PHYLOGENETIC SYSTEMATICS OF THE ULVACEAE (ULVALES, ULVOPHYCEAE) USING CHLOROPLAST AND NUCLEAR DNA SEQUENCES1

Systematic hypotheses for the Ulvaceae were tested using phylogenetic analysis of sequences for the gene encoding the large subunit of RUBISCO, small subunit rDNA and a combined data matrix. Representatives of eight putative ulvaceous genera and twelve additional taxa from the Ulvophyceae and Trebouxiophyceae were included in analyses using maximum parsimony and maximum likelihood criteria. Molecular data supported hypotheses for the Ulvaceae that are based on the early development of vegetative thalli and motile cell ultrastructure. UlvaceaesensuFloyd and O'Kelly, includingPercursariaBory de Saint‐Vincent,UlvariaRuprecht and a complex of closely related species ofChloropeltaTanner,EnteromorphaLink andUlvaL. was supported; however, monophyly ofEnteromorphaandUlvawas not supported. The Ulvales and UlotrichalessensuFloyd and O'Kelly were monophyletic.BlidingiaKylin andKornmanniaBliding were allied with the former andCapsosiphonGobi with the latter, although relationships among these and other taxa in these orders remain uncertain. The Ulvales are characterized by an isomorphic life history pattern, gametangia and sporangia that are identical in structure and development, motile cells with bilobed terminal caps and proximal sheaths consisting of two equal subunits. Method of motile cell release and the gross morphology of vegetative thalli are not systematically reliable characters.