Is Chytridiomycosis Driving Darwin’s Frogs to Extinction?

Soto‐Azat, Claudio; Valenzuela‐Sánchez, Andrés; Clarke, Barry T.; Busse, Klaus; Ortíz, Juan Carlos; Barrientos, Carlos; Cunningham, Andrew A.

doi:10.1371/journal.pone.0079862

Cited by 30 publications

(52 citation statements)

References 41 publications

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“…First, a retrospective epidemiological study based on museum specimens showed that the earliest record of Bd in Chile is from a four‐eyed toad collected from Concepción in 1970 (Soto‐Azat et al. ). Second, more recently, Valenzuela‐Sánchez et al.…”

Section: Discussionmentioning

confidence: 99%

The amphibian‐killing fungus in a biodiversity hotspot: identifying and validating high‐risk areas and refugia

et al. 2019

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Amphibian chytridiomycosis, due to infection with the fungus Batrachochytrium dendrobatidis (Bd), has been associated with the alarming decline and extinction crisis of amphibians worldwide. It is essential for conservation management to identify regions with high or low suitability for Bd. We use a species distribution model to estimate the environmental suitability of Bd in the Chilean Winter Rainfall–Valdivian Forest biodiversity hotspot. Fourteen environmental variables were used as predictors in the statistical modeling (Maxent, generalized linear models, random forest) which also included 56 independent Bd+ localities. High‐risk areas (i.e., suitability above a defined threshold) were validated through prospective field surveys conducted in 2017. As results from Maxent, which only uses presence data, were the only results retained, refugia (i.e., suitability below a defined threshold) were validated with the Bd absences (N = 12) used in the GLM and RF modeling. Our results showed that (1) suitability for Bd increased with human footprint and with shorter distances to urban centers and water bodies and decreased with elevation; (2) climate was not a major factor shaping the current distribution of Bd; and (3) the model predicted high‐risk and refugia areas fairly well. Surveys of 24 new localities in high‐risk areas confirmed that 23 were Bd+; hence, these areas warrant consideration for long‐term Bd surveillance, population monitoring, and disease mitigation. In addition, five localities with apparent Bd absence were found in the predicted high‐risk areas. Our models showed that refugia can exist near high‐risk areas and Bd+ sites. Four localities with apparent Bd absence were located within the refugia predicted by the model. Preventing Bd transmission to such refugia is of paramount importance for persistence of Bd‐susceptible amphibian populations. The identification and validation through prospective field surveys of high‐risk areas and refugia are imperative to develop strategies to prevent further arrival and establishment of Bd and also, by identifying amphibian species or populations of conservation concern in such areas, will help to guide specific actions to reduce the biodiversity loss caused by chytridiomycosis.

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Section: Discussionmentioning

confidence: 99%

The amphibian‐killing fungus in a biodiversity hotspot: identifying and validating high‐risk areas and refugia

et al. 2019

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“…Sites were chosen on the basis of having amphibian populations, good accessibility, and that contributed to a good coverage of the whole study area. In each, a search effort of one hour by two researchers was conducted using a standardized methodology, as previously described (Soto‐Azat et al ., ,b). In each locality, we performed exhaustive searches across land and aquatic environments and recorded the altitude and geographic coordinates.…”

Section: Methodsmentioning

confidence: 99%

“…In recent years, evidence for the critical involvement of EIDs in the amphibian decline phenomenon has grown and become more convincing, especially in the case of amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis ( Bd ). This disease has been associated with amphibian population declines at the global scale and is implicated in the extinction of several amphibian species from Australia, Costa Rica and Chile (Pounds et al ., ; Daszak et al ., ; Lips et al ., ; Pounds et al ., ; Schloegel et al ., ; Skerratt et al ., ; Bielby et al ., ; Wake & Vredenburg, ; Collins & Crump, ; Soto‐Azat et al ., ,b). Less than two decades exist for Bd investigation (Berger et al ., ; Longcore et al ., ), and although a substantial amount of research has been accomplished, several aspects of its basic biology, epidemiology and interaction with their hosts are still unknown (Kilpatrick et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Effects of amphibian phylogeny, climate and human impact on the occurrence of the amphibian‐killing chytrid fungus

Bacigalupe

Soto‐Azat

García‐Vera

et al. 2017

Global Change Biology

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Chytridiomycosis, due to the fungus Batrachochytrium dendrobatidis (Bd), has been associated with the alarming decline and extinction crisis of amphibians worldwide. Because conservation programs are implemented locally, it is essential to understand how the complex interactions among host species, climate and human activities contribute to Bd occurrence at regional scales. Using weighted phylogenetic regressions and model selection, we investigated geographic patterns of Bd occurrence along a latitudinal gradient of 1500 km within a biodiversity hot spot in Chile (1845 individuals sampled from 253 sites and representing 24 species), and its association with climatic, socio-demographic and economic variables. Analyses show that Bd prevalence decreases with latitude although it has increased by almost 10% between 2008 and 2013, possibly reflecting an ongoing spread of Bd following the introduction of Xenopus laevis. Occurrence of Bd was higher in regions with high gross domestic product (particularly near developed centers) and with a high variability in rainfall regimes, whereas models including other bioclimatic or geographic variables, including temperature, exhibited substantially lower fit and virtually no support based on Akaike weights. In addition, Bd prevalence exhibited a strong phylogenetic signal, with five species having high numbers of infected individuals and higher prevalence than the average of 13.3% across all species. Taken together, our results highlight that Bd in Chile might still be spreading south, facilitated by a subset of species that seem to play an important epidemiological role maintaining this pathogen in the communities, in combination with climatic and human factors affecting the availability and quality of amphibian breeding sites. This information may be employed to design conservation strategies and mitigate the impacts of Bd in the biodiversity hot spot of southern Chile, and similar studies may prove useful to disentangle the role of different factors contributing to the emergence and spread of this catastrophic disease.

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“…Certain species might be considered threatened by chytridiomycosis on the Red List even though they are later found to be unaffected by Bd (such as Plectrohyla matudai (VU), see ( Figure I-8). Yet many other species, like the two species of Darwin's frogs from southern South America (Rhinoderma), are only now having their declines attributed to chytridiomycosis (Soto-Azat et al 2013). In the Mexican context, it is clear that some of the Red List assessors, for species such as Incilius cristatus (CR) , took a cautious approach by not mentioning chytridiomycosis in the species accounts even though it is hard to imagine a scenario where Bd did not play a pivotal role in its decline.…”

Section: Chytridiomycosismentioning

confidence: 99%