The Eye of the Finch: 30 Years of Evolution in an Emerging Avian Pathogen

In October 1993, Mycoplasma galliseptum, MG, jumped the species barrier from commercial poultry into House finches. The pathogen’s presence was first detected by people watching their bird feeders just outside Baltimore. Using a large ‘citizen science’ network of 50,000 bird watchers, the Cornell Lab of Ornithology was able to track the spread of the pathogen across the entire continent. Through the collection and genetic analysis of pathogen samples, laboratory experiments on captive finches, and the development of mathematical models, we have monitored and analyzed the pathogen's evolution at the genomic level and its changing impact on infected hosts. We have also quantified the pathogen's impact at population and community levels across the continent. The project is unusual in that we have been able to integrate studies at all levels of interaction, from selection within pathogens' genomes, through the immunopathology of individual birds, to continental-level impacts on bird communities. The study illustrates that complex epidemiological patterns emerge from a series of nested interactions at a large range of spatial and temporal scales.