Heimioporus subcostatus, a new Boletaceae species from northern and northeastern Thailand

A novel bolete species, Heimioporus subcostatus, is described from northern and northeastern Thailand. It can be distinguished from the other Heimioporus species by its reddish brown to brownish red basidiomata when young becoming dull red to pale red at maturity, with raised and prominent reticulation on stipe, yellow pores, basidiospores with incomplete reticulation, and occurrence in dipterocarp forest dominated by Dipterocarpus spp. and Shorea spp. In a phylogenetic tree based on a three gene (atp6, tef1, rpb2) data set, the new species formed a clade sister to H. sinensis within the supported Heimioporus clade in the Xerocomoideae (Boletaceae). Macroscopic and microscopic descriptions, as well as illustrations of the new species are presented.