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

1. Ephemeroptera and Plecoptera in two sites of the Upper Rhone River (France) were examined using multivariate analyses to determine: (i) r elationships among seventeen species traits; (ii) habitat utilization of the fifty-five species present; (iii) the relationship between spec ies traits and habitat utilization; (iv) trends of species traits and species richness in a framework of spatial and temporal habitat variab ility. 2. The species traits having the highest correlation ratios cor respond to reproduction or life cycle, behavioural, and morphological characteristics. According to their traits, species of Baetidae, Caeni dae, and Leptophlebiidae (Ephemeroptera) are opposite species of Perli dae and Periodidae (Plecoptera). 3. The distribution of species in thi rteen habitat types of the Upper Rhone River floodplain demonstrates a transverse gradient from the main channel to the oxbow lakes. Plecopt era are restricted to the different main channel habitats; in contrast , Ephemeroptera families have a broader distribution with Baetidae and Leptophlebiidae occurring in most floodplain habitats. 4. Plecoptera exhibit a significant relationship between species traits and habitat utilization but no relationship is evident for Ephemeroptera. Baetidae use many habitat types and have diverse species traits; in contrast, Leptophlebiidae, Heptageniidae, and Caenidae use many habitat types bu t each family has a rather uniform set of traits. 5. Trends in species traits were significantly related to both the spatial and temporal va riability of habitats. Considering only temporal variability, the dist ribution of species trait modalities (= categories) corresponded well to predictions on trends in the river habitat templet for 'minimum age at reproduction' and 'potential longevity', and in general for 'desce ndants per reproductive cycle', 'reproductive cycles per year', 'poten tial size', and 'body flexibility'; trends in six other traits did not match predictions. 6. No trends in species richness were evident in s patial-temporal framework of habitat variability.