Search

Whitebark pine (WBP, Pinus albicaulis) is a white pine of subalpine regions in the Western contiguous United States and Canada. WBP has become critically threatened throughout a significant part of its natural range due to mortality from the introduced fungal pathogen white pine blister rust (WPBR, Cronartium ribicola) and additional threats from mountain pine beetle (Dendroctonus ponderosae), wildfire, and maladaptation due to changing climate. Vast acreages of WBP have suffered nearly complete mortality. Genomic technologies can contribute to a faster, more cost-effective approach to the traditional practices of identifying disease-resistant, climate-adapted seed sources for restoration. With deep-coverage Illumina short reads of haploid megagametophyte tissue and Oxford Nanopore long reads of diploid needle tissue, followed by a hybrid, multistep assembly approach, we produced a final assembly containing 27.6 Gb of sequence in 92,740 contigs (N50 537,007 bp) and 34,716 scaffolds (N50 2.0 Gb). Approximately 87.2% (24.0 Gb) of total sequence was placed on the 12 WBP chromosomes. Annotation yielded 25,362 protein-coding genes, and over 77% of the genome was characterized as repeats. WBP has demonstrated the greatest variation in resistance to WPBR among the North American white pines. Candidate genes for quantitative resistance include disease resistance genes known as nucleotide-binding leucine-rich repeat receptors (NLRs). A combination of protein domain alignments and direct genome scanning was employed to fully describe the 3 subclasses of NLRs. Our high-quality reference sequence and annotation provide a marked improvement in NLR identification compared to previous assessments that leveraged de novo-assembled transcriptomes. [ABSTRACT FROM AUTHOR]

Mountain pine beetles (MPBs) pose a substantial threat to North American pine forests, causing extensive tree mortality over large areas. Their tree‐killing ability is closely linked to mass aggregation on host trees triggered via pheromones and dependence on their symbiotic fungi. However, the influence of a changing climate on the biology of MPBs and their co‐evolved interactions with their fungal symbionts remains uncertain. To investigate this, male and female pairs of beetles were introduced into freshly cut logs from lodgepole pine trees and placed in controlled climate chambers with manipulated environmental conditions, including two levels of CO2 (ambient vs. 1000 ppm), O3 (ambient vs. 100 ppb) and humidity (33% vs. 65%). The beetle‐infested logs were left in these chambers for 1 month and then returned to ambient conditions until brood emergence. Emerging broods were collected for further analysis. Additionally, three species of fungal symbionts (Grosmannia clavigera, Ophiostoma montium and Leptographium longiclavatum) were subjected to the same CO2, O3 and humidity conditions for 5 days. Lower humidity promoted MPB reproduction and fungal growth. Elevated CO2 accelerated larval growth and emergence while improving brood pheromone production. Elevated O3 had a negative impact on MPB reproduction and brood fitness while improving its immune responses to an entomopathogenic fungus (Beauveria bassiana). It also inhibited fungal growth and reproduction, whereas elevated CO2 had varied (positive or negative) effects on fungal growth and ergosterol (proxy to fungal mass) production depending on the fungal species. Together, these findings suggest that climate change can potentially alter the interactions between MPBs and their fungal symbionts, highlighting the importance of understanding how climate change affects forest pests and their symbiotic relationships to develop effective management strategies in the future. [ABSTRACT FROM AUTHOR]

This article discusses a podcast titled "Listening to Fire Knowledges in and around the Okanagan Valley," which explores the history and challenges of using and controlling fire in the Okanagan Valley in British Columbia. The podcast features interviews with individuals who have expertise and understanding of fire, including Indigenous communities and fire suppression experts. The article highlights the increasing threat of wildfires in the region due to climate change and the need for interdisciplinary problem-solving and public engagement. It also emphasizes the importance of understanding the historical roles of fire in the landscape and the unequal impacts of wildfires on different populations. The given text includes a list of various sources related to the topic of wildfires in British Columbia, Canada. These sources cover a range of perspectives, including Indigenous knowledge and practices, community perspectives, scientific research, and historical and cultural contexts. The sources provide valuable insights into the management of wildfires, the role of Indigenous communities, and the impact of climate change. The text can be used as a resource for library patrons conducting research on wildfires and their implications in British Columbia. The given document is a list of references and sources related to the topic of wildfires and Indigenous land management in British Columbia, Canada. The sources cover a range of perspectives, including Indigenous knowledge and practices, historical reviews, scientific studies, and cultural and artistic responses to wildfires. The document provides a comprehensive collection of resources for library patrons conducting research on this topic, allowing them to explore various viewpoints and gain a deeper understanding of the subject. [Extracted from the article]

In North America, lodgepole pine is frequently subjected to attacks by various biotic agents that compromise its ability to defend against subsequent attacks by insect herbivores. We investigated whether infections of lodgepole pine by different pathogenic fungal species have varying effects on its defense chemistry. We selected two common pathogens, Atropellis canker, Atropellis piniphila, and western gall rust, Endocronartium harknessii, affecting mature lodgepole pine trees in western Canada. We also included three ophiostomatoid fungi Grosmannia clavigera, Ophiostoma montium, and Leptographium longiclavatum associated with the mountain pine beetle (Dendroctonus ponderosae), because they are commonly used to investigate induced defenses of host trees of bark beetles. We collected phloem samples from lodgepole pines infected with the rust or the canker and healthy lodgepole pines in the same stand. We also inoculated mature lodgepole pines with the three fungal symbionts and collected phloem samples 2 weeks later when the defense chemistry was at its highest level. Different fungal species differentially altered the terpene chemistry of lodgepole pine trees. E. harknessii and the fungal symbionts altered the terpene chemistry in a similar pattern while trees responded to the infection by the A. piniphila differently. Our study highlights the importance of considering specific biotic stress agents in tree susceptibility or resistance to the subsequent attacks by insect herbivores, such as mountain pine beetle. [ABSTRACT FROM AUTHOR]

Mountain pine beetle (MPB) in Canada have spread well beyond their historical range. Accurate modelling of the long-term dynamics of MPB is critical for assessing the risk of further expansion and informing management strategies, particularly in the context of climate change and variable forest resilience. Most previous models have focused on capturing a single outbreak without tree replacement. While these models are useful for understanding MPB biology and outbreak dynamics, they cannot accurately model long-term forest dynamics. Past models that incorporate forest growth tend to simplify beetle dynamics. We present a new model that couples forest growth to MPB population dynamics and accurately captures key aspects of MPB biology, including a threshold for the number of beetles needed to overcome tree defenses and beetle aggregation that facilitates mass attacks. These mechanisms lead to a demographic Allee effect, which is known to be important in beetle population dynamics. We show that as forest resilience decreases, a fold bifurcation emerges and there is a stable fixed point with a non-zero MPB population. We derive conditions for the existence of this equilibrium. We then simulate biologically relevant scenarios and show that the beetle population approaches this equilibrium with transient boom and bust cycles with period related to the time of forest recovery. As forest resilience decreases, the Allee threshold also decreases. Thus, if host resilience decreases under climate change, for example under increased stress from drought, then the lower Allee threshold makes transient outbreaks more likely to occur in the future. [ABSTRACT FROM AUTHOR]

