Revision of the classification system of Radiococcaceae FOTT ex KOMÁREK (except the subfamily Dictyochlorelloideae) ( Chlorophyta)

Abstract

Radiococcaceae (Chlorophyta) is a large and widespread family in terrestrial and freshwater habitats. The taxonomy of this family is difficult because no coherent system of generic criteria exists, fact which led to many species transfers from one genus to another with as a consequence many synonyms. Based on traditional criteria and a study of Radiococcaceae isolated from soils we propose to rearrange the generic system according to only several, easily observable features which are: 1) capacity to form spherical shaped vegetative cells, 2) presence or absence of pyrenoid, 3) number of autospores (only/mainly two or only/mainly four-eight), 4) behaviour of the sporangial cell wall during autospore release (rupture or gelatinisation). As additional secondary criteria are used 5) the capacity to form tubular branched colonies (for separation of the genus Palmodictyon), 6) number of chloroplasts (for definition of the genera Planktosphaeria and Phacomyxa), 7) capacity to form plate-like sarcinoid colonies (for the separation of the genera Dispora and Crucigloea). According to these principles 25 genera (including 10 new genera) comprising about 80 described species are recognised. The system is artifical, but allows to more easily recognise genera and species and also an easier allocation of new taxa.