Isozyme evidence for the origin of Potamogeton x sudermanicus as a hybrid between P-acutifolius and P-berchtoldii

Potamogeton x sudermanicus Hagstr. has been interpreted morphologically as a hybrid between P. acutifolius Link and P. berchtoldii Fieber. Both parent s belong to section Graminifolii where hybrids appear to be less frequent t han in other sections. This reputed hybrid has been recorded at only a few sites in Europe and at a single locality in Britain. Using seven different isozyme systems it was shown that all the bands present within the British population of the hybrid were found in P. acutifolius or P. berchtoldii, su pporting the putative origin of this taxon. In addition, the identification of two multi-enzyme phenotypes implies that this hybrid has arisen at leas t twice at this site. (C) 2001 Elsevier Science B.V. All rights reserved.