Comparative abilities of vegetative regeneration among aquatic plants growing in disturbed habitats

The regeneration (regrowth into viable plants) and colonisation (establishment in the sediment) abilities of vegetative fragments of six aquatic plant species (Elodea canadensis Michaux, Hippuris vulgaris L., Luronium natans (L.) Rafin., Potamogeton pusillus L., Ranunculus trichophyllus Chair, Sparganium emersum Rehm.) occurring in habitats frequently disturbed by floods along the Rhone River (France) were compared through a laboratory experiment. Six types of plant fragments were collected from the plants and placed in water over sediment. Their development and/or their rooting into the sediment were recorded over 10 weeks. The species exhibited different survival tactics to survive after fragmentation: (1) fragments from Sparganium and Ranunculus developed roots and rapidly established into the sediment whereas (2) fragments from Luronium, Hippuris and Elodea developed many propagules that could be dispersed but did not establish within the 10 weeks of the experiment. The fragments of P. pusillus never established nor regenerated. The results showed a trade-off between regeneration and colonisation related to the patterns of recolonisation of cleared patches of the species and their ecological requirements. Maintenance of these species in ecosystems frequently disturbed by floods can partly be explained by their high regeneration abilities, and results are discussed in terms of life-history traits and ecological strategies. (C) 1998 Elsevier Science B.V.