DNA fingerprints of Caulerpa taxifolia provide evidence for the introduction of an aquarium strain into the Mediterranean Sea and its close relationship to an Australian population

The occurrence of Caulerpa taxifolia in the Mediterranean Sea was reported for the first time in 1984. Since then the alga has spread rapidly and is n ow considered to be a potential threat to sublittoral ecosystems. Two hypot heses on the origin of the Mediterranean strain of C. taxifolia have been d iscussed in the literature. One hypothesis assumed migration of the alga fr om the Red Sea, the other introduction via a public aquarium. The hypothesi s of a descent from an aquarium strain has been supported strongly by recen t studies based on DNA sequences. The DNA fingerprints of C. taxifolia pres ented here also provide evidence for the descent of the Mediterranean C. ta xifolia from an aquarium strain. Furthermore, the present study shows that a strain of C. taxifolia from Manly Harobur/Moreton Bay (Australia) is clos ely related to the aquarium/Mediterranean strain. The feasibility of detect ing similar genotypes by restriction digests of total DNA is demonstrated, which will facilitate the ongoing search for further relatives of Mediterra nean C. taxifolia.