The genus Sidera is a polypore genus with resupinate, white to cream or buff fresh basidioma, poroid or hydnoid hymenophore, a monomitic or dimitic hyphal system with generative hyphae bearing clamp connections, the presence of rosette-like crystals and allantoid to lunate basidiospores. We study the phylogeny and diversity of Sidera herein by using both morphological and molecular methods. Phylogenetic analyses are based on the ITS dataset, the combined 2-locus dataset (5.8S + nLSU) and 7-locus dataset (ITS + nLSU + RPB1 + RPB2 + TEF1 + mtSSU + nSSU) of 15 taxa of Sidera all over the world. Among them, four species are new to science and described and illustrated in this paper, viz. S. inflata, S. malaysiana, S. punctata and S. roseo-bubalina. In addition, three taxa were treated as Sidera vulgaris sensu lato. An identification key of the 14 accepted species of Sidera worldwide is provided.
Keywords: Rickenellaceae; phylogenetic analysis; wood-rotting fungi.