• DOI:10.1111/j.1558-5646.1956.tb02825.x
• Corpus ID: 87729275

SELECTION FOR SEXUAL ISOLATION WITHIN A SPECIES

@article{Knight1956SELECTIONFS,
  title={SELECTION FOR SEXUAL ISOLATION WITHIN A SPECIES},
  author={G. R. Knight and Alan Robertson and Conrad Hal Waddington},
  journal={Evolution},
  year={1956},
  volume={10}
}

• G. R. Knight, A. Robertson, C. Waddington
• Published 1 March 1956
• Biology
• Evolution

Two mechanisms have been advanced for the origin of reproductive isolation between species. Muller (1939), dealing in the main with barriers to crossing in the later stages of species divergence, such as hybrid inviability and infertility, suggests that these arise almost by chance as a product of change in the genetic background either by genetic drift or as adaptation to different biological situations. This would lead to accelerating divergences as the process continues. or, as Muller puts it, "ever more pronounced immiscibility as an inevitable consequence of non-mixing." Dobzhansky's suggestion (1937), which is perhaps complementary rather than antagonistic to Muller's. is that when sufficient divergence between two species has arisen so that the hybrids are less well adapted for any available habitat than either parental type, there will be selection for sexual isolation. That is to say-if mating can take place and if the resulting hybrids are inviable or infertile. then natural selection will operate to reduce the chance that mating will occur. either by reducing the chance of encounter or the chance of mating with members of the other species when they are encountered. Some writers, in discussing the mechanism proposed by Dobzhansky have suggested that "natural selection will favour any mechanism which prevents the wastage of gametes involved in unsuccessful hybridisation." This seems to be unduly teleological. Natural selection will only tend to suppress crossbreeding if those individuals which hybridise will in consequence pass on fewer gametes in the form of pure-bred offspring. It would seem probable that this would be more often the case in females than in males. In Drosophila melanoqaster, for instance,