conservationists are investigating the impacts of roads on amphibians and attempting to find solutions to fragmentation and mortality effects (Langton 1989), but this concern has not yet received noticeable attention in North America. We lack studies evaluating the relative importance and integration of foraging areas, hibernacula, breeding sites, areas occupied pre- and post-breeding, and dispersal routes connecting these areas. With these kinds of information, researchers and land managers will be better able to analyze, predict, and mitigate the effects of habitat modifications that are sources of amphibian population declines.
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Techangamsuwan, Somporn, Angkana Sommanustweechai, Sumate Kamolnorranart, Boripat Siriaroonrat, Wichase Khonsue, and Nopadon Pirarat. "Emerging Chytrid Fungal Pathogen, Batrachochytrium Dendrobatidis, in Zoo Amphibians in Thailand." Acta Veterinaria 67, no. 4 (December 20, 2017): 525–39. http://dx.doi.org/10.1515/acve-2017-0042.
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AbstractChytridiomycosis, a disease in amphibians caused by Batrachochytrium dendrobatidis (Bd), has led to a population decline and extinction of frog species since 1996. The objective of this study was to determine the prevalence of and the need for establishing a surveillance system for monitoring chytridiomycosis in five national zoos and five free ranging protected areas across Thailand. A total of 492 skin swab samples were collected from live and dead animals and tested by polymerase chain reaction (PCR) for the presence of Bd. The positive specimens were confi rmed by amplicon sequencing and examined by histopathology and immunohistochemistry. From July 2009 to August 2012, the prevalence of Bd from frog skin samples was low (4.27%), monitored by PCR. All samples from live amphibians were negative. The positive cases were only from dead specimens (21/168, 12.5% dead samples) of two non-native captive species, poison dart frog (Dendrobates tinctorius) and tomato frog (Dyscophus antongilii) in one zoo. Immunohistochemistry and histopathology revealed the typical feature of fl ask-shaped zoosporangia and septate thalli, supporting the PCR-based evidence of chytridiomycosis in captive amphibians in Thailand, but detected Bd in only 7/21 of the PCR-positive samples. Although the introduction of a pathogenic strain of Bd from imported carriers might have a serious impact on the native amphibian populations in Thailand, chytridiomycosis has not currently been detected in native Thai amphibians. An active surveillance system is needed for close monitoring of the fungus crossing into Thai amphibian populations
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Bird, R. J., E. Paterson, J. R. Downie, and B. K. Mable. "Linking water quality with amphibian breeding and development: a case study comparing natural ponds and Sustainable Drainage Systems (SuDS) in East Kilbride, Scotland." Glasgow Naturalist 27, Supplement (2018): 49–66. http://dx.doi.org/10.37208/tgn27s09.
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Amphibians have declined due to habitat loss and alteration. Sustainable Drainage Systems (SuDS) provide potential habitat for amphibians in urban landscapes. However, the contaminants they accumulate may cause increased pollutant exposure, and limited research has addressed whether differences in water quality between SuDS and natural ponds might restrict their use by amphibians. This study aimed to explore the effects of water quality on amphibian breeding and development in SuDS and natural ponds in East Kilbride, Scotland. A generalised linear modelling approach was employed to determine sources of variation in common frog (Rana temporaria) breeding and development in relation to pond size, pH, electrical conductivity (EC), chlorophyll and heavy metal concentrations. Key findings included that EC indicative of salt pollution was higher in SuDS than natural ponds, amphibians bred in both site types, but frog spawn clump densities were lower in SuDS, and tadpole development rates were higher in SuDS sites but decreased when aluminium concentrations exceeded concentrations those of surface water standards. However, pond desiccation was a significant element in the 2018 study year. It was concluded that natural ponds and SuDS varied in water quality but were important in supporting amphibian populations. However, water quality might influence amphibian development more than breeding attempts; implications and management recommendations are highlighted based on these observations.
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Muths, Erin, and Robert N. Fisher. "An alternative framework for responding to the amphibian crisis." Oryx 51, no. 2 (December 16, 2015): 210–13. http://dx.doi.org/10.1017/s0030605315001131.
