Parasitoids (Hymenoptera, Ichneumonoidea) of Saproxylic beetles are affected by forest successional stage and dead wood characteristics in boreal spruce forest

Both forest type and dead wood characteristics had a significant effect on parasitoid assemblages. Grouped idiobionts and some species, such as Bracon obscurator and Ontsira antica, preferred clear-cuts, while others, such as Cosmophorus regius (Hym., Braconidae) and other koinobionts, were associated with older successional forest stages. No single dead wood substrate was sufficient to support the entire community of parasitoids in any forest type, even when the regular host was present. In particular, snags hosted a different assemblage of species from other types of dead wood, with parasitoids of Tetropium spp. such as Rhimphoctona spp. (Hym., Ichneumonidae) and Helconidea dentator (Hym., Braconidae) being abundant. These results indicate that a diversity of dead wood habitats is necessary to support complete assemblages of beetle-associated parasitoids from early successional stages of dead wood and that parasitoids may be more sensitive to habitat change than their hosts.