環境

We collected stream foam samples and submerged leaf litter in three headwater streams in the Tama River system and detected a total of 32 species of aquatic Hyphomycetes. The highest fungal species diversity was observed in the deciduous forest stream in a high elevation watershed. Fungal flora from leaf litter of Japanese cedar was distinct from that from leaf litter of Japanese zelkova. We also demonstrated a relationship between temperature and hyphal growth for three representative fungal species. As a result of litter bag experiments in the three streams, we observed (1) lower densities of leaf-shredding insects colonized on leaves in the cedar forest stream than the deciduous forest streams and (2) lower preference of many insects for cedar than zelkova leaves. We offered cedar or zelkova leaves inoculated with each of the three representative fungal species to a litter-specialist insect. Aquatic hyphomycetes facilitated consumption of zelkova leaves by insects, and a fungal species facilitating higher consumption of the litter-specialist insect was different from that of food-generalist insects. Such facilitating effect of fungi and its variation by fungal species was not detected for consumption of cedar leaves by the litter-specialist insects.

Kagaya Takashi