Understanding the evolutionary history of microbial pathogens is critical for mitigating the impacts of emerging infectious diseases on economically and ecologically important host species. We used a genome resequencing approach to resolve the evolutionary history of an important microbial pathogen, the chytrid Batrachochytrium dendrobatidis (Bd), which has been implicated in amphibian declines worldwide. We sequenced the genomes of 29 isolates of Bd from around the world, with an emphasis on North, Central, and South America because of the devastating effect that Bd has had on amphibian populations in the New World. We found a substantial amount of evolutionary complexity in Bd with deep phylogenetic diversity that predates observed global amphibian declines. By investigating the entire genome, we found that even the most recently evolved Bd clade (termed the global panzootic lineage) contained more genetic variation than previously reported. We also found dramatic differences among isolates and among genomic regions in chromosomal copy number and patterns of heterozygosity, suggesting complex and heterogeneous genome dynamics. Finally, we report evidence for selection acting on the Bd genome, supporting the hypothesis that protease genes are important in evolutionary transitions in this group. Bd is considered an emerging pathogen because of its recent effects on amphibians, but our data indicate that it has a complex evolutionary history that predates recent disease outbreaks. Therefore, it is important to consider the contemporary effects of Bd in a broader evolutionary context and identify specific mechanisms that may have led to shifts in virulence in this system.

Within the last two decades Batrachochytrium dendrobatidis (B.d.), the causative agent of chytridiomycosis, seems to have become a pandemic parasite, and is proposed as one of the more important causes of amphibian declines worldwide. In Argentina, the first report was in 2002 in Leptodactylus ocellatus. Since then, the fungus has expanded through different environments and species. In this study, we predict B.d. distribution in Argentina applying niche modelling based on reports of infected amphibians and environmental variables. The distribution hypothesis showed regions with highest suitability for B.d. including habitat types with (1) the most diverse amphibian fauna in Argentina such as the Paraná River Basin, (2) endangered species, such as north Patagonia and northwest Andean highlands, and (3) wide range of optimum precipitation and temperatures allowing development of B.d.

Amphibian populations are declining globally. In this scenario, detailed information on their ecology is crucial to determine the status and extinction risk of their populations and, therefore, better plan conservation activities. The Valcheta frog Pleurodema somuncurense is a Critically Endangered species, which is endemic to the Valcheta Stream, Patagonia, Argentina. We assessed the status of this species at the metapopulation level, which we consider is a key step in planning management activities. We conducted visual encounter surveys from 2013 to 2019 to determine the distribution range of each local population of the Valcheta frog. During 2015, we also applied a capture-recapture survey to estimate the density and apparent survival of 1 local population. We used POPAN models for density estimation and the classic model of Cormack-Jolly-Seber to estimate apparent survival, using snout-vent length as a covariate. The metapopulation of the Valcheta frog is composed of 9 isolated local populations: 7 extant and 2 extinct. The extant populations have population sizes ranging from 243 to 4516 individuals. The small size of the smaller local populations makes their long-term viability in isolation unlikely. We found a positive correlation between the apparent survival and the snout-vent length of individuals. Our results showed that management strategies should be aimed at ensuring the long-term survival of this species, with a focus on the recovery of extinct populations, the restoration of disturbed habitats and the improvement of connectivity between local populations.

The Chytridiomycota (chytrids) of Argentina are not well known from freshwater and terrestrial ecosystems. We collected samples of water and floating organic matter (vegetable debris) from a lotic environment and wet soil from four terrestrial habitats at the Reserva Natural Selva Marginal Punta Lara (Bs. As.) and added cellulosic, chitinic and keratinic baits to these samples. We also placed Rosa spp. fruits and corn leaves for colonization in the stream. We recorded 21 taxa. Four of them (Chytriomyces hyalinus var. granulatus, Cylindrochytridium johnstonii, Cladochytriumreplicatum and Septochytrium variabile) are new records for Argentina and we describe and illustrate them here.

No abstract