Simple Summary: Bark beetles are global forest pests that feed and breed in the inner bark of trees and may transfer symbiotic fungi that cause blue staining and reduce the commercial value of timber. In the present study, we examined the effects of semiochemical treatments on deterring bark beetle populations. This population reduction was measured by a reduction in the attraction to lure/trap catches, tree mortality, and attacks on trees. Based on the analysis of 863 experiments, we found that semiochemical treatments effectively reduce the bark beetle population and, therefore, represent an eco-friendly technique for forest protection. Bark beetles (Coleoptera: Curculionidae: Scolytinae) are among the most damaging tree pests globally. Rising temperatures, drought, fire, storms, cyclones, and poor forest management cause stress and loss of vigour in trees, and these conditions favour bark beetle outbreaks. While research has been conducted on push–pull strategies to deter bark beetles, using attractive and deterrent semiochemicals, the potential of this strategy to reduce bark beetle populations, particularly in the genera Dendroctonus and Ips, remains uncertain. Here, we conducted a global meta-analysis of 52 research articles to quantify the effects of semiochemical treatments on managing different species of Dendroctonus and Ips for forest protection. Based on this analysis, we found that push–pull semiochemicals can significantly reduce Dendroctonus and Ips populations measured by a reduction in the attraction to lure/trap catches, tree mortality, and attacks on trees. The overall efficacy of the push–pull semiochemical treatment shows a 66% reduction for Ips compared to control and a 54% reduction compared to control for Dendroctonus, while, at the species level, there was a 69% reduction for Dendroctonus ponderosae (Hopkins) and a 94% reduction in Ips perturbatus (Eichhoff), and a 93% reduction in Ips latidens (LeConte). Interestingly, among different treatment sources, the efficacy of conspecific semiochemicals in combination with heterospecific semiochemicals and non-host volatiles showed a 92% reduction in Dendroctonus spp., and conspecific semiochemicals in combination with non-host volatiles showed a 77% significant reduction in Ips spp., while the efficacy of heterospecific semiochemicals in reducing Ips population was about 69%, and 20% in Dendroctonus. Among different ecological regions, the use of a push–pull strategy showed a 70% reduction in Dendroctonus in central-west North America, and Ips showed a 75% reduction in southwest North America. Our results demonstrate that semiochemical-based push–pull techniques have the potential to reduce Dendroctonus and Ips bark beetle populations. Furthermore, based on our analysis, the efficacy of such eco-friendly interventions could be further improved and provide a good tool for forest managers to control these pests, at least under some circumstances. [ABSTRACT FROM AUTHOR]

Anticipating consequences of disturbance interactions on ecosystem structure and function is a critical management priority as disturbance activity increases with warming climate. Across the Northern Hemisphere, extensive tree mortality from recent bark beetle outbreaks raises concerns about potential fire behavior and post-fire forest function. Silvicultural treatments (that is, partial or complete cutting of forest stands) may reduce outbreak severity and subsequent fuel loads, but longevity of pre-outbreak treatment effects on outbreak severity and post-outbreak fuel profiles remains underexplored. Further, treatments may present tradeoffs for other management objectives focused on ecosystem services (for example, carbon storage). We measured structure in old-growth subalpine forests following a recent (early 2000s) severe mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak to examine effects of historical (1940s) cutting intensity on gray stage (~10 years after peak of outbreak) post-outbreak (1) fuel profiles and (2) aboveground biomass carbon. Compared to control (uncut) stands, historically cut stands subjected to the same MPB outbreak had approximately half the post-outbreak surface fuel loads, about 2–3x greater live canopy fuel loads, and greater within-stand spatial heterogeneity of dead canopy cover and available canopy fuel load. Post-outbreak total aboveground biomass carbon was similar across all stands, though historically cut stands had about 2x greater carbon in live biomass compared to uncut stands. These findings suggest tradeoffs with altered post-outbreak potential fire behavior and carbon storage in cut stands. Additional implications of historical silvicultural treatments for wildlife habitat, firefighting operations, and long-term carbon trajectories highlight temporal legacies of management on directing forest response to interacting disturbances. [ABSTRACT FROM AUTHOR]

Background: The mountain pine beetle, Dendroctonus ponderosae, is an irruptive bark beetle that causes extensive mortality to many pine species within the forests of western North America. Driven by climate change and wildfire suppression, a recent mountain pine beetle (MPB) outbreak has spread across more than 18 million hectares, including areas to the east of the Rocky Mountains that comprise populations and species of pines not previously affected. Despite its impacts, there are few tactics available to control MPB populations. Beauveria bassiana is an entomopathogenic fungus used as a biological agent in agriculture and forestry and has potential as a management tactic for the mountain pine beetle population. This work investigates the phenotypic and genomic variation between B. bassiana strains to identify optimal strains against a specific insect. Results: Using comparative genome and transcriptome analyses of eight B. bassiana isolates, we have identified the genetic basis of virulence, which includes oosporein production. Genes unique to the more virulent strains included functions in biosynthesis of mycotoxins, membrane transporters, and transcription factors. Significant differential expression of genes related to virulence, transmembrane transport, and stress response was identified between the different strains, as well as up to nine-fold upregulation of genes involved in the biosynthesis of oosporein. Differential correlation analysis revealed transcription factors that may be involved in regulating oosporein production. Conclusion: This study provides a foundation for the selection and/or engineering of the most effective strain of B. bassiana for the biological control of mountain pine beetle and other insect pests populations. [ABSTRACT FROM AUTHOR]

The article discusses the discovery of the mite species Tarsonemus populi Magowski, 2010 in Western Asia, specifically on the new beetle host Trachypteris picta (Buprestidae) in Iran. The study provides new insights into the phoretic associations between mites and beetles in the subgenus Schaarschmidtia, highlighting the diversity of these associations and the potential role of mites as biological control agents for beetle pests.

We modelled the potential impact of intensification of plantation management and thinning, on timber supply of an ∼500 000 ha forest in Alberta, Canada over a 200-year planning horizon. Pre-commercial and commercial thinning were applied to a portion of the better sites, which allowed shortening of the time to merchantability and earlier harvest than unthinned stands; less than 25% of the forest was thinned over the course of the plan. The sustainable harvest rate, represented here as the annual allowable cut (AAC), increased by ∼14% above baseline, when thinning was applied. Similarly, there was a 20.7% increase in AAC projected with the relaxation of even flow rules if thinning was also applied. Finally, thinning offset the expected decline in AAC after a 20-year surge in cutting of mature pine, designed to slow an epidemic of mountain pine beetle. In terms of wood supply, the volume extracted at thinning was <2% of annual supply but volume from final harvest from thinned stands, at times, surpassed that of unthinned stands of the forest. Individual tree size from thinned stands was ∼twice that from unthinned areas in the second part of the planning period, offsetting the expected decline in piece size after the era of harvest of natural forests. [ABSTRACT FROM AUTHOR]

