a1 Department of Genetics, University of Groningen, Centre of Biological Sciences, 9751 NN Haren, The Netherlands
The lack of robustness of models of the maintenance of polymorphism in a heterogeneous environment which has been pointed out by Maynard Smith & Hoekstra (1980), applies also to models based on habitat selection, on temporal variation and on density-regulated selection. Only if (partial) dominance ‘switches’ between environments such that the fitness of the heterozygote is always close to the favoured homozygote, is there reasonable robustness. This is true for all models considered. It is argued that there are good reasons for supposing that the favourable allele at a locus may show dominance, although the experimental evidence is still scanty.
(Received October 30 1984)
(Revised January 29 1985)
p1 Present address: Dept. of Physical Geography, Geological Institute, University of Groningen, 9718 EP Groningen, The Netherlands.