Molecular phylogeography of Mediterranean and Eastern Atlantic sponges of the genus Aplysina.

Aplysina spp. (Verongida: Aplysinidae) are common Demospongiae represented by 2 described species in the Mediterranean and nearby Atlantic. A. aerophoba, shallow and photophilic, is known from the entire Mediterranean and in the Macaronesian archipelagos, down to Senegal on the West African coast. A. cavernicola, almost identical except for a slightly different color and shape, usually lacks symbiotic Cyanobacteria, and has a very different ecology. A. cavernicola is sciaphilic, being often found at cave entrance or under shaded overhangs. It has been reported from the Mediterranean in the western basin to the Gibraltar Straits, in the Adriatic and the Aegean Seas. In some areas such as the NW basin, the two species have very contrasting ecologies which makes them easy to identify. However in areas such as the eastern basin or the Adriatic, the ecological transition is not so sharp and identification is sometimes difficult. Because the main difference lies in their ecology, it has been proposed by some authors to synonimize the 2 species, but the matter has remained unsettled. A third form of Aplysina (here mentioned as "n. sp.") has been found in the Atlantic from the Basque Country to the Algarve coast of Portugal and Madeira. It has the ecology of A. cavernicola but it is much smaller, encrusting, with long budding filaments. Very similar species of Aplysina occur in the Carribean, across the Atlantic, where the diversity of Verongida is high. For comparative purposes, we could study Verongida from the Carribean, Western Australia, and a putative Aplysina aerophoba from Senegal.