Urban Biogeography of Fungal Endophytes in Metrosideros Excelsa Across San Francisco

Trees in cities confer health and psychological benefits to the city's inhabitants, so the urban forest is a major component of human health in urban settings. Previous studies have shown that environmental factors can impact endophytic (within-plant) microbial communities of forest trees, but the effects that urban environmental factors may have on these communities are not well understood. Here, we characterized asymptomatic fungal communities in 30 individual Metrosideros excelsa trees from 6 distinct sites using culturing and molecular methods. We found high community diversity both within and among sites, and several patterns within these communities. For example, we found similarities between microbial communities in trees growing downtown and trees growing near a freeway, which indicates that traffic and pollution could impact these fungal communities. These biogeographic patterns indicate that urban microbiomes are perhaps as dynamic and complex as their natural counterparts.