Mediterranean Syllidae (Annelida:Polychaeta) revisited:: biogeography, diversity and species fidelity to environmental features

The species diversity of Syllidae (Annelida: Polychaeta) on different coastlines within the Mediterranean Basin was analysed, including along the Salento Peninsula (Italy), which is thought to play a crucial role as a crossroads between different biogeographic areas. Analysis of biogeography, the assignment of species into 6 bioclimatic categories, a novel method to assess inter-matrix correlation significance and the correlation between species distribution, and some environmental variables provided relevant tools to investigate the influence of a suite of ecological and historical factors on syllid distribution. Data showed that Syllidae could be considered a useful taxon for biogeographic speculations, even though bioclimatic and environmental analyses appeared significantly more informative. The Salento Peninsula revealed an affinity with some eastern Mediterranean coastlines. Syllid distribution suggested the existence of an 'Atlantism' gradient, decreasing eastwards and possibly corresponding to a temperature gradient when bioclimatic categories were analysed. In contrast to previous results, the Eastern and Western Basins did not show great differences in species diversity. The observed differences could, in part, be due to an 'author effect', due to the differing taxonomic updating of the available faunistic lists. Syllidae were found to be effective faunistic and ecological indicators, able to characterize different areas inside the Mediterranean Sea; thus, the present results could be used to stimulate further research on different aspects of the family.