Inocybaceae (Basidiomycota) in Ectomycorrhizal Symbiosis with Halimium (Cistaceae), and the Description of Two New Species of Inocybe from Sardinia (Italy)

Halimium, Cistaceae, is a genus of shrubs restricted to the western part of the Mediterranean basin, where it thrives in diverse habitats. Despite this ecological adaptability, little attention has been devoted to understanding the mycorrhizal biology of Halimium. Through the examination of both sporocarps and ectomycorrhizal root tip collections, together with a thorough study of data previously reported in the relevant literature, we revealed a rich diversity of ectomycorrhizal mycobiota associated with Halimium spp. In this study, we describe the noteworthy diversity of the basidiomycetous family Inocybaceae in Halimium stands. Some 17 species of Inocybe and Pseudosperma are currently reported as linked to Halimium spp., mostly on the basis of sporocarp occurrence in the proximity of the potential host plant. Of these species, over 40% (7 of 17) come from our own study based on observations in pure Halimium stands in southwestern Sardinia, Italy. We also describe two new species of Inocybe, I. halimiphila sp. nov. and Inocybe rupribes sp. nov., that were collected under Halimium and demonstrated to establish ectomycorrhizal symbiosis with the shrub. We discuss the main morphological and ecological characteristics that distinguish the new species, unveiling their evolutionary relationships by inferring a phylogeny based on multiple loci.