How environment and genetic architecture of unreduced gametes shape the establishment of autopolyploids

It is broadly assumed that polyploidy success results from increased fitness associated with whole genome duplication due to higher tolerance to stressful conditions. In agreement, several theoretical models found that, among other factors, a better tolerance to new environmental conditions can promote polyploidy establishment. Here, we investigated the effect of the genetic and environmental factors affecting the architecture of unreduced gamete production, to see how it affects the origin and persistence of autopolyploids in both stable and disturbed environments. We developed a theoretical model in which we modeled the joint evolution of a quantitative trait under selection and the production of unreduced gametes; both traits were pleiotropically linked. We followed the adaptation of initially diploid populations to a new environment to which tetraploid individuals were directly adapted. The generation of these autotetraploid individuals was enabled by the genetic production of unreduced gametes and by the environmental change modifying the average production of these gametes. We found that for realistic values of unreduced gamete production adaptation to new environmental conditions was mainly achieved through adaptation of diploids to the new optimum rather than the persistence of newly adapted tetraploid individuals. In broader parameter sets, we found that the adaptation process led to mixed-ploidy populations, except when the populations were swamped with unreduced gametes, and that pleiotropy and environmental effects favored the co-existence of both cytotypes.