Mountain pine beetle (Dendroctonus ponderosae Hopkins, 1902; MPB) has been causing limber pine (Pinus flexilis E. James) mortality at Great Basin National Park, Nevada, including at Wheeler Peak Campground, for many years. Research has shown that MPB voltinism and phenology are strongly influenced by climate and can vary by location and elevation, indicating the need for localized observations to inform treatment recommendations in some cases. We used emergence cages on infested tree boles, baited Lindgren funnel traps, and ambient air temperatures to describe MPB adult flight timing over 2 years. Adult MPB flight at this high-elevation site occurred from late June through early October. Based on funnel traps, peak flight occurred in early to mid-August. The majority of MPBs were captured when maximum ambient air temperatures during collection periods exceeded 21 °C, and during these periods, 2020 was warmer than 2019. In 2019, when both emergence cage and funnel trap data were available, median emergence from trees was about 10 days after median trap catch. These results highlight the appropriate timing for suppression treatments aimed at protecting high-value trees in this high-elevation, developed recreation site. [ABSTRACT FROM AUTHOR]

Insect herbivores must contend with constitutive and induced plant defenses. The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae) has expanded its range east of the Rocky Mountains into the western boreal forest and is encountering evolutionarily naïve lodgepole pines (Pinus contorta) and jack pines (Pinus banksiana). Pinus contorta and P. banksiana in the expanded range have different constitutive and induced defenses in response to wounding and inoculation with fungal associates of D. ponderosae. In the historic range, previous studies have examined phloem terpene content prior to and just after D. ponderosae mass attack, but the terpene profile of attacked trees post-overwintering is unknown. We examined the response of mature P. contorta and P. banksiana trees to experimentally-applied mass attack by D. ponderosae and quantified phloem terpenes at three time points, pre-attack, post-attack (same season), and the following spring, post-overwintering. Phloem content of total terpenes as well as many individual terpenes increased after D. ponderosae attack but were only significantly higher than pre-attack levels at the post-overwintering time point in both P. contorta and P. banksiana. The absence of a significant increase in phloem terpenes in the month following attack in naïve pines is a potential cause for increased D. ponderosae offspring production reported in naïve P. contorta. Beetle attack density did not influence the phloem terpene profiles of either species and there was no significant interaction between attack density and sampling time on terpene content. High phloem terpenes in trees that are attacked at low densities could prime these trees for defense against attacks in the following season but it could also make these trees more apparent to early-foraging beetles and facilitate efficient mass attack at low D. ponderosae population densities in the expanded range. [ABSTRACT FROM AUTHOR]

The mountain pine beetle (MPB) has infested over 16 million hectares of pine forests in western Canada, killing over 50% of mature lodgepole pine, Pinus contorta, in British Columbia alone. There are few tools available to manage irruptive bark beetle populations and to mitigate tree mortality. Beauveria bassiana is an entomopathogenic fungus that causes mortality to several bark beetle species. However, the potential for B. bassiana as a biocontrol agent against pine beetle populations is unknown. We selected three strains of B. bassiana from several culture collections and evaluated their conidial stability under cold storage, in planta (greenhouse, and pine bolts) and in natura (forest stand, pine bolts, and live pines) conditions. The stability assays showed that all fungal strains maintained a minimum effective conidial yield through the assay durations (3–12 weeks). In addition, we adapted a biphasic liquid–solid fermentation approach for the large-scale production of conidial biomass, yielding up to a 100-fold increase in production. In greenhouse virulence assays, the mean lethal time of MPBs was reduced to 3–4 days upon treatment with B. bassiana, where high B. bassiana-associated mycosis was also observed. Furthermore, the application of B. bassiana formulation substantially affected the gallery network of MPBs in bolts in the field, resulting in shorter larval galleries and significantly reduced offspring production. Indeed, high titer treatments reduced the mean larvae per gallery to virtually zero. Together these results demonstrate that B. bassiana may be a viable biocontrol tool to reduce mountain pine beetle populations in pine forests in western Canada. Key points: • Three B. bassiana strains identified to be stable at various test conditions. • Large-scale conidial biomass production using liquid–solid biphasic fermentation. • Reproductive success of D. ponderosae significantly reduced by B. bassiana formulation. [ABSTRACT FROM AUTHOR]

Whitebark pine (Pinus albicaulis) forest ecosystems in California are diverse and unique, yet their current status and condition are uncertain. Using a combination of geospatial and field plot data, we assessed patterns in the structure, composition, and health of whitebark pine ecosystems on national forests throughout the state of California to evaluate potential signs of declining ecosystem integrity. We found whitebark pine ecosystems to be structurally, compositionally, and functionally distinct among subregions of California, and all subregions displayed some evidence of declining ecological integrity. Whitebark pine forests in northern California exhibited signs of greater stand densification (Cascade–Klamath), potential encroachment by shade-tolerant conifer species (Cascade–Klamath and Warner Mountains), and increased tree mortality associated with mountain pine beetle outbreaks (Warner Mountains) than elsewhere in California. Whitebark pine stands in the Sierra Nevada showed signs of stand densification (central Sierra) and localized mountain pine beetle outbreaks (southern Sierra east). Notwithstanding these negative signs, much of the state's whitebark pine ecosystems on national forestlands appear to be relatively healthy and intact compared to more northern latitudes. Active management may be required to restore whitebark pine ecosystems on national forests in California with declining integrity, including stands experiencing substantial stand densification, encroachment by shade-tolerant conifers, and mountain pine beetle outbreaks. [ABSTRACT FROM AUTHOR]

The Mountain Pine Beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), a destructive pest found in the pine forests of Western North America, has exhibited range expansion and unprecedented population growth due to climate change. As this insect disperses by flight, understanding its flight mechanics may help to model and predict its rate of spread through the environment. In this work, aerodynamic scaling relationships—previously identified in idealized, predominantly two-dimensional and numerical cases—are applied to the case of live flight. In particular, this aims to improve the statistical confidence in predicting sex and age differences in flight performance, which have historically been analyzed in ecology using dimensional quantities. Thrust coefficient is found to scale with the square of Strouhal number, as has been found in prior studies. However, with respect to Reynolds number, scaling was with the inverse of Reynolds number, rather than the inverse of the square root. We demonstrate here that the established Strouhal number and Reynolds number scaling of force coefficient can be successfully extended not just to highly three-dimensional flows, and lower Reynolds number flows, but remains robust even across distinct individuals within a population of beetles. Using this scaling, we observe that males fly with a greater mean thrust coefficient and Strouhal number compared to females (p < 0.001), which is a significant improvement in statistical confidence over prior studies, which could not identify a major difference between sexes (p > 0.05). Meanwhile, there is also a significant difference in thrust coefficient between different age cohorts, with younger beetles exhibiting a lower magnitude than other age groups (p < 0.05). [ABSTRACT FROM AUTHOR]

The article describes the rare occurrence of Red-breasted Nuthatches using a nest box and successfully double brooding in the Berkeley Hills of coastal central California in 2021 and 2022. The authors document the behavior of the nuthatches, including the application of resin to the nest box entrance and the surrounding area, and discuss the potential reasons behind this behavior, such as deterring competitors and predators.

