Diachea mitchellii: A new myxomycete species from high elevation forests in the tropical Andes of Peru.

A new species of the genus Diachea (order Physarales, Myxomycetes, Amoebozoa) is described from Peru. Relevant details on spore germination, as well as morphological and phylogenetic data, are provided. At first glance, the new species shares some morphological similarities with both D. leucopodia, type of the genus, and D. koazei, but it strikingly differs from all other species of its genus by combining a short dark stalk, with a reticulate columella, and clustered spores. Moreover, it seems to be the only species of Diachea exclusively associated with Polylepis tropical forests at elevations above 3500 m. Apart from a comprehensive morphological study of 31 specimens, we here provide phylogenetic evidence to confirm the inclusion of this species in the genus Diachea. Specifically, our phylogenetic analyses of the nuclear 18S rDNA (18S), mitochondrial 17S rDNA (17S), and elongation factor-1 alpha (EF-1α) genes show that the new species is related to D. leucopodia and D. bulbillosa. The remarkably different morphological characters distinguishing the new Diachea from all other species of its genus, along with its particular ecological preferences and geographic distribution, indicate that it is a distinct entity deserving recognition as an independent species.

Didymium pseudonivicola: A new myxomycete from the austral Andes emerges from broad-scale morphological and molecular analyses of D. nivicola collections.

A new nivicolous myxomycete is described as a result of a comprehensive study of Didymium nivicola collections from the entire range of its occurrence. Statistical analysis of 12 morphological characters, phylogenetic analyses of nuc 18S rDNA and elongation factor 1-alpha gene (EF1A), and a delimitation method (automatic barcode gap diversity) have been applied to corroborate the identity of the new species. A preliminary morphological analysis of D. nivicola revealed high variability of South American populations where four types of spore ornamentation were noted. However, results of molecular study and statistical analysis of morphological characters did not support recognition of these four forms but the distinction of two morphotypes. Consequently, two species have been recognized: D. nivicola and the newly proposed D. pseudonivicola. The new species can be distinguished from D. nivicola by distinctly larger and mostly plasmodiocarpic sporophores, which are scattered to gregarious, paler spores, and by the paler, more delicate and more elastic capillitium. Spore ornamentation of D. pseudonivicola is uniform and can be described as distinctly spiny (pilate under scanning electron microscope [SEM]), whereas those of D. nivicola is more variable, where spines (pilae under SEM) are delicate, distinct, or conspicuous. Additionally, whereas D. nivicola is a species distributed worldwide, D. pseudonivicola occurs only in the austral Andes of Argentina and Chile.