Bioclimatic and anthropogenic variables shape the occurrence of Batrachochytrium dendrobatidis over a large latitudinal gradient

Abstract

Amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has caused the greatest known loss of biodiversity due to an infectious disease. We used Bd infection data from quantitative real-time PCR (qPCR) assays of amphibian skin swabs collected across Chile during 2008–2018 to model Bd occurrence with the aim to determine bioclimatic and anthropogenic variables associated with Bd infection. Also, we used Bd presence/absence records to identify geographical Bd high-risk areas and compare Bd prevalence and infection loads between amphibian families, ecoregions, and host ecology. Data comprised 4155 Bd-specific qPCR assays from 162 locations across a latitudinal gradient of 3700 km (18º to 51ºS). Results showed a significant clustering of Bd associated with urban centres and anthropogenically highly disturbed ecosystems in central-south Chile. Both Bd prevalence and Bd infection loads were higher in aquatic than terrestrial amphibian species. Our model indicated positive associations of Bd prevalence with altitude, temperature, precipitation and human-modified landscapes. Also, we found that macroscale drivers, such as land use change and climate, shape the occurrence of Bd at the landscape level. Our study provides with new evidence that can improve the effectiveness of strategies to mitigate biodiversity loss due to amphibian chytridiomycosis.

Nor climate nor human impact factors: Chytrid infection shapes the skin bacterial communities of an endemic amphibian in a biodiversity hotspot

“…In particular, infected and non‐infected individuals share 391 (79%) bacterial families out of a total of 495, while Bd + individuals only have 8.5% ( N = 42) and Bd − 12.5% ( N = 62) exclusive families. We hypothesize that similar to what was found in other species (Longo et al., 2015 ), P. thaul , being generally resistant to developing chytridiomycosis (Alvarado‐Rybak et al., 2021 ), might experience seasonal Bd infections, where throughout the year, individuals alternate their status between being infected, clearing the fungus, and becoming re‐infected again (e.g., Longo et al., 2015 ). Thus, it is possible that in those periods of re‐infection, Bd + individuals may recruit beneficial bacterial families to clear Bd .…”

“…In particular, infected and non-infected individuals share 391 (79%) bacterial families out of a total of 495, while Bd+ individuals only have 8.5% (N = 42) and Bd− 12.5% (N = 62) exclusive families. We hypothesize that similar to what was found in other species(Longo et al, 2015), P. thaul, being generally resistant to developing chytridiomycosis(Alvarado-Rybak et al, 2021), might experience seasonal Bd infections, where throughout the year, indi-…”

“…Complete details on the swabbing and Bd diagnostic analysis can be found in Alvarado‐Rybak et al. ( 2021 ). Briefly, the extracted DNA was diluted at a ratio of 1:10 in double‐distilled water and subjected to analysis using a quantitative real‐time PCR Taqman assay (qPCR).…”

“…The amphibian skin microbiome was obtained from tadpoles, juveniles, and adults of P. thaul from 16 localities spanning almost 1800 km in latitude (Table 1). Complete details on the swabbing and Bd diagnostic analysis can be found in Alvarado-Rybak et al (2021).…”

Prevalence of Batrachochytrium dendrobatidis in Amphibians From 2000 to 2021: A Global Systematic Review and Meta-Analysis

“…Bd is regarded as a generalist pathogen (18) and is distributed across different ecosystems (19,20). The prevalence and infection intensity of Bd are associated with abiotic factors (21) and may vary according to host species, age and individual susceptibility (22).…”