MEPS 452:171-178 (2012)  -  DOI: https://doi.org/10.3354/meps09611

ABSTRACT: The polychaete Hediste diversicolor is characterised by a high degree of genetic structure among populations. The genetic differentiation has been related to the presence of cryptic species, corresponding to Atlantic and Mediterranean lineages whose divergence may have been driven by vicariance and/or selection. In the present study we used DNA inter-simple sequence repeat (ISSR) markers to validate the genetic structure in 9 populations from the northwestern Mediterranean. We also analysed patterns of genetic differentiation among Mediterranean and Atlantic samples to assess the occurrence of further cryptic species in the northwestern Mediterranean. We compared our results with previous mitochondrial DNA data to assess whether nuclear and mitochondrial genetic patterns were consistent. Analysis of ISSR banding patterns showed: (1) a geographical structuring within the northwestern Mediterranean, and (2) a sharp genetic differentiation between Atlantic and Mediterranean groups of populations, confirming the findings from previous mitochondrial DNA surveys. The pattern of genetic variability found in the northwestern Mediterranean is unlikely to reflect the occurrence of cryptic species in this area. On the other hand, our results are consistent with the occurrence of 2 cryptic species in the Mediterranean and Atlantic, whose genetic differentiation may have been driven by vicariance. Finally, the present study further highlights the usefulness and effectiveness of ISSR markers for monitoring genetic diversity in aquatic invertebrates.

KEY WORDS: Hediste diversicolor · ISSR markers · Genetic diversity · Cryptic species · Habitat fragmentation · Bayesian analysis