Phylogeographical structure of the Dover sole Microstomus pacificus: the larval retention hypothesis and genetic divergence along the deep continental slope of the northeastern Pacific Ocean

Population genetic variability and phylogeographical structure of the Dover sole, Microstomus pacificus (Teleostei: Pleuronectidae), were examined alo ng the continental slope of the northeastern Pacific Ocean using sequences of the left domain of the mitochondrial DNA (mtDNA) control region. Six sit es were sampled in three primary biogeographical provinces (based on surfac e water temperatures), ranging from the subarctic to the warm temperate zon es. Many haplotypes were discerned, totalling 90 for 110 individuals. Neigh bour joining and parsimony analyses of the entire data set showed that some groups of haplotypes of adult Dover sole were widely distributed, suggesti ng either panmixia or homoplasy and reversals. However, a substantial numbe r of groups of related haplotypes were geographically circumscribed, and th ere were significant differences among sites in the distribution of restric ted haplotypes (based on a reduced number of characters), supporting geogra phical structure. Geographical differentiation of populations appeared to b e consistent with the member-vagrant hypothesis for retention of the pelagi c larvae in currents and recruitment to adult habitats, reducing long-dista nce dispersal, Results of this study indicate phylogeographical structure a mong some populations, despite extended pelagic larval periods, and apparen t environmental homogeneity in the adult habitats along the continental slo pe.