DISTRIBUTION AND SYSTEMATICS OF THE FRESH-WATER GENUS SIRODOTIA (BATRACHOSPERMALES, RHODOPHYTA) IN NORTH-AMERICA

Multivariate morphometrics and image analysis were used to determine t he number of well-delineated infrageneric taxa of Sirodotia in North A merica. Three groupings were distinguished from 25 populations examine d from Newfoundland and Quebec in the north to central Mexico in the s outh. These groupings were statistically related to 10 type specimens, and the following species were recognized: Sirodotia huillensis (Welw itsch ex W. et G. S. West) Skuja (syn. S. ateleia Skuja), S. suecica K ylin (syn. S. acuminata Skuja ex Flint and S. fennica Skuja), and S. t enuissima (Collins) Skuja ex Flint. These species are differentiated o n the basis of whorl shape and degree of separation at maturity (S. su ecica, rounded and appressed; S. huillensis and S. tenuissima, truncat ed apex and separated), the density of spermatangia (S. huillensis, de nse clusters, S. suecica and S. tenuissima, sparsely aggregated), and the mode of germination of the gonimoblast initial (S. suecica and S. tenuissima,from the nonprotuberant side of the fertilized carpogonium; S. huillensis from the protuberant side). Sirodotia huillensis was fo und only in the desert-chaparral, whereas S. suecica and S. tenuissima occurred from south-temperate to boreal regions in cool (temperature 8-18-degrees-C), low ion (specific conductance 10-99 muS.cm-1), and mi ldly acidic to neutral (pH 5.7-7.3) waters.