Species interactions and seasonal transmission of fungal diseases in plant populations: experimental tests of historical contingency

The goal of this project is to understand how pathogen transmission can be influenced both by interactions of pathogens within hosts and by the environment. Across humans, non-human animals, and plants, many epidemics are seasonal – that is, they are started or accelerated by shifts in the seasonal environment. Prediction of future epidemics may be improved by a more precise understanding of how shifts in the seasonal environment cause epidemics. A challenge for understanding the causes of seasonal epidemics is that these epidemics often involve ecological interactions such as competition among multiple species of organisms. To address this challenge, this project will conduct a series of experiments under field conditions on interactions between multiple fungal pathogens infecting a shared plant host. To increase the public’s involvement in science, the project scientists will partner with a science museum to apply current methods for effective engagement of the public, to integrate the project’s approaches and findings into K-12 educational curricula, and to develop interactive exhibits for the public. This project will use a model system to develop innovative approaches that can be applied in other systems to understand the causes of seasonal epidemics, improve agricultural practices, and improve our capacity to predict epidemics. Recent theory predicts that the outcome of species interactions between pathogens or parasites within a host individual can be influenced by the community context in which they are embedded. As ecological communities assemble over time, these context-dependent interactions create historical contingency. To resolve the roles of species interactions and environmental conditions in seasonal epidemics, this project will manipulate within-host interactions and quantify disease transmission in the context of seasonally varying environmental conditions. The project will leverage an experimentally tractable field system: two fungal pathogens (Rhizoctoniasolani and Colletotrichum cereale) that infect leaves of the widespread and agriculturally important grass species tall fescue (Lolium arundinaceum). Using this system, the researchers will conduct field experiments that manipulate the history of disease transmission. The project will employ an integrative approach that uses field experiments conducted at two ecological levels – host individuals and populations – and bridges across those levels with a dynamical model. In this integrative framework, the project will investigate additional layers of biological complexity, including the seasonal dynamics of parasite genetic lineages, and influences of the host microbiome on disease transmission. Ultimately, this project will further our understanding of when within-host species interactions, in concert with environmental conditions, can govern seasonal shifts in disease transmission.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.