LOW DIVERGENCE IN RDNA ITS SEQUENCES AMONG 5 SPECIES OF FUCUS (PHAEOPHYCEAE) SUGGESTS A VERY RECENT RADIATION

Sequences from the two ribosomal DNA internal transcribed spacers (ITS 1 and ITS2) were compared among five species of Fucus. Based on the pr esent taxon sampling, parsimony analysis showed that Fucus serratus is the sister-group of the remaining Fucus species when Ascophyllum nodo sum was used as an outgroup. The topology of the tree was (Fucus serra tus (F. lutarius (F. vesiculosus (F. spiralis + F. ceranoides)))). The extremely low variation observed suggests a very recent radiation of the genus which supports the view widely accepted that the Fucales are among the most evolutionarily advanced of the brown algae. We further note that sequence differences between Fucus and Ascophyllum were 28% : this does not rule out the utility of ITS sequences within the Fucac eae. The very low number of informative positions allows to demonstrat e empirically that distance matrix methods group on the basis of sympl esiomorphies.