© Entomologica Fennica. 16 July 2004 Insect assemblage associated with the polypore Fomitopsis pinicola: a comparison across Fennoscandia Atte Komonen, Mats Jonsell, Bjørn Økland, Anne Sverdrup-Thygeson & Karl Thunes Komonen, A., Jonsell, M., Økland, B., Sverdrup-Thygeson, A. & Thunes, K. 2004: Insect assemblage associated with the polypore Fomitopsis pinicola:a comparison across Fennoscandia. — Entomol. Fennica 15: 102–112. We compiled the data on the insect assemblage occurring within the polypore Fomitopsis pinicola from six regions in Finland, Sweden and Norway. The spe- cies composition and diversity of the primary fungivorous beetles (Cisidae and Anobidae) were similar across Fennoscandia. The beetles Cis glabratus Mellié (Cisidae) and C. quadridens Mellié were the most frequent species occurring in 70% and 23% of the fruiting bodies on average. Sulcacis fronticornis (Panzer) and Ennearthron cornutum (Gyllenhal) were relatively common in southern Sweden, while absent from the study regions in Norway and Finland. Similarly, Cis bidentatus (Olivier) and Cis dentatus Mellié were rather common in Norway, but almost absent from the Finnish samples. Species relative abundances in the six study regions exhibit more variation, which to some extent corresponds the biogeographical zones. Our results on the high similarity in species composition indicate deterministic nature of the F.pinicola-associated insect assemblage over large spatial scales. On the other hand, climatic factors probably have an impact on the relative abundance of species. Atte Komonen, Faculty of Forestry, University of Joensuu, P.O. Box 111, FIN- 80101 Joensuu, Finland; E-mail: [email protected] Mats Jonsell, Department of Entomology, Swedish University of Agricultural Sciences, P. O. Box 7044, S-750 07 Uppsala, Sweden; E-mail: mats.jonsell@ entom.slu.se Bjørn Økland, Skogforsk, Hogskoleveien 12, N-1432 As, Norway; E-mail: [email protected] Anne Sverdrup-Thygeson, Norwegian Institute for Nature Research, NINA, P.O. Box 735 Sentrum, N-0105 Oslo, Norway; E-mail: anne.sverdrup-thygeson @nina.no Karl Thunes, Norwegian Forest Research Institute, Fanaflaten 4, N-5244 Fana, Norway; Email: [email protected] Received 9 April 2003, accepted 12 December 2003 ENTOMOL. FENNICA Vol. 15 • Insects in Fomitopsis pinicola 103 1. Introduction al. 2001). Research on polypore-dwelling in- sects, predominantly in boreal forests in Fenno- The magnitude of spatial variation in species dis- scandia, has focused on species composition, di- tribution and abundance is one of the basic ques- versity and community structure (Økland & tions in ecology. In addition, the scale of variation Hågvar 1994, Thunes 1994, Økland 1995, Thu- is important for many applied questions, such as nes & Willassen 1997, Thunes et al. 2000, Ko- in assessing the effects of habitat loss and frag- monen 2001, Komonen et al. 2001), substrate as- mentation on natural biota (Edwards et al. 1994). sociations (Nilsson 1997, Fossli & Andersen For example, if a given ecological community is 1998, Jonsell et al. 2001), extinction and coloni- relatively constant in species composition and zation (Whitlock 1992, Jonsson et al. 1997, ecological structure over large areas, then man- Jonsell et al. 1999), and spatial variation, espe- agement practices (e.g. timber felling) could op- cially on the effects of forest fragmentation erate at coarser basis than if there is plenty of (Rukke & Midtgaard 1998, Sverdrup-Thygeson small-scale variation. However, most ecological & Midtgaard 1998, Kehler & Bondrup-Nielsen studies operate at small spatial scales (Edwards et 1999, Jonsson et al. 2001, Komonen et al. 2000, al. 1994, Gaston & Blackburn 2000) and infor- Jonsell & Nordlander 2002). Most of these stud- mation on large-scale spatial variation is urgently ies have operated at relatively small spatial scales, needed, not only because it provides the basis for and the largest distances between study regions understanding the spatial variation in smaller have been ca. 500 km (Komonen 2001). Thus, scale studies, but also to fully evaluate the conse- comparisons over large spatial scales are crucial quences of habitat loss and fragmentation (Harri- to fully understand patterns of variation in these son & Bruna 1999). fungal-insect systems in boreal forests. Many insect communities occur inside rela- In this paper, we analyse the large-scale spa- tively small and discrete resource patches, such as tial variation in species composition, diversity decaying trees, ant mounds, dung patches or fun- and community structure of the insect fauna oc- gal fruiting bodies (Hammond & Lawrence 1989, curring within the polypore Fomitopsis pinicola Hanski & Cambefort 1991, Siitonen 2001, (Swartz: Fr.) Karst. (Aphyllophorales: Polypora- Päivinen et al. 2002). These insect assemblages ceae) in Fennoscandian boreal forests. We com- are relatively species-rich considering the small piled the data on this insect assemblage collected habitat size, comprise many specialized species by the authors of the present paper from Finland, which are unable to reproduce outside their