Breeding behavior and its possible consequences for gene flow in Taraxacum sect. Erythrosperma (H. Lindb.) Dahlst.

Studies of pollen, seed set and experimental hybridizations were carried out to clarify breeding behavior and gene flow pathways in Taraxacum sect. Erythrosperma . Seeds from hybridization (106 samples), open pollinated (34) and bagged (43) capitula were analyzed for breeding system using a flow–cytometric seed screen. In the section Erythrosperma , diploids are obligate sexuals, mostly allogamous; however, autogamy also occurs (in 28% of unpollinated capitula). Triploids are apomicts with residual sexuality (in 13% of capitula pollinated by pollen of diploids). Pollen of diploids in Taraxacum is usually approximately the same size (regular pollen). In our study, in the section Erythrosperma , many diploids (24%) produced pollen grains of different sizes (irregular pollen) and one plant produced no pollen. The pollen of triploids is either irregular (33%) or the triploids produce no pollen (67%). Consequently, the method of ploidy level assessment on the basis of pollen characteristics is not suitable for Taraxacum sect. Erythrosperma . Low potential for polyploid hybrid formation between diploid maternal plants and polyploid pollen donors, considerable tendency to autogamy and no evidence of the formation of diploid progeny by polyploid maternal plants (facultative apomixis) indicates low intensity of gene flow within Taraxacum sect. Erythrosperma. This, together with a lower population density and spatial isolation of ploidy levels, is expected to result in a lower rate of formation of new apomictic lineages. Thus, Taraxacum sect. Erythrosperma appears evolutionarily more stable and taxonomically less complicated than sect. Ruderalia . The present study supports the agamospecies concept of Taraxacum sect. Erythrosperma .