Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. This study uses enzymatic and mitochondrial genes to infer the relative importance of historical processes and contemporary hydrodynamic features on the observed patterns of genetic structure in subdivided populations of Pectinaria koreni Polychaeta: Pectinariidae along the coasts of Brittany and the English Channel.
Deep sequence divergence with fixed haplotype differences and the inversion of allele frequencies at two enzyme loci suggests the occurrence of potential cryptic or sibling species of P.
The two clades showed opposite features. Channel populations exhibited bimodal match—mismatch curves due to two highly divergent haplotypes occurring at high frequencies and no overall heterozygote deficiencies at enzyme loci, suggesting respectively, a historic secondary contact between two differentiated populations followed by contemporary panmixia. On the contrary, Brittany populations displayed unimodal curves with low nucleotide diversity and highly significant heterozygote deficiencies, probably reminiscent of a recent population expansion and recolonisation of Brittany with contemporary admixture of divergent populations.
Marine biogeographic boundaries are transition zones of significant ecological complexity ie because of overlaps in faunal assemblages; see Holt and Keitt, for biological complexities arising from species range limits and important in terms of evolutionary processes ie mating isolation, maintenance of hybrid zones, speciation.
Such boundaries may give rise to biogeographic barriers, which are filters for many species depending on their ability to disperse, reproduce and survive various environmental conditions and the level of habitat fragmentation, potentially leading to differences in the genetic structure of populations on either side.
