Drivers of salamander extirpation mediated by Batrachochytrium salamandrivorans

Abstract

The recent arrival of Batrachochytrium salamandrivorans in Europe was followed by rapid expansion of its geographical distribution and host range, confirming the unprecedented threat that this chytrid fungus poses to western Palaearctic amphibians. Mitigating this hazard requires a thorough understanding of the pathogen's disease ecology that is driving the extinction process. Here, we monitored infection, disease and host population dynamics in a Belgian fire salamander (Salamandra salamandra) population for two years immediately after the first signs of infection. We show that arrival of this chytrid is associated with rapid population collapse without any sign of recovery, largely due to lack of increased resistance in the surviving salamanders and a demographic shift that prevents compensation for mortality. The pathogen adopts a dual transmission strategy, with environmentally resistant non-motile spores in addition to the motile spores identified in its sister species B. dendrobatidis. The fungus retains its virulence not only in water and soil, but also in anurans and less susceptible urodelan species that function as infection reservoirs. The combined characteristics of the disease ecology suggest that further expansion of this fungus will behave as a 'perfect storm' that is able to rapidly extirpate highly susceptible salamander populations across Europe.

Efficacy of chemical disinfectants for the containment of the salamander chytrid fungus Batrachochytrium salamandrivorans

“…This has also been observed for Bd [19]. Unique to Bsal is the production of encysted spores inside sporangia [33]. The cell wall of the zoosporangium and the encysted spores within it, provide a double barrier against the action of the disinfectants.…”

Decision‐making for mitigating wildlife diseases: From theory to practice for an emerging fungal pathogen of amphibians

“…We used the European fire salamander S. salamandra as the target species, since it is a widespread species in Europe at great extinction risk from Bsal (Stegen et al., ). We considered the management of a single salamander population over a short time frame of 3 months, chosen on the basis of the rapid Bsal ‐driven population crashes in fire salamanders (Schmidt et al., ; Stegen et al., ). We assumed optimal climatic conditions for Bsal growth and transmission (Stegen et al., ).…”

“…We considered the management of a single salamander population over a short time frame of 3 months, chosen on the basis of the rapid Bsal ‐driven population crashes in fire salamanders (Schmidt et al., ; Stegen et al., ). We assumed optimal climatic conditions for Bsal growth and transmission (Stegen et al., ). We envisaged management would have two general objectives: minimizing the risk of population extinction and minimizing the potential for further geographic disease spread.…”

“…Furthermore, for the initial density derived from Stegen et al. () we used a negative binomial distribution, and for the mean survival probability of infected individuals, also from Stegen et al. (), we used a beta distribution.…”

Gene drives do not always increase in frequency: from genetic models to risk assessment

“…This could potentially be of vital importance for the rapid introduction of resistance alleles in populations of species that are now threatened by exotic fungi and viruses from which they have always been isolated (Stegen et al 2017). Application of GD in breeding programs is based on the same idea (Gonen et al 2017).…”