Genetic affinity of Ectocarpus siliculosus (Dillw.) Lyngb. from the Mediterranean, North Atlantic and Australia

Abstract

Sexual compatibility in the marine brown alga Ectocarpus siliculosus was studied using clonal laboratory cultures from various geographic areas. Complete interfertility was found in European material ranging from the Mediterranean to Norway. Plasmogamy was also found between strains from Florida, North Carolina and all European clones. Male and female plants from Massachusetts were almost fully, female plants from Texas partially sterile with strains from other localities. In addition, South Australian Ectocarpus siliculosus was interfertile with almost all other strains examined. These findings are interpreted to show that local populations of the species are related closely enough to permit plasmogamy on a world-wide basis. Some local populations (Massachusetts and Texas), however, are in the process of isolating themselves from the original gene pool.