THE APPLICATION OF HABITAT TEMPLETS AND TRAITS TO HYPHOMYCETE FUNGI IN A MID-EUROPEAN RIVER SYSTEM

1. The general knowledge about hyphomycetes is summarized and traits o f some of these organisms in the Rhone floodplain are described to ass ess compliance with the river habitat templet (RHT) and patch dynamics concept (PDC) hypotheses. This investigation corresponds with those f or other taxonomic groups reported in a recent Freshwater Biology Spec ial Issue on the Ecology of the Upper Rhone River (Statzner, Resh & Do ledec, 1994). 2. Three groups of fungi were considered: aquatic, terre strial, and aero-aquatic hyphomycetes. 3. The main factors controlling distribution of these micro-organisms are food (mostly organic matter ), dissolved oxygen and biotic interactions. 4. With contrasting strat egies, hyphomycetes exploit both fallen leaves, a discrete ephemeral r esource, and wood fragments, which are more durable. 5. Fungal propagu les (spores, hyphae) are distributed in the water, and even the air, l argely throughout the year. This explains the resilience of these orga nisms to disturbance. 6. A major problem is the spatial (boundary laye r, dead zones) and temporal (leaf input) scale at which these micro-or ganisms live and their interactions at the scale adopted for the other organisms referred to in the Special Issue on the Ecology of the Uppe r Rhone. 7. Our scant knowledge of the microbial ecology in the Rhone floodplain, together with the scale problem and high microbial resilie nce to environmental stress, render the RHT and PDC hypotheses difficu lt to test. Only three traits could be tested on hyphomycetes, but all three confirmed the RHT hypotheses. 8. Hyphomycete communities appear to be biologically controlled in more favourable and temporally stabl e environments, and physico-chemically controlled in harsher and more perturbed environments.