Molecular confirmation of Potamogeton × bottnicus (P. pectinatus × P. vaginatus, Potamogetonaceae) in Britain

Restriction fragment length polymorphisms in the internal transcribed spacer region of ribosomal DNA and in the chloroplast genome combine to confirm the existence of Potamogeton×bottnicus (P. pectinatus×P. vaginatus) in Britain. One of the parents, P. vaginatus, is not currently a member of the British flora, but did occur here in the past (the latest fossil fruits date from 30 000 BP) and the hybrid may therefore owe its origin to ancient cross-pollination involving indigenous material or to more recent long-distance dispersal.