Sample collection
From spring 2019 to early winter 2021, a total of 31 sites (27 field sites and 4 captive sites) were surveyed throughout the Guangxi region in China (Fig. 1A), which shares its southwestern border with Vietnam, a country known to harbor Bsal (Laking et al., 2017). The pathogen was detected in an individual of a salamander species, Pachytriton wuguanfui in Guangxi region (Yuan et al., 2018). It is now known that basal Asian and global lineages of Bd exist in this region (Fig. 1B, Sun et al., 2023). Occasionally, Bsal can spill over from captive populations into wildlife communities (Cunningham et al., 2015; Fitzpatrick et al., 2018; Sabino-Pinto et al., 2015). To account for this, random samples were collected from pet markets and frog farms within the region. Skin swabs were collected following the sampling protocol for chytrid pathogens in amphibians, as described in Hyatt et al. (2007). Water samples were collected from bodies of water forBsal detection in relation to local populations, to be used for environmental DNA (eDNA) analysis; eDNA can be used for pathogen detection in the absence of hosts (Kirshtein et al., 2007; Schulz et al., 2020). For this, approximately 1 L of water was sampled for each water body, then filtered through the 0.40 μm polycarbonate filter membrane using a sterile 100 ml syringe.
Ethical clearance for this study was obtained from the Institutional Animal Care and Use Committee of Guangxi University (GXU2018-048, with an extension of GXU2020-501).