Biotic filtering of endophytic fungal communities in Bromus tectorum
The assembly of horizontally transmitted endophytic fungi within plant tissues may be affected by “biotic filtering”. In other words, only particular endophytic fungal taxa from the available inoculum pool may be able to colonize a given plant species. We tested that hypothesis in Bromus tectorum, an important invasive species in the arid, western United States. We collected seed from Bromus tectorum and sources of inoculum for endophytic fungi including soil and various kinds of plant litter at a field site in central Utah. We characterized, using Illumina sequencing, the endophytic fungal communities in the various inoculum sources, inoculated Bromus tectorum seedlings under gnotobiotic conditions with the various sources, and then characterized the communities of endophytic fungi that assembled in their roots and leaves. Different inoculum sources containing significantly different endophytic fungal communities produced complex communities of endophytic fungi in leaves and roots of Bromus tectorum. In leaves, the communities assembling from the various inoculum sources were not significantly different from each other and, in roots, they were only slightly different from each other, mainly due to variation in a single fungal OTU, Coprinopsis brunneofibrillosa. Consequently, there was significantly more variation in the structure of the communities of endophytic fungi among the inoculum sources than in the resultant endophytic fungal communities in the leaves and roots of Bromus tectorum. These results are consistent with biotic filtering playing a significant role in endophytic fungal community assembly.
KeywordsCommunity assembly Horizontal transmission Inoculum Plant–microbe interactions Symbiosis
Funding was provided by Brigham Young University, The Charles Redd Center for Western Studies, The Roger and Victoria Sant Endowment for a Sustainable Environment, and the Sustainable Bioenergy Research Program of the USDA National Institute of Food and Agriculture (# 2011-67009-20072).
Author contribution statement
KDR and RTK conceived the study and collected the data. KDR analyzed the data. KDR and RTK wrote the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest. We thank three anonymous reviewers for comments leading to substantial improvements in the manuscript.
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