Summary
In order to improve our understanding of the combined influence of mating system components on genotypic structures in zygotes, it may be better to consider the selective effects in each of the two sex functions separately. In this paper, two diallelic selection models for plant populations with mixed self-fertilization and random gametic fusion are considered: (A) Selection on the production of free pollen (i.e., pollen not reserved for self-fertilization and thus subject to competition), and (B) selection on the production of ovules (all of which are fertilized). It is well known that sexually asymmetrical fertility selection produces a heterozygotic excess, whereas self-fertilization generally leads to a homozygotic excess relative to Hardy–Weinberg proportions. The combined influence of the two factors is investigated for the diallelic case with special emphasis on three topics: (i) Estimation of limits for the amount of genotypic equilibrium deviations from Hardy–Weinberg proportions, (ii) determination and illustration of the location of genotypic equilibria, and (iii) conditions for protectedness of polymorphisms and alleles. With respect to these aspects, the models A and B are compared with the classical symmetrical fertility model.
The results and figures serve to interpret the combined influence of fertility selection and partial self-fertilization on zygotic genotypic structures. In addition, the frequently used argument that in predominantly self-fertilizing organisms only strong overdominance is capable of constituting a polymorphism turns out to require modification.
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Ziehe, M. Zygotic genotypic frequencies under selection on female or male gamete production in partially self-fertilizing plant populations. Heredity 49, 271–290 (1982). https://doi.org/10.1038/hdy.1982.101
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DOI: https://doi.org/10.1038/hdy.1982.101
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