Past Lab Members
I started as a PhD student in 2001. I am interested in terrestrial population- and community-level ecology, especially as they relate to conservation. Part of my research is on zoochorous seed dispersal, a plant-animal interaction considered to be crucial to the maintenance of diversity in tropical forests, in Thailand. I am comparing the functional similarity of three mammalian frugivores, white-handed gibbons (Hylobates lar), sambar deer (Cervus unicolor), and muntjac deer (Muntiacus muntjac), with regards to their effects on seed dissemination and seedling demography of the dominant canopy tree Choerospondias axillaris (Anacardiaceae). I am also trying to document patterns of C. axillaris regeneration across national parks where the mammals have been subjected to varying levels of illegal hunting.
A second project I am working on, in collaboration with Dr. Matt Kauffman, is an analysis of the effects of wolf (Canis lupus) reintroduction on the interaction between elk (Cervus elaphus) and aspen (Populus tremuloides) in Yellowstone National Park.
This is my sixth year as a PhD student. I am generally interested in population ecology and am focusing my dissertation research on invasive species. Specifically, I am interested in understanding how exotic plants that often occur at low densities in their native range able to grow at high densities where they are introduced. I am studying a noxious weed invader of western North America, houndstongue (Cynoglossum officinale) both in its invasive range in Montana and its native range in central Europe, where I have field sites in eastern Germany. I am using parallel experiments in the native and introduced range to explore whether escape from specialist insect herbivores, small-scale disturbances, and a life history switch from semelparity to iteroparity may contribute to houndstongue's increased success where it is introduced. I am also using data from demographic monitoring of plants in both ranges to parameterize integral projection models. These models will allow me to quantify specific life stages of houndstongue that most limit population growth in each range and, in combination with experimental results, to translate the effects of different factors on performance into effects on population growth.
I started as a PhD student in 2003, with a general interest in species interactions. My dissertation work focuses on how the population dynamics of two long-lived perennial forbs (Lupinus sericeus and Lithospermum ruderale) are affected by small mammal seed predators. I am taking a combined demographic and experimental approach to this question, by monitoring natural populations in order to build population models, and by using rodent exclosures to experimentally examine how small mammal predation affects the seed-to seedling transition rates. This project is based in the Blackfoot Valley in Western Montana, and much of it is in collaboration with John, and his project on the cascading effects of top predators.
I am broadly interested in how ecological interactions influence and shape community structure. I am currently exploring how large herbivores modify plant communities and ecosystem processes, and how they can act as ecosystem engineers by modifying habitats for co-occurring species. My work has focused on understanding the effects of abundant Rocky Mountain elk (Cervus elaphus) in northern Arizona along the Mogollon plateau in Coconino National Forest.
Specifically, I am using a long term ungulate exclusion experiment started in 2004 with three large (~10 ha exclosures) and three paired non-fenced drainages to determine whether elk influence plant and small mammal community structure, and whether elk have the potential to influence ecosystem processes by modifying plant-soil feedbacks.
Iam also interested in mutualisms and how mutualistic interactions change across environmental gradients. I worked with an undergraduate researcher to understand how abiotic factors affected the size and effectiveness of extra-floral nectaries (EFN) in attracting ant defenders and reducing herbivory in Bracken fern (Pteridium aquilinum). We compared the size, number, and nectar production of nectaries of bracken fern in different locations that varied in shade, plant community composition, soil, and elevation, and we also experimentally added shade, water, and water/fertilizer to see how this affected herbivory and EFN production.
I started as a PhD student in 2006. I am interested in plant-insect interactions and their influence on demographic processes and abundance. My dissertation research explores how plant invasion influences solitary bee abundance and the pollination services they provide. There are over 27,000 species of bee, and 90% of these are solitary, meaning that females nest individually rather than forming colonies like the more familiar honey bees and bumblebees. Despite their diversity, importance, and well-documented global declines, we know very little about what influences the abundance of solitary bees.
Invasion by nectar-rich exotic forbs such as leafy spurge, spotted knapweed, and Dalmatian toadflax could increase the number of native bees by increasing food resources. Alternatively, the loss of native forbs that accompanies plant invasion could reduce the number of native bees. I am also exploring whether patterns of bee abundance are due to underlying changes in demographic processes such as reproduction and offspring survival, by observing nesting by Osmia lignaria, a native solitary bee. Finally, I am exploring how changes in bee abundance that accompany plant invasion influence pollination of two native forb species, Linum lewisii and Clarkia pulchella.
I started my PhD in 2008. My two broad interests are the causes and consequences of dominance and rarity in plant communities. As part of my dissertation work I will use manipulative experiments to examine whether dominant or common species have a larger impact on establishment of new species, and whether seed predators change this relationship. I will further examine whether the strength of competition within or between species differs for dominant and rare species. Dominant species comprise the bulk of community biomass and rare species comprise most of the species richness, so both have the potential to influence the community, but likely through different mechanisms. Another portion of my dissertation will examine the consequences of community structure for stability. More specifically, I will examine the feedbacks between community structure, invasion and response to a disturbance.
I began my Master's work in 2010. I am interested in the interactions between plants and mycorrhizae. Specifically, I am interested in how arbuscular-mycorrhizal fungi (AMF) may influence the invasion success of the annual invasive weed, Centaurea solstitialis. My research focuses on variation in mycorrhizal response by native and invasive genotypes of this forb and the influence of AMF on competitive interactions between native and invasive C. solstitialis and the native bunchgrass, Nassella pulchra.
I started managing a long-term ecology research project, Cascading Effects of Top Predators, in 2010 for University of Montana Professor Dr. John Maron and Rocky Mountain Research Station Research Ecologist Dr. Dean Pearson. The goal of the study, initiated in 2002 in the Blackfoot Valley of Western Montana, is to determine the indirect effects of top predators on plant communities. The primary tasks of this position involve supervising the research crews in the summer, maintaining our predator, ungulate, and rodent exclosures, collecting data on plants and small mammals, and managing data. We seek to identify mechanisms which bring about changes in habitat use and species diversity and abundance. Several new and ongoing experiments target small mammal consumption by predators, and the effects of seed predation, seed dispersal, competition, disturbance, and nutrient availability on plant communities to understand this intact system on multiple ecological levels.