Research

Research Interests

Present or planned work at my laboratory focuses on the following five major questions in invasion biology and forest entomology.

Does invasion of a host plant by one organism alter the host suitability for the subsequent attacker?
Does tree defense mechanism vary in response to native vs. exotic insects or diseases?
What roles do environment and climate play in altering tree defenses against invasion by insects and diseases?
Do tree defense strategies against invading insects and diseases change under different C and N regimes?
What are the consequences of plant defenses in short & long-term fitness of invading insect herbivores?

Current Research Projects

Ecology and management of emerging forest pest complexes (Opening for Ph.D. and post-doc)
Effects of prescribed fire on population dynamics of mountain pine beetle in Alberta?
Fertilization and thinning as means of increasing the vigour of lodgepole pine trees against mountain pine beetle attacks
Mountain pine beetle system genomics (Tria Project): Assessing effects of host tree species and environment influencing tree defense mechanisms against mountain pine beetle
Implementation of national recovery strategies for the Mormon metalmark butterfly (Opening for M.Sc. and Ph.D.)
Role of plant growth and biomass in tolerance and resistance of aspen for forest tent caterpillar in western Canada
Understanding the role of induced tree defenses in behavior and ecology of bark beetles
Spatiotemporal dynamics of introduced bark beetles: Implications to resource competition, invasion risk and management

Current Funding

International Funding

US – Department of Agriculture – NAFI – Agriculture and Food Research Initiative

Federal Funding

Provincial Funding

Current Research Projects

Ecology and management of emerging forest pest complexes

Bark beetles are some of the most important pests of temperate forests. As the mountain pine beetle (MPB) has spread from British Columbia into Alberta, there is possibility that it will invade to the jack pine (JP) forest in western Canada extending from Alberta to the eastern Canada (Figure 1).

Figure 1. Distribution of jack pine (Yellow), lodgepole pine (green shadow), white pine (red shadow)

The probability of this invasion has increased as global climate changes is expected to promote warmer winter temperatures in northerly latitudes and higher elevations. If MPB successfully invades and survives in JP, it may spread across Canada and cause serious ecological and economical problems throughout the boreal forests. In my research program, I use MPB as a model system to study an insect invasion into a new ecosystem. Such investigations are timely because potential MPB invasion of JP forest could provide many new insights about insect invasion into a new habitat and host. The fundamental difference between the historical habitat of MPB and JP system is the presence of a serious defoliator, jack pine budworm (JPBW) , and absence of outbreak species of bark beetles in the JP system.

distribution of jack pine
Figure 2. jack pine budworm (JPBW)

In this long-term NSERC-Discovery funded project, my students and I focus on several aspects of JP-MPB-JPBW interactions. We investigate interactions between MPB and JPBW because both species will likely to interact on the same tree, although MPB will occur on stem and JPB will occur on foliage. Tree chemical defenses has been evaluated as possible mechanisms that influence the outcome of JP-MPB-JPBW interactions because chemical defenses are important mechanisms for conifers against herbivores and fungi. Developing deeper understandings of how MPB invasion would affect the JP forest system will be important contribution of this project. Such understanding is important to elucidate the general structure and behavior of the JP system against MPB and will be critical for the development of the integrated pest management of MPB in the JP forest.

Currently I have two MSc students (Jessie Colgan and Jenny Lazebnik) investigating the implications to the host and range expansion of the mountain pine beetle in the boreal forests of Canada.

I am also looking for one PhD student and one post-doctoral fellow starting on January 2011 on this subject.

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Effects prescribed fire on population dynamics of mountain pine beetle in Alberta?