focal Sweden and Norway (e.g. Økland & Hågvar resource patch, and play an important role in the 1994, Thunes et al. 2000, Jonsell et al. 2001, decomposition of organic matter and thus pro- Komonen 2003), and examined the spatial varia- mote nutrient cycling (e.g. Hanski & Cambefort tion across six regions. Firstly, we provide an 1991, Samuelsson et al. 1994, Siitonen 2001). overview of the full insect assemblages encoun- Thus, these kinds of insect assemblages are likely tered in the different regions. Secondly, we focus to contribute greatly to the local biodiversity and on the obligate fungivorous species, particularly ecosystem functioning. Partly due to the con- Cisidae (Coleoptera). cealed life style, however, very little is known about the distribution, abundance and ecology of species in these systems, especially at large spa- 2. Material and methods tial scales. In forests, polypores (Aphyllophorales: Poly- 2.1. The fungus poraceae) constitute an important component of ecosystem as symbionts, parasites and de- Fomitopsis pinicola is a conspicuous and often composers of wood (Swift 1982). The fruiting the most abundant polypore in Fennoscandian bodies of polypores also host speciose insect boreal forests (Ryvarden & Gilbertson 1993). Al- communities, including many species that are though the species is common in managed for- monophagous on a particular host fungus or uti- ests, its population density is considerably higher lize a few fungal species (Hanski 1989, Jonsell et in areas with large amounts of suitable coarse 104 Komonen et al. • ENTOMOL. FENNICA Vol. 15 Fig. 1. Map of the study regions and boreal vegetation zones. HB = hemiboreal, SB = southern boreal, MB = middle boreal, NB = northern boreal. woody debris (CWD), particularly in the old- climate ranges from oceanic in the west (Norway) growth forests (Lindblad 1998, pers. obs.). The to more continental in the east (Finland) (Anon. fungal fruiting bodies grow predominantly on 1992). There is also a south–north gradient in cli- stumps, snags and downed logs of dead and dying mate ranging from the hemiboreal vegetation Norway spruce (Picea abies (L.) Karst.), al- zone to the middle boreal zone in the northern- though they can be found on numerous other tree most sites (Ahti et al. 1968). species (Ryvarden & Gilbertson 1993). The fruit- The Häme region in Finland (61–62ºN, 23– ing bodies of F.pinicola are perennial and the old- 25oE) is situated in the transition zone between est can reach a size of about 40 cm in cap diameter the southern and middle boreal zone. The Kuhmo (Ryvarden & Gilbertson 1993). The insect mate- region (. 64oN, 29–30oE) is the easternmost rial in this study was obtained from within fungal study region belonging to the middle boreal zone. fruiting bodies that were collected from the field The mean annual precipitation in Häme and and taken into laboratory in order to rear the in- Kuhmo is 550–600 mm, and the mean annual sects living inside; Collembola was not recorded. temperature +2–4oCand+1oC, respectively (data The nomenclature of Coleoptera follows Silfver- from the Finnish Meteorological Institute). berg (1992). The province of Uppland in Sweden (59°30’– 60°30’N, 17°–18°E) was the southernmost study region, belonging to the hemiboreal zone. 2.2. Study areas Dalarna (60°30’N, 14–15°E) and Västerbotten (64°N, 19–20°E) are situated in the middle boreal We sampled polypore fruiting bodies from six zone. The mean annual precipitation and temper- Fennoscandian regions, representing different ature is 544 mm and 5.6°C in Uppland, 730 mm climatic and biogeographical zones (Fig. 1). The and 2.6°C in Dalarna, and 591mm and 1.5°C in ENTOMOL. FENNICA Vol. 15 • Insects in Fomitopsis pinicola 105 Västerbotten (data from the Swedish Meteoro- ent in the different countries. In Norway and Fin- logical Institute). land insects were reared in cloth-covered plastic The westernmost region belongs to Akershus funnels (Norway) or boxes (Finland), which were and Buskerud counties in Norway (59°51’N– kept in outdoor temperature; 122 fruiting bodies 60°30’N, 10°40’E–11°05’E) and is situated in the in Norway were kept in plastic boxes indoors. southern boreal zone. The mean annual precipita- The rearings were checked for insects continu- tion is 760–1200 mm, and the mean annual tem- ously until the end of September. The fruiting perature +2.9oC (data from the Norwegian Mete- bodies sampled in 1997 in Norway were dis- orological Institute). sected afterwards. In Sweden, polypores were The studied forest areas are dominated by placed indoors in 1-litre containers of waxed pa- Norway spruce on mesic and moist sites, while per (milk containers). A glass vial was inserted Scots pine (Pinus sylvestris Linnaeus) is the pre- into the container so that emerging photopositive dominant tree species on dry ridges, hill tops and insects could be easily collected; the non-photo- pine bogs. Birch (Betula Linnaeus spp.) and as- positive insects were collected by hand. Rearings pen (Populus tremula Linnaeus) are less frequent were checked for insects over a half a year, after in the study areas.