BIOGEOGRAPHY AND SYSTEMATICS OF BANGIA (BANGIALES, RHODOPHYTA) BASED ON THE RUBISCO SPACER, RBCL GENE AND 18S RIBOSOMAL-RNA GENE-SEQUENCES AND MORPHOMETRIC ANALYSES - 1 - NORTH-AMERICA

Marine and freshwater populations of the red alga Bangia were sampled throughout most of the known geographic range in North America. Marine samples were obtained from the Pacific and Atlantic coasts, central A rctic, Gulf of Mexico, and the Virgin Islands. Freshwater samples came from populations in the Laurentian Great Lakes, St. Lawrence River, a nd Lake Simcoe. In addition, specimens from freshwater populations fro m Italy, England, and Ireland were included for comparison. DNA sequen ce analyses of the Rubisco spacer, rbcL gene, and 18S rRNA gene, plus morphometric analysis, were used to discern possible biogeographic and taxonomic trends. No correlation was detected between the molecular a nd morphological analyses; however, some trends were consistent among the three molecular analyses. For example, all the freshwater collecti ons were nearly identical, indicating that a single lineage may exist in freshwater systems. In addition, the Virgin Islands sample was dist inct from all others in both the rbcL and 18S rRNA gene sequences, but quite similar in morphology to those collections with small filament diameter. The Alaska sample clustered consistently with a primarily At lantic clade with few sequence differences. This finding may indicate a transarctic invasion. Sequence analysis of the 18S rRNA gene yielded a previously unreported intron (in Bangia) located between helices 21 and 20'. All freshwater collections contained this intron, but it was present only in some marine collections. Considerable sequence diverg ence occurred among groups of collections in both the rbcL (0-16%) and 18S rRNA (0-10.6%) genes with little corresponding diversity in morph ology. These values are higher than those reported previously for inte generic, intrafamilial, or interfamilial comparisons in higher red alg al taxa, but are consistent with those reported for the members of the Bangiales. Sequence analysis of the 18S rRNA gene of Bangia collectio ns with six Porphyra species yielded a tree in which Porphyra is parap hyletic within Bangia. In addition, the molecular divergence appears t o be quite low between the two genera.