Collaborators: Alberta Sustainable Resource Development and Parks Canada

Prescribed fires in Alberta are currently used to slow the spread of the mountain pine beetle (MPB) outbreak in lodgepole pine forests and reduce the overall landscape level MPB susceptibility by killing potential host trees prior to MPB arrival (Left picture below).

distribution of

However, one potential risk associated with using fire to control MPB is the possibility of creating stressed trees in and around the burned stands. These stressed trees have been reported to be more prone to successful bark beetle colonization (right picture, above). Significant levels of post-fire beetle-induced mortality have been observed in burned areas in Alberta, but are rarely quantified; therefore more comprehensive studies are needed to investigate the potential impact of prescribed fires on population dynamics of MPB across landscape of lodgepole pine forests in Alberta. The main objectives of this project are to determine (1) if fire will increase concentration and contribute to population growth of MPB attack in burned and neighboring unburned stands of lodgepole pine forest and (2) if burned forest stands will become a sink or source for MPB populations across landscapes. We are estimating MPB population size in burned and neighboring unburned stands before and after fire, and will monitor beetle population growth in both burned and unburned stands until 2012. The resulting information will be useful to understand the role of prescribed fire in short- and long- term population dynamics of MPB, and hence will be invaluable for using fire as a tool for MPB management.

Currently I have one PhD student (Crisia Tabacaru) working on this project.

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Fertilization and thinning as means of increasing the vigour of lodgepole pine trees against mountain pine beetle attacks

Collaborators: Drs. Vic Lieffers and Simon Landhausser from University of Alberta

Conifer trees are equipped with sophisticated defenses that integrate physical, chemical, and histological mechanisms. Upon wounding, conifers exude resin that imposes a physical barrier and also contains a blend of toxic compounds, primarily terpenes. Terpene concentrations rise rapidly in response to attack, and within only a few days can vastly exceed the tolerance level of the beetles and their microbial symbionts. These biochemical changes are accompanied by histological responses, including autonecrosis that rapidly confines the insect - fungal complex. Nearly all trees respond, but there is high intraspecific variation in the rate and extent of response, often reflecting physiological stresses. There is a considerable body of literature describing tree defenses in relation to mountain pine beetle (MPB) attack. Warring and Pitman (1985) suggest that trees that grow vigorously are more likely to ward off attack from the beetle. The large experiment on fertilization and thinning established by the Foothills Growth and Yield Association offered a great opportunity to investigate the influence of fertilization on the defensive characteristics of lodgepole pine (LP) that would help make them more resistant to future attack. Our objective is to examine if fertilization and thinning improve in relation to development of both constituent and induced defenses against MPB in LP forest. Effectiveness of induced defenses is determined by challenging trees with inoculation by fungal associates of MPB and measuring its relative response in relation to features such as lesion lengths (Figure 1 and 2, see above), non-structural carbohydrate reserves, and the potential mobilization of these reserves to boost up terpene and pitch production.

Currently I have one PhD student (Devin Goodsman) co-supervised by Dr. Vic Lieffers working on this project.

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Effects of interactions between bacteria and fungi on mountain pine beetle reproduction in three host tree species

Collaborators: Drs. Kenneth F Raffa and Cameron R Currie from the University of Wisconsin, Madison and Brian H Aukema from Canadian Forest Service in Prince George, British Columbia, Canada

distribution of pine beetle The mountain pine beetle (MPB) is a major pest of North American forests. Intermittent outbreaks have historically occurred, but warming conditions have allowed the current eruption to expand beyond the beetle’s previous range. It has recently begun killing lodgepole and hybrid lodgepole-jack pines (JP) in Alberta. Since JP extends continuously from Alberta into the US, and intermingles with red and white pines (Right), eastern US forests are now threatened. The extent to which this pest will undergo outbreaks in hybrid and jack pines, and whether this will provide a bridge for expansion into eastern forests are unknown. We are investigating a critical component of this question, how interactions among bacteria, fungi, and phytochemistry affect beetle reproduction. Fungi play crucial and complex roles in bark beetle ecology, from beneficial to antagonistic. It was recently reported that beetle- and tree- associated bacteria strongly affect gallery fungal composition. The objectives of this interdisciplinary project are to: (1) Compare bacterial and fungal flora associated with infested and uninfested lodgepole, jack, and hybrid pines; (2) Assay interactions among microorganisms, and how phytochemicals affect them; (3) Determine how these interactions affect beetle reproduction. This work will help guide management responses to a climate-induced biological invasion, and contribute to our understanding of how symbionts mediate herbivore-host plant interactions.

