Loroxanthin, a Phylogenetically Useful Character in Chlamydomonas and Other Chlorophycean Flagellates1

The distribution of loroxanthin in chlorophycean flagellates is consistent with their phylogeny as inferred from molecular and organismal characters. Although polarity of this character cannot yet be determined, if the absence of loroxanthin is plesiomorphic for chlorophycean flagellates, the presence of loroxanthin defines a clade that includes the Euchlamydomonas morphological group, two other species of Chlamydomonas, C. asymmetrica and C. oblonga, and Gonium pectorale. A subsequent reversal to loroxanthin absence is apomorphic for the more complex volvocacean taxa. These results suggest that loroxanthin distribution will be useful for resolving phylogenetic questions in green algae.