Widespread occurrence of bd in French Guiana, South America.

Elodie A Courtois,Dirk S Schmeller,Jérôme Chave,Philippe Gaucher,Matthew C Fisher

doi:10.1371/journal.pone.0125128

Abstract

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) is a purported agent of decline and extinction of many amphibian populations worldwide. Its occurrence remains poorly documented in many tropical regions, including the Guiana Shield, despite the area’s high amphibian diversity. We conducted a comprehensive assessment of Bd in French Guiana in order to (1) determine its geographical distribution, (2) test variation of Bd prevalence among species in French Guiana and compare it to earlier reported values in other South American anuran species (http://www.bd-maps.net; 123 species from 15 genera) to define sentinel species for future work, (3) track changes in prevalence through time and (4) determine if Bd presence had a negative effect on one selected species. We tested the presence of Bd in 14 species at 11 sites for a total of 1053 samples (306 in 2009 and 747 in 2012). At least one Bd-positive individual was found at eight out of 11 sites, suggesting a wide distribution of Bd in French Guiana. The pathogen was not uniformly distributed among the studied amphibian hosts, with Dendrobatidae species displaying the highest prevalence (12.4%) as compared to Bufonidae (2.6 %) and Hylidae (1.5%). In contrast to earlier reported values, we found highest prevalence for three Dendrobatidae species and two of them displayed an increase in Bd prevalence from 2009 to 2012. Those three species might be the sentinel species of choice for French Guiana. For Dendrobates tinctorius, of key conservation value in the Guiana Shield, smaller female individuals were more likely to be infected, suggesting either that frogs can outgrow their chytrid infections or that the disease induces developmental stress limiting growth. Generally, our study supports the idea that Bd is more widespread than previously thought and occurs at remote places in the lowland forest of the Guiana shield.

Highlights

Over a third of extant amphibian species are currently considered at an elevated threat of extinction [1,2,3]
In pristine amphibian rich areas, especially in Central America, amphibian declines have been associated with outbreaks of the chytrid fungus Batrachochytrium dendrobatidis (Bd), the agent of chytridiomycosis [5,6]
In 2011–2012, prevalence of Bd across species varied from 0% to 43.3% with the highest prevalence found for Allobates femoralis (43.3%), followed by Ranitomeya amazonica (13.3%), Anomaloglossus baeobatrachus (12.1%), and Dendrobates tinctorius (9.3%; Table 3)

Summary

Introduction

Over a third of extant amphibian species are currently considered at an elevated threat of extinction [1,2,3]. Bd has locally been reported in Ecuador [9], Uruguay [10], Venezuela [11], Peru [12], Argentina [13], Chile [14], Colombia [15] and coastal Brazil [16] and in nearly the entirety of South America. Despite these numerous studies, we currently lack a comprehensive understanding of Bd distribution in South America. Previous sampling for Bd in Suriname [17] and a recent study of Bd in French Guiana caecilians [18] have yielded negative results, but in 2009, the presence of Bd has been unambiguously confirmed from two sites in French Guiana [19]

Objectives

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Results

Conclusion