Eur. J. Entomol. 99: 43-52, 2002 ISSN 1210-5759 Fungivorous beetles in basidiocarpsFomesfomentarius of respond differently to microhabitat variables Bj0rn Arne RUKKE* Division of Zoology, Department of Biology, University of Oslo, P.O. Box 1050 Blindem, N-0316 Oslo, Norway e-mail: [email protected] Key words. Fungivorous beetles, Fomesfomentarius, habitat preferences, microhabitat variables, heterogeneous resource, spatial scale, conservation Abstract. This study investigates the influence of microhabitat on the presence of several species of fungivorous beetles in basidiocarps of Fomes fomentarius (L.) Kickx. All dead basidiocarps ofF. fomentarius from fragments of forest in an agricultural landscape in Norway were sampled and dissected, and their content of Cisjacquemarti Mellie, 1848/C.alter (Silvferberg, 1991) (did not distinguish between individuals of these two species), C. bidentatus (Olivier, 1790), C. lineatocribratus Mellie, 1848,Ennear- thron cornutum (Gyllenhal, 1827) (Ciidae) andDorcatoma dresdensis Herbst, 1792 (Anobiidae) were identified. Multiple logistic regression models revealed that these species responded differently to the microhabitat variables. The incidence of these beetles was associated with the size (volume), position (height above ground) and moisture content of the basidiocarps. The analyses also indi­ cated possible interspecific interactions between some of the beetles. The presence of some of the species mainly in basidiocarps at particular stages of degradation indicates a successional pattern of occurrence of these species. Together these results indicate that basidiocarps of F. fomentarius are a heterogeneous resource for fungivorous beetles. This has implications for conservation: To pre­ serve the diversity of fungivores, sufficient dead wood has to be left in forests to assure an adequate supply of F. fomentarius basidiocarps of different quality. INTRODUCTION lié, 1848/C.alter (Silvferberg, 1991) (individuals of these Many species live in patchily distributed habitats, and two species were not distinguished), C. bidentatus these environmental discontinuities affect the distribution (Olivier, 1790), C. lineatocribratus Mellié, 1848,Ennear- of organisms (Wiens, 1976). At larger scales, landscape thron cornutum (Gyllenhal, 1827) (Ciidae) andDorca­ variables like isolation and habitat size may strongly toma dresdensis Herbst, 1792 (Anobiidae) decreases with affect species occurrence (e.g. Kindvall & Ahlen, 1992), increased habitat isolation and reduced habitat size while more locally, microhabitat conditions may deter­ (Rukke, 2000 - in this paper C. alter — C. nitidius (Fabri- mine their spatial distribution (e.g. Midtgaard et al., cius, 1792)). Additionally, an incidence study at a lower 1998). Therefore, a multiple scale approach to habitat scale has shown the effect of several microhabitat vari­ requirements is more likely to increase our knowledge of ables on the presence of B. reticulatus in basidiocarps species distribution than a single-scale approach. (Midtgaardetal., 1998). Both landscape and microhabitat variables affect the Since dead wood and its associated fungi are greatly occurrence of beetles in basidiocarps of fungi growing on reduced in quantity in today’s forests due to forestry prac­ dead wood. The basidiocarp habitat is an example of a tices (Haila et al., 1994; Bader et al., 1995; Esseen et al., spatial hierarchy with more or less clearly defined patches 1997), information on the habitat requirements of the bee­ at several nested scales. Basidiocarps are nested within tles associated with such habitats is particularly inter­ trees, trees within groups of trees and groups of trees esting for conservation purposes. To prevent habitat within forests. Incidence studies (Rukke & Midtgaard, depletion and subsequent population decline, a better 1998; Sverdrup-Thygeson & Midtgaard, 1998), a mark- knowledge of a species’ habitat requirements, at all rele­ recapture study (Nilsson, 1997) and a genetic survey vant scales, is required. (Knutsen et al., 2000) have revealed effects of the large- The present study aims to add information about small- scale variables isolation and habitat size on the population scale habitat requirements of beetles associated with fungi dynamics of Bolitophagus reticulatus (Linnaeus, 1767) living on dead wood. The effects of several microhabitat (Tenebrionidae), which is monophagous on basidiocarps variables on the presence of C. jacquemarti/C. alter, C. of Fomes fomentarius (L.) Kickx. Another large-scale bidentatus, C. lineatocribratus, E. cornutum and D. dres­ study showed that several other species inhabiting densis in the basidiocarps of F. fomentarius were investi­ basidiocarps of F. fomentarius are also affected by gated in an attempt to reveal whether the species have changes in degree of habitat isolation and habitat size. particular habitat preferences. Like B. reticulatus, the incidence of Cisjacquemarti Mel- * Current address: Kranveien 4, 0684 Oslo, Norway. 