To clarify deep relationships among species lineages within Bacidia s. str., and to investigate the robustness of the deeper branches, we combined data from three traditionally used RNA-coding genes (nrITS, nrLSU and mtSSU) with two protein-coding genes (RPB1 and RPB2). The multigene phylogeny contained 48 newly generated sequences from the Russian Far East and all Bacidia s. str. sequences from GenBank (131 sequences). We subjected the alignments for the single and concatenated data sets to Bayesian inference (BI) and two maximum likelihood (ML) analyses (RAxML and IQ-TREE). The topologies of phylogenetic trees recovered from BI and ML analyses were highly concordant. The multilocus phylogeny of Bacidia s. str. was congruent with previous results based on nrITS sequences from the Russian Far East but with considerably higher support values for most of the deeper branches. A correlation between the recovered clades and apothecial pigments in the upper part of the hymenium and lateral exciple was observed. Based on morphological and molecular evidence, Bacidia obtecta is described as new to science. It was recovered as the sister lineage of B. elongata. The two species are alike in having up to four enlarged lumina cells along the exciple edge, but B. obtecta differs in the abundant crystals found in the upper hymenium and lateral exciple, and by having spores with fewer septa.

Leiorreuma subpatellulum is described as new to science. The new species has a completely carbonized exciple, an inspersed hymenium and brown ascospores with 6–12 locules, tapering at one end.