Insect colonisation of fruiting bodies of the wood-decaying fungus Fomitopsis pinicola at different distances from an old-growth forest

Abstract

We studied the colonisation rate of insects inhabiting fruiting bodies of the wood-decaying fungus Fomitopsis pinicola both within and at different distances (up to 1610 m) from an old-growth forest reserve. The colonisation rate of most species was not affected by the distance from the reserve, and none of the species were affected by the size of local sources of fruiting bodies in the managed forest. We suggest that many insect species inhabiting fruiting bodies of wood-decaying fungi can colonise fruiting bodies at a high enough rate to persist in managed forests of Fennoscandia. However, the colonisation rates of the fungivorous beetle Cis quadridens and the predatory fly Medetera apicalis were negatively affected by distance from the reserve. Cis quadridens is rare in many managed forests, but often quite common at sites with high substrate densities. The rarity of this species may therefore be due to weak ability to colonize distant patches. The same may also be true for M. apicalis, but less is known about the biology of this species. Medetera apicalis was the most common insect predator in the old-growth forest, but it was rare at the largest distances from it in the managed forest. Therefore, it seems likely that the overall pressure from natural enemies significantly declined with distance from the reserve.