MATE CHOICE IN HYLOBITTACUS APICALIS (INSECTA: MECOPTERA) AND ITS RELATION TO SOME MODELS OF FEMALE CHOICE.

Abstract

Darwin's (1874) theory of sexual selection includes two components: competition within one sex for individuals of the opposite sex (intrasexual selection), and preferential choice by members of one sex for individuals of the opposite sex (intersexual selection). Darwin believed both forms could be very potent and that . . the power to charm the female has sometimes been more important than the power to conquer other males . (1874, p. 257). Darwin felt both components of sexual selection would have a stronger effect on males than on females. The importance of male-male competition for females has not been seriously disputed since Darwin proposed it as a powerful form of selection, for example, Campbell (1972), Wilson (1975), Bradbury (1977), Davies (1978), Halliday (1978), and Alcock (1979) (but see Wallace, 1889, p. 296, and Huxley, 1963, p. xviii-xix). Female preference of conspecific over heterospecific males as mates is widely accepted as playing an important role in maintaining the integrity of species in nature (e.g., Wallace, 1889; Mayr, 1963; Wilson, 1975; Alcock, 1979). However, the role that Darwin attributed to female preference has been frequently criticized (e.g., Wallace, 1889; Huxley, 1938; Halliday, 1978; Maynard Smith, 1978). The paucity of evidence for Darwinian female preference in nature remains an important problem in understanding the role of female choice in the evolution of male traits. Most evidence for female choice is indirect and is based on the distribution of females around males of different ages and/or sizes or around males that possess different amounts of some resource (e.g., territory, food, etc.) (see studies discussed in Wilson, 1975; Emlen and Oring, 1977; Davies, 1978; Halliday, 1978; Alcock, 1979; Downhower and Brown, in press). Also, female choice is often inferred merely when females mate with some conspecific males and not others (e.g., McCauley and Wade, 1978). Also contributing to our lack of understanding of female choice as a selective force is the paucity of studies which indicate that female choice is adaptive in terms of increasing the discriminating female's fitness or that of her offspring (see Maynard Smith, 1966; O'Donald, 1973; Thornhill, 1976a, 1979a). The role of adaptive female choice is especially controversial when applied to species in which males show no parental care or no protection or nurturing of the females and only contribute genes to offspring (Williams, 1975; Halliday, 1978; Maynard Smith, 1978; Borgia, 1979; Harpending, 1979). Females appear to choose males in some such species (e.g., lekking birds). But according to population genetics theory there should be no increased fitness resulting from choice: males should be very similar or identical genetically because of strong intersexual selection in the past. Borgia (1979) provides a discussion of how the necessary genetic variations may be maintained despite high levels of polygyny. Whether females actually choose males in nature and whether choices are adaptive can probably best be answered by direct observations of females interacting with different mates and the reproductive outcomes of these interactions. Both forms of sexual selection apparently contribute to variance in male copulatory success in the hangingfly Hylobittacus apicalis. I have reported detailed