Potamogeton ×fluitans (P. natans × P. lucens) in the Czech Republic. II. Isozyme analysis.

Evidence from isozyme electrophoresis confirmed previous hypothesis on the occurrence of interspecific hybridization between Potamogeton natans L. and P. lucens L. formulated on the basis of morphology and stem anatomy. Isozyme phenotypes of the morphologically intermediate plants were compared with those obtained from the putative parents growing in the same locality. P. natans and P. lucens differed consistently in at least 12 loci and possessed different alleles at 7 loci. The hybrid had no unique alleles and exhibited an additive “hybrid” isozyme pattern for all 7 loci that could be reliably analysed and where the parents displayed different enzyme patterns. Both true parental genotypes were detected among samples of plants of P. lucens and P. natans from the same locality. The hybrid plants represent a recent F1 hybrid generation resulting from a single hybridization event. Consistent differences in enzyme activity between submerged and floating leaves of P. natans and P. ×fluitans were observed in all interpretable enzyme systems.