Ecological features of Syllidae (Polychaeta) from shallow-water benthic environments of the Aegean Sea, eastern Mediterranean

Ecological features of Syllidae inhabiting shallow-water benthic habitats of the Aegean Sea were analysed by utilizing some univariate and multivariate statistical methods. A total of 121 benthic materials collected in a variety of substrata and depths (0-76 m) contained 90 syllid species belonging to the four subfamilies Autolytinae, Exogoninae, Eusyllinae and Syllinae. Among the subfamilies, Syllinae were characterized by a high number of species and Exogoninae by a high number of individuals. Although dominant species varied according to substrata, the two species, Grubeosyllis clavata and Syllis prolifera, accounted for up to 51% of the total syllid populations in the area. Among the biotopes sampled, Posidonia oceanica seems to be particularly suitable for the settlement of syllid species, whereas bare sand and mud harbour only a few species, mainly Exogoninae. The cluster- and ordination analyses detected species associations on soft and hard substrata, and suggested that syllid assemblages are strongly affected by the habitat structure. Species compositions associated with algae appear to be related to complexity of the algae, so that the ones with relatively small thalli, such as Padina pavonica and Halopteris spp., constituted a group with a high similarity-index value. Samples of Posidonia oceanica collected at different stations showed a high consistency in terms of syllid assemblages.