HABITAT VARIABILITY AND SPACE UTILIZATION BY THE AMPHIBIAN COMMUNITIES OF THE FRENCH UPPER-RHONE FLOODPLAIN

In order to study the relationship between community organization and spatial-temporal variability, species richness and abundance of amphibian species were estimated in 17 sites of the French Upper Rhone floodplain. These sites were chosen because they were representative of the diversity of successional processes, age and connection with the active channel. Ecological variation among these sites was estimated by the analysis of 14 mesological, hydrological, and biotic variables, by means of correspondence analysis. Level of disturbance, eutrophication, water origin, presence of fish and water persistence were the main determinants of site typology. Amphibian species richness was highest in temporary sites experiencing intermediate level of disturbance. Three species (Rana ridibunda, Rana dalmatina, Triturus helveticus) were ubiquitous, three species (Hyla arborea, Bufo calamita, Pelodytes punctatus) were characteristic of habitats with intermediate variability and four (Triturus cristatus, Triturus alpestris, Bufo bufo, Bombina variegata) were rare in the floodplain. The most abundant species in the floodplain appeared to be r-selected and most of them showed a temporal flexibility of reproduction. These reproduction traits were assumed to respond to the balance between habitat unpredictability and interspecific constraint by making the adjustment to both availability and suitability of breeding habitats possible.