Distribution of benthic polychaetous annelids in the Adriatic Sea with zoogeographic consideration

Abstract

Biogeographia vol. XXIV — 2003 (Printed October, 31st 2003) Marine biogeography of the Mediterranean Sea: patterns and dynamics of biodiversity Distribution of benthic polychaetous annelids in the Adriatic Sea with zoogeographic considerations GRAZIA CAN TONE Dipzzrzinzmto di Biologizz Animzzle qll/[zzrce/[0 La Greta ” Via Arzdrone 8], 1395124 Camnizz (Italy) e—mzzz'[: czziztogm @um'ct. it Key words: biodiversity, biogeography, Polycltaeta, Adriatic Sea, Mediterranean Sea. SUMMARY Purpose of this paper is to estimate the biodiversity oFtl1e benthic Polychaeta along the Adriatic Sea and to discuss their biogeographical distribution. It is shown that from this sea 580 species, belonging to 57 families, have been so far reported: 401 from the northern Adriatic, 373 from the Central Adriatic, 332 from the southern Adriatic. The dominant biogeogrziphical group is constituted by the Atlantic-Mediterranean species, but well represented are also the cosmopolitan and the endemic ones. T he same pattern is present in all the latitudinal sectors of Adriatic, with little differences in the frequencies of the various categories. INTRODUCTION Differently from the biogeography of terrestrial animals that is known long since, the studies on the distribution of marine fauna and the definition of zoogeographical areas for the marine species are still insufficient. In fact for long it has been a widespread belief, because of the continuity of the water, that marine organisms were cosmopolitan. Many famous polychaetologists, (Fauvel, 1923, 1927; Rullier, 1958; Day, 1967) had the same conviction. I-Iolthe, 1978, in his study on the zoogeography of the Terebellomorpha of the Northern European waters, showed that despite of the tendency towards widespread geographical distribution and eurybathy within this class of Annelids, Polychaeta can contribute to the understanding of marine zoogeography. Recently some scientists have been engaged in clarifying the problem of the wide distribution of this taxon that, according to Fauchald, 1984, might depend on its ancient origin, estimated going back to the Precambrian. The “cosmopolitan” species in many cases are complexes of species with different geographic distribution (\Williams, 1984; Hartley, 1984; Dauvin and Thiebaut, 1994) or “sibling” species