An analysis of trichocyte and spore germination attributes as taxonomic characters in the Pneophyllum–Fosliella complex (Corallinaceae, Rhodophyta)

Abstract

Quantitative studies on field populations of five species and on cultured populations of two species of the Pneophyllum (syn. Heteroderma)–Fosliella complex (Corallinaceae, Rhodophyta) have led to the conclusions that trichocyte presence/absence and trichocyte arrangment are influenced by light and temperature and/or vary within field populations to the extent that they are not reliable characters for use in generic delineation. Trichocyte position, in contrast, was constant within hypothallial filaments in all field populations and was not affected by various combinations of light and temperature. In field populations, spore germination resulted in discs with segmentation patterns that were constant within each species; each disc contained either a four-celled or an eight-celled central element. Some variation in spore germination pattern occurred in all culture populations, but in no case did a species with a four-celled central element produce eight-celled variants or vice versa. These results support Chamberlain's conclusion that two genera should be recognized: Pneophyllum for taxa with intercalary hypothallial trichocytes and eight-celled central elements, and Fosliella for taxa with terminal hypothallial trichocytes and four-celled central elements.