Plant mycorrhizal status indicates partner selectivity in arbuscular mycorrhizal networks

Mycorrhizal symbioses, specifically arbuscular mycorrhiza, is one of Earth's oldest and most widespread symbioses. Existing evidence suggests that plant species differ in their associations with mycorrhizal partners, with different species reported to be always (obligately mycorrhizal, OM), sometimes (facultatively mycorrhizal, FM), or never (non7 mycorrhizal, NM) associating with arbuscular mycorrhizal (AM) fungi. However, very little is known how host plant mycorrhizal status is shaping network topology of interacting AM fungi. Here, we use a standardized sampling scheme to test whether plant species with different mycorrhizal statuses differ in mean AM fungal hyphal colonization and various indices of the AM fungal networks such as nestedness rank and resource range. We sampled the roots and rhizosphere soil of 19 plant species from five families, each from three distinct habitats. We determined AM fungal colonization in the roots and AM fungal community composition in roots and rhizosphere soil using molecular methods. We found that previously reported NM plant species had lower mean AM fungal colonization than FM plant species, but no differences were found between FM and OM plant species. Network analyses indicated that AM fungal communities in the roots of FM plant species had higher nestedness rank and resource range than networks associated with OM plant species, suggesting that the latter are more generalist regarding partner selection and interact with a wider range of fungal partners. Therefore, plant mycorrhizal status conveys useful information about the characteristics of AM fungal networks, revealing that plant species consistently associated with AM fungi are less selective towards their fungal partners.