Extensive tree mortality in forests can change the community composition of soil fungi altering seedling establishment, a process critical to forest restoration. Disturbances that result in the loss of ectomycorrhizal fungi, in particular, may impede the establishment of tree species reliant on these symbionts for their survival. Inoculation of seedlings with soil from intact forests may improve the establishment of seedlings in such disturbances but the method has rarely been tested in the field. Here, we assess whether soil inoculation improves lodgepole pine (Pinus contorta var. latifolia) seedling performance in conspecific stands with high levels of tree mortality caused by a mountain pine beetle (Dendroctonus ponderosae) outbreak and whether underlying soil type modifies inoculation effects. We first inoculated seedlings in a growth chamber with small amounts of soils (5% volume) originating from either intact (<10%) or "beetle‐killed" (>70% pine basal area killed) conspecific stands or added no soil inoculum and, after 4 months, transplanted them into 15 beetle‐killed stands. After two growing seasons, root‐associated fungal communities of seedlings receiving inoculum from intact stands differed in composition from those receiving inoculum from beetle‐killed stands or no inoculum. However, inoculation had no effect on seedling survival, height, or biomass. Site properties, including soil texture and the resident fungal community composition, overwhelmed the effect of soil inoculation on seedling performance. Seedling survival and shoot mass was higher in sandy than loamy soils. Restoration to improve seedling performance in beetle‐killed stands should consider stand‐level treatments as soil inoculation at the level evaluated was ineffective. [ABSTRACT FROM AUTHOR]

Amplified by warming temperatures and drought, recent outbreaks of native bark beetles (Curculionidae: Scolytinae) have caused extensive tree mortality throughout Europe and North America. Despite their ubiquitous nature and important effects on ecosystems, forest recovery following such disturbances is poorly understood, particularly across regions with varying abiotic conditions and outbreak effects.To better understand post‐outbreak recovery across a topographically complex region, we synthesized data from 16 field studies spanning subalpine forests in the Southern Rocky Mountains, USA. From 1997 to 2019, these forests were heavily affected by outbreaks of three native bark beetle species (Dendroctonus ponderosae, Dendroctonus rufipennis and Dryocoetes confusus). We compared pre‐ and post‐outbreak forest conditions and developed region‐wide predictive maps of post‐outbreak (1) live basal areas, (2) juvenile densities and (3) height growth rates for the most abundant tree species – aspen (Populus tremuloides), Engelmann spruce (Picea engelmannii), lodgepole pine (Pinus contorta) and subalpine fir (Abies lasiocarpa).Beetle‐caused tree mortality reduced the average diameter of live trees by 28.4% (5.6 cm), and species dominance was altered on 27.8% of field plots with shifts away from pine and spruce. However, most plots (82.1%) were likely to recover towards pre‐outbreak tree densities without additional regeneration. Region‐wide maps indicated that fir and aspen, non‐host species for bark beetle species with the most severe effects (i.e. Dendroctonus spp.), will benefit from outbreaks through increased compositional dominance. After accounting for individual size, height growth for all conifer species was more rapid in sites with low winter precipitation, high winter temperatures and severe outbreaks.Synthesis. In subalpine forests of the US Rocky Mountains, recent bark beetle outbreaks have reduced tree size and altered species composition. While eventual recovery of the pre‐outbreak forest structure is likely in most places, changes in species composition may persist for decades. Still, forest communities following bark beetle outbreaks are widely variable due to differences in pre‐outbreak conditions, outbreak severity and abiotic gradients. This regional variability has critical implications for ecosystem services and susceptibility to future disturbances. [ABSTRACT FROM AUTHOR]

Background: Biological invasions are responsible for substantial environmental and economic losses. The red turpentine beetle (RTB), Dendroctonus valens LeConte, is an important invasive bark beetle from North America that has caused substantial tree mortality in China. The lack of a high-quality reference genome seriously limits deciphering the extent to which genetic adaptions resulted in a secondary pest becoming so destructive in its invaded area. Results: Here, we present a 322.41 Mb chromosome-scale reference genome of RTB, of which 98% of assembled sequences are anchored onto fourteen linkage groups including the X chromosome with a N50 size of 24.36 Mb, which is significantly greater than other Coleoptera species. Repetitive sequences make up 45.22% of the genome, which is higher than four other Coleoptera species, i.e., Mountain pine beetle Dendroctonus ponderosae, red flour beetle Tribolium castaneum, blister beetle Hycleus cichorii, and Colorado potato beetle Leptinotarsa decemlineata. We identify rapidly expanded gene families and positively selected genes in RTB, which may be responsible for its rapid environmental adaptation. Population genetic structure of RTB was revealed by genome resequencing of geographic populations in native and invaded regions, suggesting substantial divergence of the North American population and illustrates the possible invasion and spread route in China. Selective sweep analysis highlighted the enhanced ability of Chinese populations in environmental adaptation. Conclusions: Overall, our high-quality reference genome represents an important resource for genomics study of invasive bark beetles, which will facilitate the functional study and decipher mechanism underlying invasion success of RTB by integrating the Pinus tabuliformis genome. [ABSTRACT FROM AUTHOR]

Plants resist herbivores and pathogens by using constitutive (baseline) and inducible (change in defense after an attack) defenses. Inducibility has long been predicted to trade off with constitutive defense, reflecting the economic use of resources. However, empirical evidence for such tradeoffs is variable, and we still lack understanding about when and where defense trade-offs occur. We tested for tradeoffs between constitutive and induced defenses in natural populations of three species of long-lived pines (Pinus balfouriana, P. flexilis, P. longaeva) that differ greatly in constitutive defense and resistance to mountain pine beetle (MPB, Dendroctonus ponderosae). We also assessed how climate influenced constitutive and inducible defenses. At seven high-elevation sites in the western U.S., we simulated MPB attack to induce defenses and measured concentrations of terpene-based phloem defenses on days 0, 15, and 30. Constitutive and induced defenses did not trade off among or within species. Simulated MPB attack induced large increases in defense concentrations in all species independent of constitutive levels. MPB and its symbiotic fungi typically kill trees and thus could be selective forces maintaining strong inducibility within and among species. The contrasting constitutive concentrations in these species could be driven by the adaptation for specializing in harsh, high-elevation environments (e.g., P. balfouriana and P. longaeva) or by competition (e.g., P. flexilis), though these hypotheses have not been empirically examined. Climate influenced defenses, with the greatest concentrations of constitutive and induced defenses occurring at the coldest and driest sites. The interactions between climate and defenses have implications for these species under climate change. [ABSTRACT FROM AUTHOR]

Successful host plant colonization by tree-killing bark beetle-symbiotic fungal complexes depends on host suitability, which is largely determined by host defense metabolites such as monoterpenes. Studies have shown the ability of specific blends of host monoterpenes to influence bark beetles or their fungal symbionts, but how biologically relevant blends of host monoterpenes influence bark beetle-symbiotic fungal interaction is unknown. We tested how interactions between two host species (lodgepole pine or jack pine) and two fungal symbionts of mountain pine beetle (Grosmannia clavigera or Ophiostoma montium) affect the performance of adult female beetles in vitro. Beetles treated with the propagules of G. clavigera or O. montium or not treated (natural fungal load) were introduced into media amended with a blend of the entire monoterpene profile of either host species and beetle performance was compared. Overall, host blends altered beetle performance depending on the fungal species used in the beetle amendment. When beetles were amended with G. clavigera, their performance was superior over beetles amended with O. montium in either host blend. Furthermore, G. clavigera-amended beetles performed better in media amended with host blends than without a host blend; in contrast, O. montium-amended beetles performed better in media without a host blend than with a host blend. Overall, this study showed that host defense metabolites affect host suitability to bark beetles through influencing their fungal symbionts and that different species of fungal symbionts respond differentlly to host defense metabolites. [ABSTRACT FROM AUTHOR]

