Anthropized environments as reservoirs of hidden and exotic diversity in marine annelids: sicilian ports as a case study

Marine annelids are key components of benthic ecosystems, yet their diversity remains unevenly documented, particularly in anthropized habitats. In Sicily (Mediterranean Sea), significant knowledge gaps persist regarding port benthic communities and their role in the spread of non-indigenous species (NIS). This study provides the first characterization of polychaete assemblages in Sicilian ports in over three decades, with a specific focus on biodiversity patterns and NIS occurrence. Standardized sampling of fouling material was conducted over a year in four major Sicilian ports; the collected specimens were identified combining morphological analyses with molecular markers (COI, 16S, CytB, ITS1). In total, 296 individuals were assigned to 52 taxa across 16 families, including 15 species newly recorded for Sicily, two new records for the Tyrrhenian Sea, and a species (Proceraea megarensis sp. nov.) and two further taxa potentially new to science. Eleven species were identified as NIS and two as cryptogenic. In terms of species numbers, NIS represent a substantial proportion of port assemblages, reaching over 50% of the identified species at specific sites and sampling periods. These findings suggest that Sicilian ports may play a major role in the biological invasions in the Mediterranean, highlighting the need for continuous monitoring to improve early detection and management of NIS.