XVI International Botanical Congess

Along a unique freshwater tidal zone of the river Schelde (Belgium), Scirpus species occur primarily in small and fragmented clumps. Most of these are native S. lacustris, S. pungens, S. triqueter, S. tabernaemontani or morphological intermediates. However, three cultivated S. tabernaemontani strains were introduced recently to stabilize riverbanks. A genetic diversity (isozymes, RAPD) analysis, enabled to identify unambiguously the different Scirpus taxa ocurring along the river. Hybridization between S. triqueter and S. tabernaemontani is documented. Among the introduced clones at least two different origins could be distinguished. Clumps of the introduced S. tabernaemontani clones were clearly different from the native ones, providing arguments for safeguarding the native hybrid complex from potential genetic pollution.