Introduction
Amphibians worldwide face considerable threats, including habitat loss,
climate change, and disease, which contribute to severe population
declines and biodiversity loss (Amphibiaweb, 2023). Chytridiomycosis, a
disease caused by the chytrid fungi Batrachochytrium
dendrobatidis (Bd ) and B. salamandrivorans (Bsal ),
is a major driver of these declines (Longcore et al., 1999; Martel et
al., 2013; Scheele et al., 2019). Both Bd and Bsal are
thought to have originated in Asia, with Bd portraying multiple
lineages in the region (Martel et al., 2014; O’hanlon et al., 2018).Bd affects all three amphibian orders and has caused widespread
declines, particularly in anuran species across all amphibian-inhabited
continents (Scheele et al., 2019). In contrast, although present in
Asia, Bsal has led to severe declines of native salamanders only
in Europe so far (Fisher & Garner, 2020), however, the impending threat
for the highly diverse Northern American and Neotropical urodelans is
significant (Carter et al., 2020; Crawshaw et al., 2022;
García-Rodríguez et al., 2022; Moubarak et al., 2022; North AmericanBsal Task Force, 2022; Yap et al., 2015).
Although Bsal primarily infects urodelans, recent studies show
that anurans can act as reservoir hosts or as transmitters (Lötters et
al., 2020; Nguyen et al., 2017; Schulz et al., 2020; Stegen et al.,
2017; Towe et al., 2021). This role increases disease risk to sensitive
salamander species and populations. Therefore, identifying reservoir
hosts is crucial for understanding infection dynamics and potential
occurrences as Bsal continues to expand its range and threaten
biodiversity (Martel et al., 2020; Spitzen-Van Der Sluijs et al., 2016).
Bsal has restricted distributional areas, co-occurring withBd in several microhabitats (Laking et al., 2017; Lötters et al.,
2020). Bd -Bsal occurrences can potentially generate new
genotypes with heightened pathogenicity (Farrer et al., 2011; Fisher &
Garner, 2020; Wacker et al., 2023). Bsal has stronger
pathogenicity compared to Bd within a shared host species,
leading to more severe infection outcomes (Farrer et al., 2017). Out of
documented 67 susceptible host species for Bsal , nearly 32
species also can be infected by Bd (Castro Monzon et al., 2023;
Olson et al., 2021), these shared species could serve as the
hyper-reservoirs or gain greater impacts from both pathogens.
Importantly, Bd -Bsal coinfections have been reported in
three urodelean species in natural habitats (Lötters et al., 2020;
Lötters et al., 2018), and such coinfections are known to increase
infection severity and disease risk under the laboratory experimental
conditions (Longo et al., 2019; Ribas et al., 2022). These emphasize the
importance of Bsal screening in natural habitats where Bdoccurs.
In Southeast Asia (Vietnam), Bsal co-occurs together with the
globalized genotype Bd GPL (Laking et al., 2017). However,
knowledge on Bsal infection is scarce in other Asian amphibian
hotspots where different Bd lineages are found. South China, for
example, harbors the unique Asian genotype Bd Asia3 alongsideBd GPL (Byrne et al., 2019).
Here, we hypothesize that Bsal co-occurs together with Bdpopulations in South China. To investigate this, we screened forBsal in salamanders and potential anuran reservoir hosts within
regional amphibian hotspot in South China, which is recognized for its
diverse Bd genotypes spanning various natural habitats. We also
assessed the influence of climatic factors on Bsal distribution
by estimating its potential range under the current climatic conditions.
Analyzing the presence of Bsal in areas with high Bddiversity will enhance our comprehension of Bsal niche dynamics
and pathogenicity. This has significant implications for amphibian
conservation in the context of pathogen virulence evolution.