• DOI:10.1038/hdy.1948.21
• Corpus ID: 30834037

Intra-sexual selection in Drosophila

@article{Bateman1948IntrasexualSI,
  title={Intra-sexual selection in Drosophila},
  author={A. J. Bateman},
  journal={Heredity},
  year={1948},
  volume={2},
  pages={349-368}
}

• A. Bateman
• Published 1948
• Biology
• Heredity

SINCE Darwin first wrote on the subject in 1871, sexual selection has been generally accepted as one of the basic facts of biology. The evidence in its favour seems, however, to be mainly circumstantial. Its existence has usually been inferred from sex differences depending on what are called secondary sexual characters which are supposed to have arisen as results of that selection. Such an approach has its dangers, and Huxley (1938) has made important criticisms of the original concept of sexual selection. He has shown that a large number of characters which have been attributed to sexual selection are unconnected with competition for mates. This is particularly the case in monogamous birds which offer some of the most striking examples of secondary sexual differences. In the first place monogamy, at least when the sexes are numerically equal, is the mating system least likely to develop sexual selection. In the second place, and more important, observations on bird behaviour have shown that much of the display of birds occurs after pairing, when competition must have ceased. Such sexual differences are concerned, either with inducing the female to copulate, or with maintaining the association of the sexes as long as it is necessary for the rearing of the young. Huxley therefore introduced the term epigamic to apply to characters which increased the fertility of a given mating and therefore had a selective value for the species as a whole. Epigamic selection includes the major part of what Darwin meant by sexual selection. It also includes selection for characters to which Darwin did not refer, such as the structure of copulatory organs, sex differences in frequency of crossing over, and the XY mechanism. It is only a special case of natural selection as generally understood. What remains of Darwinian sexual selection has been called intra-sexual selection, which denotes that it involves competition between members of one sex for mates. It can only indirectly affect the survival of the species and then is often deleterious (e.g. the cumbersome antlers of the stag). There is not invariably, however, a clear distinction between epigamic and intrasexual selection. In a promiscuous species like Drosophila pairing and copulation are synchronous. Courtship behaviour determines the number of mates and therefore enters into intra-sexual selection.