Multi-gene phylogeny and taxonomy of Hydnum (Hydnaceae, Cantharellales) including a global phylogeny of ITS sequences for the genus

<i>Hydnum</i> species are called "hedgehogs" or "tooth fungi" because of their spinose hymenophores. Considering its edible and ectomycorrhizal nature, <i>Hydnum</i> has been found to possess high economic and ecological values. In the present study, a multi-gene (ITS-nLSU-<i>tef1α</i>) phylogenetic analysis and detailed morphological observations of the genus <i>Hydnum</i> were carried out. Based on the distinctive morphological characteristics and the phylogenetic evidence, two new species were described: <i>H. flosculoides</i> <b>sp. nov</b>. and <i>H. robustum</i> <b>sp. nov</b>. from China. Moreover, ITS is the most frequently used DNA region for identification of <i>Hydnum</i> species, but its effectiveness is uncertain. A total of 1,293 ITS sequences of <i>Hydnum</i> could be attributed to six subgenera and four clades with uncertain position (Clade <i>Insulana</i> and Incertae sedis 1, 2, 3), representing 84 morphologically and phylogenetically identified species, 14 putatively new phylospecies and 17 singletons. Furthermore, two new species were described and provided with illustrations. The morphological characters, phylogenetic delimitation, geographic distribution and habitat preferences of <i>Hydnum</i> were discussed, and the effectiveness of the ITS region was also evaluated to enhance rapid identification.