BIOGEOGRAPHY OF BATRACHOSPERMUM-GELATINOSUM (BATRACHOSPERMALES, RHODOPHYTA) IN NORTH-AMERICA BASED ON MOLECULAR AND MORPHOLOGICAL DATA

Fifteen populations of the widespread freshwater red alga Batrachosper mum gelatinosum (L.) De Candolle were sampled throughout the geographi c range in North America from central Alabama, U.S.A. (33 degrees N), to Ellesmere Island Northwest Territories (NWT), Canada (80 degrees N) . Analysis of ribosomal DNA internal transcribed spacer (ITS) 1 and 2 sequences yielded a parsimony tree with a large polytomy consisting of most populations plus a branch with one Nova Scotia and two NWT popul ations. The nucleotide variation, both within the polytomy and within the branch, was small (<1%). The sequence divergence between the branc h and polytomy was 3%. The lengths of the ITS 1 and 2 sequences of B. gelatinosum, 216-229 and 448-458 base pairs, respectively, fall within the very broad ranges reported for other red algae. The cluster analy sis of 11 morphometric characteristics revealed three groupings of pop ulations, partly based on geographic distribution. All tundra, eastern boreal forest, and midwestern hemlock-hardwood populations were in on e grouping, whereas the deciduous forest, coastal plain, and eastern h emlock-hardwood populations were in a second. However, one deciduous f orest population from Rhode Island, U.S.A. was unassociated. There was considerable overlap in morphometric characteristics among the three groupings. Based on this fact and the relatively small nucleotide vari ation in ITS sequences, we conclude that B. gelatinosum is a morpholog ically variable and geographically widespread species that is a valid taxonomic entity.