The six extant species of Limnoporus water striders provide an unusual opportunity to compare allozyme and mitochondrial DNA (mtDNA) divergences with both morphological divergences and information on interspecific hybrid inviability. Parsimony analyses of mtDNA, allozymes, and morphology did not differ greatly, and each data type provided useful information on at least some nodes in the phylogeny. Simultaneous analysis of the combined data gave a better resolved and supported tree than did any single data type. Several measures of hybrid inviability bore no relationship to genetic distances between species, thus demonstrating the poor value of hybrid compatibility as an indicator of phylogenetic relationships. When genetic distances were related to estimates of time of divergence based on fossils, standard molecular clocks for mtDNA and allozymes showed as much as a 10-fold underestimate of absolute time. The phylogeny of Limnoporus allows more rigorous evaluation of several prior hypotheses of ecological or developmental processes in water striders. In particular, the phylogeny supports the evolutionary lability of wing dimorphism, sexual size dimorphism, and local differentiation of ontogenetic traits.
