Local plants, not soils, are the primary source of foliar fungal community assembly in a C4 grass

Authors: Whitaker, Briana; GIAUQUE, HANNAH - University Of Texas; TIMMERMAN, COREY - University Of Texas; BIRK, NICOLAS - University Of Texas; HAWKES, CHRISTINE - North Carolina State University

Submitted to: Microbial Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2021
Publication Date: 8/18/2021
Citation: Whitaker, B.K., Giauque, H., Timmerman, C., Birk, N., Hawkes, C.V. 2021. Local plants, not soils, are the primary source of foliar fungal community assembly in a C4 grass. Microbial Ecology. 84:122–130. https://doi.org/10.1007/s00248-021-01836-2.
DOI: https://doi.org/10.1007/s00248-021-01836-2

Interpretive Summary: The microbial communities living on plants can greatly contribute to overall plant heath and productivity, but where precisely plants get their microbiomes remains unclear. Researchers discovered that soil fungi only marginally contributed to microbial communities on plant leaves. Other surrounding plants were the primary source of fungi to the leaf microbiome. Additionally, the extent to which other plants contributed to leaf microbiomes was dependent on precipitation with more rain leading to more plant to plant fungal spread. This knowledge can be applied to understanding how microbes spread within natural and agricultural communities.

Technical Abstract: Microbial communities, like their macroorganismal counterparts, assemble from multiple source populations and by processes acting at multiple spatial scales. However, the relative importance of different sources to the plant microbiome, such as locallyabundant hosts or soil, and at what spatial scale assembly occurs, remains unclear. In this study, we tested whether source pool variation in the foliar fungal microbiome of a focal C4 grass differed between locally abundant hosts and soil, or across an abiotic gradient and three different spatial scales. Specifically, we sequenced leaf samples from Panicum hallii, the focal sink host, and two separate plant functional groups, as well as soil, from 10 sites spanning a mean annual precipitation gradient of 400-900mm. The three spatial scales tested limited source pool comparisons to either the local site alone, the local and adjacent sites (regional), or all sites from the gradient. Analyses revealed that the plant functional groups were equally important sources of fungi to the foliar sink and were more important sources at drier relative to wetter sites. Soil fungi were only marginal contributors to the foliar sink. The source-sink analysis, combined with results partitioning source-sink beta-diversity into nestedness and turnover components, indicated high dispersal limitation and/or strong environmental filtering, consistent with predominately local source-sink dynamics. Thus, our results suggest that the source-sink dynamics of foliar fungi are primarily local, but that the abiotic environment may indirectly affect fungal community sourcing via its effect on host communities and plant functional groups.