Insect assembly gathering on sporocarps of Ganoderma applanatum (Ganodermataceae, Basidiomycota) in western Japan

Insect-fungus interactions take part in many processes of forest ecosystems. The genus of Ganoderma (Fungi) has been known to produce enormous number of spores with thick outer-wall. Ganoderma applanatum sensu lato, wood rotting fungi, is one of the most common species in warm temperate Japan and yields abundant spores those rarely germinate.  Tuno (1999) proved that most dominating spore feeding insects are species of beetles (Coleoptera) and Mycodrosophila species (Drosophilidae, Diptera)  and suggested that flies may contribute to fungal spore dispersal since flies excrement consists of number of intact spores. In this study we identified insect assembly visiting on several sporocarps of Ganoderma applanatum sensu lato as well as measurement of variation in spore size and germination rate. We located several G. applanatum sl in Kanazawa city, Ishikawa prf. to sample insects visiting and discharged spores between May to November in 2012. A total of 499 individuals of insect was collected.  Beetles (66.53%) were most abundant group in number, followed by flies (27.66%) and other orders (5.81%). The sampled insects consisted of mycophagies and  predators of mycophagies. Most of mycophagies were found to be spore feeders through their excrement observation. The number and species composition greatly varied among sporocarps. The spore size also varied in time. Shimotoku and Tuno (unpubl. Data in 2011) found that most beetle feeders destroyed Ganoderma spores, whereas, Mycodrosophila flies do not damage the spores germination ability. We discuss about the ecological roles of spore feeding insects those could be antagonistic or mutualistic. 

Key words:   mutualism, mycophagy, Mycodrosophila, Scaphidiidae, Ganoderma