General areas of research and specific projects are highlighted on this page:

Plant Responses to Herbivory
Most members of this group are interested in understanding how plants respond to being eaten.   


Hik has demonstrated that these responses can be explained in terms of interacting processes at the individual plant and leaf levels.  Increases in photosynthesis and shifts in C and N allocation contribute to the ability of plants to tolerate herbivory.  Grazing by native herbivores can have positive effects on subsequent nutrient availability, but the response is contingent on environmental conditions such as flooding, fire, and temperature (Hik and Merrill).  


Merrill and Dale are actively researching how the effects of herbivory on individual plants may result in patterns at the landscape level.  For example, Dale has found snowshoe hare browsing to have dramatic effects on the spatial distribution of regenerating white spruce in the boreal forest, with significant implications for the basic functioning of these systems and their management.  


Historically, studies of herbivory have focused primarily on interactions above ground.  The effects of belowground feeding on community structure is practically unknown, and is an active line of research of Cahill and Merrill.  Cahill is using a “root periscope” to determine when roots are eaten, and whether changes in root structure influence the probability of attack.  This technology is also being used by Cahill to determine how grazing alters root age/size structure, and the effects these changes on plant function.  The ultimate goal of this project is to determine whether aboveground management decisions can be modified to maximize rangeland drought resistance.  


Cahill, Hik and Merrill are part of a collaborative effort to develop a state-of-the-art multi-trophic study center at the Kinsella Research Ranch of the University of Alberta.  Their objectives are to determine the effects of grazing on grasslands, depending on whether these effects are viewed from the perspective of plant diversity, primary production, nutrient cycling or consumer population dynamics. This diversity of views emphasizes the necessity of approaching questions about the role of herbivory from different levels of biological organization, a strength within this group.  


Considerable effort in the group is also focused on understanding how the simple act of visiting plants during field studies influences the intensity of herbivory (Cahill, Hik, Constabel).  Cahill has demonstrated that the effects of researchers in communities are significant, potentially influencing plant apparancy, chemistry, and allometry.  


This work is also tied to research projects of Roland and Spence, who focus on understanding the interactions among plants, herbivores, and parasitoids.  Plant cues which parasitoids use to locate their herbivore hosts have significant implications for both the general understanding of the dynamics of the complicated systems as well as for the design of biocontrol strategies.




Herbivore Responses to Variation in Host Plants and Landscape Structure
The dynamics of plant herbivore interactions and herbivore population sizes depend on the spatial-temporal variation within a system.  


In a 10 year study of forest tent caterpillar dynamics, Roland has found that forest fragmentation decouples caterpillar growth from their classic growth regulators (parasitoids and viruses).  As a result, Roland has been able to provide a mechanism for the long-standing observation of longer pest outbreaks in fragmented forests, potentially leading to a solution to this problem of enormous economic importance. 


Dale too is interested in the effects of plant spatial patterns on herbivore populations, and is studying the effects of variation in the relative proportion of preferred and non-preferred food plants on herbivore production.  


Merrill has focused on understanding the effects of spatial-temporal variation created by seasonal/annual dynamics in the environment on feedbacks in plant-herbivore systems at different scales.  For example, Merrill has found that variation in plant phenology influences the  long-term dynamics of the elk-vegetation system in Yellowstone National Park.  


At the landscape scale, both Merrill and Roland have shown that factors influencing plant quality (season, isolation, patch size) influence animal movement and feeding biology (Roland, Alpine Butterflies; Merrill, Elk in Mt St. Helens).  Merrill is using aerial videography to describe spatial patterning of plants to understand herbivore movement and habitat permeability in relation to landscape disturbances.  


At the community scale, Cahill has found that the movement of humans within a field influences the diversity and abundance of insects within the field.  Current effort is focused on investigating the mechanisms behind such patterns, and whether ungulate movement causes similar changes to insect diversity. 



Biochemistry and Molecular Biology of Plant-Herbivore Defense
Plant-animal interactions are being studied at the level of genes and proteins by members of the group. 

A number of projects aim to investigate the defensive biochemistry which mediates plant-animal interactions. For example, collaboration between field and laboratory researchers (Spence, Constabel) has identified key defense chemicals which are associated with strong resistance of trembling aspen to forest tent caterpillar. Several genes encoding defensive proteins have been isolated and characterized from aspen and poplar. Using a collaborative approach and modern biochemical and molecular tools, these are being studied directly for anti-herbivore activity (Constabel, Keddie). 

Plant transformation is being applied to these genes and proteins, and their effects on herbivory can be assessed in both transgenic crop and forest plants. Studies on defense gene expression are providing detailed knowledge of how herbivore defense is regulated.  Many of the defenses are expressed only following attack, which implies the existence of sensitive perceptive and signaling systems within plants. Accumulated data suggests that a host of defense proteins and chemicals are induced via a master regulator, and it may be possible to use this switch to modulate the entire defense response. A goal of a related line of research is to relate sub cellular processes of induced responses within the plant to ecological processes in the field (Cahill, Constabel). 



Evolution of Plant-Animal Interactions
Several member of the working group are interested in understanding the evolution of plant-animal interactions.  

Addicott focuses primarily on mutualisms (aphids and ants, yuccas and yucca moths, and figs and fig wasps), with experimental tests and computer models designed to determine what processes regulate the costs and benefits of cooperative interactions, under what conditions should individuals fail to cooperate and cheat, and how cooperative interactions vary as a function of the environment, density of the species, and quality of the species.  Addicott’s work has been central to the recent realization amongst ecologists that mutualisms are a common and vastly understudied form of plant-animal interactions.  

Sperling is interested in the phylogenetic study of the origin of plant-animal interactions.  A significant component of which is in understanding the patterns of coevolution of insects and plants – specifically many plant-pest combinations of economic importance.  

Spence and Hik have conducted numerous studies into how plants adapt to being eaten by insect (Spence) and vertebrate (Hik) herbivores.  They have specifically focused on the long-term changes and adaptations by plants in response to herbivory (chemistry, morphology, physiology), including the finding that long-term grazing may result in overcompensation – with increased plant growth when eaten compared to plants without herbivores. 



Microbial-Plant-Animal Interactions
One of the least understood areas of biology are the interactions between microbes, plants, and associated animals.  

Currah’s main research focus is in understanding the biology and distribution of mycorrhizal fungi - whose reproductive structures are a source of food for many animals.  Currah is also examining the food-vector relationships among wood decaying fungi and a variety of animal species.  Micro- and mesofauna that rely on standing and fallen timber for habitat, carry decay and disease-causing fungi from site to site, facilitating the establishment of pathogenic and decomposer species that, in turn, soften the wood and serve as food for invertebrates.  

Keddie is studying how the microbes naturally found associated with plant roots may impact insect populations.  Little is known about the functioning of the soil community, how it changes through space and time, whether plant chemistry impacts the level of severity of any associated diseases, and whether some of these microbes act as forage themselves.


This page last updated 01/11/01