In this paper, considering the effect of environmental factors such as climate change, temperature and drought on the growth of forests and beetles as well as the pine forests death and economic loss caused by outbreaks of mountain pine beetles, we first develop a stochastic mountain pine beetle model with pesticide application, and then consider its near‐optimal control (NOC) problem. The problem NOC is formulated by decreasing the mountain pine beetles while keeping the cost of pesticide application to a minimum. By Pontryagin stochastic maximum principle, we establish some sufficient and necessary conditions of the near‐optimality. Some numerical simulations are carried out to illustrate the theoretical results, which indicate that the pesticide application could effectively control the number of beetles and relieve the pressure from the attacking of beetles on the pines. To some extent, this control strategy could protect the pine forests and reduce economic losses caused by the mountain pine beetles. [ABSTRACT FROM AUTHOR]

Although the attacks of I X. crassiusculus i on cocoa pods were similar to those recently recorded on areca nuts [[18]], the modest number of plants attacked suggests that spermatophagy on cocoa pods is sporadic. Hence, an infestation of I X. crassiusculus i with fungal symbionts could interfere in the fermentation process of fresh cocoa beans and ultimately affect the marketable quality of dry cocoa beans. However, all the concealed damage symptoms (appearance of galleries inside pod husk, mucilage, and beans, and the location of immature stages of the pest within the infested pods) were systematically recorded after cutting open the infested pods ( I n i = 20) in the laboratory. Graph: Figure 6 (a) adult X. crassiusculus boring on an immature cocoa bean; (b) adult X. crassiusculus tunneling on mature cocoa bean; (c) staining of insect galleries with whitish-grey fungal hyphae; (d) eggs of X. crassiusculus with fungal symbionts in cocoa bean. [Extracted from the article]

Forest disturbances can alter mycorrhizal fungal communities with consequences for subsequent plant establishment and growth. One possible mitigation strategy to promote forest recovery following disturbances is inoculation with soil from late‐successional forests. However, whether these soil transfers change the composition of resident fungal communities and how seedling growth responds to such transfers is unknown.To test whether soil transfers can mitigate disturbance‐mediated impacts on ectomycorrhizal fungal (EMF) communities, we transferred soils containing fungal inoculum collected from conspecific late‐successional forests into stands disturbed by wildfire, mountain pine beetle outbreak, clear‐cut logging or salvage logging. Afterward, lodgepole pine seeds were sown to measure germination, establishment and growth of seedlings, and to characterize root‐associated and soil EMF communities by sequencing the ITS1 rDNA region.Despite evidence that soil inocula contained viable EMF communities, transfers did not impact the root‐associated or soil EMF community composition, or seed germination, seedling establishment and growth. Resident EMF community composition remained unchanged upon transfers of fungi from late‐stage successional forests, and disturbance type singularly explained the EMF community composition associated with roots and soils.Ectomycorrhizal fungal taxa typically associated with mature pine forests were particularly abundant on roots of seedlings growing in plots impacted by beetle outbreak, while 'early‐stage' EMF taxa were associated with seedlings growing in wildfire and logging disturbances.Synthesis and applications. Following disturbances, soil and root‐associated EMF exhibit high functional redundancy, as seedling performance did not vary with differences in EMF community composition across disturbance types. Our findings suggest that soil transfers are unlikely to be an effective strategy in these stands and may be better targeted to highly degraded forests. The presence and abundance of EMF in disturbed forests should be assessed before committing to soil transfers as part of restoration. [ABSTRACT FROM AUTHOR]

Background: Biological invasions are responsible for substantial environmental and economic losses. The red turpentine beetle (RTB), Dendroctonus valens LeConte, is an important invasive bark beetle from North America that has caused substantial tree mortality in China. The lack of a high-quality reference genome seriously limits deciphering the extent to which genetic adaptions resulted in a secondary pest becoming so destructive in its invaded area. Results: Here, we present a 322.41 Mb chromosome-scale reference genome of RTB, of which 98% of assembled sequences are anchored onto fourteen linkage groups including the X chromosome with a N50 size of 24.36 Mb, which is significantly greater than other Coleoptera species. Repetitive sequences make up 45.22% of the genome, which is higher than four other Coleoptera species, i.e., Mountain pine beetle Dendroctonus ponderosae, red flour beetle Tribolium castaneum, blister beetle Hycleus cichorii, and Colorado potato beetle Leptinotarsa decemlineata. We identify rapidly expanded gene families and positively selected genes in RTB, which may be responsible for its rapid environmental adaptation. Population genetic structure of RTB was revealed by genome resequencing of geographic populations in native and invaded regions, suggesting substantial divergence of the North American population and illustrates the possible invasion and spread route in China. Selective sweep analysis highlighted the enhanced ability of Chinese populations in environmental adaptation. Conclusions: Overall, our high-quality reference genome represents an important resource for genomics study of invasive bark beetles, which will facilitate the functional study and decipher mechanism underlying invasion success of RTB by integrating the Pinus tabuliformis genome. [ABSTRACT FROM AUTHOR]

To model the global distribution pattern of maximum tree age (age of the oldest tree at a given site), we included only living trees that were >= 100 years old in the ITRDB (most sites have trees exceeding 100 years old) (Liu et al., 2019a). Keywords: global distribution; large old trees; longevity; tallest trees; tree ring; anillo de árbol; árboles más altos; árboles viejos grandes; distribución mundial; longevidad; : ; ; ; ; EN global distribution large old trees longevity tallest trees tree ring anillo de árbol árboles más altos árboles viejos grandes distribución mundial longevidad : 1 10 10 08/01/22 20220801 NES 220801 INTRODUCTION Extremely old trees are natural features that have important roles, such as generating insights about historical climatic events (Di Filippo et al., 2012; Yang et al., 2014), maintaining biodiversity and ecosystem function (Lindenmayer & Laurance, 2017; Stephenson et al., 2014), and providing social and cultural benefits to people (Blicharska & Mikusi'nski, 2014). According to the ITRDB database, there were 197,855 cored old trees, 620 trees (0.31%) >=1000 years, 18 trees (0.009%) >=2000 years, and 1 tree >3000 years old. Therefore, unlike the frequently reported extremely old trees >=2000 years in many countries (e.g., Black et al., 2018; Liu et al., 2019a), we found that local estimates of tree ages for extremely old trees based on tree diameters or tree height are probably inaccurate. [Extracted from the article]

