Diversity, divergence time, and biogeography of the genus <i>Albatrellus</i> (Agaricomycetes, Russulales)

The genus <i>Albatrellus</i> is an important group of stipitate terrestrial fungi in the order Russulales. Some species in the genus form ectomycorrhizae, mostly with trees of Pinaceae; some are well-known edible mushrooms. However, its diversity and biogeography are unclear. Taxonomic and phylogenetic studies on <i>Albatrellus</i> were carried out by morphological examination, which included detailed observations of the fruiting body, spore shape and size, and other key features, together with potential hosts. These observations were then compared and analysed using multi-locus molecular phylogenetic analyses, including the internal transcribed spacer regions (ITS), the large subunit nuclear ribosomal RNA gene (nLSU), the translation elongation factor 1-α gene (<i>tef1</i>), the largest subunit of RNA polymerase II (<i>rpb1</i>), the second largest subunit of RNA polymerase II (<i>rpb2</i>), the small subunit mitochondrial rRNA gene (mtSSU), and the small subunit of the nuclear ribosomal RNA gene (nucSSU). The results demonstrated that the species of <i>Albatrellus</i> formed eight clades. Nine new species are described and illustrated, and two new combinations are proposed. A total of 38 species are accepted in <i>Albatrellus</i> worldwide. Of those species, 26, 7, and 8 species are distributed in Asia, Europe, and North America, respectively. The divergence time indicated that the maximum crown age of <i>Albatrellus</i> was approximately 70.5 million years ago, and East Asia and North America are the likely ancestral areas. Dispersal and differentiation to other continents occurred during the late Paleocene and Miocene. Three kinds of dispersal routes are proposed: East Asia and Europe, East Asia and North America, and Europe and North America.