Ecology and diversity of Mediterranean hard-bottom Syllidae (Annelida): a community-level approach

The Syllidae are geographically widespread polychaetes, particularly diverse and abundant on marine hard bottoms and in seagrass meadows. Hydrodynamics, habitat complexity and biological traits are hypothesized to influence syllid bathymetric distribution. Little is known about the consistency of, or variation in, horizontal distribution patterns with varying depth. I analyzed hard-bottom Syllidae at 2 depths (1.5 and 5 m) at the scale of 1000s of metres, located around the Torre Guaceto marine protected area (MPA) (SE Italy) in order to (1) quantify syllid diversity and abundance, (2) describe their distribution pattern and (3) identify potentially important factors influencing their distribution. The Syllidae were dominant and highly diverse, and new biogeographic records were reported. Horizontal distribution patterns changed with depth, being more variable at 1.5 than 5 m. The presence of the MPA had little effect on alongshore variation in individual species abundance and assemblage structure. Contrary to expectations, there was no consistent relationship between Syllidae distribution and habitat-forming algal species. In contrast, syllid abundance varied with that of other invertebrates, suggesting that future research should focus on the role of interspecific interactions in syllid ecology. Syllidae are a highly diversified and widespread taxon that deserves special attention when analyzing biodiversity patterns of hard-bottom benthic communities.