EVOLUTIONARILY STABLE SEX RATIOS AND MUTATION LOAD |
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| Authors: | Josh Hough Simone Immler Spencer C H Barrett Sarah P Otto |
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| Institution: | 1. Department of Ecology and Evolutionary Biology, University of Toronto, , Toronto, Ontario, Canada, M5S 3B2;2. Department of Ecology and Genetics, Evolutionary Biology, Uppsala University, , Uppsala, 75236 Sweden;3. Department of Zoology and Biodiversity Research Centre, University of British Columbia, , Vancouver, British Columbia, Canada, V6T 1Z4 |
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| Abstract: | Frequency‐dependent selection should drive dioecious populations toward a 1:1 sex ratio, but biased sex ratios are widespread, especially among plants with sex chromosomes. Here, we develop population genetic models to investigate the relationships between evolutionarily stable sex ratios, haploid selection, and deleterious mutation load. We confirm that when haploid selection acts only on the relative fitness of X‐ and Y‐bearing pollen and the sex ratio is controlled by the maternal genotype, seed sex ratios evolve toward 1:1. When we also consider haploid selection acting on deleterious mutations, however, we find that biased sex ratios can be stably maintained, reflecting a balance between the advantages of purging deleterious mutations via haploid selection, and the disadvantages of haploid selection on the sex ratio. Our results provide a plausible evolutionary explanation for biased sex ratios in dioecious plants, given the extensive gene expression that occurs across plant genomes at the haploid stage. |
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| Keywords: | Evolutionarily stable strategy gametophytic selection heteromorphic sex chromosomes mutation load plant life cycles sex‐ratio evolution |
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