Dr. Michael Bradshaw
HUH Research Fellow
Harvard University

Title: Powdery mildews: The world’s best plant taxonomists

Abstract: Molecular clocks placed the evolution of powdery mildews, ~40 million years after the first appearance of angiosperms in the fossil record, during the Cretaceous period around 100 million years ago (MYA). Their radiation occurred ~76 MYA coinciding with the large-scale radiation of the angiosperms (~108-91 MYA). The rapid diversification of angiosperms led to a radiation event of host specific fungi within these Ascomycota and there are now over 900 species of powdery mildews that infect an estimated 10,125 angiosperm hosts. In groups of fungi that have co-evolved with their host plants, it is inevitable that in areas representing high plant diversity, such as botanical gardens, there will be concomitant levels of increased fungal diversity. In this study I set-up a citizen science project in botanical gardens throughout North America to determine the level of fungal diversity present in these living museums. Additionally, I mined publicly available databases to ascertain the host range/preference of powdery mildews and their geographical spread. In this research, I used phylogenetic approaches, to reveal that there is more species diversity in powdery mildews than detected in traditional morphological studies and they tend to be highly host specific with an evolutionary history that often mirrors their angiosperm hosts.

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