Currently I have one MSc student (Janet Ariss) working on this project.

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Mountain pine beetle system genomics (Tria Project): Assessing effects of host tree species and environment influencing tree defense mechanisms against mountain pine beetle

There are several collaborators on this project (Tria Project). My group focuses on understanding the role of drought on tree defenses mediating interaction between host trees and mountain pine beetle.

Conifer forests provide largest renewable source of lignocellulose in Canada. Sustainable use of these resources for bioenergy production would secure continuous flow of lignocellulose to the forestry sector. Outbreak species of mountain pine beetle (MPB) poses one of the greatest challenge to the sustainability of these forestry resources. The current MPB epidemic has provided a key opportunity to assess and improve modeling tools required for prediction of a sustainable lignocellulose feedstock supply for the bioenergy industry. As the unprecedented landscape-level MPB outbreak is spreading from British Columbia (BC) across the Rocky Mountains into Alberta, new associations with host trees not previously exposed to outbreaking MPB populations present unique challenges in understanding system behaviour. Our collaborate project integrates large-sale genomics research with ecological risk modeling and economic analysis to develop and improve genomics-enhanced tools for accurate prediction of bioenergy feedstock availability from conifer forests impacted by (or at risk of) pest disturbance. Our project focuses on all important elements of the MPB system, including three host pine trees (lodgepole pine; jack pine; and their hybrids), MPB, and MPB associated tree killing fungi (e.g., Grosmannia clavigera). The overall goal of this applied genomics project is to generate new genomics-based information and tools for improved prediction of renewable bioenergy feedstock supply from conifer forests, using the current MPB epidemic as a highly relevant host-pest system.

Currently I have one post-doctoral fellow (Dr. Inka Lusebrink) co-supervised by Dr. Maya Evenden working on this project.

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Implementation of national recovery strategies for the Mormon metalmark butterfly

Collaborators: Drs. John R Spence from University of Alberta and Shelley Pruss from Parks Canada

distribution of pine beetle The Mormon metalmark (MM) is a medium-sized butterfly (Left) of arid regions that is named for white metallic markings on both of its wings. In Canada, there are two populations of MM. The Southern Mountain population in the Similkameen River Valley of British Columbia is listed as “endangered”. The second population referred to as the Prairie population is located in southwestern Saskatchewan within the current and proposed Grasslands National Park (GNP) boundaries. The recovery strategy addresses the Prairie population as Threatened in 2002. However, knowledge of habitat requirements for the Canadian Prairie population is extremely limited and most of the current information comes from the US. Although information is limited, it appears that in Saskatchewan, MM typically occur on hillsides, slopes, or embankments on barren clay or heavy clay soil where its host plant, the branched umbrella plant (Eriogonum pauciflorum) occurs. Adult metalmarks require mature, robust branched umbrella plants for oviposition and both the flowering branched umbrella plant and the rubber rabbitbrush (Ericameria nauseosa) for foraging.

distribution of pine beetle MM larvae utilise the branched umbrella plant for feeding and require the woody stems or underlying leaf litter for hibernation. In general, the main threats to the species are invasive exotic species, pollution, accidental mortality, potential climate change, and habitat loss and degradation due to urban and agricultural development, agricultural practices, all-terrain vehicle traffic, and wild fire. The recovery goal for the Prairie population of MM is to maintain suitable habitat and ecological linkages within the known range of the Prairie population of MM, which preserves the opportunity for natural processes to shape the population dynamics and the evolution of the species.

I am looking for one MSc/PhD student starting on September 2010 or January 2011 on this subject.

