I. 2000. Forest fragmentation truncates a food chain based on an old-growth forest bracket fungus. -Oikos 90: 119-126.We studied the effect of forest fragmentation on the insect community inhabiting an old-growth forest specialist bracket fungus, Fomitopsis rosea, in eastern Finland. Samples of the fungus from large non-isolated control areas were compared with samples from forest fragments in two isolation time classes; 2 -7 yr and 12 -32 yr since isolation. Fomitopsis rosea hosted a species-rich community with relatively many specialized old-growth forest insects. The numerically dominant food chain consisted of F. rosea, the tineid moth Agnathosia mendicella and the tachinid fly Elfia cingulata, a specialist parasitoid of A. mendicella. The frequency of F. rosea on suitable fallen spruce logs and the frequency of A. mendicella in fruiting bodies were significantly lower in the forest fragments than in the control areas. The median number of trophic levels decreased from three in the control areas to one in the fragments that had been isolated for the longest period of time. The parasitoid was completely missing from the fragments isolated for 12 -32 yr. Our results show that in boreal forests habitat loss and fragmentation truncate food chains of specialized species in the course of time since isolation.

Greatly reduced area of old‐growth forests and the very low amount of dead wood in managed forests in northern Europe have caused a marked decline in the populations of saproxylic species. It is less clear at which spatial and temporal scales these adverse changes are taking place, and more information is needed to reliably predict which species are especially sensitive to loss and fragmentation of habitat. Here we compare species richness, incidence of occurrence in forest fragments, and abundance of polyporous fungal species and species groups between two regions in Finland with contrasting histories of forestry and a marked difference in the amount and spatial configuration of old‐growth forests. We also analyse the consequences of increasing loss of connectivity on the presence and abundance of polypores in a study region with a documented short‐term history of old‐growth fragmentation. Our results show that the species number, incidence of occurrence, and abundance of especially the rare, threatened, and near‐threatened species are much lower in the old‐growth fragments in Häme in southern Finland in comparison with Kuhmo in eastern Finland, most probably because of the longer history of intensive forestry in Häme. Among the rare species, the species that show the greatest difference between the two regions (at the scale of 500 km) also tended to respond most strongly to the more recent forest fragmentation within the study region in Kuhmo (at the scale of 50 km). Polypores associated with spruce seem to be more strongly affected by forestry than species associated with pine, possibly reflecting the differences in the natural dynamics of spruce‐dominated and pine‐dominated forests.

Leningrad Region, Russia; this is the second find of the species after its description from Siberia. Junghuhnia fimbriate/la (Peck) RyYarden was found in Leningrad Region; this is the first record in northern Europe. Skeletocutis borealis Niemela and many other rare species are discussed, including new localities from Finland and/or NW Russia. Some of them are illustrated, and many species are supplied w ith detailed spore measurements. 143 polypore species were recorded and collected by the authors and their co-workers in virgin forests of Russian Karelia in wide sense; 12 of them are new to the area.

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The cestode Hymenolepis microps is an intestinal parasite of tetraonid birds, including the willow ptarmigan (Lagopus lagopus). This parasite is able to maintain a high prevalence and intensity throughout the year, even in a subarctic environment in bird populations with relatively low host densities, indicating effective transmission routes. Willow ptarmigan consume mainly vegetal material and active consumption of invertebrates is confined to the first two or three weeks of life. Ptarmigan are infected by different species of ectoparasites, of which two species of feather lice, Lagopoecus affinis and Goniodes lagopi, are the most abundant. In this study, we explored the hypothesis that feather lice may be suitable intermediate hosts for H. microps. We applied histological techniques and light microscopy to investigate lice for the presence of larval cestode stages (cysticercoids). We found 12 cysticercoid-like structures inside chewing lice collected on L. lagopus hosts harbouring H. microps. In addition, a polymerase chain reaction (PCR) screening of Ischnocera lice DNA, targeting the 18S rRNA gene of the cestode, showed positive results for two different short fragments of the 18S rRNA gene of H. microps which were sequenced from lice collected on birds. Both independent lines of evidence support the hypothesis that Ischnocera lice might be suitable intermediate hosts in the life cycle of H. microps in L. lagopus.