Host choice mechanisms in tree killing bark beetles

摘要: Bark beetles with the capacity to kill and colonize living trees are main pests of coniferous forests around world. The European spruce bark beetle, Ips typographus, belongs a group possessing facultative attack patterns. For long periods I. typographus is in low populations only on seriously weakened hosts. However, following disturbances like storms or drought periods, amount suitable breading material increases dramatically population size may rise within short time epidemic levels. In phase behaves aggressively, attacking healthy destroying large areas Norway forest. this pattern behaviour exploiting different ecological niche than during endemic, phase: broken hosts they exploit relatively poor source nutrients without dealing host defences. Instead have deal higher degree interspecific competition. On other hand, provides breeding material, which rich free from competition, but there fight defence responses tree. Host defences can be overcome by mass thousands same tree, coordinated aggregation pheromones. trade-off between evaluating quality risk rating great challenge for pioneering beetles, that initiate an before any pheromone plumes exist. choice mechanism divided several distinct steps: 1. habitat location flight 2. host flight 3. host evaluation after landing, involving detection suitability spacing species individuals avoid inter- intraspecific competition. 4. risk entrance into phloem. The question whether beetles’ ruled attraction alone guided markers has been issue debate decades. The peripheral nervous system possesses olfactory receptor neurons both pheromones, volatiles non-host volatiles. Several studies support theory cues play important role habitat location, while involved finding acceptance, either through modulating attraction. consist physical barriers chemical compounds detrimental invaders. Conifers maintain certain level preformed (constitutive) enhanced attacks, e.g. increased production defensive metabolites development structures. evaluate trees’ ability, guide them their decision enter host. Because density factor influencing success overwhelming defence, it hypothesized also will modulate behaviour, directly its influence quality. This introductory paper written obtain overview over literature aspects beetle exhibiting so called aggressive colonisation behaviour. Different hypotheses importance discussed. Finally, I propose model typographus.