Questions: Global climate change is predicted to cause widespread shifts in the distribution and composition of forests, particularly in mountain environments where climate exerts strong controls on tree community arrangement. The upslope movement of vegetation has been observed in association with warming temperatures and is especially evident in ecotones—the transition zones between vegetation types. We explored the role of drought and tree mortality on recent changes in high‐elevation forests. Location: Greater Yellowstone Ecosystem, USA. Methods: We established 19 forest demography plots along an elevational gradient spanning dominant high‐elevation vegetation types. Results: Tree establishment dates indicated the upslope movement of Pinus albicaulis (whitebark pine) treeline and ecotone shift from meadow to forest starting in the 1950s. An expansion of the growing season likely contributed to the upward expansion of the treeline. Comparisons between overstory and understory tree composition suggested ongoing succession in the absence of fire at lower elevations, namely the replacement of Pinus contorta (lodgepole pine) by Abies lasiocarpa (subalpine fir). P. contorta seedlings were distributed at higher elevations than overstory trees of the same species, suggesting some potential for upslope movement with warming conditions; P. albicaulis seedlings, conversely, were distributed throughout all elevations of the transect. Significant tree mortality occurred in Pinus spp. and disproportionately affected P. albicaulis, as a result of a regional Dendroctonus ponderosae (mountain pine beetle) outbreak (2008–2012). Mortality events were strongly associated with drier than average conditions 2–3 years prior to tree death. Conclusion: Rising sensitivity to arid conditions in the mid‐20th century amid already dense, aging forests appears to have increased susceptibility to beetle‐induced mortality during the most recent drought. Tree species in the study area responded individually to global change stressors, which acted on these forests in complex ways and led to both ecotone shifts and stability. This work highlights the interplay between succession, forest disturbances and climate‐related growth responses in driving forest compositional change in subalpine and treeline environments. [ABSTRACT FROM AUTHOR]

Whitebark pine (Pinus albicaulis) plays a vital role in colonizing newly disturbed areas, providing shade for other tree species to germinate, and supplying food for a variety of birds and mammals, such as Clark's Nutcrackers (Nucifraga columbiana) and grizzly bears (Ursus arctos horribilis). Decline of whitebark pine populations has been attributed to several factors, including white pine blister rust (Cronartium ribicola), mountain pine beetle (Dendroctonus ponderosae) outbreaks, and fire exclusion. In 2009, the U.S. Forest Service began to install permanent plots in whitebark pine stands in Washington and Oregon as part of a Pacific Northwest restoration strategy to track blister rust and mountain pine beetle mortality. Forest Service crews conducted surveys on these plots that included standard tree inventory measurements and assessments of blister rust, mountain pine beetle, and fire activity. During summer 2020/2021, we remeasured 12 of these plots located in 3 areas of the Okanogan-Wenatchee National Forest (Mission Ridge, Clover Springs, and Lake Ann) and 1 area within the Ahtanum State Forest (Darland Mountain). On average, 15% of trees were newly infected by blister rust, 5% of trees died from blister rust, and 12.6% died from all causes combined in the 11-12 years between surveys. Despite this, the density of live whitebark pine trees experienced a nonsignificant increase due to regeneration, while the density of whitebark pine snags increased significantly and the density of whitebark pine seedlings decreased significantly. The percentages of trees with blister rust infection, seedlings with blister rust infection, and live trees with mountain pine beetle damage were heterogeneous over space and time. Our results help quantify parameters that are central to understanding the population dynamics of whitebark pine in the Pacific Northwest and informing management decisions, but the findings should be interpreted in light of the limited sample size and spatial extent of our data. Regular monitoring of a wider array of permanent whitebark pine plots will be critical to management of this tree species. [ABSTRACT FROM AUTHOR]

Insects are able to detect a plethora of olfactory cues using a divergent family of odorant receptors (ORs). Despite the divergent nature of this family, related species frequently express several evolutionarily conserved OR orthologues. In the largest order of insects, Coleoptera, it remains unknown whether OR orthologues have conserved or divergent functions in different species. Using HEK293 cells, we addressed this question through functional characterization of two groups of OR orthologues in three species of the Curculionidae (weevil) family, the conifer‐feeding bark beetles Ips typographus L. ("Ityp") and Dendroctonus ponderosae Hopkins ("Dpon") (Scolytinae), and the pine weevil Hylobius abietis L. ("Habi"; Molytinae). The ORs of H. abietis were annotated from antennal transcriptomes. The results show highly conserved response specificities, with one group of orthologues (HabiOR3/DponOR8/ItypOR6) responding exclusively to 2‐phenylethanol (2‐PE), and the other group (HabiOR4/DponOR9/ItypOR5) responding to angiosperm green leaf volatiles (GLVs). Both groups of orthologues belong to the coleopteran OR subfamily 2B, and share a common ancestor with OR5 in the cerambycid Megacyllene caryae, also tuned to 2‐PE, suggesting a shared evolutionary history of 2‐PE receptors across two beetle superfamilies. The detected compounds are ecologically relevant for conifer‐feeding curculionids, and are probably linked to fitness, with GLVs being used to avoid angiosperm nonhost plants, and 2‐PE being important for intraspecific communication and/or playing a putative role in beetle–microbe symbioses. To our knowledge, this study is the first to reveal evolutionary conservation of OR functions across several beetle species and hence sheds new light on the functional evolution of insect ORs. [ABSTRACT FROM AUTHOR]

The article discusses the importance of unburnt patches (refugia) within the wildfire of Alberta for survival of organisms. Topics discussed include that the forests throughout Alberta experience wildfire as a naturally occurring disturbance that has dominated and molded the landscape, it defines the term refugia and its role in preserving the forest and the animal habitat of the forest; and presents an image showing examples of organisms using different refugia types and scales.

Environmental change associated with warmer temperatures is creating unprecedented conditions in natural regions and ecosystems. In Jasper National Park, Alberta, climate change, historical fire management practices, and the mountain pine beetle infestation are combining to increase the risk of a major wildfire. The intent of this short viewpoint is to provide a primer for decision makers. The application of an adaptation readiness framework highlights areas where the Park's level of preparedness for wildfire adaptation is well developed and areas in need of further attention. Areas where adaptation is well developed include political leadership, decision making, and stakeholder engagement. Further attention is necessary around institutional organizations, funding, and public support. Key Messages: Risk of wildfire in Jasper National Park is increasing due to combined impacts of climate change, historical fire management practices, and mountain pine beetle infestation.There is need for a long‐term adaptation strategy, including engagement and collaboration between planners, industry professionals, and the community to reduce the risk of wildfire.Areas where adaptation is well developed include political leadership, decision making, and stakeholder engagement, while further attention is necessary around institutional organizations, funding, and public support. [ABSTRACT FROM AUTHOR]

At the beginning of this century, an unprecedented mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak expanded across western North America. Methods are needed to quantify its impact on forests. Although aerial survey data of infestation are readily available, their translation to tree mortality estimates is challenging because the polygons sketched by aerial surveyors to delimit infested regions often overlap from one year to the next, which produces a lack of independence in yearly estimates of infested landscape. This problem manifests when annual proportions of infested land are summed over years because the sum often exceeds one. Cumulative proportions of infested land larger than one implies overestimation of tree mortality if initial densities of available host trees are multiplied by annual proportions of infested landscape. To address this problem, we developed a probabilistic method for correcting for nonindependence in proportions of infested land recorded using overlapping polygons. We demonstrate our approach in Jasper National Park where the probabilistic correction reduces overestimation bias in regions that were infested multiple years when predictions are compared to validation data. The approach and the spatial raster data sets we generated will be useful to forest managers seeking to quantify the impact of mountain pine beetles. [ABSTRACT FROM AUTHOR]

