CLASSIFICATION, PHYLOGENY, AND ZOOGEOGRAPHY OF THE POND SKATER GENUS GERRIS FABRICIUS (HEMIPTERA, GERRIDAE)

The primarily Holarctic pond skater genus Gerris Fabricius is redescri bed and compared with two other northern temperate water strider gener a, Aquarius Schellenberg and Limnoporus Stal. The subgenus Gerriselloi des Hungerford and Matsuda is redefined and Macrogerris subgen.nov. is described to hold a group of eight eastern Palearctic species. Monoph yletic species groups of the subgenus Gem's s.str. are diagnosed and t heir species composition is delimited. Gerris brevirostris Bergroth is synonymized with G. lacustris (L.), syn.nov. Keys for identification are provided for all species of Gerris. The phylogenetic relationships among species of Limnoporus, Aquarius, and Gerris are analyzed. The d ata set comprises 63 structural characters coded for 2 species of Limn oporus, 7 species of Aquarius, and 19 species of Gerris. In particular , the metathoracic scent apparatus, male genitalia, female ovipositor, and gynatrial complex reveal characters of phylogenetic importance. T he data set is subjected to cladistic analyses using the parsimony pro gram Hennig86. Character polarities are determined using either a hypo thetical taxon or the species Gigantometra gigas (southeastern Asia) a s out-group. Through cladistic analysis, evidence is brought forward s upporting one particular hypothesis of the relationships between Aquar ius, Limnoporus, and Gerris, and between subgenera and monophyletic sp ecies-groups of Gerris. The reconstructed phylogeny is used to infer e volutionary sequences in patterns of wing polymorphism, habitat prefer ences, and sexual size dimorphism among temperate water striders, and to discuss their geographical distribution and historical biogeography .