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AbstractVolumes of data illustrate the severity of the crisis affecting amphibians, where > 32% of amphibians worldwide are threatened with declining populations. Although there have been isolated victories, the current approach to the issue is unsuccessful. We suggest that a radically different approach, something akin to human emergency response management (i.e. the Incident Command System), is one alternative to addressing the inertia and lack of cohesion in responding to amphibian issues. We acknowledge existing efforts and the useful research that has been conducted, but we suggest that a change is warranted and that the identification of a new amphibian chytrid provides the impetus for such a change. Our goal is to recognize that without a centralized effort we (collectively) are likely to fail in responding to this challenge.
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McMillan, Katelyn A. M., and Melanie R. Power Coombs. "Review: Examining the Natural Role of Amphibian Antimicrobial Peptide Magainin." Molecules 25, no. 22 (November 20, 2020): 5436. http://dx.doi.org/10.3390/molecules25225436.
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Host defense peptides (HDPs) are a group of antimicrobial peptides (AMPs) that are crucial components of the innate immune system of many different organisms. These small peptides actively kill microbes and prevent infection. Despite the presence of AMPs in the amphibian immune system, populations of these organisms are in decline globally. Magainin is an AMP derived from the African clawed frog (Xenopus laevis) and has displayed potent antimicrobial effects against a wide variety of microbes. Included in this group of microbes are known pathogens of the African clawed frog and other amphibian species. Arguably, the most deleterious amphibious pathogen is Batrachochytrium dendrobatidis, a chytrid fungus. Investigating the mechanism of action of magainin can help understand how to effectively fight off infection. By understanding amphibian AMPs’ role in the frog, a potential conservation strategy can be developed for other species of amphibians that are susceptible to infections, such as the North American green frog (Rana clamitans). Considering that population declines of these organisms are occurring globally, this effort is crucial to protect not only these organisms but the ecosystems they inhabit as well.
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Lisachov, Artem P., Lada S. Lisachova, and Evgeniy Simonov. "First record of ranavirus (Ranavirus sp.) in Siberia, Russia." Herpetozoa 35 (February 7, 2022): 33–37. http://dx.doi.org/10.3897/herpetozoa.35.e79490.
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Ranaviruses are a group of double-strand DNA viruses that infect fish, amphibians and reptiles. These viruses are responsible for mass fish and amphibian mortality events worldwide, both in the wild and at fish and amphibian farms. The number of detected epizootics has grown significantly in recent years. In Eastern Europe and Northern Asia, including Russia, very few ranavirus monitoring studies have been conducted, in contrast with Western Europe and America. In the present work, we used a qPCR assay to survey for the first time the amphibian populations of West Siberia (Russia) for the presence of ranaviruses. In total, we studied 252 tissue samples from six amphibian species, collected across West Siberia from the south to the Arctic regions. We report a single infected sample: a common toad (Bufo bufo) captured near Tyumen city. The phylogenetic analysis showed that the detected virus strain belongs to the CMTV lineage. This is only the second observation of Ranavirus in Russia.
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Sánchez-Montes, Gregorio, Íñigo Martínez-Solano, Carmen Díaz-Paniagua, Antonio Vilches, Arturo H. Ariño, and Ivan Gomez-Mestre. "Telomere attrition with age in a wild amphibian population." Biology Letters 16, no. 7 (July 2020): 20200168. http://dx.doi.org/10.1098/rsbl.2020.0168.
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Telomere shortening with age has been documented in many organisms, but few studies have reported telomere length measurements in amphibians, and no information is available for growth after metamorphosis, nor in wild populations. We provide both cross-sectional and longitudinal evidence of net telomere attrition with age in a wild amphibian population of natterjack toads ( Epidalea calamita ). Based on age-estimation by skeletochronology and qPCR telomere length measurements in the framework of an individual-based monitoring programme, we confirmed telomere attrition in recaptured males. Our results support that toads experience telomere attrition throughout their ontogeny, and that most attrition occurs during the first 1–2 years. We did not find associations between telomere length and inbreeding or body condition. Our results on telomere length dynamics under natural conditions confirm telomere shortening with age in amphibians and provide quantification of wide telomere length variation within and among age-classes in a wild breeding population.
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Patla, Debra, and Charles Peterson. "The Effects of Habitat Modification on a Spotted Frog Population in Yellowstone National Park." UW National Parks Service Research Station Annual Reports 17 (January 1, 1993): 3–13. http://dx.doi.org/10.13001/uwnpsrc.1993.3129.
