Summary
Distyly is characterized by a diallelic incompatibility system. Crowe (1964) hypothesized that this has arisen by a loss of alleles from multiallelic systems. I have examined a mechanism for such a loss in a simulated population with sporophytic incompatibility and four alleles at the incompatibility locus. If a second locus is tightly linked to the incompatibility locus and a favoured new mutation spreads at this second locus, two of the four alleles at the incompatibility locus may be driven to extinction, leaving only the incompatibility allele originally linked to the favoured new mutation, and a second incompatibility allele that is dominant to the first. The two selection pressures responsible for this behaviour are the higher fitness of the new mutation at the second locus and the ever-acting selection for maximal cross-compatibility at the incompatibility locus. The implications of the model for the evolution of distyly are discussed.
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Muenchow, G. A loss-of-alleles model for the evolution of distyly. Heredity 49, 81–93 (1982). https://doi.org/10.1038/hdy.1982.67
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DOI: https://doi.org/10.1038/hdy.1982.67
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