Genome sequencing methods and assembly tools have improved dramatically since the 2013 publication of draft genome assemblies for the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae). We conducted proximity ligation library sequencing and scaffolding to improve contiguity, and then used linkage mapping and recent bioinformatic tools for correction and further improvement. The new assemblies have dramatically improved contiguity and gaps compared to the originals: N50 values increased 26‐ to 36‐fold, and the number of gaps were reduced by half. Ninety per cent of the content of the assemblies is now contained in 12 and 11 scaffolds for the female and male assemblies, respectively. Based on linkage mapping information, the 12 largest scaffolds in both assemblies represent all 11 autosomal chromosomes and the neo‐X chromosome. These assemblies now have nearly chromosome‐sized scaffolds and will be instrumental for studying genomic architecture, chromosome evolution, population genomics, functional genomics, and adaptation in this and other pest insects. We also identified regions in two chromosomes, including the ancestral‐X portion of the neo‐X chromosome, with elevated differentiation between northern and southern Canadian populations. [ABSTRACT FROM AUTHOR]

Aims: The response of understory plants is an important, yet understudied element of forest dynamics associated with mountain pine beetle (MPB) disturbance. Here, we provide a detailed assessment of both the changes in understory species and communities over a 5‐year period following severe MPB‐induced lodgepole pine mortality. Specifically, we examine species turnover, rarity and mobility over time, and evaluate shifts in community composition, including the potential for post‐outbreak community homogenization or differentiation. Location: Western Rocky Mountain National Park in the southern Rocky Mountains, Colorado. Methods: We collected species occurrence data across lodgepole pine‐dominated forest understories using repeated sampling of the same study sites (during the peak of MPB activity and 5 years after). Results: More species appeared than disappeared 5 years after the peak of the outbreak. New species were comprised of both early‐ and late‐successional species, suggesting the presence of rather high microhabitat heterogeneity. Although most species remained relatively rare, the number of exceedingly rare species decreased, and the number of highly common species increased. Several species were able to take advantage of the new stand conditions and expand throughout the study area. Some species appeared to spread locally over short distances mainly via vegetative reproduction, others expanded primarily upwards in elevation, probably through long‐distance dispersal and some spread over both short and long distances. Non‐native species doubled in occurrence and tended to spread upslope, towards the interior of the park, yet remained a small component of the understory overall. Shifts in community composition were minimal, but a slight convergence of plant community groups suggests a trend towards community homogenization. Conclusions: Our results demonstrate that even relatively sparse and depauperate lodgepole pine forest understories may be altered in diverse ways following MPB‐induced overstory mortality, depending on the unique ability of species to respond to changes in site conditions and resource availability. [ABSTRACT FROM AUTHOR]

Irruptive forest insects such as bark beetles undergo intermittent outbreaks that cause landscape-scale tree mortality. Despite their enormous economic and ecological impacts, we still have only limited understanding of the dynamics by which populations transition from normally stable endemic to irruptive densities. We investigated density-dependent changes in mountain pine beetle reliance on stressed hosts, host selection, spatial configuration of attacks, and the interaction of host selection and spatial configuration by performing a complete census of lodgepole pine across six stands and 6 years. In addition, we compared the dynamics of mountain pine beetle with those of other bark beetles. We found that as population size increased, reliance on stressed trees decreased and new attacks shifted to larger trees with thicker phloem and higher growth rates that can support higher offspring production. Moreover, the spatial configuration of beetle-attacked trees shifted from random to spatially aggregated. Further, we found evidence that beetle utilization of larger trees was related to aggregation behavior as the size of tree attacked was positively correlated at 10–25 m, within the effective distance of pheromone-mediated signaling. In contrast, non-irruptive bark beetle species did not exhibit such density-dependent spatial aggregation at the stand scale or switches in host selection behavior. These results identify how density-dependent linkages between spatial configuration and host utilization can converge to drive population transitions from endemic to irruptive phases. Specifically, a combination of stand-level spatial aggregation, behavioral shifts, and higher quality of attainable hosts defines a critical threshold beyond which continual population growth becomes self-driving. [ABSTRACT FROM AUTHOR]

This is the first study testing the effectiveness of semiochemical treatments to protect individual trees from a range-expanding mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins, 1902) attack into newly exposed host populations of endangered whitebark pine (Pinus albicaulis Engelm.). We investigated the effectiveness of a combination of verbenone and green-leaf volatiles (GLV) to protect rare and valuable disease-resistant trees during a MPB epidemic from 2015 to 2018 in Jasper National Park, Canada. Treatments reduced the proportion of trees attacked by MPB for all diameter classes, across all stands, from 46% to 60%. We also evaluated the effect of the exotic disease white pine blister rust (caused by the fungus Cronartium ribicola J.C. Fisch.) — the species' other main regional threat. MPB were less likely to attack large rust-infected trees than healthy trees, emphasizing the value of the semiochemical treatment. Protecting large cone-bearing disease-resistant whitebark pine trees is fundamental to whitebark pine recovery. Maintaining reproductive trees on the landscape increases the frequency and diversity of rust-resistant genotypes more effectively than just planting seedlings to replace MPB-killed trees, because this slow-growing species takes over 80 years to reproduce. Our study confirmed that protecting large rust-resistant trees with verbenone and GLV is a proactive and effective treatment against MPB for whitebark pine in naïve populations. [ABSTRACT FROM AUTHOR]

Bark beetles, fossil wood, Upper Cretaceous, wood-colonizing fungi, Araucariaceae, Ascomycota Here we describe a fungus colonizing wood of the extinct conifer I Agathoxylon i Hartig from the Upper Cretaceous Mzamba Formation of Pondoland (South Africa), and we draw comparisons with a blue stain fungus colonizing the wood of extant I Pinus strobus i . Keywords: Araucariaceae; Ascomycota; bark beetles; fossil wood; Upper Cretaceous; wood-colonizing fungi EN Araucariaceae Ascomycota bark beetles fossil wood Upper Cretaceous wood-colonizing fungi 1032 1037 6 01/10/22 20220201 NES 220201 Introduction Fossil fungi are frequently observed in association with fossil plants in a geological record that dates back over 400 Myr to the beginning of the Devonian Period (e.g. Strullu-Derrien I et al i ., 2014, 2018; Taylor I et al i ., 2015; Krings I et al i ., 2018; Krings & Harper, 2019). In most modern trees, two types of wood can be recognized: sapwood is the outer, pale-coloured wood, and heartwood the inner, mostly darker wood (Githiomi & Dougal, 2012). [Extracted from the article]

Capa peptides are of great importance for both understanding the control of salt balance by neuropeptides and revealing the mechanisms of response to cold stress. Presently, research on the physiological function of neuropeptides typically includes identifying and analysing specific receptors and their interactions. Given their role in osmotic balance and the importance of cold tolerance, this study attempted to identify the sequence and function of Capa peptide receptors (CapaRs) in Dendroctonus armandi and to prove that CapaRs play an important role in the cold stress responses. In this study, two full‐length cDNAs encoding more than 400 amino acids of Dendroctonus armandi Capa peptide receptor genes (DaCapaRs) and their sequence features were identified using bioinformatic analysis methods. The alignment of DaCapaRs with homologous proteins from other species indicated that the most similar are Dendroctonus ponderosae Capa peptide receptors. The expression of DaCapaRs was high in December and in the larvae, adults and head and midgut of Dendroctonus armandi. In addition, with decreasing temperatures and long‐term exposure to cold conditions, the expression of DaCapaRs increased markedly when the temperature was 4 to –10°C. RNA interference analysis demonstrated that DaCapaRs play an important role in the cold tolerance of overwintering larvae and indicated that a reverse interaction occurs between DaCapaRs and aquaporins. The results showed that DaCapaRs play an essential role in understanding the neuropeptide regulation of cold tolerance in overwintering Dendroctonus armandi larvae and that it can assist in understanding adaptive evolution of Dendroctonus armandi and its relationship with the ecological environment of the Qinling Mountains. [ABSTRACT FROM AUTHOR]

