Invasive grass dominance over native forbs is linked to shifts in the bacterial rhizosphere microbiome

Abstract

BackgroundRhizosphere microbiomes have received growing attention in recent years for their role in plant health, stress tolerance, soil nutrition, and invasive species dominance. Still, relatively little is known about how these microbial communities are altered under plant competition, and even less about whether these shifts are tied to competitive outcomes between native and invasive plant species. We investigated the structure and diversity of rhizosphere bacterial and fungal microbiomes of native annual forbs and invasive annual grasses individually and in competition using high-throughput amplicon sequencing of the bacterial 16S rRNA gene and the fungal ITS region. We assessed how significant shifts in key microbial families correlate to plant competitive responses through changes in biomass (log competitive response ratios).ResultsWe find that bacterial diversity and structure differ between invasive grasses and native forbs, but fungal diversity and structure do not. Further, bacterial community structures under competition are distinct from both individual forb and grass bacterial community structures. We identified four bacterial families (Burkholderiaceae, Methylophilaceae, Clostridiaceae_1, and Fibrobacteraceae) that varied in relative abundance between treatments and that were significantly correlated with plant competitive responses.ConclusionsInvasive grass dominance may be partially due to effects on the rhizosphere community of native forbs, with changes in specific bacterial families potentially benefiting grasses at the expense of native forbs. Our study underscores the importance of considering plant-rhizosphere interactions for understanding outcomes of plant invasion on grassland ecosystems.