Abstract
Sidera, belonging to the Rickenella clade of Hymenochaetales, is a worldwide genus with mostly poroid hymenophore of wood-inhabiting fungi. Two new species in the genus, Sideraamericana and S.borealis, are described and illustrated from China and North America based on morphological and molecular evidence. They were mainly found growing on rotten wood of Abies, Picea and Pinus. S.americana is characterized by annual, resupinate basidiomata with silk sheen when dry, round pores (9-11 per mm), a dimitic hyphal system, and allantoid basidiospores measuring 3.5-4.2 × 1 μm. S.borealis is characterized by annual, resupinate basidiomata with cream to pinkish buff dry pore surface, angular pores (6-7 per mm), a dimitic hyphal system, and allantoid basidiospores measuring 3.9-4.1 × 1-1.1 μm. Phylogenetic analysis based on a combined 2-locus dataset [ITS1-5.8S-ITS2 (ITS) + nuclear large subunit RNA (nLSU)] shows that the two species are members of Sidera, and they are compared with morphologically similar and phylogenetically related species, respectively. An identification key to 18 accepted species of Sidera in worldwide is provided.