Effects of wood decay fungi and tree species on saproxylic beetles: A field experiment using sawdust blocks

Abstract Wood litter provides both a food resource and habitat for diverse saproxylic insects, and variation in substrate quality can influence community structure. To examine the effects of tree and fungal species on beetle assemblages, I prepared sawdust blocks from four tree species ( Fagus crenata , Quercus crispula , Zelkova serrata and Cryptomeria japonica ) that were artificially decayed by inoculation with one of four white‐rot fungi ( Bjerkandera adusta , Sarcomyxa edulis , Phlebia tremellosa and Trametes versicolor ). These blocks were placed in the field and retrieved after 3 months to survey beetles occurring within the blocks. In total, 429 individuals representing eight species from six families were recorded, with Anthicomorphus cruralis comprising over 99% of all specimens. Beetle abundance was significantly affected by fungal species, with notably higher densities in blocks colonized by P. tremellosa , but no significant effect of tree species was detected. These results indicate that some saproxylic beetles depend more strongly on fungal species than on tree species, suggesting that fungal species identity may be a key factor shaping insect assemblages in intermediate to late stages of wood decay.