The presence of apomicts in sexual Sorbus populations leads to the generation of novel polyploid cytotypes that can have a significant effect on population structure. Hajrudinović et al. use flow cytometry to assess genome size and ploidy levels within pure and sympatric populations of diploid S. aria and tetraploid apomictic S. austriaca, and also determine mating systems. They find that the coexistence of apomictic tetraploids and sexual diploids drives the production of novel polyploid cytotypes with predominantly apomictic reproductive modes. The interacting sexual and asexual lineages and mixtures of cytotypes in the Sorbus population complexes thus represent potential reservoirs of new biodiversity.