PLASTID DNA RESTRICTION ANALYSIS LINKS THE HETEROMORPHIC PHASES OF AN APOMICTIC RED ALGAL LIFE-HISTORY

Gymnogongrus sp. (Phyllophoraceae) from Nova Scotia, Canada, identified tentatively as G. devoniensis (Greville) Schotter, grows in association with an Erythrodermis-like crust that forms chains of tetrasporangia or bisporangia. The crust resembles tetrasporophytic phases of other Gymnogongrus species, but in culture both it and the G. ?devoniensis gametophytes cycle independently by apomictic reproduction. A method was developed for extracting organelle DNA from this carrageenophyte genus involving purification of nucleic acids by binding to hydroxylapatite. Plastid DNA from G. ?devoniensis and bisporangial Erythrodermis-like crusts was compared with that of G. devoniensis and G. crenulatus (Turner) J. Agardh from France and of G. furcellatue (C. Agardh) J. Agardh from Chile. Plastid genomes of all Gymnogongrus species and the Erythrodermis-like crust were approximately 175 kb long. A single 3.5-kb plasmid DNA species was found in G. ?devoniensis and the Erythrodermis-like bisporophyte but not in other samples. Digestion of plastid DNA with several restriction endonucleases produced identical patterns in G. ?devoniensis and the Erythrodermis-like bisporophyte from the same location, indicating clearly that these entities represent two phases of an uncoupled life history. These results were confirmed with heterologous probes. A restriction fragment length ploymorphism was identified between two Nova Scotia G. ?devoniensis populations. There was no similarity in restriction patterns between G. ?devoniensis from Nova Scotia, G. ?devoniensis from France, G. crenulatus or G. furcellatus, suggesting that molecular taxonomic methods could be important in delineating members of this morphologically variable genus. Further study is necessary to determine whether either Nova Scotian G. ?devoniensis or Franch G. devoniensis corresponds to type populations of G. devoniensis from Devon, England.