THEORETICAL HABITAT TEMPLETS, SPECIES TRAITS, AND SPECIES RICHNESS - AQUATIC COLEOPTERA IN THE UPPER RHONE RIVER AND ITS FLOODPLAIN

1. To test predictions of the river habitat templet and the patch dyna mics concept, trends in species traits and species richness of aquatic beetles were related to the spatial - temporal variability of eightee n habitat types in the alluvial floodplain of the French Upper Rhone R iver. One hundred and twenty species of beetles were used in this anal ysis. 2. The basic information was obtained either from the literature (for most of the species traits) or from observations made at approxi mately 500 sampling sites in the Bregnier-Cordon and Jons sections ove r the past 19 years (for habitat utilization). This information was st ructured by a fuzzy coding technique and examined by ordination analys es. 3. Analyses of the relationships among nineteen species traits rev ealed a clear distinction according to traits such as body form (for a dults), functional feeding type and food (adults and larvae), attachme nt to the substrate and dissemination potential (adults and larvae), a nd patterns of aquatic and/or terrestrial life of adults and larvae. S pecies traits such as number of descendants per reproductive cycle, an d number of reproductive cycles per year or per individual showed less contrast, because these traits are rather homogeneous in aquatic beet les. 4. Analyses of the habitat utilization by the aquatic beetles rev ealed a vertical gradient that separates interstitial from superficial habitats, and a transverse gradient for the superficial habitats, whi ch extends from the main channel towards permanent oxbow lakes and tem porary waters. 5. The significant relationship betweeen species traits and habitat utilization demonstrates that most beetle species use a p articular set of habitat types with a particular set of species trait modalities. 6. Species traits of aquatic beetles are homogeneous but e vidently very successful and are adapted to many potential conditions of spatial-temporal variability. Because of this homogeneity, observat ions on aquatic beetles do not support trends of traits in the framewo rk of spatial-temporal variability predicted from the river habitat te mplet. 7. The observed species richness of aquatic beetles is low in h abitat types with a low spatial-temporal variability, increases as spa tial variability increases, and tends to be highest at intermediate te mporal variability. This pattern matches predictions of the patch dyna mics concept.