Adaptive significance of wing dimorphism in the absence of dispersal: a comparative study of wing morphs in the waterstrider, Gerris remigis

Gerris remigis Say (Hemiptera; Gerridae) is primarily apterous, but populations with up to 33% macropters have been reported. The macropters seldom fly, and field studies have revealed no detectable differences between wing morphs in movement or survival at any time of year. In this paper, life history traits of macropterous and apterous G. remigis are compared in an attempt to determine the mechanisms responsible for the maintenance of macroptery in this species in spite of the very low flight capacity and infrequent flight of macropters. Development time, proportion breeding without diapause, and overwinter survival do not differ between morphs. However, pre‐diapause macropterous females have a significantly shorter pre‐oviposition period than apterous females. In contrast, post‐diapause macropters begin reproducing later than apters, and have a lower cumulative fecundity. These results suggest that macropters may be at a selective advantage in warm habitats which favour pre‐diapause reproduction, but that apters should be favoured in the preferred, cool, lotic habitats. However, crossing and rearing experiments indicate that wing morphology is primarily environmentally controlled in this species, and that the heritability of wing morphology is low, at best. In light of this, the relative impacts of purely phenotypic (environmental) variation, random effects, and the observed fitness differences on the maintenance of macroptery in this species are discussed.