Functional Diversity in Arbuscular Mycorrhizas: Exploitation of Soil Patches with Different Phosphate Enrichment Differs among Fungal Species

ABSTRACTMost 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 32P 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 33P 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.