Résumé
Dolphinfish (
Coryphaena hippurus) samples were collected over four consecutive years from four locations in the eastern central Pacific to evaluate the genetic variation in a 751
bp segment of the mitochondrial NADH subunit 1 (ND1) to test for the presence of genetic population structure. Sequence analyses revealed no significant differences among collections from the same location in the different years sampled nor between locations. Mismatch distributions, estimations of population expansion parameters, and neutrality tests revealed significant fluctuations in population size in coincidence with past glacial and interglacial periods during the late Pleistocene. The low levels of nucleotide diversities and shallow coalescence of mtDNA genealogies observed were coincident with the estimated demographic parameters and neutrality tests, in suggesting the presence of important past population size fluctuations or range expansion. The prevention of the accumulation of deep lineages independently on how it was originated, probably delayed the emergence of a population divergence process which might account for the lack of genetic differences detected.