Papers in the Biological Sciences


Date of this Version

May 1984


Published in Evolution, 38(5), 1984, pp. 1023–1032. Copyright © 1984 by Society for the Study of Evolution; published by Blackwell Publishing. Used by permission.


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 short-winged 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 with a particular morph, even in phylogenetically distant species. For example, faster development rate, higher fecundity, and earlier age of first reproduction are almost always associated with the short-winged or wingless morphs. Thus, difference in wing length is the most obvious external manifestation for difference in a diverse set of coordinated traits; these alternate sets of traits represent reproductive/sedentary versus diapause/ dispersing life-history strategies (i.e., the flight-oogensis syndrome, Johnson, 1969).

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