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1998

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Sammendrag

Effects of isolation, habitat size and several microhabitat variables on presence/absence of the monophagous Bolitophagus reticulatus (L.) (Coleoptera, Tenebrionidae) were investigated in 58 forest fragments in an agricultural landscape (15 km2) in south-eastern Norway. All potential habitats of the beetle, dead Fomes fomentarius (L.) Kickx basidiocarps (n=587), were collected from trees (n=185) within the study area. The basidiocarps were dissected and the number of B. reticulatus specimens (larvae, pupae and adults) counted. The material was analysed at four distinguishable spatial scales: basidiocarp-, tree-, tree-group- and forest island level. Different patterns of beetle presence emerged at the different scales. Increasing habitat size and decreasing degree of isolation increased the probability of B. reticulatus presence at three (basidiocarp-, tree- and forest island level) and one (tree level) scales, respectively, whilst no such trends were found at the fourth level (tree-group level). Increasing insolation and thereby higher ambient temperatures, indicated by several microhabitat variables, improved the probability of beetle presence amongst the trees. The number of beetle specimens correlated positively with an increase in the habitat size at the tree level.

Sammendrag

1. Habitat use of Bolitophagus reticulatus (L.) (Coleoptera, Tenebrionidae), living in the basidiocarps of Fomes fomentarius (L.) Kickx, was investigated in three forest areas in south-eastern Norway: (1) a continuous, coniferous forest, (2) an agricultural area with mostly deciduous forest islands in a matrix of cultivated land and (3) a homogeneous, old deciduous forest stand. B. reticulatus was almost exclusively found inside dead basidiocarps. 2. The size of the basidiocarp was the most important variable for predicting the probability of B. reticulatus presence in the basidiocarps from all three study areas. 3. Drier basidiocarps had a higher probability of beetle presence than the wetter ones. Basidiocarps situated above the ground level had a higher probability of beetle presence than those close to or on the ground level. 4. The disappearance of beetles from previously inhabited basidiocarps seemed to be due to depletion of resources. 5. In the first study area, the presence of Cisidae was found to reduce the probability of B. reticulatus presence perhaps as a result of competition.