SELECTION OF MICROFUNGAL FOOD BY 6 ORIBATID MITE SPECIES (ORIBATIDA, ACARI) FROM 2 DIFFERENT BEECH FORESTS

Feeding preferences for microfungi of six oribatid mites from two beec h forests (Fagus sylvatica) in Germany, Gottinger Wald and Selling, we re investigated. Six microfungi which were isolated from the L2-litter layer of the Gottinger Wald (Cladosporium herbarum, Trichoderma virid e, Mortierella elongata, Mucor hiemalis, Penicillium sp.1 and a steril e dark form) were first offered simultaneously and then separately to three species of oribatid mites from this site (Steganacarus magnus, A crogalumna longipluma and Hypodamaeus riparius). Also, six microfungi from similar fungal taxa which were isolated from the F-horizon of Sol ling (Cladosporium cladosporioides, Mortierella ramanniana, Mortierell a parvispora, Mucor hiemalis, Penicillium sp.2 and a sterile dark form ) were offered simultaneously and separately to three species of oriba tid mites from this site (Cepheus dentatus, Nothrus silvestris and Hyp ochthonius rufulus). Feeding choice experiments were carried out separ ately for each oribatid mite species. Generally, oribatid mites from t he two different forests preferred similar microfungal taxa as food su bstrate. The ranking of fungal taxa was very similar in tests where fu ngi had been offered simultaneously and separately. The oribatid mites studied preferred dark, pigmented fungi (Dematiacea) to hyaline forms . The reason for this preference remains speculative; food quality of dematiaceous fungi might be superior to that of hyaline fungi or oriba tid mites may prefer to feed on dematiaceous fungi because they produc e more effective exoenzymes ('external rumen'). Despite the general pr eference for dematiaceous fungi, food selectivity of the oribatid mite species studied differed and the species were ranked in respect to th eir food specialization: Steganacarus magnus > Acrogalumna longipluma > Cepheus dentatus > Nothrus silvestris > Hypodamaeus riparius, Hypoch thonius rufulus. The consequences of selective feeding of oribatid mit es on the structure of fungal communities are discussed.