Functional diversity in arbuscular mycorrhizas: exploitation of soil patches with different phosphate enrichment differs among fungal species

ABSTRACT Most terrestrial plant species form associations with arbuscular mycorrhizal fungi (AMF) that transfer soil P to the plant via their external hyphae. The distribution of nutrients in soils is typically patchy (heterogeneous) but little is known about the ability of AMF to exploit P patches in soil. This was studied by growing symbioses of Linum usitatissimum and three AMF ( Glomus intraradices , G. mosseae and Gigaspora margarita ) in pots with two side‐arms, which were accessible to hyphae, but not to roots. Soil in one side‐arm was either unamended (P0) or enriched with P; simultaneous labelling of this soil with 32 P revealed that G. intraradices responded to P enrichment both in terms of hyphal proliferation and P uptake, whereas the other AMF did not. Labelling with 33 P of P0 soil in the other side arm revealed that the increased P uptake by G. intraradices from the P‐enriched patch was paralleled by decreased P uptake by other parts of the mycelium. This is the first demonstration of variation in growth and nutrient uptake by an AMF as influenced by a localized P enrichment of the soil. The results are discussed in the context of functional diversity of AMF.