RIBOSOMAL DNA-SEQUENCES SUPPORT TAXONOMIC SEPARATION OF THE 2 SPECIESOF CHORDA - REINSTATEMENT OF HALOSIPHON-TOMENTOSUS (LYNGBYE) JAASUND (PHAEOPHYCEAE, LAMINARIALES)

The brown algal family Chordaceae contains the single genus Chorda wit h two terete unbranched species, C. filum and C. tomentosa. They share a similar superficial morphology, but differences in anatomy and repr oductive characters have made assignment to a single genus controversi al. Comparison of DNA sequences of variable parts of the small subunit of the nuclear ribosomal cistron, and of relatively conserved areas o f both internal transcribed spacers, of several taxa of the Sporochnal es-Desmarestiales-Laminariales complex revealed that the two species o f Chorda are not closely related and do not form a clade. This is take n as support for recognition of Halosiphon tomentosus (Lyngbye) Jaasun d, although it was originally based on the erroneous observation of a Streblonema-like gametophyte in the life history of H. lomentosus.