Global amphibian decline: emerging infectious diseases and local extinctions

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Extinction is a common fate to any species. However, determining the causes and processes is often difficult. Increasing evidence suggests that amphibians are actually facing a global decline representing a singular opportunity to study the biology of extinction. Among other causes, emerging infectious diseases are involved in this decline. They consist of a fungal infection responsible in extinctions all around the world as well as another group of amphibian pathogens, ranaviruses, which have been shown to only cause local mortality but no known extinction. While the physiological mechanisms of these pathogens are well understood, the ecological and genetic components of the host-pathogen relationship remain to be studied. Understanding infectious disease ecology and evolution is a key to the more general investigation of extinction. Therefore amphibians are an excellent model for studying such a process in the wild. Not only do they suffer from these emerging infectious diseases but they also face anthropogenic and ecological pressure in many of their habitats. Only by exploring the role of these diseases in broad context will we be able to both test pathogen-induced extinctions and address appropriate conservation solutions. To this end, I will establish a long-term program in northern Ontario, where a matrix of disturbed and undisturbed habitats are present, and the diseases have been recently recorded. Using a combination of field observations and experiments, I will be able to investigate the pathogen mechanisms leading to the decline of local populations. Considering the current knowledge and theory on population genetics and EIDs, the hypotheses that will be tested in this application are (1) host differences in susceptibility and mortality have a significant genetic component (2) EIDs are not only causing mass mortalities within populations, but also affect individual development and (3) environmental factors affect the extensive spread of the diseases and the susceptibility of infection. In the context of the global amphibian decline, the program can be viewed as an attempt to bridge ecology and genetics to create a field that might be termed as evolutionary conservation genetics.