The Effects of Climate Change on Plant Pathogen Epidemiology: Melampsora Lini as a Tractable Model for Within-Host Pathogen Spread

Abstract

Fungal pathogens are highly susceptible to changes in climate, and we expect to see subsequent changes in epidemiological patterns over the coming century as environmental conditions shift. These changes threaten the stability and output of food systems worldwide, to which fungal pathogens already significantly destroy each year. In attempt to provide scientific evidence to these challenges, this study investigates the effects of changing climate conditions on the epidemiology of pathogens. Using the fungal pathogen Melampsora lini of the flax wildflower Linum lewisii as a model, I studied the traits of within-host spread across a range of elevations in the Rocky Mountains of Colorado. These elevations capture variations in climate conditions of temperature and humidity. Within-host pathogen spread was measured at four distinct scales: the size of the pustule, the number of pustules on a stem, the total length of stem tissue infected, and the number of infected stems of a plant. I used regression models to examine the impact of temperature and humidity on the spread of disease at each of these scales. These results show that the effects of climate on pathogen spread are nuanced and dependent on the interaction between temperature, humidity, and infection density of a plant. There is also evidence of trends linking the individual within-host scales to each other and to broader population-level epidemics, highlighting the future applications of these methods.