A Genetic Comparison of Allopatric Populations of Shore Fish Species from the Eastern and Central Pacific Ocean: Dispersal or Vicariance?

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Abstract
More than 50 species of tropical shore fishes occur on both sides of the Pacific, despite the 5000 km separating the islands of the central Pacific from the offshore islands of the eastern Pacific. We examined 12 such trans-Pacific species, using populations from Hawaii [USA] and the eastern Pacific, with starch gel electrophoresis, in order to determine whether the allopatric populations are characterized by significant genetic differences. Values of genetic distance (D), computed for an average of 35 presumptive gene loci, ranged from < 0.01-0.06. These values are markedly lower than those reported for amphi-American populations separated by the Isthmus of Panama for about three million years. For Priacanthus cruentatus which is circumtropical, comparison of the Pacific samples gave a D of < 0.01, but the Atlantic vs Pacific comparison gave a D of 0.14. The results are compatible with a long-range dispersal hypothesis, with either recent dispersal or continuing gene flow. They are not consistent with a vicariant hypothesis which would regard the trans-Pacific species as relicts of a former world-wide, Tethyan distribution.