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Comparative Analysis of Skin Bacterial Diversity and Its Potential Antifungal Function Between Desert and Pine Forest Populations of Boreal Toads Anaxyrus boreas


The skin microbiome in amphibians has gained a lot of attention as some of its members play a protective role against pathogens such as the fungus Batrachochytrium dendrobatidis (Bd). The composition of skin bacterial communities has been suggested as one of the factors explaining differences in susceptibility to Bd among amphibian species and populations. The boreal toad Anaxyrus boreas is known to be susceptible to Bd, and severe population declines in its southeastern range have been documented. However, throughout A. boreas distribution, populations present differences in susceptibility to Bd infections which may be associated with differences in skin microbial diversity. This study compared the skin bacterial diversity and Bd infection levels of A. boreas in one desert population and one pine forest population from Baja California, Mexico. We found that desert and pine forest toad populations exhibit differences in skin bacterial community structure but show similar Bd infection levels. Using a predictive method, we found that the abundance of bacteria with potential Bd-inhibitory properties differed between uninfected and infected individuals but not between populations. Our data suggest that several bacteria in the skin community may be offering protection from Bd infections in these A. boreas populations. This study provides foundational evidence for future studies seeking to understand the skin-microbial variation among boreal toads’ populations and its relation with Bd susceptibility.

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Data Availability

Sequencing data of this study are publicly available through the NCBI Sequence Read Archive under NCBI Bioproject PRJNA723361.

Code Availability

Not applicable.


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MDB thanks the Posgrado en Ciencias Biológicas programme, Universidad Nacional Autónoma de México and CONACyT for a scholarship grant (CVU/Becario: 509293/288791). MDB and GPO thank the CONACyT for assistant research scholarship (CVU/Exp.Ayte/Exp. Inv.: 509293/19525/26435). We would also like to thank Laura Márquez-Valdemar and Andrea Jimenez for assisting us with laboratory procedures and Molly Bletz and Douglas Woodhams for sharing us the updated database of ASVs with potential Bd-inhibitory properties. Finally, we thank Jorge Sánchez-Solís, Cristina Del Río, and Ibes Dávila for field assistance. Collection permits were provided by the Secretaría del Medio Ambiente y Recursos Naturales (SEMARNAT) SGPA/DGVS/003513/18, SGPA/DGVS/002176/18, and SPA-ENS/305/18.


This study was funded by the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica (PAPIIT-UNAM) IN205521 and UC MEXUS CONACyT CN 18–127 to GPO.

Author information




MDB, MGC, and GPO designed the project. MDB and MGC collected the samples. MDB, GPO, and EAR contributed to laboratory procedures. MDB performed analyses, and all authors interpreted the data. MDB wrote the first draft of the manuscript, and all authors contributed to the improvement of the manuscript.

Corresponding author

Correspondence to Gabriela Parra Olea.

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Basanta, M.D., Rebollar, E.A., García-Castillo, M.G. et al. Comparative Analysis of Skin Bacterial Diversity and Its Potential Antifungal Function Between Desert and Pine Forest Populations of Boreal Toads Anaxyrus boreas. Microb Ecol (2021).

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  • Disease ecology
  • Chytridiomycosis
  • Skin microbiota
  • Amphibian
  • Antifungal