Phylogeny and mtDNA phylogeography of two widespread European pond skater species (Hemiptera-Heteroptera: Gerridae: Gerris Fabricius)

This study addresses the phylogenetic relationships within and between two widespread Palaearctic pond skater species, Gerris costae and G. thoracicus, by including new DNA sequence data from the Central Asian G. sahlbergi, traditionally assigned as a close relative of G. costae. The results support the assignment of G. costae and G. thoracicus to two individual species groups that are not closely related, but also that G. sahlbergi is nested within G. costae (including subspecies costae, fieberi and poissoni) thus suggesting a new subspecific rank as G. c. sahlbergi. A broad geographical sampling of mitochondrial DNA from populations of G. thoracicus and G. costae (incl. G. c. sahlbergi) shows that the two species are strikingly similar in terms of genetic diversity and lack of geographical substructure, thus adding further evidence for the G. costae group comprising a single, widespread species.