Parallela Flint: its phylogenetic position in the Chlorophyceae and the polyphyly of Radiofilum Schmidle

Abstract

Novis P.M., Lorenz M., Broady P.A. and Flint E.A. 2010. Parallela Flint: its phylogenetic position in the Chlorophyceae and the polyphyly of Radiofilum Schmidle. Phycologia 49: 373–383. DOI: 10.2216/09-65.1Analysis of chloroplast protein sequences from the genes atpB, rbcL and psaB demonstrates that the ribbon-forming freshwater alga Parallela novae-zelandiae is a member of the Chlorophyceae. We reject earlier classifications of Parallela as a member of the Tetrasporales or Gloeotilales and also confirm the splitting of the latter order. Molecular analysis shows that it is closely related to Radiofilum transversale but not R. conjunctivum, the latter associating with green algae having counterclockwise-displaced flagellar apparatuses. Since R. conjunctivum is the type species of the genus, we refer R. transversale to Parallela transversale. The two species of Parallela share a ribbon-forming mucilaginous habit and an absence of pyrenoids and layered mucilage. Parallela novae-zelandiae differs from P. transversale in lacking bipartite cell walls and has consistently multiseriate filaments, which are only sporadically present in P. transversale and are entirely absent in R. conjunctivum and other described species of Radiofilum. Radiofilum conjunctivum also contains pyrenoids. The bipartite wall condition has apparently evolved more than once during the evolution of the Chlorophyta.