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Role of plant growth and biomass in tolerance and resistance of aspen for forest tent caterpillar in western Canada

Collaborators: Dr. Simon Landhausser

distribution of pine beetle Trembling aspen is one of the fastest growing trees in North America. The performance of aspen as a pioneer tree species is mainly due to a set of chemical and physiological defences that allow resistance or tolerance to biotic and abiotic stress agents. Physiological traits include for example rapid growth to escape browsing and chemical aspects of defence are tightly related to secondary compounds production. Observations in nature suggest that aspen’ growing conditions highly affect its foliage quality and plant fitness. Thus variations of environmental conditions including soil quality, nutrient availability, CO2 concentration, light regimes and temperatures resulted in a differential chemical pattern of aspen foliage. For example, aspen saplings grown in low nutrients had more salicortin, tremulacin and condensed tannins, all involved in defensive chemistry, than aspen grown in high nutrients conditions. Others showed that sun grown aspen was more preferred by Forest Tent Caterpillar (FTC) than the ones grown under shade conditions. We hypothesize that plant growing conditions, such as different levels of sunlight or soil nutrients, affect herbivory performance on the plant by changing plant chemical defenses against the herbivore. Our objective is to (1) determine if FTC fitness will vary with different levels of carbon and nutrient contents of seedlings, (2) evaluate if differences observed in the fitness of FTC will be explained by the plant secondary chemical compounds, (3) evaluate if aspen seedlings with different carbon and nutrient status will have different defensive strategy against herbivory by differentially allocating its resources to defenses, and (4) evaluate if observed changes in aspen secondary chemistry and FTC fitness will be parallel to the molecular analysis characterizing aspen defenses.

Currently I have one MSc student (Ahmed Najar) co-supervised by Dr. Simon Landhausser from the University of Alberta working on this project.

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Understanding the role of induced tree defenses in behavior and ecology of bark beetles

Collaborators: Dr. Paal Krokene from Norwegian Forest Research Institute

distribution of pine beetle I have been collaborating with scientists at the Norwegian University of Life Sciences (NULS) under the umbrella of the CONDEF (Conifer Defenses) working group in Europe since 2004. The CONDEF is an interdisciplinary research group aimed at understanding the mechanisms of conifer defenses against bark beetles. Our model in Norway is Norway spruce and the spruce bark beetle. The spruce bark beetle, a distant relative of the mountain pine beetle in western Canada, is the most destructive insect pest of Norway spruce in Eurasia.Several institutions, including NULS, in Europe and North America are involved in different aspects of conifer defenses in different model systems for over 10 years. The annual CONDEF meeting brings together researchers from different countries and fosters international collaboration. The overall objective of our multidisciplinary program is to identify the interactions among key biological components of our study system, and then integrate them in an ecologically sound model which might provide a strong foundation for the development of integrated management of the spruce bark beetle, and potentially other forest pest insects.

During the first few years of our investigations, we explored how plant inducible defenses, primarily chemical and anatomical, mediate Norway spruce-the spruce bark beetle interactions. We used methyl jasmonate to manipulate the biochemistry and anatomy of mature Norway spruce trees against the beetle. Within a short time, we demonstrated that the increased amount of terpenoid resin, a primary component of tree chemical defenses, and increased traumatic resin ducts, a primary component of tree anatomical defenses, present in methyl jasmonate-treated trees were directly responsible for the observed decrease in the bark beetle activity on the host.

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Spatiotemporal dynamics of introduced bark beetles: Implications to resource competition, invasion risk and management

Collaborators: Dr. Bjorn Økland from Norwegian Forest Research Institute

Ips typographus is the most important tree-killing bark beetle species on Norway spruce in Eurasia. Ips typographus has been intercepted many times by port inspectors in the US for the last two decades, but it has not yet become established in North America. This could be a failure of detection in which beetles may be present at lower levels than the detection threshold. Their failure to get established may also be due to ecological factors that are causing Allee effects. For the last two years, we have been investigating on the ability of I. typographus to colonize and reproduce on some North American spruce species to understand whether the resulting information would provide any evidence for the possibility of future establishment in North America. Because field experiments with live I. typographus in North America is not possible, we are utilizing North American spruce species growing with Norway spruce in the same environment in Norway. The objectives of our study is to (1) determine if beetles can colonize and produce brood on exotic spruce species, and (2) evaluate whether there is a risk of establishment of I. typographus in North America.

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