Genetic divergence between subpopulations of the eastern Pacific goose barnacle Pollicipes elegans: mitochondrial cytochrome c subunit 1 nucleotide sequences.

Nucleotide sequence data derived from polymerase chain reaction products from the cytochrome oxidase subunit 1 gene of mitochondrial DNA provide evidence for interrupted gene flow and subsequent genetic divergence between geographically separate subpopulations of the edible goose barnacle, Pollicipes elegans, with a 4400-km latitudinal distribution in the eastern Pacific Ocean. The amphitropical subpopulations of Pollicipes elegans have a net nucleotide sequence divergence of about 1.2%. A range of mutation rates are applied to calculate estimates for the timing of this divergence. The earliest estimated time of divergence agrees with a Pliocene time of general warming in the eastern Pacific. The latest estimated times coincide with the Pleistocene epoch and periods of cooling and warming that could have allowed for a series of expansions and contractions of P. elegans populations in the eastern tropical Pacific. These expansions and contractions may, therefore, represent alternating periods of genetic exchange and isolation of the two populations.