43 Table 1. Species of Coleóptera found in the dead basidiocarps of Fomes fomentarius (n = 587) from the study area. Included are number of specimens (S) and number of occurrences (O). Species Family S O Species Family S O Cisjacquemarti/alter Ciidae 6783 386 Phyllotreta striolata Chrysomelidae 1 1 Bolitophagus reticulatus Tenebrionidae 2153 134 Phyllotreta undulata Chrysomelidae 1 1 Dorcatoma dresdensis Anobiidae 181 40 Atomariafuscata Cryptophagidae 1 1 Cis bidentatus Ciidae 168 46 Atomaria impressa Cryptophagidae 1 1 Ennearthron cornutum Ciidae 122 55 Dalopius marginatus Elateridae 1 1 Cis lineatocribratus Ciidae 110 32 Selatosomus aeneus Elateridae 1 1 Cis quadridens Ciidae 58 7 Liestes seminigra Endomychidae 1 1 Ropalodontusperforatus Ciidae 20 3 Xylophilus corticalis Eucnemidae 1 1 Leptusafumida Staphylinidae 12 9 Cyphon sp. Helodidae 1 1 Rhizophagus dispar Rhizophagidae 9 8 Agathidium badium Leiodidae 1 1 Leptusapulchella Staphylinidae 6 6 Malachius bipustulatusMalachiidae 1 1 Acrulia inflata Staphylinidae 5 4 Rhizophagus bipustulatusRhizophagidae 1 1 Dinaraea aequata Staphylinidae 3 3 Rhizophagus nitidulusRhizophagidae 1 1 Dryocoetes alni Scolytidae 3 2 Athetafungi Staphylinidae 1 1 Ennearthron laricinum Ciidae 2 1 Atheta nigricornis Staphylinidae 1 1 Agonum micans Carabidae 1 1 Gabrius sp. Staphylinidae 1 1 Pterostichus oblongopunctatusCarabidae 1 1 Quedius xanthopus Staphylinidae 1 1 Cerylon histeroides Cerylonidae 1 1 MATERIAL AND METHODS trees harbour several basidiocarps, which usually do not die The study area consisted of 58 forest patches (“forest simultaneously, sometimes making a tree bearing basidiocarps a islands”) in an agricultural area (1585 ha) in the Lier munici­ suitable habitat patch for more than a decade. pality (59°48'N, 10°16'E), Norway. The size of the forest The basidiocarps in this study were earlier used to study the islands varied from 729 to 63386 m2. Data was collected from effect of habitat and landscape variables on the presence of the April to mid June 1993. In the study area all 587 dead basidio­ same beetle species at higher spatial scales, i.e. at the level of carps of F. fomentarius (as defined by Matthewman & Pielou individual trees with basidiocarps (the tree level) and the level (1971) were collected from 185 trees (125 birches(Betula of forest islands (see Rukke, 2000). At the tree level, both pubescens) and 60 grey alder (Alnus incana)) and dissected to habitat isolation and habitat size were found to influence the reveal their content of beetles. Boreal deciduous trees were the presence of each of the beetle species on a tree. To reduce the dominant tree species in the forest islands, and F. fomentarius influence of these tree-related variables in the present study, basidiocarps were by far the most common basidiocarps on dead only basidiocarps from trees having a certain minimum prob­ wood in the study area (pers. obs.). ability of beetle presence were included in the analyses. These All adult beetles in the basidiocarps were recorded (Table 1). probabilities were estimated for each of the beetle species from In the identification of the beetles, it was difficult to separate their respective multiple logistic regression model at the tree individuals of the species C. glabratus Mellie, 1848,C. jacque- level. For C. jacquemarti/alter the criterion was set to 70%, marti and C. alter because they were desiccated (Sindre whilst it was set to 50% for the four other species in order to Ligaard, pers. comm.). Since C. glabratus is rarely found in include a sufficient number of basidiocarps in the analyses. basidiocarps of F. fomentarius (e.g. 0kland, 1995; Fossli & Additionally, all dead basidiocarps from trees having at least Andersen, 1998; Jonsell, 1999), all these individuals were one basidiocarp inhabited by the respective species were treated as an assemblage of the two species C. jacquemarti and included. Being able to colonise a tree, a beetle species also has C. alter, which is abbreviated to C. jacquemarti/alter. Only C. the possibility to inhabit all the other basidiocarps on that tree, jacquemarti/alter and the four species C. bidentatus, C. lineato- and consequently be tested for microhabitat preferences there. cribratus, E. cornutum and D. dresdensis were common enough Univariate and forward, stepwise, multiple logistic regres­ for further analyses (except for B. reticulatus, which is treated sions (enter- and check-back-criteria were p < 0,05 and p < 0,06 in Midtgaard et al. (1998)). respectively) (see