A New Concept for the Taxonomy of the Family Dictyosteliaceae (Cellular Slime Molds)

In addition to the typical whorls of branches, fruiting bodies of the genus Polysphondylium bear spores that are characterized by the presence of polar spore granules (PG). This spore character is highly correlated with less easily assessible features of the life cycle such as the nature of the chemotactic response towards cAMP, mode of center initiation, absence of preaggregative cell adhesiveness and overall morphogenetic pattern. Many new strains were isolated which possess the PG character and the cluster of associated features but produce sorocarps which are not regularly branched. This newly recognized group represents a clearly separate unit with common, defined properties. Its taxonomic position in relation to the presently accepted genera of the Dictyosteliaceae, namely Dictyostelium and Polysphondylium , is discussed.