Host availability drives distributions of fungal endophytes in the imperilled boreal realm

Boreal forests represent the world's largest terrestrial biome and provide ecosystem services of global importance. Highly imperilled by climate change, these forests host Earth's greatest phylogenetic diversity of endophytes, a hyperdiverse group of symbionts that are defined by their occurrence within living, symptomless plant and lichen tissues. Endophytes shape the ecological and evolutionary trajectories of plants and are therefore key to the function and resilience of terrestrial ecosystems. A critical step in linking the ecological functions of endophytes with those of their hosts is to understand the distributions of these symbionts at the global scale; however, turnover in host taxa with geography and climate can confound insights into endophyte biogeography. As a result, global drivers of endophyte diversity and distributions are not known. Here, we leverage sampling from phylogenetically diverse boreal plants and lichens across North America and Eurasia to show that host filtering in distinctive environments, rather than turnover with geographical or environmental distance, is the main determinant of the community composition and diversity of endophytes. We reveal the distinctiveness of boreal endophytes relative to soil fungi worldwide and endophytes from diverse temperate biomes, highlighting a high degree of global endemism. Overall, the distributions of endophytes are directly linked to the availability of compatible hosts, highlighting the role of biotic interactions in shaping fungal communities across large spatial scales, and the threat that climate change poses to biological diversity and function in the imperilled boreal realm.US National Science Foundation (NSF) Dimensions of Biodiversity program [DEB-1045766, DEB-1046167, DEB-1045608, DEB-1046065]; Huron Mountain Wildlife Foundation; Gordon and Betty Moore FoundationGordon and Betty Moore Foundation [GBMF 2550.03]; National Institutes of Health (NIH)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [5 R01 GM1264635]; NSFNational Science Foundation (NSF) [DBI-1759844, TG-DEB090011]; NIH (COBRE grant)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [P30GM103324]6 month embargo; published online: 23 September 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu