Bryozoan diversity in the Mediterranean Sea

Abstract

Biogeographia vol. XXIV — 2003 (Printed October, 31st 2003) Marine biogeography of the Mediterranean Sea: patterns and dynamics of biodiversity Bryozoan diversity in the Mediterranean Sea ANTONIETTA ROSSO Dz]Jm*tz'772mt0 517' Scimze Geologic/7e (Sezimze Oceanologia e Pzzleoecolagizz), Unit/e7‘5z7n‘z di Czztzmizz (Italy) e—mzzz'[: 727550 @mzict. it Key words: biodiversity. Bryozoa, Recent, Mediterranean. SUMMARY The present study constitutes an updated evaluation of the Mediterranean biyozoan biodiversity aFter the paper by Harmelin (1992) based on Zabala and Maluquer (1988) list, and uses a new data base established using the most recent records of species from the area. This allowed the number of bryozoan taxa known from this sea to be incremented up to 476 species and 27 subspecies grouped into 195 genera and 89 Families, thus outnumbering by 95 species the biodiversity evaluated by Harmelin (1992). The added species include: 1) newly described species from the Gibraltar Straits and the near Alboran Sea, whose distribution appears presently restricted to this area and species previously known from boreal, mostly deep-waters, of the eastern Atlantic and newly reported From the same area; 2) a few new species previously synonimised with Atlantic taxa from which they have been separated recently; 3) some species only recorded from the Adriatic Sea; 4) several species from the eastern basin; 5) a poor stock oF“Non—Indigenous Species” (NIS). Comparisons have been made among Mediterranean bryozoan biodiversity and data from some well known areas and the world as a whole, from which it appears as Mediterranean bryozoans are not extremely diversified, also in relation to the peculiar geological, hydrological and climatic history of this basin. Taxonomic structure at order, family, genus and species rank together with the finding and distribution of some species and their meaning have been discussed. INTRODUCTION Bryozoans are colonial organisms, one of the most diversified benthic phyla, following arthropods, molluscs, Cnidarians and annelids, somewhat paralleling echinoderms and sponges (cf. Bianchi and Morri, 2000). Recent bryozoans are differentiated into three classes with Phylactolaemata exclusively thriving in fresh Waters and Stenolaemata and Gymolaemata almost exclusively represented by fully marine species. These latter show a Wide range of morphological and ecological adaptations enabling them to colonize a great variety of habitats, from the shallow intertidal to abyssal environments, where suitable substrata are available and food supply is enough, only being limited in very starved biotopes and in high sedimentation rate conditions (McKinney and Jackson, 1989). Notwithstanding, their distribution covers all latitudes and they peak in non— tropical continental shelf bottoms largely contributing to benthic diversity (Taylor, 2000).