Effects of host species and environmental factors on the prevalence of Batrachochytrium dendrobatidis in northern Europe

The fungal pathogen Batrachochytrium dendrobatidis (Bd) is a major threat to amphibian populations. Here we asked if the prevalence of Bd differs between amphibian species and whether it is related to local environmental factors in breeding habitats as well as landscape variables measured at three scales (500, 2000 and 5000 m radius) in southernmost Sweden. We sampled 947 anurans from six species in 31 ponds. Canopy cover, pond perimeter, pH and temperature were treated as local scale pond characteristics. Number of surrounding ponds, area of arable land, area of mature forest and number of resident people were treated as landscape variables. Bufo bufo and Rana temporaria had a prevalence of 0.5-1.0% which differed strongly from the other four species (Bombina bombina, Bufotes variabilis, Epidalea calamita, Rana arvalis) showing 13-64% prevalence. Bd prevalence in these four species was higher in ponds with higher pH, surrounded by a landscape with less mature forest and few wetlands. Our results show that the infection dynamics of Bd are complex and depend on local pond characteristics, host community composition and the spatial scale under investigation. Information on environmental factors associated with Bd and species differences in susceptibility may mitigate further spread of the disease through public information and guide conservational action plans, especially for the most threatened species.