Classification and phylogeny of the Holarctic water strider genus Limnoporus Stål (Hemiptera, Gerridae)

Abstract

The Holarctic water strider genus Limnoporus Stål is redescribed, a key and diagnoses are provided for the six species described, and their distributions are documented. The geographic variation of the Palearctic and northwestern Nearctic L. rufoscutellatus (Latreille) is surveyed. Male specimens from Fairbanks, Alaska, and the Yukon Territory (described as Gerris nearcticus Kelton, syn.nov.), cannot be separated from L. rufoscutellatus from Europe or the former Asian USSR. Limnoporus genitalis (Miyamoto), stat.nov., was originally described as an insular subspecies (from Hokkaido, the Kurile Islands, and Sakhalin) of L. rufoscutellatus but is clearly diagnosable and deserves specific status. The boreal Nearctic L. dissortis (Drake and Harris) and the western Nearctic L. notabilis (Drake and Hottes) are very similar to each other, but males of the two species show practically no overlap in size, L. notabilis being distinctly larger than L. dissortis. However, males, and more especially females, can be difficult to identify in areas where the two species hybridize. The two species of Limnoporus with smaller body size, the eastern Nearctic L. canaliculars (Say) and the east Asian L. esakii (Miyamoto), are more distinct from each other than are the remaining four species of the genus. A cladistic analysis of relationships between species was conducted, mainly on the basis of the structural characteristics of adults, and with species of Aquarius and Gerris as out-groups. The reconstructed phylogeny is discussed in relation to previous standard as well as molecular taxonomic work about species relationships and previous ambiguities are resolved. The phylogeny is further used to infer evolutionary sequences in habitat preference, wing polymorphism, and phenology, and to discuss the geographical distribution and historical zoogeography of Limnoporus species.