Eyespan reflects reproductive quality in wild stalk-eyed flies
- 362 Downloads
Handicap models of sexual selection propose that females use male sexual ornaments as a cue in mate choice because they reflect commodities that increase female fitness, either directly or indirectly. In contrast to studies on vertebrates, most investigations of ornaments in insects and other invertebrate taxa have been conducted under laboratory conditions. There is a pressing need to address questions relating to sexual signalling of quality in natural populations, as the arbitrary and uniform environments found in the laboratory fail to reflect the world under which animals have evolved. We investigated associations between male ornaments (exaggerated eyespan), attractiveness, and reproductive quality in a wild population of the sexually ornamented stalk-eyed fly, Teleopsis dalmanni. We also explored the relationship between eyespan and reproductive quality in females to evaluate the potential for sexually antagonistic selection on eyespan. We show that eyespan is a generic correlate of reproductive quality, acting as a reliable mirror of variation in reproductive fitness in both sexes. Our findings suggest that male ornaments signal commodities that are of interest to females in the natural environment in which they, and mate preferences for them, have evolved. In addition, the covariance between female eyespan and reproductive output suggests that the former may be a reliable cue of quality in its own right. Our data provide important insights into the evolutionary forces that shape the evolution of exaggerated eyespan in wild populations of this species.
KeywordsSexual selection Ornaments Wild Stalk-eyed fly Testis Accessory glands Fecundity Fertility
This work was supported by awards from the Association for the Study of Animal Behaviour (A.P. and R.H.), the Royal Society (A.P. and R.H.), the BBSRC (grants to K. Fowler, A.P., T. Chapman and H. Smith; studentship to J.S.), the Department of Biology, University College London (J.S. and A.P.), and a NERC Fellowship (S.C.). We thank two anonymous reviewers for comments on a previous version of the manuscript, and staff at the Gombak Valley Field Research Centre, University of Malaya, Kuala Lumpur for assistance.
- Andersson M (1994) Sexual selection. Princeton University Press, PrincetonGoogle Scholar
- Baker RH, Wilkinson GS (2001) Phylogenetic analysis of sexual dimorphism and eyespan allometry in stalk-eyed flies (Diopsidae). Evol Int J Org Evol 55:1373–1385Google Scholar
- Cotton S, Fowler K, Pomiankowski A (2004b) Condition dependence of sexual ornament size and variation in the stalk-eyed fly Cyrtodiopsis dalmanni (Diptera: Diopsidae). Evol Int J Org Evol 58:1038–1046Google Scholar
- Fisher RA (1958) The genetical theory of natural selection. Clarendon Press, Oxford (reprinted 1999, Oxford Univ Press, Oxford)Google Scholar
- Greenfield MD (1997) Sexual selection in resource defense polygamy: lessons from territorial grasshoppers. In: Chloe J, Crespi B (eds) The evolution of mating systems in insects and arachnids. Cambridge University Press, Cambridge, pp 75–88Google Scholar
- King RC (1970) Ovarian development in Drosophila melanogaster. Academic Press, New YorkGoogle Scholar
- Maynard Smith J, Harper D (2003) Animal signals. Oxford University Press, OxfordGoogle Scholar
- Pomiankowski A (1988) The evolution of female mate preferences for male genetic quality. Ox Surv Evol Biol 5:136–184Google Scholar
- Wilkinson GS, Dodson GN (1997) Function and evolution of antlers and eye stalks in flies. In: Chloe J, Crespi B (eds) The evolution of mating systems in insects and arachnids. Cambridge University Press, Cambridge, pp 310–328Google Scholar