US-Israel Collab: Are parasites in complex communities more evolvable? Bridging ecology and evolution with computational modeling and rodent-bacteria evolution experiments

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There is a growing appreciation that evolution plays a central role in the emergence and reemergence of infectious diseases. However, our understanding of why some pathogens and parasites rapidly adapt to novel environments, while others don't, remains incomplete. This ability of some parasites to evolve rapidly (i.e., evolvability) allows them to "jump" into infecting new host species. This project will examine whether and how some natural communities of interacting animals and microbes generate conditions that favor the evolution of evolvability. Understanding why variation in evolvability arises can help to identify potential emerging diseases and inform management strategies that reduce their ability to spread. It makes intuitive sense that greater evolvability is beneficial for the parasite, but evolvability does not directly increase the parasite's reproduction or survivorship. Thus, it is less clear how it arises or is maintained in populations. Results from computer simulations suggest that evolvability is advantageous in unpredictable and constantly changing environments. The project uses computer simulations of host-parasite coevolution as well as field and laboratory experiments using a natural bacteria-rodent system to identify specific aspects of parasite ecology that promote or hinder the evolution of evolvability. This project is a collaboration with Israeli scientists. It will develop new computational tools for the scientific community, materials for undergraduate and secondary school classrooms, as well as teacher training and research experience for teachers in Michigan. Parasite populations typically evolve in complex communities, where multiple host species have overlapping ranges, and multiple infections occur within a single host. This project will address four central aims: 1) quantifying the effect of host heterogeneity on parasite evolvability and diversity; 2) measuring how host heterogeneity influences the prevalence and intensity of coinfection by multiple parasite species; 3) identifying the effect of parasite coinfection on evolvability and diversity; and 4) quantifying the combined effects of host heterogeneity and parasite coinfection on evolvability and diversity. Experiments using Avida, a computational platform where digital hosts and parasites evolve in an open-ended fashion, will be complemented by a combination of field-site sampling and laboratory evolution experiments using Bartonella parasites and their wild rodent hosts in the Israeli Negev Dunes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.