Breeding matters: Natal experience influences population state-dependent host acceptance by an eruptive insect herbivore

Abstract

Eruptive forest insects are highly influential agents of change in forest ecosystems, and their effects have increased with recent climate change. State-dependent life histories contribute significantly to the population dynamics of eruptive forest insect herbivores; however, the proximate mechanisms by which these species shift between states is poorly understood. Laboratory bioassays were conducted using the mountain pine beetle (Dendroctonus ponderosae) to determine the effect of maternal host selection on offspring host preferences, as they apply to population state-dependent behaviors. Female mountain pine beetles exhibited state-dependent preference for artificial host material amended with monoterpenes in the absence of other cues, such that individuals reared in high-density epidemic-state simulations rejected low monoterpene conditions, while low-density endemic-state beetles accepted low monoterpene conditions. State-specific behavior in offspring was dependent on rearing conditions, as a function of maternal host selection, and these effects were observed within one generation. Density-dependent host selection behaviors exhibited by female mountain pine beetle offspring is reinforced by context-dependent maternal effects arising from parental host selection, and in situ exposure to conspecifics. These results demonstrate potential proximate mechanisms that control population dynamics in eruptive forest insects, and will allow for more accurate predictions of continued impact and spread of these species.

Consequences of distributional asymmetry in a warming environment: invasion of novel forests by the mountain pine beetle

“…, Bentz et al. , Burke and Carroll ). Interestingly, as a consequence of forest management efforts that have increased the amount of susceptible hosts over the landscape in western Canada (Taylor and Carroll , Taylor et al.…”

“…However, given the propensity for positive feedbacks to amplify across scales for an eruptive herbivore such as MPB, when population densities increase sufficiently, outbreaks will occur regardless of tree resistance (Raffa et al 2008). Indeed, once MPB populations breach the endemic/epidemic threshold, beetles will preferentially colonize even the most defensive trees (Boone et al 2011, Burke and Carroll 2017. Interestingly, as a consequence of forest management efforts that have increased the amount of susceptible hosts over the landscape in western Canada Carroll 2004, Taylor et al 2006), the most recent MPB outbreak reached an unprecedented size and resulted in unusually high levels of tree mortality (Cudmore et al 2010, Safranyik et al 2010, potentially negating any selective advantage associated with coevolved lodgepole pine populations, and depending on genotypes of lodgepole pine trees selected for reforestation following control and salvage harvesting, may have implications for the susceptibility of the future forest.…”

The cytochrome P450 CYP6DE1 catalyzes the conversion of α-pinene into the mountain pine beetle aggregation pheromone trans-verbenol

“…The mountain pine beetle ( Dendroctonus ponderosae ; MPB) is a pest of several pine ( Pinus ) species in western North America 1 . While endemic MPB populations are mostly confined to weakened host trees, during epidemic outbreaks MPB successfully colonize healthy mature trees 2,3 . Pines and other conifers are generally well defended against most herbivores by their production, accumulation and secretion of oleoresin terpenes 4–6 .…”

Translocation experiment reveals capacity for mountain pine beetle persistence under climate warming

“…Experimental bolts of the same species were infested by drilling a small hole vertically into the phloem at the anatomical bottom of the bolt, inserting first a female then a male beetle, and stapling a mesh screen over each hole to prevent beetle escape. To minimize potential maternal effects due to host species (Burke and Carroll 2017), P UT were reared in P. flexilis and P AZ in P. flexilis/ strobiformis hybrids that were harvested from the same locations as infested bolts (Table 1). Individuals were randomized by sex and mating pairs were infested 6 cm apart, with 10–13 pairs per bolt depending on bolt circumference.…”