Classification, phylogeny, and zoogeography of the pond skater genus Gerris Fabricius (Hemiptera: Gerridae)

Abstract

The primarily Holarctic pond skater genus Gerris Fabricius is redescribed and compared with two other northern temperate water strider genera, Aquarius Schellenberg and Limnoporus Stål. The subgenus Gerriselloides Hungerford and Matsuda is redefined and Macrogerris subgen.nov. is described to hold a group of eight eastern Palearctic species. Monophyletic species-groups of the subgenus Gerris s.str. are diagnosed and their 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 data set comprises 63 structural characters coded for 2 species of Limnoporus, 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. The data set is subjected to cladistic analyses using the parsimony program Hennig86. Character polarities are determined using either a hypothetical taxon or the species Gigantometra gigas (southeastern Asia) as out-group. Through cladistic analysis, evidence is brought forward supporting one particular hypothesis of the relationships between Aquarius, Limnoporus, and Gerris, and between subgenera and monophyletic species-groups of Gerris. The reconstructed phylogeny is used to infer evolutionary sequences in patterns of wing polymorphism, habitat preferences, and sexual size dimorphism among temperate water striders, and to discuss their geographical distribution and historical biogeography.