Full textAbstract:
Declines and extinctions of many populations of amphibians have been noted worldwide in recent years (Corn and Fogelman 1984, Beiswenger 1986, McAllister and Leonard 1990, Wake and Morowitz 1990, Wake 1991, Adler 1992). Habitat modifications due to human activities may contribute to many of these declines. Habitat may be destroyed overtly, or it may be fragmented. Fragmentation results in reduced area, a differential loss of important habitat components, and increased isolation of populations (Wyman 1990). The persistence of amphibians in areas where modifications short of total habitat destruction occur depends on the preservation of essential habitat components and landscape connectivity that allows individual animals access to breeding, foraging, and wintering sites (Sinsch 1989). Long-term persistence also may rely on the immigration of individuals from other populations (Pechmann et al. 1991, Sjogren 1991). Our efforts to conserve amphibian species and to establish methods of sustainable resource use depend on our understanding of habitat fragmentation and knowledge of the behavioral and population responses to different types of habitat modifications (Gibbons 1988, Groom and Schumaker 1993). Few studies have addressed these types of questions. Notable exceptions include some studies on the effects of logging (Corn and Bury 1989) and acidification (Wyman and Hawksley-Lescault 1988, Harte and Hoffman 1989, Corn and Vertucci 1992). In Europe, researchers and wildlife conservationists are investigating the impacts of roads on amphibians and attempting to find solutions to fragmentation and mortality effects (Langton 1989), but this concern has not yet received noticeable attention in North America. We lack studies evaluating the relative importance and integration of foraging areas, hibernacula, breeding sites, areas occupied pre- and post-breeding, and dispersal routes connecting these areas. With these kinds of information, researchers and land managers will acquire the ability to better analyze, predict, and mitigate the effects of habitat modifications that are sources of amphibian population declines.
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Kouba, Andrew J., and Carrie K. Vance. "Applied reproductive technologies and genetic resource banking for amphibian conservation." Reproduction, Fertility and Development 21, no. 6 (2009): 719. http://dx.doi.org/10.1071/rd09038.
Full textAbstract:
As amphibian populations continue to decline, both government and non-government organisations are establishing captive assurance colonies to secure populations deemed at risk of extinction if left in the wild. For the most part, little is known about the nutritional ecology, reproductive biology or husbandry needs of the animals placed into captive breeding programs. Because of this lack of knowledge, conservation biologists are currently facing the difficult task of maintaining and reproducing these species. Academic and zoo scientists are beginning to examine different technologies for maintaining the genetic diversity of founder populations brought out of the wild before the animals become extinct from rapidly spreading epizootic diseases. One such technology is genetic resource banking and applied reproductive technologies for species that are difficult to reproduce reliably in captivity. Significant advances have been made in the last decade for amphibian assisted reproduction including the use of exogenous hormones for induction of spermiation and ovulation, in vitro fertilisation, short-term cold storage of gametes and long-term cryopreservation of spermatozoa. These scientific breakthroughs for a select few species will no doubt serve as models for future assisted breeding protocols and the increasing number of amphibians requiring conservation intervention. However, the development of specialised assisted breeding protocols that can be applied to many different families of amphibians will likely require species-specific modifications considering their wide range of reproductive modes. The purpose of this review is to summarise the current state of knowledge in the area of assisted reproduction technologies and gene banking for the conservation of amphibians.
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Phillips, Ben L., and Robert Puschendorf. "Do pathogens become more virulent as they spread? Evidence from the amphibian declines in Central America." Proceedings of the Royal Society B: Biological Sciences 280, no. 1766 (September 7, 2013): 20131290. http://dx.doi.org/10.1098/rspb.2013.1290.
