Synthesis of batrachochytrium dendrobatidis infection in South America: amphibian species under risk and areas to focus research and disease mitigation

Amphibian chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd),
has been recognized as the infectious disease causing the most
catastrophic loss of biodiversity known to science, with South America
being the most impacted region. We tested whether Bd prevalence is
distributed among host taxonomy, ecoregion, conservation status and
habitat preference in South America. Here we provide a synthesis on the
extent of Bd infection across South America based on 21,648 molecular
diagnostic assays, roles of certain species in the epidemiology of Bd and
explore its association with the reported amphibian catastrophic declines
in the region. We show that Bd is widespread, with a continental
prevalence of 23.2%. Its occurrence in the region shows a phylogenetic
signal and the probability of infection is determined by ecoregion,
preferred habitat, and extinction risk hosts’ traits. The taxa exhibiting
highest Bd occurrence, were mostly aquatic amphibians, including Ranidae,
Telmatobiidae, Hylodidae, Calyptocephalellidae and Pipidae. Surprisingly,
families exhibiting unusually low Bd prevalence included species in which
lethal chytridiomycosis and population declines have been described (genus
Atelopus, Rhinoderma and Eleutherodactylus). Higher than expected
prevalence of Bd occurred mainly in amphibians living associated with
mountain environments in the Andes and Atlantic forests, reflecting highly
favourable Bd habitats in these areas. Invasive amphibian species (e.g.
Lithobates catesbeianus and Xenopus laevis) exhibited high Bd prevalence,
as thus we suggest using these as sentinels to understand their potential
role as reservoirs, vectors or spreaders of Bd that can be subjected to
management. Our results guide on the prioritization of conservation
actions to prevent further biodiversity loss due to chytridiomycosis in
the world’s most amphibian diverse region.