A new species of Physarum (Myxomycetes) from Christmas Island (Australia)

Abstract

A new species of Physarum (Myxomycetes), described herein as P. australiense, appeared on a sample of aerial litter in a moist chamber culture prepared as part of a survey of the myxomycetes of Christmas Island in the Indian Ocean. The morphology of representative sporocarps was examined by light and scanning electron microscopy, and micrographs of relevant morphological details of sporocarps and spores are provided. The species is characterized by distinct and unique morphological features, including brownish-red lime knobs or large squamae on the surface of the single layered peridium, a limeless brittle, black stalk, a large clavate columella that attains the center of the sporotheca, and a capillitium with large white angular or rod-like nodes. The combination of these characteristics makes P. australiense a well-defined morphospecies when compared to all other species of Physarum. In addition to the morphological description, partial sequences of three genetic markers of this new species (SSU, EF1α, and COI) were obtained and submitted to GenBank. Phylogeny, based on the small ribosomal subunit gene (SSU), indicates an affinity of the new species with P. bogoriense and P. hongkongense.