Molecular phylogenetics and biogeography of galaxiid fishes (Osteichthyes : Galaxiidae): Dispersal, vicariance, and the position of Lepidogalaxias salamandroides

The galaxiid fishes exhibit a gondwanan distribution. We use mitochondrial DNA sequences to test conflicting vicariant and dispersal biogeographic hyp otheses regarding the Southern Hemisphere range of this freshwater group. A lthough phylogenetic resolution of cytochrome b and 16S rRNA sequences is l argely limited to more recent divergences, our data indicate that the radia tion can be interpreted as several relatively recent dispersal events super imposed on an ancient gondwanan radiation. Genetic relationships contradict the findings of recent morphological analyses of galaxioid fishes. In part icular, we examine several hypotheses regarding phylogenetic placement of t he enigmatic Lepidogalaxias. Although most workers consider Lepidogalaxias to be an unusual scaled member of the Southern Hemisphere galaxioids, it ha s also been suggested that this species is related to the Northern Hemisphe re esocoids. Our data strongly suggest that this species is not a galaxiid, and the alternative hypothesized esocoid relationship cannot be rejected. The species-rich genus Galaxias is shown to be polyphyletic and the generic taxonomy of the Galaxiinae is reassessed in the light of phylogenetic rela tionships. Juvenile saltwater-tolerance is phylogenetically distributed thr oughout the Galaxiinae, and the loss of this migratory phase may be a major cause of speciation.