Austrobates rivularis gen. et sp. nov., a freshwater relative of Halobates Eschscholtz (Hemiptera : Gerridae), with a new perspective on the evolution of sea skaters

Abstract

The sea skaters, genus Halobates Eschscholtz (Gerridae : Halobatinae), include the only known oceanic insects, although most species of Halobates and the related genus Asclepios Distant are found in sheltered coastal waters. In this paper we describe a freshwater relative of these marine genera, Austrobates rivularis, gen. et sp. nov., from Cape York Peninsula, Queensland, Australia. Although the new species has a mixture of characters shared with Asclepios and Halobates (tribe Halobatini) a phylogenetic (cladistic) analysis places Austrobates as sister-group of Halobates. The implications of this finding for the historical biogeography and ecology of sea skaters are discussed. We hypothesise that Halobates originated somewhere in the area that now includes the northernmost part of the Australian continent. Finally, we offer a narrative hypothesis explaining the evolution of the marine habit in halobatine water striders.