Can ploidy changes propel the evolution of allogamy in a selfing species complex?

BACKGROUND: The transition to self-fertilization has occurred repeatedly across diverse plant groups, and the evolutionary consequences of selfing typically suggest that a shift toward outcrossing is unlikely. However, we propose that polyploidization could drive changes in reproductive strategies by influencing traits associated with pollination. We explored various traits linked to the mating system across different ploidy levels within the polyploid Erysimum incanum species complex, which is generally considered a predominantly selfing species. RESULTS: Our results revealed significant variation in self-fertilization success across different ploidies and we also found significant differences among populations within the same ploidy level. Inbreeding depression is absent in diploids, it was present in hexaploids, while tetraploids exhibited intermediate values. Additionally, polyploids showed traits more commonly associated with outcrossing rather than self-fertilization. Finally, the high values of heterozygosity found in polyploid populations were contrary to our expectations due to the selfing evolutionary history of this species. CONCLUSIONS: These findings suggest that polyploidy may facilitate the emergence of alternative reproductive strategies, driving diversification in mating systems within this selfing species complex. This phenomenon, not previously observed in the wild, opens new perspectives on the evolution of plant mating systems. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12870-025-06868-1.