Effects of forest fire and the ecology of fire-adapted insects

Abstract: Fire is widely recognised for its major impact on boreal forest ecosystems. The altereddisturbance regime due to effective fire suppression and extensive forestry may be a majorthreat to biodiversity.If logging preceded burning, the pyrophilous (Gr. fire-loving) beetle Sericoda quadripunctata failed to reproduce. Because fires had a moderate impact on survival of ground- andwood-living beetles, pyrophilous species arriving at burned clear-cuts may face competitionfrom a fauna already adapted to open habitat conditions.Burning affected species composition through both habitat and substrate change.Comparing fire-scorched and unburned logs in a burned area, and unburned logs at a clear-cutand in a forest, revealed that: 1) fewer phloem-feeding and more ascomycete-feedingarthropods emerged from fire-scorched spruce and birch logs; 2) species richness of beetleswas unaffected by burning; 3) diversity was highest in the burned area; and, 4) host-treespecificity was lower in more disturbed sites and in burned logs.The mycangia of the beetle Henoticus serratus contained Trichoderma, an ascomycetegenus suggested to be an important food source for many pyrophilous insects. These insectscan be divided into two groups: mycophagous species that need burned substrate per sebecause ascomycete fungi am favoured, and phloem-feeders and predators that needcompetitive release.The need to find forest fires over large geographical and temporal distances may posestrong selection on these species. The pyrophilous beetle Melanophila acuminata had lowerwing load and greater flight-muscle mass than two closely related nonpyrophilous species.This increased allocation to dispersal coincided with fewer eggs and ovarioles, despite alarger body size. This suggests a trade-off between dispersal and fecundity. Adult M.acuminata also emerged over a greater time span within and between years than closelyrelated species, and records made in the field were more extended over the season. Asimulation test, where records were compared with the seasonal distribution of natural firesrevealed that M acuminata does not maximise, but rather optimises, its chance to find fires.