Full textAbstract:
The virulence of a pathogen can vary strongly through time. While cyclical variation in virulence is regularly observed, directional shifts in virulence are less commonly observed and are typically associated with decreasing virulence of biological control agents through coevolution. It is increasingly appreciated, however, that spatial effects can lead to evolutionary trajectories that differ from standard expectations. One such possibility is that, as a pathogen spreads through a naive host population, its virulence increases on the invasion front. In Central America, there is compelling evidence for the recent spread of pathogenic Batrachochytrium dendrobatidis (Bd) and for its strong impact on amphibian populations. Here, we re-examine data on Bd prevalence and amphibian population decline across 13 sites from southern Mexico through Central America, and show that, in the initial phases of the Bd invasion, amphibian population decline lagged approximately 9 years behind the arrival of the pathogen, but that this lag diminished markedly over time. In total, our analysis suggests an increase in Bd virulence as it spread southwards, a pattern consistent with rapid evolution of increased virulence on Bd's invading front. The impact of Bd on amphibians might therefore be driven by rapid evolution in addition to more proximate environmental drivers.
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Yahner, Richard, William Bramble, and W. Richard Byrnes. "Response of Amphibian and Reptile Populations to Vegetation Maintenance of an Electric Transmission Line Right-Of-Way." Arboriculture & Urban Forestry 27, no. 4 (July 1, 2001): 215–21. http://dx.doi.org/10.48044/jauf.2001.023.
Full textAbstract:
A 2-year study of amphibian and reptile populations was conducted on a 500-kV transmission line right-of-way (ROW) of PECO Energy in the Piedmont Physiographic Province, Montgomery County, Pennsylvania, U.S., from June through July 1999, September through October 1999, and March through October 2000. The objectives were to compare the diversity and relative abundance of amphibians and reptiles between the ROW and the adjacent forest, among five treatment units on the ROW, and between wire and borders zones on treatments on the ROW. Eight species were observed during the study, and the two most common species were Jefferson salamanders (Ambystoma jeffersonianum) and redback salamanders (Plethodon tinereus). All eight species were noted on the ROW, but only Jefferson and redback salamanders occurred in the adjacent forest. The number of species ranged from six species in the mowing plus herbicide unit to three each in the stem—foliage spray and foliage spray units. All species were found in the wire zones compared to only five species in the border zones. The ROW contained a greater diversity of amphibian and reptile species than the adjacent forest. Because forest-management practices can have negative impacts on populations of amphibians and reptiles, this study provides valuable information on forest-management practices required for the conservation of amphibians and reptiles.
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Saucedo, Bernardo, José M. Serrano, Mónica Jacinto-Maldonado, Rob S. E. W. Leuven, Abraham A. Rocha García, Adriana Méndez Bernal, Andrea Gröne, Steven J. Van Beurden, and César M. Escobedo-Bonilla. "Pathogen Risk Analysis for Wild Amphibian Populations Following the First Report of a Ranavirus Outbreak in Farmed American Bullfrogs (Lithobates catesbeianus) from Northern Mexico." Viruses 11, no. 1 (January 3, 2019): 26. http://dx.doi.org/10.3390/v11010026.
Full textAbstract:
Ranaviruses are the second deadliest pathogens for amphibian populations throughout the world. Despite their wide distribution in America, these viruses have never been reported in Mexico, the country with the fifth highest amphibian diversity in the world. This paper is the first to address an outbreak of ranavirus in captive American bullfrogs (Lithobates catesbeianus) from Sinaloa, Mexico. The farm experienced high mortality in an undetermined number of juveniles and sub-adult bullfrogs. Affected animals displayed clinical signs and gross lesions such as lethargy, edema, skin ulcers, and hemorrhages consistent with ranavirus infection. The main microscopic lesions included mild renal tubular necrosis and moderate congestion in several organs. Immunohistochemical analyses revealed scant infected hepatocytes and renal tubular epithelial cells. Phylogenetic analysis of five partial ranavirus genes showed that the causative agent clustered within the Frog virus 3 clade. Risk assessment with the Pandora+ protocol demonstrated a high risk for the pathogen to affect amphibians from neighboring regions (overall Pandora risk score: 0.619). Given the risk of American bullfrogs escaping and spreading the disease to wild amphibians, efforts should focus on implementing effective containment strategies and surveillance programs for ranavirus at facilities undertaking intensive farming of amphibians.
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Blaustein, Andrew R., and David B. Wake. "The Puzzle of Declining Amphibian Populations." Scientific American 272, no. 4 (April 1995): 52–57. http://dx.doi.org/10.1038/scientificamerican0495-52.
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Blaustein, Andrew R., and David B. Wake. "Declining amphibian populations: A global phenomenon?" Trends in Ecology & Evolution 5, no. 7 (July 1990): 203–4. http://dx.doi.org/10.1016/0169-5347(90)90129-2.
