A map location of the New Caledonia archipelago including sites used in the current study is presented in Fig. 1. The ultramafic sites were located in the south of the main island: Bois du Sud (site1, Fig. 1) and Mont Dore (site 2, Fig. 1), and located in the north of New Caledonia: Pindaï Peninsula (site 3, Fig. 1) and Koniambo Massif (sites 4 and 5, Fig. 1). A full description of the ultramafic sites including climate, geology, geomorphology, vegetation structure, site geographical location, soil sampling and mineral analyses has been previously described in Jaffré (1992). The ultramafic topsoil geochemical analyses from the different sites were carried out as reported in Perrier et al. (2006b) and data are summarized in ESM Table 1. The description of Pisolithus albus isolates used in this study is presented in Table 1, which includes isolate codes, site loca-
tion of collection, DNA ITS Genbank accession number, ergosterol content of mycelium cultivated in vitro (the method is described in more detail below) and references.