Summary

This paper reports a recently discovered population of Caulerpa prolifera in the Azores (NE Atlantic), which becomes the westernmost record of this species in European waters. Morphological, anatomical and molecular characters were investigated for species recognition. The occurrence of the species in the Azores represents a northern expansion of its distributional range, covering now the whole Macaronesia region. It may have been brought by rafting from the western Atlantic through the Gulf Stream, but human-assisted transport may also have been involved in its arrival or dispersion.