50 Million Years of Structural Stasis in Water Striders (Hemiptera: Gerridae)

Phylogenetic reconstruction is coupled with information from the fossil record to infer timing of major evolutionary events in the diversification of north temperate water striders. We refer fossil gerrids from the Middle Eocene of British Columbia to a modern species group and, along with other Paleogene gerrine fossils, place them on a phylogenetic diagram. Using the estimated ages of these fossils, we infer that two monophyletic groups of Limnoporus Stål diverged >50 million years ago, much longer ago than estimated using data from protein electrophoresis and assumptions of a standard molecular clock. The observed structural stasis in Tertiary fossils suggests that gerrid specializations for life on freshwater surfaces have not been associated with high rates of speciation or extinction.