Abstract
In Japan, a fungus described as Mucidula mucida ("Japanese M. mucida", Japanese name: "Numeritsubatake") was identified as M. mucida var. asiatica based on morphological features and phylogenetic analysis of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. This variety differs macromorphologically from M. mucida var. venosolamellata (Japanese name: "Numeritsubatakemodoki") mainly in that the latter possesses reticulate, anastomosed veins on the lamellae. However, mating compatibility tests between M. mucida var. asiatica (="Japanese M. mucida") and var. venosolamellata appeared compatible in all pairings. Furthermore, the basidiomata derived from the mating-compatible mycelia possessed intermediate macro- and micromorphological features between M. mucida var. asiatica and var. venosolamellata. In our molecular phylogenetic tree, the two fungi formed a clade of "Japanese M. mucida"/M. mucida var. asiatica/M. mucida var. venosolamellata, and specimens of the two fungi were randomly scattered within this clade. These results strongly suggest that fungi belonging to the clade should not be divided into intraspecific taxa. Mucidula mucida var. venosolamellata (= var. asiatica) differed from M. mucida var. mucida in their pileipellis structure, basidiospore size and ITS-based phylogenetic analysis. These differences indicate that M. mucida var. venosolamellata and var. mucida are different at the specific level.
