Genetic analysis of post‐epizootic amphibian chytrid strains in Bolivia: Adding a piece to the puzzle

Abstract

The evolutionary history and dispersal pattern of Batrachochytrium dendrobatidis (Bd), an emergent fungal pathogen responsible for the decline and extinctions of many species of amphibians worldwide, is still not well understood. In South America, the tropical Andes are known as an important site for amphibian diversification, but also for being a place where hosts are at greater risk of chytridiomycosis. In an attempt to understand the history and the geographic pattern of Bd‐associated amphibian declines in Bolivia, we isolated Bd from hosts at two locations that differ in their chronology of Bd prevalence and host survival outcome, the cloud forests of the Amazonian slopes of the Andes and Lake Titicaca in the altiplano. We genotyped Bd from both locations and sequenced the genome from the cloud forest isolate and then compared them to reference sequences of other Bd strains across the world. We found that the Bolivian chytrid isolates were nearly genotypically identical and that they belong to the global panzootic lineage (Bd‐GPL). The Bolivian Bd strain grouped with other tropical New World strains but was closest to those from the Brazilian Atlantic Forest. Our results extend the presence of Bd‐GPL to the central Andes in South America and report this hypervirulent strain at Lago Titicaca, where Bd has been detected since 1863, without evidence of amphibian declines. These findings suggest a more complex evolutionary history for this pathogen in Bolivia and may point to the existence of an old lineage of Bd that has since been extirpated following the arrival of the panzootic Bd‐GPL or that the timing of Bd‐GPL emergence is earlier than generally acknowledged.

Chytridiomycosis Outbreak in a Chilean Giant Frog (Calyptocephalella gayi) Captive Breeding Program: Genomic Characterization and Pathological Findings

“…Despite South America being the region with the greatest loss of biodiversity due to Bd (6), only low numbers of Bd isolates from this region have been genetically characterized (14,(21)(22)(23)(24)(25)(26). This limits our capacity to adequately understand the epidemiological processes that have led to impacts of chytridiomycosis on South American native amphibians.…”

Range expansion to record-breaking elevations influences, but does not eliminate, Batrachochytrium dendrobatidis infections for Andean anurans

“…Our data cannot exclude the possibility that BdGPL circulated in the Vilcanota prior to the local epizootics of the early 2000s. However, in the context of prior regional studies (Lips et al 2008, Catenazzi et al 2011, Burrowes et al 2020, the most likely explanations are that BdGPL-2 housed substantial standing genetic variation upon its introduction or that it was introduced to the Vilcanota multiple times. Our analyses place Vilcanota Bd in a large, global polytomy within BdGPL-2.…”

Peer Review #2 of "Fungal infection, decline and persistence in the only obligate troglodytic Neotropical salamander (v0.1)"

“…This early positive record was detected by qPCR, and histological examination was suggestive but inconclusive (Burrowes and De la Riva 2017). In cases of very early detection of Bd in countries where declines occurred much later, it is possible that early detections correspond to endemic strains while declines were caused only by the arrival of the more virulent Bd-GPL, but genetic data to support this hypothesis are currently lacking (Burrowes and De la Riva 2017;Burrowes et al 2020). Retrospective surveys of key species in museum collections, together with the use of genomic methods to identify Bd lineage, offer a promising avenue to fill gaps in our knowledge related to the arrival and impact of Bd in the Neotropics.…”