PhD student Ian Miller spent part of his summer outside of Crested Butte, Colorado, studying wild flax and its fungal rust pathogen. The flax-rust system is the classic "gene-for-gene" system, in which pathogens evolve "virulence alleles" that allow them to infect hosts that have evolved "resistance alleles." The ability to infect hosts is always beneficial to pathogens, yet substantial variation in the number of virulence alleles that flax rust pathogens possess has been documented. Why don't all pathogens have all of the virulence alleles? What are the costs infection ability? Miller is investigating how the transmission and host damage rates of rust pathogens change with the presence of virulence alleles, and how this limits the evolution of infectivity.