Faunal affinities of the Sponges (Porifera) of the Balearic Islands with those of other biogeographical areas

An evaluation is made of the affinities of the marine sponge fauna of the Balearic Islands (158 species; Bibiloni, 1990) with those of other biogeographical areas and regions of the world, as well as with those of other Mediterranean areas (on the basis of the literature and interpreting the synonymies), by the simple method of calculating the percentage of Balearic species cited for the other areas considered. With respect to other Mediterranean areas, the greatest affinity of the Balearic sponge fauna is with those in the Gulf of Lyons (79.3%) and the Tyrrhenian Sea (56.8%); with respect to other areas in the world, the greatest affinity is with those in the Mauritanian-Senegalian (46.2%) and boreal regions (45.6%). If the results are compared with those of Vacelet (1980) for the Demospongiae of the whole Mediterranean, the sponges of the Balearic Islands show marked subtropical characteristics.