Hourangia, a new genus of Boletaceae to accommodate Xerocomus cheoi and its allied species

Hourangia, a new genus in the Boletaceae, is erected to accommodate Xerocomus cheoi and allied species based on molecular phylogenetic analyses and morphological study. This genus can easily be distinguished from other genera of Boletaceae by the combination of the context of the stipe becoming first bluish, then reddish to brownish red, and finally brownish to blackish when cut, the thick hymenophore being 3–5 (7) times that of the pileal context, and the basidiospore surface with bacillate ornamentation. The phylogenetic analyses based on five gene markers (ITS, nrLSU, tef1-α, rpb1 and rpb2) recognized five distinct taxa. Four of them are treated here, with one undescribed due to lack of adequate material. A key to the four species of Hourangia is provided. Xerocomus punctilifer is treated as a synonym of H. cheoi according to the macro-morphological and micro-morphological comparative study. Epitypes are designated for H. cheoi, H. microcarpa and H. nigropunctata. Phylloporus pumilus, originally described from Indonesia, is transferred to Hourangia.