Exploring behavioural and physiological adaptations in mountain pine beetle in response to elevated ozone concentrations.

ABSTRACT

Elevated ozone (eO3) concentrations pose a threat to insect populations by potentially altering their behaviour and physiology. This study investigates the effects of eO3 concentrations on the mountain pine beetle which is a major tree-killing species of conifers in northwestern North America. We are particularly interested in understanding the effects of eO3 concentrations on beetle behaviour and physiology and possible transgenerational impacts on bark beetle broods. We conducted O3-enrichment experiments in a controlled laboratory setting using different O3 concentrations (100-200 ppb; projected for 2050-2100) and assessed various beetle responses, including CO2 respiration, mating behaviour, survival probability, locomotion, and attraction behaviour. Transgenerational impacts on the first and second generations were also analyzed by studying brood morphology, mating behaviour, survival, and pheromone production. We found that beetles exposed to eO3 concentrations had shorter oviposition galleries and reduced brood production. Beetle pheromones were also degraded by eO3 exposure. However, exposure to eO3 also prompted various adaptive responses in beetles. Despite reduced respiration, eO3 improved locomotor activity and the olfactory response of beetles. Surprisingly, beetle survival probability was also improved both in the parents and their broods. We also observed transgenerational plasticity in the broods of eO3-exposed parents, suggesting potential stress resistance mechanisms. This was evident by similar mating success, oviposition gallery length, and brood numbers produced in both control and eO3 concentration treatments. This study demonstrates the sensitivity of mountain pine beetles to increased O3 concentrations, contributing crucial insights into the ecological implications of eO3 concentrations on their populations. Overall, the outcome of this study contributes to informed climate change mitigation strategies and adaptive management practices for the development of resilient forests in response to emerging forest insect pests worldwide.