160705.pdf.txt

Abstract

Plant pathogens cause the loss of 20% of global crop yields annually and are poised to become an even larger threat with climate change. The expected warmer temperatures and altered precipitation regimes may increase the replication rate of fungal pathogens, but have uncertain consequences for the epidemiology and evolution of plant-pathogen systems. Using an altitude-for-temperature framework to estimate future climate impacts, we carried out a field study on a plant-pathogen system in the Rocky Mountains of Colorado. We surveyed populations of the subalpine wildflower Linum lewisii at different altitudes and tracked the spread of its fungal pathogen Melampsora lini over the course of a growing season. I found evidence that increases in temperature corresponded to faster spread of the disease within a host plant as well as across a population. Furthermore, through simulations of the system under different scenarios of end-of-century climatic warming, I discovered that fungal pathogen epidemics will become more severe as temperatures increase. I showed that resistance structure in natural populations may explain some of the underlying differences between study populations and demonstrated that populations with greater levels of resistance show slower rates of disease spread. My results have implications for agricultural systems and may help guide better crop engineering interventions to effectively build resilience against the increasing threat of fungal pathogens. Future research should aim to integrate transmission processes across multiple scales of observation, investigate empirically the relationship between plant resistance and pathogen virulence, and track the impacts of disease on population dynamics.