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Title: A heritable symbiont and host-associated factors shape fungal endophyte communities across spatial scales

item HARRISON, JOSHUA - University Of Nevada
item PARCHMAN, THOMAS - University Of Nevada
item Cook, Daniel
item Gardner, Dale
item FORISTER, MATTHEW - University Of Nevada

Submitted to: Journal of Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2018
Publication Date: 2/26/2018
Citation: Harrison, J.G., Parchman, T.L., Cook, D., Gardner, D.R., Forister, M.L. 2018. A heritable symbiont and host-associated factors shape fungal endophyte communities across spatial scales. Journal of Ecology. 1-13.

Interpretive Summary: Microbial ecologists have traditionally focused on characterizing the abiotic factors, and host-associations that filter microbial taxa from regional species pools into local hosts. Our study adds to the emerging perspective that, in addition to these filters, biotic interactions among microbes fundamentally affect microbial community assembly. Just as keystone species disproportionately influence communities of macroorganisms, we report that a dominant, heritable, plant-associated fungus mediates assembly of co-occurring symbiotic fungi at both regional and local geographical scales.

Technical Abstract: Microbial ecologists are intensely interested in the processes governing microbial community assembly, progress has been limited by a lack of studies that span multiple geographical scales and levels of biological organization. High throughput sequencing was used to characterize foliar fungal endophyte communities and host plant genetic structure both within, and among, 24 populations of spotted locoweed (Astragalus lentiginosus) across the Great Basin Desert. Across the Great Basin, both within, and among populations of the host plant, fungal endophyte richness was predicted by plant size and variation in the seed-borne, heritable fungus, Alternaria fulva, which produces the bioactive alkaloid swainsonine. The degree of between-plant turnover in the endophyte community was inversely related to host plant inbreeding and average plant size, and positively related to the relative abundance of A. fulva. Plant size was inversely related to endophyte community richness, both among, and within populations. The genetic and physical distance between host populations was not predictive of differences in fungal community structure. Through pairing intensive local- and regional sampling, we uncovered a primacy of deterministic forces imposed by a heritable symbiont on the community structure of locoweed endophytes.