The fine-scale ecological determinants for wood-inhabiting aphyllophoroid basidiomycetes

15 The fine-scale ecological determinants for wood-inhabiting aphyllophoroid basidiomycetes 16 were investigated with statistical analyses of the occurrence of fruit bodies on woody debris 17 collected in Switzerland and Ukraine. Three substrate descriptors were considered: diameter, 18 degree of decomposition and host tree species. 19 By means of Multiple Regression Trees, thresholds in the response of fungal communities to 20 these local environmental descriptors were detected. Three classes for diameter, as well as for 21 degree of decomposition were thus delimited. They revealed the importance of very small sizes, 22 which were not reported in the literature so far: the relevant diameter class limits were about 23 0.72 cm and 1.35 cm. Within the host tree species, a clear distinction between coniferous and 24 broadleaf species was found. The next splits followed rather climatic determinants of tree 25 distribution than taxonomical entities such as families or genera. 26 The fidelity of the 59 fungal species to diameter classes, decomposition classes and host tree 27 species was measured by the Dufrêne-Legendre index and only significant responses after 28 permutation tests were retained. This brought new insights on the ecology of many wood-29 inhabiting aphyllophoroid basidiomycetes. 30 Redundancy Analysis was applied to investigate the response of fungal species to diameter and 31 degree of decomposition of woody debris from the most common host tree species, Fagus Author manuscript, published in "Fungal Diversity 30 (2008) 83-95" 2 sylvatica. This direct gradient analysis made it possible to reconstruct the succession of fungal 1 species along the wood decomposition process.