EAGER: The evolutionary consequences of subtle biases in the outcome of meiosis

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The central assumption of Mendelian genetics is that an individual has as good a chance of passing on a gene that it received from its mother as one that it received from its father. In general, this assumption holds. Yet striking exceptions, in which either the maternal or paternal gene selfishly transmits itself to the next generation, are known from well-studied plants and animals. Are these cases rare exceptions, or are they the tip of a non-Mendelian iceberg? New genetic tools have now enabled researchers to find more subtle deviations from 50:50 ratios in wild plants and animals, suggesting that selfish genes may be more frequent and varied than previously appreciated. This is important because even a gene that causes a genetic abnormality can persist if it has a slightly better than 50:50 chance of making it to the next generation. This project will study the effects of non-50:50 transmission of genes on fitness in the moss model system Ceratodon purpureus. Combining new mathematical models and genetic data from this simple moss system will reveal insight into the genetics of infertility, the outcome of reproduction, and its influence on the structure of the genome. This proposal presents a comprehensive plan to link genome-wide patterns of segregation distortion with fitness in the moss model system Ceratodon purpureus. The PIs central hypothesis is that segregation distortion is common across the genome and contributes to the maintenance of genetic variation for fitness, one of the central problems in evolutionary biology. The rationale for this proposal is to develop a new system to understand, at a mechanistic level, previously unexplored links between the outcome of meiosis and quantitative trait variation. To accomplish this goal, the PIs will combine genome-wide polymorphism data from natural populations of C. purpureus with new statistical models that treat segregation ratio as a quantitative trait whose architecture will be inferred. Because mosses have a haploid-dominant lifecycle, the PIs can efficiently survey the products of meiosis and generate simple yet powerful tests for specific associations between genes exhibiting biased transmission and fitness variation in natural populations.