Our research explores how fungal biodiversity originates, evolves, and changes through time. We use phylogenetics, systematics, genomics, and natural history collections to investigate species boundaries, diversification, host specialization, and the evolutionary processes that generate fungal diversity. Although more than 150,000 fungal species have been formally described, estimates suggest that millions remain undiscovered, leaving major gaps in our understanding of fungal evolution and ecology.

Powdery mildews are one of our primary systems for studying these questions. These obligate plant pathogens comprise hundreds of species associated with diverse plant lineages and provide a powerful framework for investigating host shifts, specialization, geographic isolation, and diversification. Recent work from our lab has shown how host specialization can remain hidden despite nearly identical commonly used DNA barcodes, reconstructed the global movement of pathogens alongside their cultivated hosts, and revealed distinct evolutionary histories of closely related pathogens infecting the same crop species (Bradshaw et al. 2025, New Phytologist, Crouch et al. 2026, Proceedings of the National Academy of Sciences ). By integrating molecular data with morphology, host associations, geography, and historical specimens, we reconstruct evolutionary relationships and examine how fungal lineages have diversified across hosts and environments.

Our work extends across diverse groups of fungi and combines species discovery with broader evolutionary questions. We have described more than 50 fungal taxa, but describing biodiversity is only one part of this work. Accurate taxonomy provides the foundation for recognizing biological patterns that can otherwise remain hidden, including differences in host range, geographic distribution, evolutionary history, and disease emergence (Bradshaw et al. 2026, Plant Disease). By resolving species boundaries and evolutionary relationships, we can uncover previously unrecognized host shifts, cryptic specialization, and patterns of pathogen movement. Through this research, we aim to understand both the diversity of fungi and the evolutionary processes responsible for generating and shaping it.

Powdery mildew diseases on strawberry (A), raspberry (B), and blueberry (C, D), with representative sexual (E, G) and asexual (F, H) structures. Powdery mildews are widespread, obligate plant pathogens that infect thousands of plant species worldwide.