The criteria by which plants select symbiotic partners are largely
unknown, but functional complementarity of partner traits could be
important to symbioses such as arbuscular mycorrhizas. Specifically,
coarse-rooted plants are more likely to be limited by nutrient diffusion
compared with fine-rooted plants, and therefore more reliant on fungi
that can compensate with traits that maximize soil exploration. However
there remains no evidence directly linking plant root traits and fungal
functional traits. We transplanted the root microbiome of 30 native and
exotic plant species ranging in root diameter, onto an unrelated host
plant species in multi-compartment pots. We then quantified fungal
hyphal exploration and characterized the fungal community near and far
from roots. We found that arbuscular mycorrhizal fungi from
coarse-rooted plants produced more hyphal biomass and explored further
away from the plant roots. This study provides the first evidence of
functional complementarity between plant roots and arbuscular
mycorrhizal fungi.