1. Rice, W. R. & Hostert, E. E. Evolution 47, 1637–1653 (1993).
2. Dobzhansky, T. Genetics and the Origin of Species (Columbia Univ. Press, New York, 1937).
3. Butlin, R. K. in Speciation and its Consequences (eds Otte, D. A. & Endler, J. A.) 158-179 (Sinauer, Sunderland, MA, 1989).
4. Sætre, G.-P.et al. Nature 387, 589–592 (1997).
5. Sætre, G.-P.et al. J. Anim. Ecol. 64, 21–30 (1995).