A study on the intraspecies structure of Scytosiphon lomentaria (Phaeophyceae)

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Scytosiphon lomentaria is a common brown alga in the cold and temperate coasts of the world. In Japan, some genetic diversity have been found in the ITS regions of nrDNA and the mitochondrial cox3 gene. The aim of this study is to delimit the cryptic species in this morphological species, using combinations of ITS2 and cox3 haplotypes that are independently inherited, and to conduct crossing experiments in order to evaluate the delimitation of the cryptic species that was suggested by the haplotype analyses. 90 samples from various localities in Japan were examined, and 26 haplotypes were found in ITS2, and 31 haplotypes in cox3. Results of phylogenetic analyses suggested 8 haplotype groups in ITS2 and 11 haplotype groups in cox3. The combinations of the haplotype groups between ITS2 and cox3 suggested the existence of three cryptic species. Crossing experiments were conducted using cultured isolates of 14 females and 11 males. Results of the crossing experiments suggested three breeding groups. The three breeding groups corresponded to the cryptic species that were suggested by the combinations of the haplotype groups. The present study demonstrated that the analyses of combinations of independently inherited haplotypes are useful for delimitation of cryptic species.