Genetic structure of the submersed Ranunculus baudotii (sect. Batrachium) population in a lowland stream in Denmark

•Ranunculus baudotii is mainly dispersed vegetatively in River Aarhus.•Populations are genetically distinct and have a different genetic structure.•Occasional establishment of seeds and putative hybrids contribute genetic diversity.•Reproduction mode and mating system shape genetic structure.•Selfing and genetic drift differentiate populations along the stream.