The effects of resource distribution and spatial scale on the distribution of two species of bark beetle: Polygraphus rufipennis (Kirby) and Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae)

Bark and ambrosia beetles (Scolytidae) are forest insects that inhabit the bark and sapwood of many trees. The spatial scale at which bark beetles respond to environmental variation may affect their distributions. I examined the distribution of two bark beetles, Trypodendron lineatum (Olivier) and Polygraphus rufipennis (Kirby), in relation to different spatial scales of environmental variation. The abundance of both species in a stand increased with the proportion of host trees. However only T. lineatum responded to the changes in resource abundance following harvesting. Settlement of T. lineatum among stumps was not influenced by landscape variation, but instead stump diameter. P. rufipennis settlement among resources differed from T. lineatum in that settlement densities were primarily influenced by landscape level variation. This study shows that species with similar life history traits may be affected differently by environmental variation at different spatial scales.