Vicia cracca (vetch, Fabaceae) is a perennial herb with a contact zone of diploids and tetraploids in Central Europe. Eliášová et al. study genetic diversity, heterozygosity and mating systems and confirm the autopolyploid origin of V. cracca tetraploids, which have higher allelic richness compared with diploids. A pollination experiment suggests that the breeding system in both cytotypes is mixed-mating with prevailing outcrossing, but that polyploids tolerate a higher rate of autogamy. The results support the hypothesis that polyploids may be better colonizers because they possess higher genetic diversity, and thus the ability to adapt to changing conditions, and also have lower inbreeding depression.