Peering into the Mediterranean black box: ectomycorrhizas on .

We describe the morpho-anatomical features of the ectomycorrhizas (ECMs) formed by on , a genus of about 20 species of woody shrubs typical of the Mediterranean maquis. The description of mycorrhizas on is the first ECM description of a species belonging to subgen. . The ECM identity was verified through molecular tools. Anatomically, the characteristic of mycorrhiza is the presence of abundant, long "bottle-shaped" cystidia on mantle surface. Indeed, the overwhelming majority of milkcap mycorrhizas are acystidiate. This is the third mycorrhiza to have been described associated with , the others being and . The phylogenetic distance between all these taxa is reflected by the diversity of the principal features of their ECMs, which share host-depending ECM features known for but are otherwise distinguishable on the host roots. Comparison of ECM with those formed by and on reveals elevated intrageneric diversity of mycorrhizal structures. Such a diversity is supported by analysis of ITS sequences of relevant species within European species. Our study extends knowledge of mycorrhizal biology and confirms the informative value of mycorrhizal structures in understanding phylogenetic relationships in ECM fungi.