A Tri-Oceanic Perspective: DNA Barcoding Reveals Geographic Structure and Cryptic Diversity in Canadian Polychaetes

Although polychaetes are one of the dominant taxa in marine communities, their distributions and taxonomic diversity are poorly understood. Recent studies have shown that many species thought to have broad distributions are actually a complex of allied species. In Canada, 12% of polychaete species are thought to occur in Atlantic, Arctic, and Pacific Oceans, but the extent of gene flow among their populations has not been tested.Sequence variation in a segment of the mitochondrial cytochrome c oxidase I (COI) gene was employed to compare morphological versus molecular diversity estimates, to examine gene flow among populations of widespread species, and to explore connectivity patterns among Canada's three oceans. Analysis of 1876 specimens, representing 333 provisional species, revealed 40 times more sequence divergence between than within species (16.5% versus 0.38%). Genetic data suggest that one quarter of previously recognized species actually include two or more divergent lineages, indicating that richness in this region is currently underestimated. Few species with a tri-oceanic distribution showed genetic cohesion. Instead, large genetic breaks occur between Pacific and Atlantic-Arctic lineages, suggesting their long-term separation. High connectivity among Arctic and Atlantic regions and low connectivity with the Pacific further supports the conclusion that Canadian polychaetes are partitioned into two distinct faunas.Results of this study confirm that COI sequences are an effective tool for species identification in polychaetes, and suggest that DNA barcoding will aid the recognition of species overlooked by the current taxonomic system. The consistent geographic structuring within presumed widespread species suggests that historical range fragmentation during the Pleistocene ultimately increased Canadian polychaete diversity and that the coastal British Columbia fauna played a minor role in Arctic recolonization following deglaciation. This study highlights the value of DNA barcoding for providing rapid insights into species distributions and biogeographic patterns in understudied groups

Inter-population variability and character description in the sponge-associated Haplosyllis spongicola complex (Polychaeta: Syllidae)

18 páginas, 17 figuras, 3 tablas.Haplosyllis spongicola is probably the most representative symbiotic syllid harboured by sponges and has been widely reported from tropical, subtropical and temperate seas. Its external morphology seems to be very well adapted for its life-style, with all chaetae being simple and having two small teeth and a large main fang. However, the species has been the subject of a long-lasting taxonomic controversy, which gave rise to more than 15 synonymies, with hundreds of records worldwide. The present paper is based on the study of more than 28 populations obtained from around the world. These populations have been carefully analysed using different approaches (morphometry, morphology and biology). As a consequence, the existence of a pseudo-sibling species-complex within the socalled cosmopolitan H. spongicola has been revealed. The most relevant characters (as well as their variability) that will allow a future identification of the species involved in the complex are fully described, illustrated and analysed.The study has been partly financed by a research contract between the CEAB (CSIC) and French company CREOCEAN and has been partly sponsored by TOTAL. This paper is a contribution to the research project INTAS–OPEN–97–0916.Peer reviewe