Chloroplast evidence for the multiple origins of the hybrid Potamogeton × fluitans

Previous studies of Potamogeton × fluitans Roth. have supported the putative origin of this taxon as a result of hybridization between Potamogeton lucens L. and Potamogeton natans L. In the British Isles P. × fluitans is restricted to only a few sites, while both its parents are relatively common. Previous studies have shown that most of these hybrid populations are monomorphic, with the exception of the Moors River, in Hampshire and Dorset, where multiple genotypes have been identified. This is despite the fact that here the hybrid grows in the absence of one its parents, P. lucens. In this study, species-specific differences in the TrnL (UAA) chloroplast region, a maternally inherited marker, were used to identify the original seed-bearing parent of the hybrids within this river system. It was shown that both species have been maternal parents in the creation of this hybrid population.