A new nivicolous species of Diderma (Myxomycetes) from Kamchatka, Russia

Abstract

A new species of Diderma, described herein as D. kamchaticum, was found on ground litter in subalpine vegetation (National Park "Vulkany Kamchatki") of the Kamchatka Peninsula. The morphology of representative specimens was examined by light and scanning electron microscopy. D. kamchaticum shows a unique combination of morphological characters among the nivicolous species of Diderma and is characterized by large (2-4 mm in diam.), sessile or subsessile sporocaips with a convex sporotheca. The double-layered peridium consists of an egg-shell-like outer layer closely connected with the inner layer; the latter is thin, slightly iridescent, transparent, and shows no visible lime concretions. Other key characters of the new species are the pale translucent tubes of the capillitium (seen under a dissecting microscope), a very large, yellowish white (creamy), subglobose or globose columella, and spinulose spores. The stability of the taxonomic characters of the species was confirmed by several collections obtained in different localities of the National Park. In addition, examination of six specimens of D. meyerae from the French Alps revealed a single European record of D. kamchaticum. A phylogenetic analysis based on partial sequences of two genetic markers (SSU, EF1 alpha) confirmed its separation from other Diderma species with similar morphology. A macro- and micro-morphological description, photographs, and comparisons with the morphologically similar and ecologically related nivicolous species D. alpinum, D. europaeum, D. meyerae, D. microcarpum, and D. niveum are provided.