POLYPHYLY OF TETRASPORALEAN GREEN ALGAE INFERRED FROM NUCLEAR SMALL-SUBUNIT RIBOSOMAL DNA

• Published in: Journal of phycology Vol. 34; no. 2; pp. 306 - 311
• Main Authors: Booton, Gregory C, Floyd, Gary L, Fuerst, Paul A
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.04.1998
• Subjects: Brackish; Chaetopeltis; Chlorophyta evolution; Freshwater; Marine; SSU rRNA; Tetraspora; Tetrasporales
• ISSN: 0022-3646; 1529-8817
• DOI: 10.1046/j.1529-8817.1998.340306.x

Ultrastructural studies of tetrasporalean green algae have suggested the order is polyphyletic. These features, including the absolute orientation of the flagellar apparatus and the bi- versus quadriflagellated motile cell morphology, suggest that Chaetopeltis as well as a number of others, may be ancestral to a group that includes Tetraspora. In this study, we examine the phylogenetic relationships of selected tetrasporalean taxa based on analysis of 18S ribosomal RNA gene sequences. Results show that the tetrasporalean taxa are polyphyletic. Biflagellated genera group with biflagellated volvocalean taxa, whereas the quadriflagellated species compose a distinct monophyletic clade not closely related to the biflagellated taxa. In addition, tetrasporalean taxa group with other chlorophycean algal species with similar flagellar apparatus absolute orientation, but the quadriflagellated Tetrasporales do not appear to be ancestral to the entire Chlorophyceae. These results are concordant with previous conclusions drawn from ultrastructural data and further confirm the utility of (small-subunit) ribosomal RNA gene sequences to discern green algal evolutionary relationships.