Problematical taxonomic criteria in the Chytridiales: comparative morphology of 10 Entophlyctis sp. isolates

Abstract

The criteria generally used in distinguishing taxa among the Chytridiales are size and structure of the zoospores, sporangium wall ornamentations, discharge papillae and tubes, presence or absence and structure of apophyses, nature and structure of rhizoids and number and position of rhizoidal axes, thallus development and relation to the substratum, monocentricity or polycentricity, and operculation. A review of the literature, however, reveals that these criteria are not sharply defined but highly variable and unstable for purposes of exact identification. This variability has become evident from a study of 10 single spore isolates of an Entophlyctis species collected in western Canada and the U.S.A. and grown on pollen grains and a synthetic medium. A comparison of the variations common to all isolates relates this species to several different established species of the genus which grade into one another and result in only three valid taxa, E. apiculata, E. crenata, and E. reticulospora. Also, the variations of the isolates relate this Entophlyctis sp. to different genera, subfamilies, families, and series, and make various current taxonomic dispositions and concepts of little value.