Hydrozoan species richness in the Mediterranean Sea: past and present
Article first published online: 17 FEB 2013
© 2013 Blackwell Verlag GmbH
Special Issue: Current Trends in Hydrozoan Biology - VI. Guest Editors: S. Piraino, C.W. Cunningham, F. Boero. CONISMA (Italian National Inter University Consortium for Marine Sciences) and Wiley have published this supplement without financial support.
Volume 34, Issue Supplement s1, pages 41–62, February 2013
How to Cite
Gravili, C., Di Camillo, C. G., Piraino, S. and Boero, F. (2013), Hydrozoan species richness in the Mediterranean Sea: past and present. Marine Ecology, 34: 41–62. doi: 10.1111/maec.12023
- Issue published online: 17 FEB 2013
- Article first published online: 17 FEB 2013
- Manuscript Accepted: 2 OCT 2012
- Ministero dell'Università e della Ricerca Scientifica e Tecnologica
- Ministry of Environment and Protection of Land and Sea
- Mediterranean Sea;
- nonindigenous species;
The Mediterranean hydrozoan fauna (Siphonophora excluded) comprises 400 species; most (68%) occur in the Atlantic Ocean, 20% are endemic to the Mediterranean, 8% are of Indo-Pacific origin, and 4% are non-classifiable. There are 69 nonindigenous (NIS) species in the basin: 44% of these are casual (recorded just one or very few times), 28% established (widely recorded in the basin), 6% invasive (established NIS that are able rapidly or largely to disseminate away from the area of initial introduction, having a noticeable impact on the recipient community), and 22% questionable (of doubtful taxonomic status). Entry through the Suez Canal and range expansion through the Gibraltar Strait, often enhanced by ship traffic, appear to be the main processes for recent species introductions, but uncertainties remain for many NIS. Species additions immediately result in larger local or regional species pools, but the newcomers might impact on populations of native species, altering extinction probabilities. A more reliable evaluation of the species pool can be accomplished by adding new species when they enter the taxonomic record (i.e. the records of any taxon in all types of literature), and by removing species that have not been found for a ‘reasonable’ time (e.g. several decades). Of the 400 non-siphonophoran hydrozoan species known to occur in the Mediterranean Sea, positive records in the last 10 years are available for 156 species (39%), whereas records of the remaining 244 species are older than a decade: 67 species have not been recorded for 41 years, 13 for 31–40 years, 79 for 21–30 years, and 85 for 11–20 years.