PHYLOGENY OF THE VLE-14 CHLAMYDOMONAS (CHLOROPHYCEAE) GROUP - A STUDYOF 18S RIBOSOMAL-RNA GENE-SEQUENCES

Comparative specificity of sporangial wall autolysins (i.e. vegetative lytic enzymes [VLE]) derived from sporulating cultures has been wed t o group Chlamydomonas taxa into 15 different VLE types. The VLE-14 gro up including isolates of C. geitleri, C. noctigama, C. monoica, C. pin icola, C. terricola, and C. hindakii, is one of the largest of these V LE groups. Genetic studies have shown that a number of the VLE-14 taxa are interfertile, albeit with little or reduced viability of progeny. A reevaluation of the VLE-14 group suggested that all members should be regarded as distinct isolates of C. noctigama. The present investig ation tests the phylogenetic implications of the VLE evidence and exam ines the validity of the taxonomic reevaluation in a phylogenetic cont ext by analysis of 18S rRNA gene sequence data. Results from analyses of the sequence data are consistent with an interpretation of the VLE evidence as indicative of monophyletic taxa. Phylogenetic analyses of the sequence data are also consistent with the taxonomic reevaluation and reidentification of the group. However, at least some of the VLE-1 4 isolates studied in this investigation fit criteria for distinct bio logic or phylogenetic species. It is concluded that the VLE-14 taxa re present a very closely allied group that includes some isolates that a re in the early stages of speciation by reproductive isolation.