A new iridescent corticolous myxomycete species (Licea: Liceaceae: Liceales) and crystals on American elm tree bark in Texas, U.S.A.

Abstract

A Licea species new to science is described on the bark surface of living American elm (Ulmus americana L.) cultured in moist chambers. It is characterized by an iridescent peridium on the sides of the sporangium, a black apical circular patch of globular debris, and dark reddish black spores that are smooth over half the surface and ridged-reticulate over the other half with the paler thinner wall collapsing into a coffee-bean shape. This combination of morphological characters is distinct and separates this taxon from all other species of Licea. The history of moist chamber culture use and field collection of corticolous myxomycetes is reviewed. The discovery of crystals of unknown origin on the bark surface of American elms associated with Licea species are illustrated with light microscope photography and scanning electron microscopy. Light microscope images and habit photographs were made using multi-focus imaging and computer stacking to increase depth of field and provide illustrations in color of sporangial structures of the new Licea species. This tiny short-stalked Licea approximately 100 um in height, and with distinctive external and internal morphological characters, was photographed using scanning electron microscopy. Dark-spored versus light-spored species of Licea are reviewed and compared with the most recent molecular analysis as this relates to the genus Licea. This paper is the first in a series that will document the discovery of Licea fruiting bodies of four new species on American elms in nature parks near Fort Worth, Texas.