PHYLOGENETIC-RELATIONSHIPS WITHIN THE APLOCHEILOID FISH GENUS RIVULUS(CYPRINODONTIFORMES, RIVULIDAE) - IMPLICATIONS FOR CARIBBEAN AND CENTRAL-AMERICAN BIOGEOGRAPHY

We examined the phylogenetic relationships of 16 northern species of t he aplocheiloid genus Rivulus inhabiting the Caribbean, Central Americ a, and South America. A total of 714 base pairs per taxon were sequenc ed from two segments of the mitochondrial genome, 12S rRNA and cytochr ome b. Both parsimony and neighbor-joining analyses suggest an ancient vicariant origin of the Greater Antillean taxa, in addition to a quit e recent dispersal of species into the Lesser Antilles from the South American mainland. Combined analyses support the monophyly of the nort hern South American assemblage as the sister group of a Central Americ an/Columbian biota. However, the monophyly of the Central American bio ta remains uncertain. Divergence estimates for the Central American ta xa are calibrated from the Late Cretaceous separation of the proto-Ant illes from the Americas. Those data suggest that the extant Central Am erican taxa represent the descendants of at least two separate invasio ns during the Cenozoic, prior to the closing of the Panamanian isthmus . Times are consistent with the extensive evidence for reptilian and m ammalian exchange throughout the Cenozoic.