New Caledonia is a recognized hotspot of biodiversity where one third of the island surface is composed of ultramafic soils containing high concentration of nickel, chromium, manganese and cobalt.

Arbuscular mycorrhizal fungi (AMF) colonize nearly all the endemic plant species enabling, among others, to reduce metal toxicity. Mycorrhizal populations can vary according to plant species, and also according to the chemical composition of the soils. However, less is known about the diversity of species encountered on ultramafic or non-ultramafic soils. This question is however of prime importance due to the widely hypothesized role of AMF in the tolerance towards high metal concentrations.

Based on molecular analysis of 18S rDNA, we have analysed the diversity of AMF present in different soils. This has been performed within roots of two plant genera: Phyllanthus and Psychotria that are highly represented in both soils and exhibit species that have developed alternative strategies towards the nickel. Indeed, Psychotria gabriellae and Phyllanthus favieri are nickel hyperaccumulators and the comparison of their associated AMF could let us better understand the role of AMF in the tolerance to heavy metals in ultramafic soils.