Phylogeny and reclassification of species groups in Aquarius Schellenberg, Limnoporus Stal and Gerris Fabricius (Insecta : Hemiptera-Heteroptera, Gerridae)

We investigated phylogenetic relationships of water striders (Hemiptera-Heteroptera: Gerridae) from the three principal Holarctic genera, Aquarius Schellenberg, Limnoporus Stal and Gerris Fabricius with parsimony analyses of sixty-six morphological characters and DNA sequences from mitochondrial (cytochrome c oxidase subunit I + II; large mitochondrial ribosomal subunit) and nuclear (elongation factor 1-alpha) genes. The taxon sampling included all species of Aquarius and Limnoporus, and a dense, near complete, sample of Gerris species with representatives from all subgenera and species groups, and Gigantometra gigas (China) was selected as an outgroup species. A simultaneous analysis of all data sets gave eight equally parsimonious trees, and a strict consensus tree left only a few relationships within Gerris unresolved. While Limnoporus and Gerris each were resolved as monophyletic entities, Aquarius was found to be polyphyletic, because the Nearctic Aquarius remigis-group, comprising A. remigis (Say), A. amplus (Drake and Harris), A. nyctalis (Drake and Hottes) and A. remigoides Gallant and Fairbairn, was placed as sister group to Gerris, while the Andean Aquarius chilensis (Berg) was sister group to all three genera. Remaining species of Aquarius comprised a sister group to the Gerris + the A. remigis-group clade. Based on our phylogenetic reconstruction we discuss relationships within and among the three genera, reassess and diagnose species groups, and discuss zoogeographical relationships among all taxa.