Plant pathogens provide clues to the potential origin of bat white-nose syndrome .

White-nose syndrome has killed millions of bats, yet both the origins and infection strategy of the causative fungus, , remain elusive. We provide evidence for a novel hypothesis that emerged from plant-associated fungi and retained invasion strategies affiliated with fungal pathogens of plants. We demonstrate that invades bat skin in successive biotrophic and necrotrophic stages (hemibiotrophic infection), a mechanism previously only described in plant fungal pathogens. Further, the convergence of hyphae at hair follicles suggests nutrient tropism. Tropism, biotrophy, and necrotrophy are often associated with structures termed appressoria in plant fungal pathogens; the penetrating hyphae produced by resemble appressoria. Finally, we conducted a phylogenomic analysis of a taxonomically diverse collection of fungi. Despite gaps in genetic sampling of prehistoric and contemporary fungal species, we estimate an 88% probability the ancestral state of the clade containing was a plant-associated fungus.