ECOLOGICAL PHYLOGENETICS OF MATING SYSTEMS AND SEXUAL DIMORPHISM IN WATER STRIDERS (HETEROPTERA: GERRIDAE)

Water striders of the heteropteran family Gerridae are conspicuously adapted for life on the water surface, especially with respect to locomotion, feeding, and reproductive behavior. Sexual dimorphism and a significant allometric relationship between sexual size dimorphism and overall size is well documented in temperate Water strider are also dimorphic with respect to both primary and secondary sexual traits, especially shape and size of fore legs and structure of terminal abdominal segments and genitalia. In this paper the approach called ecological phylogenetics is used to study patterns of sexual dimorphism and mating systems in the monophyletic subfamily Gerrinae, focusing on the evolution of sexual dimorphism in relation to mating systems and the coevolution of male clasping and female anticlasper devices. There are no obvious, global phylogenetic effects or "constraints" on sexual dimorphism in the group, but phylogency has played a certain role in shaping pattern of F/M size ratios,male clasping devices, and female anticlasper devices withiin clades. There is no support for the hypothesis that male and female genitalia and other structures have been involved in a coevolutionary "arms race" . Finally, the phylogenetic effects on patterns of mating behavior are negligible as demonstrated by the large amount of interspecific variation in some genera, and by the fact that males of the same species may show alternative mating tactics depending on ecological circumstances.