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Awkerman, Jill A., and Cathryn H. Greenberg. "Projected Climate and Hydroregime Variability Constrain Ephemeral Wetland-Dependent Amphibian Populations in Simulations of Southern Toads." Ecologies 3, no. 2 (June 17, 2022): 235–48. http://dx.doi.org/10.3390/ecologies3020018.
Full textAbstract:
Amphibian populations are threatened globally by stressors, including diminishing availability of suitable wetland breeding sites, altered hydroregimes driven by changing weather patterns, and exposure to contaminants. Ecological risk assessment should encompass spatial and temporal scales that capture influential ecological processes and demographic responses. Following the PopGUIDE framework of population model development for risk assessment, we used matrix population models, in conjunction with existing hydroregime predictions, under a climate change scenario to evaluate the effects of environmental stochasticity and aquatic pesticide exposure on amphibians that are dependent on ephemeral wetlands. Using southern toads (Anaxyrus terrestris) as an example, we simulated population dynamics with breeding success dependent on hydroregime suitability. Years were defined as optimal, marginal, or insufficient for successful toad recruitment, based on the duration of their potential breeding season and rate of larval development to metamorphosis. We simulated both probabilistic and chronologically specific population projections, including variable annual fecundity, based on hydroregime suitability and reduced larval survival from carbaryl exposure. In our simulations, populations were more negatively impacted by prolonged drought, and consequently multiple sequential years of reproductive failure, than by aquatic pesticide exposure. These results highlight the necessity of reliable climate projections to accurately represent the effects of altered hydroregimes on amphibian populations. Risk assessment approaches could be improved with flexible modifications that allow inclusion of various extrinsic stressors and identification of demographic and ecological vulnerabilities when precise data are lacking.
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Smith, Paul, Pier Cacciali, Karina Atkinson, Helen Pheasey, and Martha Motte. "New distributional records of amphibians for Departamento San Pedro, Paraguay (Amphibia)." Check List 8, no. 5 (September 1, 2012): 903. http://dx.doi.org/10.15560/8.5.903.
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New distributional data are provided for 12 species of amphibian in Departamento San Pedro, Paraguay. Records are from the Reserva Natural Laguna Blanca, a small private reserve located in an area of transition from Atlantic Forest to Cerrado-type habitats. The chronic under-sampling of amphibian populations in Paraguay is highlighted.
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Lambert, Max R., Tien Tran, Andrzej Kilian, Tariq Ezaz, and David K. Skelly. "Molecular evidence for sex reversal in wild populations of green frogs (Rana clamitans)." PeerJ 7 (February 8, 2019): e6449. http://dx.doi.org/10.7717/peerj.6449.
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In vertebrates, sex determination occurs along a continuum from strictly genotypic (GSD), where sex is entirely guided by genes, to strictly environmental (ESD), where rearing conditions, like temperature, determine phenotypic sex. Along this continuum are taxa which have combined genetic and environmental contributions to sex determination (GSD + EE), where some individuals experience environmental effects which cause them to sex reverse and develop their phenotypic sex opposite their genotypic sex. Amphibians are often assumed to be strictly GSD with sex reversal typically considered abnormal. Despite calls to understand the relative natural and anthropogenic causes of amphibian sex reversal, sex reversal has not been closely studied across populations of any wild amphibian, particularly in contrasting environmental conditions. Here, we use sex-linked molecular markers to discover sex reversal in wild populations of green frogs (Rana clamitans) inhabiting ponds in either undeveloped, forested landscapes or in suburban neighborhoods. Our work here begins to suggest that sex reversal may be common within and across green frog populations, occurring in 12 of 16 populations and with frequencies of 2–16% of individuals sampled within populations. Additionally, our results also suggest that intersex phenotypic males and sex reversal are not correlated with each other and are also not correlated with suburban land use. While sex reversal and intersex are often considered aberrant responses to human activities and associated pollution, we found no such associations here. Our data perhaps begin to suggest that, relative to what is often suggested, sex reversal may be a relatively natural process in amphibians. Future research should focus on assessing interactions between genes and the environment to understand the molecular and exogenous basis of sex determination in green frogs and in other amphibians.