DISTRIBUTION AND SYSTEMATICS OF THE FRESH-WATER GENUS TUOMEYA (RHODOPHYTA, BATRACHOSPERMACEAE)

Twenty-seven populations of Tuomeya, including the types of Tuomeya fluviatilis Harvey and Baileya americana Kutzing, were analyzed from the entire known range of the genus: northern Newfoundland to northern Florida and east of the Mississippi River. Key morphological features were examined in detail since it has been recently proposed that Tuomeya should be reduced to a section of the genus Batrachospermum. Our observations confirmed the presence of several characteristics unique to Tuomeya: gametophyte development from a basal mass Of undifferentiated cells rather than a chantransia stage, pseudoparenchymatous growth, and carpogonia with obliquely to perpendicularly attached trichogynes. Based on these findings, we conclude that the genus Tuomeya should be retained. Using multivariate morphometrics, two groupings were found that differed significantly in plant length (XBAR = 14.1 and 24.1 mm, respectively). However, since there was no other morphometric, environmental, or geographic basis for separation of the groupings, only one species is recognized, T. americana (Kutzing) Papenfuss. Populations tend to occur in large streams (>2.8 m wide) with low ion content (less-than-or-equal-to 100 muS.cm-1).