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Abstract. The range of many Holarctic forest insects does not comprise the entire range of their hosts, as they are often limited to more southern latitudes by the adverse effects of cold temperatures. Global climate warming has led to the increased potential for forest insects to invade novel habitats of native hosts within the same landmass. The mountain pine beetle (MPB; Dendroctonus ponderosae) has recently expanded into higher-latitude forests of the principal host, lodgepole pine (Pinus contorta var. latifolia), and the susceptibility of trees is greater in these systems compared to forests in the native range. We assessed the contribution of the induced defensive response of hosts to this elevated susceptibility, and whether these discrepancies are the result of coevolution with host populations within the historic native range of the insect. We challenged trees using paired treatments of a beetle-attack simulation and a generic defensive response elicitor (methyl jasmonate) to mitigate variability in the induced response among trees within and among populations, from within and outside the historic range of the beetle. We then assessed the production of monoterpene chemicals by the trees in response to treatments using gas chromatography/mass spectrometry. The differential induction of monoterpenes in response to simulated beetle attack relative to the generic elicitor was highest in populations with the highest putative historic exposure to MPB. Elevated susceptibility and invasion potential of the beetle in novel systems is the proximate result of reduced defensive capacity, ultimately arising from a lack of coevolution with the beetle in novel systems. In forested systems with climate-driven herbivore-host distributional asymmetry, continued warming will potentially exacerbate the impacts of aggressive insect herbivores as they invade defensively na€ ıve host populations.

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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.

Exotic earthworms are drivers of biotic communities in invaded North American forest stands. Here we used ecologically important oribatid mite (Arachnida: Acari) communities, as model organisms to study the responses of litter-and soil-dwelling microarthropod communities to exotic earthworm invasion in a northern temperate forest. Litter-and soil-dwelling mites were sampled in 2008-2009 from forest areas: (1) with no earthworms; (2) those with epigeic and endogeic species, including Lumbricus rubellus Hoffmeister; and (3) those with epigeic, endogeic, and anecic earthworms including L. terrestris L. Species richness and diversity of litter-and soil-dwelling (0-2 cm soil depth) oribatid mites was 1-2 times higher in sites without earthworms than in sites with worms. Similarly, litter-dwelling oribatid mites were between 72 and 1,210 times more abundant in earthworm-free sites than in sites with worms. Among earthworm invaded sites, abundance of litter-dwelling oribatid mites in sites without the anecic L. terrestris was twice as high in May and 28 times higher in October, compared to sites with L. terrestris. Species richness, diversity, and abundance of oribatid mites were greater in litter-layers than in the soil-layers that showed a varied response to earthworm invasion. Species compositions of both litter-and soil-dwelling oribatid mite communities of forests with no earthworms were markedly different from those with earthworms. We conclude that exotic earthworm invasions are associated with significant declines of species OPEN ACCESSDiversity 2011, 3 156 diversity, numbers, and compositional shifts in litter-and soil-inhabiting communities. These faunal shifts may contribute to earthworm effects on soil processes and food web dynamics in historically earthworm-free, northern temperate forests.

In this exploratory work, we investigate the relationship between the role identity "farmer" and farmers' land management practices using data from 30 semistructured interviews with farmers in southeastern Idaho. Guided by social identity principles, we examine how farmers' collective identity influences environmental attitudes and behaviors. Overall, we find that most farmers have implemented some conservation practices on their land, particularly those related to soil and water, and see themselves and other farmers as good environmental stewards. However, we also find that many of their chosen conservation practices required little to no sacrifice, and in addition to benefiting the environment, were also cost-minimizing business decisions. We find that as a group, these farmers' beliefs, attitudes, and behaviors are largely focused on productive efficiency. We argue that this focus often puts them in competition with other social groups, which ultimately reinforces group saliency and adversely affects relations between farmers and other groups seeking to influence farming practices.

Either bifenthrin or carbaryl can be used to exclude subcortical beetles from loblolly pine trees. Trapping data reflect known vertical partitioning on the bole by these insects. Double-pane traps were slightly more effective than single-pane traps in catching subcortical beetles.

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