MOLECULES, MORPHOLOGY, AND AREA CLADOGRAMS - A CLADISTIC AND BIOGEOGRAPHIC ANALYSIS OF GAMBUSIA (TELEOSTEI, POECILIIDAE)

Researchers investigating historical biogeography rely on taxon cladog rams to infer the relationships of different areas of endemism. Unfort unately, systematists are often faced with many equally parsimonious t axon cladograms from a single data set or conflicting phylogenetic hyp otheses from independent data sets. We present an analysis of congruen ce between two conflicting phylogenetic hypotheses of the poeciliid fi sh genus Gambusia, one based on mitochondrial DNA sequences and the ot her based on morphological characters. We explore how different phylog enetic hypotheses alter interpretations of area relationships and prop ose a set of area relationships for the genus. Furthermore, we compare d the area relationships depicted for Gambusia with that of two Middle American fish genera (Xiphophorus and Heterandria) with similar distr ibutional limits. Our analysis revealed areas of congruence among taxa from nuclear Central America but areas of incongruence among taxa fro m the Panuco basin and North American components. We discuss the impli cations of our findings in light of conventional hypotheses regarding Caribbean biogeography. This study illustrates the importance of consi dering alternative phylogenetic hy potheses fully before attempting to interpret the biogeographic history of a taxon or region.