| Amphibian populations worldwide are vulnerable to a variety of threats, and one serious cause of population declines and extinctions is the amphibian pathogenic fungus Batrachochytrium dendrobatidis (Bd). Amphibian species of tropical, montane regions have suffered the greatest impacts of Bd- related declines, extirpations, and extinctions. Bd is also present in temperate regions, but the effects of Bd on temperate amphibian species appear to be less severe although remain poorly understood. Bd impacts populations, species, and individuals differentially and environmental factors affect host – pathogen relationships. Temperature varies along seasonal, altitudinal, and landscape gradients and is much more variable in temperate ecosystems than in tropical montane ecosystems. I examine the relationship between amphibian hosts and the pathogen Bd in the framework of temperature along these gradients and in these ecosystems. I reviewed the literature and identified a need to support Bd temperature regimes identified by laboratory studies with research conducted among wild populations. In a temperate ecosystem, I found high rates of Bd with widespread geographic (19.5% Bd positive) and amphibian taxonomic distribution (68% of species infected) in Ohio, USA. When patterns were examined more closely among green frogs (Lithobates clamitans) and bullfrogs (L. catesbeianus), I found high rates of Bd prevalence were associated with cooler temperatures such as those experienced in springtime (89% prevalence) and stream habitats (54%). In contrast, I found high infection intensities among amphibians were associated with warmer temperatures such as those experienced in summer (8,240 ± 31,852 ZE) and emergent streams (72,645 ± 18,092 ZE). In a tropical montane ecosystem, I found that Bd is geographically widespread but persists at low prevalence (7%) among Gastrotheca pseustes tadpoles collected from mid to high elevation sites in the Ecuadorian Andes. Infected tadpoles were of poor body condition compared to their uninfected conspecifics. Bd persists in high montane environments despite cool temperatures and negatively impacts tadpole growth, but may be less virulent at mid to high elevation sites compared to low altitudes. This may provide rationale for the persistence of an endemic harlequin frog, Atelopus exiguus, that persists at 3100 masl while many harlequin frog species distributed at lower elevations have recently gone extinct. Together, these chapters provide perspective on the relationship between amphibians and the fungal pathogen, Bd and recommendations to inform future efforts in global amphibian conservation. |
