Plant cheaters preferentially target arbuscular mycorrhizal fungi that are highly connected to mutualistic plants

Abstract

AbstractTo address how arbuscular mycorrhizal networks sustain cheaters – mycoheterotrophic plants that obtain both carbon and soil nutrients from fungi – here we investigate how mutualistic and antagonistic mycorrhizal networks are interlinked.We sampled root tips of mutualistic and cheater plants in two tropical forest plots and assembled the combined network between fungi linked to mutualistic and cheater plants (i.e., tripartite network) using DNA sequencing. We compared the interactions of the fungi in the mutualistic and antagonistic networks and searched for motifs (simple subgraphs that are overrepresented in complex networks) representing simultaneous links of particular mutualist and cheater plants to pairs of fungi to investigate fungal association preferences.Within the tripartite network, cheater plants are highly connected and interact with the majority of available fungal partners (74%), and we find that fungi that share interactions with the same mutualistic plants also share interactions with sets of cheaters. The motif analysis demonstrates that cheaters preferentially interact with sets of fungi that are linked to particular plant species.Our findings indicate that cheaters preferentially interact with fungi that are well-connected to particular mutualistic plants. We hypothesize that these non-random interactions may result from trait-based selection and that this strategy maximizes carbon availability for cheaters.