SELECTION FOR GAMETE LETHALS AND S-ALLELES IN COMPLEX HETEROZYGOTES

Some hypotheses are proposed for the origin of gamete lethals and S-alleles in complex heterozygotes with zygotic lethality. It is shown that egg or pollen detrimentals or lethals are nearly neutral in highly selfing populations, so that a translocation complex which fails to be transmitted through gametes of one sex may be selected if it confers a slight advantage to the sporophyte. Once an asymmetry in transmission of this sort has been established, there is a selective advantage to mutations causing asymmetry in the opposite sense, either by gamete lethality or because of incompatibility (in cases when egg lethality has been established first). © 1979 The Genetical Society of Great Britain.