Taxonomic observations on some uncommon and new Gongrosira species (Chaetophorales sensu stricto, division Chlorophyta)

Abstract

Three species of Gongrosira were isolated from freshwater habitats in England and Denmark. Developmental morphology and reproduction of the isolated strains were studied over a wide range of light and temperature regimes by means of a cross-gradient apparatus. Some of the traits traditionally used for defining infraspecific taxa (e.g. comparative development of prostrate and erect branches, position of zoosporangia) were found to be of questionable diagnostic value. New information is provided on previously described species and the isolates compared with cultures of related taxa. Gongrosira scourfieldii was collected from its type locality and culture-based observations have enabled an improved description of this little-known alga. A new species of Gongrosira is described, G. pseudoprostrata L. Johnson nov. sp., characterized by the presence of a well-defined primary prostrate axis and secondary axes. Problems of defining some of the main character traits and the possible ecological implications of the results from culture studies are discussed.