Two new Mycena section Calodontes species: One newly discovered and the other new to Japan

Abstract

In 2017, two candidate species of Mycena were reported from Japan, with the Japanese names "Togari-sakura-take" and "Mitsuhida-sakura-take". However, to date, no taxonomic study or formal description has been undertaken for these two species. In the present study, we conducted comprehensive morphological and molecular phylogenetic examinations of "Togari-sakura-take" and "Mitsuhida-sakura-take", and compared them to known species within the genus Mycena. We performed phylogenetic analyses on a concatenated dataset, including the internal transcribed spacer region of ribosomal RNA, RNA polymerase II largest subunit, and translation elongation factor-1 alpha genes. "Togari-sakura-take" formed a clade with Mycena subulata, which was recently described from China, whereas "Mitsuhida-sakura-take" formed a distinct independent clade. We identified the former as M. subulata based on molecular phylogenetic analyses and morphological observations. However, the Japanese specimens displayed dextrinoid cheilocystidia and caulocystidia as well as the inamyloidity of basidiospores, which differed from the original description of M. subulata based on the materials from China. "Mitsuhida-sakura-take" was characterized by its remarkably dense lamellae and could be distinguished from known Mycena species by the combination of absent pleurocystidia and presence of bowling pin-shaped cheilocystidia. Here, we describe "Mitsuhida-sakura-take" as a new species, named Mycena densilamellata, in the section Calodontes.

Keywords: 1 new taxon; Mycenaceae; molecular phylogeny; morphology; new to Japan.

Fig. 1 - Maximum likelihood (ML) tree of the Mycena sect. Calodontes inferred from concatenated multigene (ITS, RPB1, TEF1) sequences using RAxML. Statistical supports at the nodes are ML bootstrap support (MLBS)/Bayesian posterior probability (BPP). Thick nodes indicate strong support (MLBS≥90 % and BPP≥0.95) and omission of the support value shows less than 60 % in MLBS and 0.90 in BPP. Sequences determined in this study are shown in bold letters and the other sequences were obtained from the NCBI database.

Fig. 2 - Species delimitation based on the genealogical concordance phylogenetic species recognition (GCPSR) concept. Topology of the three-loci-concatenated tree was employed. “Concordance” shows the node that all three independent trees (ITS, TEF1 and RPB1) corresponded to each other, and “Conflict” shows the node that those independent trees did not correspond to each other. Statistical supports at the nodes are ML bootstrap support (MLBS)/Bayesian posterior probability (BPP). (see also Supplementary Figs. S2-S4).

Fig. 3 - Mycena subulata. Macroscopic (A-F) and microscopic (G-N) images. A, B: Basidiomata (A: TUMH 65484; B: TUMH 65483), C: Pileus (TUMH 65485), D, E: Lamellae (D; TUMH 65484, E; TUMH 65485), F: Stipe (TUMH 65483). G: Basidiospore in 3% KOH (TUMH 65484), H: Basidiospores in Melzer's reagent (TUMH 65484), I: Basidium (TUMH 65485), J: awl-shaped cheilocystidia (TUMH 65484), K: Obclavate cheilocystidia (TNS-F-75058). L: awl-shaped cheilocystidia dyeing with Melzer's reagent (TUMH 65483), M: Obclavate cheilocystidia dyeing with Melzer's reagent (TNS-F-75058), N: Caulocystidium dyeing with Melzer's reagent (TUMH 65485). Bars: A, B 15 mm; C-F 5 mm; G, H 5 µm; I-N 10 µm.

Fig. 4 - Mycena densilamellata. Macroscopic (A-F) and microscopic (G-N) images. A, B: Basidiomata (A: TUMH 65481, holotype; B: TUMH 65482), C: Pileus (TUMH 65486), D: Lamellae (TUMH 65482), E: Decurrent lamellae (TUMH 65486), F: Stipes (TUMH 65486). G: Basidiospores (TUMH 65481), H: Pip-shaped basidiospores (TUMH 654826), I: Basidiospores dyeing with Melzer's reagent (TUMH 65481), J: Basidium (TNS-F-75029), K: Cheilocystidium with protruding tip (TUMH 65481). L: Clavate and bowling-pin shaped cheilocystidia (TUMH 65486), M: Hymenium and lamellar edge (TUMH 65482), N: Caulocystidia in Melzer's reagent (TUMH 65486). Bars: A, B 20 mm; C, E 10 mm; D, F 5 mm; G-I 5 µm; J-L, N 10 µm; M 50 µm.