DIFFERENCES IN SURVIVORSHIP, DEVELOPMENT RATE AND FERTILITY BETWEEN THE LONGWINGED AND WINGLESS MORPHS OF THE WATERSTRIDER, LIMNOPORUS CANALICULATUS.

Abstract

Species of waterstriders (Gerridae: Hemiptera) exhibit a remarkable diversity in degree of winglessness (Vepsalainen, 1978; Calabrese, 1980; Zera, 1981). Some species consist exclusively of fully-winged individuals, while other species are composed almost exclusively of wingless individuals; many species exhibit the intermediate case of wing polymorphism and consist of various proportions of fully-winged, short-winged and/or wingless morphs. Wing-polymorphic species often exhibit dramatic spatial and/or temporal variation in morph ratios, both among populations of the same species and among species. Because of this diversity, waterstriders, especially wing polymorphic species, are ideal candidates for the study of the evolution of winglessness (or conversely, the evolution of dispersal). One of the major questions in the study of the evolutionary forces which influence wing polymorphism concerns fitness differences among the morphs. In many non-gerrids, dramatic differences between the fully-winged and the shortwinged or functionally equivalent (Anderson, 1973) wingless morph have been documented in a variety of fitness-associated traits (for reviews, see Harrison, 1980; Dingle, 1982). These include differences in such traits as survivorship under stress, duration of larval or nymphal development, age of first reproduction, and fecundity. Moreover, one of the most important results of these studies is the demonstration that differences in fitness traits are often consistently associated