Warming temperatures are allowing native insect herbivores to expand into regions that previously exceeded their thermal tolerance, encounter new host species, and pose significant threats to native communities. However, the dynamics of these expansions remain poorly understood, particularly in the extent to which outbreaks remain reliant on emigration from historical hosts or are driven by local reproduction within novel hosts in the expanded range. We tested these non‐mutually exclusive hypotheses using spatially explicit data on mountain pine beetle (Dendroctonus ponderosae), which historically undergoes intermittent outbreaks in low‐elevation lodgepole pine (Pinus contorta), but is now causing severe mortality in a high‐elevation endangered species, whitebark pine (Pinus albicaulis). We compiled data from 2000 to 2019 across British Columbia, Canada, at 1‐km2 resolution, and analyzed spatiotemporal patterns of beetle infestations, lodgepole pine distributions, expansion into habitats dominated by whitebark pine, and the likelihood of future outbreaks in all pine communities under simulated conditions. Overall, we found strong support for the hypothesis of emigration from the historical host species continuing to be a major driver of outbreaks in the more recently accessed host. First, beetle population pressure was consistently the best predictor of infestation severity in both lodgepole and whitebark pine, and appeared to be mostly unidirectional from lodgepole to whitebark pine. Second, infestations in lodgepole pine were of a longer duration than those in whitebark pine, which appeared too brief to sustain transitions from endemic to eruptive dynamics. Furthermore, resource depletion appears to drive emigration from lodgepole pine, whereas in whitebark pine drought appears to favor establishment of immigrants although bioclimatic factors and stand structure preclude self‐sustaining outbreaks. Finally, we project that most pine in British Columbia will be at risk in the event of a new major outbreak. We describe implications for conserving and protecting whitebark pine and to other climate‐driven range expansions. [ABSTRACT FROM AUTHOR]

Planning forest management relies on predicting insect outbreaks such as mountain pine beetle, particularly in the intermediate‐term future, e.g., 5‐year. Machine‐learning algorithms are potential solutions to this challenging problem due to their many successes across a variety of prediction tasks. However, there are many subtle challenges in applying them: identifying the best learning models and the best subset of available covariates (including time lags) and properly evaluating the models to avoid misleading performance‐measures. We systematically address these issues in predicting the chance of a mountain pine beetle outbreak in the Cypress Hills area and seek models with the best performance at predicting future 1‐, 3‐, 5‐ and 7‐year infestations. We train nine machine‐learning models, including two generalized boosted regression trees (GBM) that predict future 1‐ and 3‐year infestations with 92% and 88% AUC, and two novel mixed models that predict future 5‐ and 7‐year infestations with 86% and 84% AUC, respectively. We also consider forming the train and test datasets by splitting the original dataset randomly rather than using the appropriate year‐based approach and show that this may obtain models that score high on the test dataset but low in practice, resulting in inaccurate performance evaluations. For example, a k‐nearest neighbor model with the actual performance of 68% AUC, scores the misleadingly high 78% on a test dataset obtained from a random split, but the more accurate 66% on a year‐based split. We then investigate how the prediction accuracy varies with respect to the provided history length of the covariates and find that neural network and naive Bayes, predict more accurately as history‐length increases, particularly for future 1‐ and 3‐year predictions, and roughly the same holds with GBM. Our approach is applicable to other invasive species. The resulting predictors can be used in planning forest and pest management and planning sampling locations in field studies. [ABSTRACT FROM AUTHOR]

Over 18 million hectares of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) forests have been affected by a massive mountain pine beetle outbreak in western Canada. The ensuing need for reforestation compels forest managers to deploy more drought-resistant stock in anticipation of a hotter and drier future climate. Recent studies suggest that naturally occurring lodgepole pine × jack pine (Pinus banksiana Lamb.) hybrids may be more drought-resistant than pure lodgepole pine. We used single-nucleotide polymorphism markers to determine the level of jack pine introgression present in the region J lodgepole pine seed orchard, in northwest Alberta, and we identified six hybrid genotypes with 10%–18% jack pine introgression for further study. We compared the performance of open-pollinated seedlings of lodgepole, jack, and hybrid pines under well-watered and drought conditions in a greenhouse experiment. Seedlings were subjected to repeg ated drought cycles, withholding water for either 2 or 3 weeks. We found that hybrid pines grew significantly faster than lodgepole pine under well-watered conditions while retaining the high tolerance to prolonged drought exhibited by lodgepole pine seedlings, a particularly beneficial combination of traits during the critical stage of establishment. We therefore suggest the deployment of hybrid lodgepole pine as a strategy to promote adaptation to hotter and drier future climates. [ABSTRACT FROM AUTHOR]

In this paper, we examine the implications of managing for sustained yield in a world characterized by growing risk and uncertainty. We review the history of sustained yield (SY) forestry in North America, with an emphasis on economic benefits and the persistence of the SY paradigm today, despite a publicized shift towards managing for a wider range of forest values called sustainable forest management (SFM). We show that current forest management goals around sustainability as well as SFM indicators are still predicated on maximizing harvest levels and timber flows. We build a simple model to explore the implications of SY under extreme (fat-tailed) risk assumptions to show that maximizing a level of harvest without adequately accounting for risk leads towards the depletion of the forest stock with a corresponding decline in the forest economy. We discuss these results in relation to real-world events such as the increase in catastrophic fires and pest outbreaks like the mountain pine beetle in Western Canada. We then examine the theoretical and practical implications that flow from this model and analysis. [ABSTRACT FROM AUTHOR]

A key component in understanding plant-insect interactions is the nature of host defenses. Research on defense traits among Pinus species has focused on specialized metabolites and axial resin ducts, but the role of lignin in defense within diverse systems is unclear. We investigated lignin levels in the outer bark and phloem of P. longaeva, P. balfouriana, and P. flexilis; tree species growing at high elevations in the western United States known to differ in susceptibility to mountain pine beetle (Dendroctonus ponderosae; MPB). Pinus longaeva and P. balfouriana are attacked by MPB less frequently than P. flexilis, and MPB brood production in P. longaeva is limited. Because greater lignification of feeding tissues has been shown to provide defense against bark beetles in related genera, such as Picea, we hypothesized that P. longaeva and P. balfouriana would have greater lignin concentrations than P. flexilis. Contrary to expectations, we found that the more MPB-susceptible P. flexilis had greater phloem lignin levels than the less susceptible P. longaeva and P. balfouriana. No differences in outer bark lignin levels among the species were found. We conclude that lignification in Pinus phloem and outer bark is likely not adaptive as a physical defense against MPB. [ABSTRACT FROM AUTHOR]