Abstract

We carried out a biogeographical analysis of the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chlorophyta), as well as the species in the three genera pooled together, in the western Mediterranean Sea and Adriatic Sea. For this purpose, the continental shelves close to 13 hydrographical watersheds were used as operational geographical units. The analysis was performed in accordance with a hypothetical-deductive approach. Four weak boundaries and five biotic regions were obtained for Audouinella; one strong and two weak boundaries, separating four biotic regions, were found for Cystoseira; two weak boundaries delimiting three biotic regions were obtained for Cladophora. The species of the three genera pooled together allowed us to separate three biotic regions delimited by two weak boundaries. The environmental factors that can explain the presence of the boundaries between biotic regions were run-off, distance of a given region from the Strait of Gibraltar following the course of the main current of the Mediterranean Sea, current flow, and salinity. The characterization of each biotic region and the relationships with the environmental factors that could explain the biotic boundaries are discussed.