Understanding the genetic variability of hybrids provides information on their current and future evolutionary role. In this paper, we focus on the interspecific hybrid Ranunculus circinatus × R. fluitans that forms spontaneously within the group Ranuculus L. sect. Batrachium DC. (Ranunculaceae Juss.). Genome-wide DNA fingerprinting using amplified fragment length polymorphisms (AFLP) was employed to determine the genetic variation among 36 riverine populations of the hybrid and their parental species. The results demonstrate a strong genetic structure of R. circinatus × R. fluitans within Poland (Central Europe), which is attributed to independent hybridization events, sterility of hybrid individuals, vegetative propagation, and isolation through geographical distance within populations. The hybrid R. circinatus × R. fluitans is a sterile triploid, but, as we have shown in this study, it may participate in subsequent hybridization events, resulting in a ploidy change that can lead to spontaneous fertility recovery. The ability to produce unreduced female gametes of the hybrid R. circinatus × R. fluitans and the parental species R. fluitans is an important evolutionary mechanism in Ranunculus sect. Batrachium that could give rise to new taxa.

Department of Botany Faculty of Science University of South Bohemia Branišovská 31 370 05 České Budějovice Czech Republic

Department of Ecology and Environmental Protection Poznan University of Life Sciences Wojska Polskiego 28 60 637 Poznań Poland

Institute of Botany Czech Academy of Sciences Zámek 1 252 43 Průhonice Czech Republic

Institute of Botany Faculty of Biology Jagiellonian University Gronostajowa 3 30 387 Kraków Poland

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Identifying the richness and evolutionary relationships of Ranunculus sect. Batrachium in its diversity centre in south-western Europe