Host evolution in the wake of contemporary outbreaks of disease

HOST EVOLUTION IN THE WAKE OF CONTEMPORARY OUTBREAKS OF DISEASE Project Summary/Abstract In the wake of the spillover or introduction of a novel parasite or pathogen into a naïve host population, attention focuses on the resulting host morbidity and mortality. However, emerging disease has much broader effects on host populations, including demographic shifts, life history changes, and genetic and epigenetic evolution. These extended effects have shaped human evolution and remain relevant in an era of biodiversity loss and increasing zoonotic disease risk. Nevertheless, studying the evolutionary consequences of disease remains challenging because historical disease events leave diffuse and complex genomic signatures and because attributing changes in the host population to parasites can be difficult without adequate replication and controls. The investigating team works in the Galapagos Islands, an iconic natural laboratory, to study the real-time evolution of hosts to emerging disease. Over the next five years, the team will leverage the natural experiments created by two separate parasite introductions that occurred ~125 years ago and ~25 years ago to study changes in avian host populations in response to these novel challenges. The Galapagos songbird (passerine) community is dominated by two endemic radiations: Darwin’s finches and Galapagos mockingbirds. The species within each of these groups provide the replication to test hypotheses about how host defenses against disease arise and spread, and to determine how repeatable co-evolution is between hosts and novel parasites. Three fundamental questions guide the overall focus on how hosts change in the wake of emerging disease: 1) How do population size and genetic diversity govern adaptation to a novel virus? Variation in host population size and parasite pressure among Galapagos islands will help identify how demography and diversity shape the response to hosts to novel disease. 2) What mechanisms underlie adaptation to a novel virus? The team’s existing work uniquely prepares them to study to what extent regulatory and epigenetic changes drive host adaptation to novel pathogens and how routes to adaptation may vary among host species. 3) How do hosts evolve in response to a novel parasite? Contemporary host genomes will be compared to host genomes from before the parasite introduction to identify regions and genes under selection. With over a decade of experience working in the Galapagos Islands and extensive local connections, the McNew Lab is uniquely prepared to conduct the ambitious experiments in the study of host-parasite coevolution. The results will illuminate the processes that shaped human evolution and anticipate consequences of future emerging diseases on Earth.