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

Abstract

O_LIHow antagonists - mycoheterotrophic plants that obtain carbon and soil nutrients from fungi - are integrated in the usually mutualistic arbuscular mycorrhizal networks is unknown. Here, we compare mutualistic and antagonistic plant associations with arbuscular mycorrhizal fungi and use network analysis to investigate fungal association preferences in the tripartite network. C_LIO_LIWe sequenced root tips from mutualistic and antagonistic plants in a tropical forest to assemble the combined tripartite network between mutualistic plants, mycorrhizal fungi, and antagonistic plants. We compared the fungal ecological similarity between mutualistic and antagonist networks, and searched for modules (an antagonistic and a mutualistic plant interacting with the same pair of fungi) to investigate whether pairs of fungi simultaneously linked to plant species from each interaction type were overrepresented throughout the network. C_LIO_LIAntagonistic plants interacted with approximately half the fungi detected in mutualistic plants. Antagonists were indirectly linked to any of the detected mutualistic plants, and fungal pairwise ecological distances were correlated in both network types. Moreover, pairs of fungi sharing the same antagonistic and mutualistic plant species occurred more often than expected by chance. C_LIO_LIWe hypothesize that the maintenance of antagonistic interactions is maximized by targeting well-linked mutualistic fungi, thereby minimizing the risk of carbon supply shortages. C_LI