Stability of self-incompatibility systems.
Multi-locus self-incompatibility systems offer few obvious adaptive advantages to the species possessing them. However, the gametophytic system's independent gene action allows the separate genes in a two gene system to behave as if they were individually not involved in a systematic disruption of panmixia. Under such circumstances, fixation of one of the two genes is readily obtained if an allele possesses a selective advantage. The resulting single gene system (the classic Nicotiana system) is then resistant to disruption, except by genes which allow selfing, which rapidly reach fixation.
Biometry Section, Waite Agricultural Research Institute, The University of Adelaide, Adelaide, Australia.
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