cludes an ecologically, reproductively, and morphologi-Phylogenetic analyses of nuclear-encoded small-subcally diverse array of biflagellate and quadriflagellate unit rRNA sequences and chloroplast-encoded largetaxa. Two chlamydomonadalean genera, Chlamydomosubunit rRNA sequences from flagellate green algae nas and Carteria, have been the focus of recent phylogerepresenting the order Chlamydomonadales were netic investigations. Results from studies of nuclearfound to show considerable congruence. In general, encoded small-subunit (SSU) rRNA sequence data the chloroplast data set exhibited more robust support (Buchheim et al., 1990;Buchheim and Chapman, 1991) for comparable lineages than the nuclear data set. The and chloroplast-encoded large-subunit (LSU) rRNA sephylogenetic inferences derived from the independent quence data (Turmel et al., 1993) have demonstrated data sets support some, but also challenge many, tradithat the genus Chlamydomonas is tremendously ditional taxonomic and phylogenetic concepts regarding verse at the molecular level and probably does not conthe green flagellates. Results from phylogenetic analystitute a monophyletic group as it is currently deses of both molecular data sets support six distinct linlimited (Buchheim et al., 1990). Similar observations, eages that include taxa from the biflagellate genus, based on studies of nuclear-encoded rRNA data, have Chlamydomonas, and a basal lineage that comprises been made regarding the quadriflagellate genus Cartaxa from the quadriflagellate genus, Carteria. Both teria (Buchheim and Chapman, 1992).
data sets support the conclusion that Chlamydomonas
In the present investigation, we have addressed sevis not monophyletic. Although the chloroplast data are eral unanswered questions from the aforementioned ambiguous regarding the question of Carteria monophylogenetic studies. These include the following. (1) phyly, the nuclear data fail to support Carteria mono-Are hypotheses of nonmonophyly for the genus Chlaphyly. The chlorococcalean genus Chlorococcum was mydomonas (Buchheim et al., 1990) robust to addifound to have affinities with the Chlamydomonadales, indicating that the traditional concepts of both Chlo-tional taxon and character sampling of the nuclear rococcales and Chlamydomonadales may need revi-genes? (2) Using a broad taxon sampling scheme covsion. The genus Dunaliella is allied within the Chlaering several chlamydomonadalean genera, do the mydomonadales, supporting the contention that it chloroplast data corroborate the hypothesis of nonhas lost a typical glycoprotein cell wall.