Dean E. Pearson
800 Block East Beckwith
Missoula, MT 59801
Contact Dean E. Pearson
1) I conduct basic research in community ecology to understand how communities are structured. This information provides a baseline for understanding how to manage systems and for developing realistic management and restoration targets. One example includes large-scale predator, ungulate, and rodent exclusion work in the Blackfoot Valley of western Montana.2) I conduct research on biological invasions to try to understand the causes and consequences of invasions in order to better manage this problem. This involves three components:a. international research focused on determining the causes of invasions by examining the biogeographic basis of invasions, i.e., comparing invaders in the native and introduced ranges (current studies include Turkey, Argentina, Germany, California, and Montana),b. studying the processes of invasion and impacts of invaders in the introduced range, including the ecological and evolutionary response of natives to invaders,c. studying the efficacy of management tools for mitigating invader impacts (e.g., biological control and herbicides).
My primary research interest is to advance community ecology through studies of biological invasions and to use this information to improve invasive species management. Biological invasions serve as grand natural experiments that provide unique opportunities to view the processes that structure ecological communities. Even in the most recently assembled natural communities organisms have had hundreds or thousands of years to interact and sort themselves into the modern assemblages we see. This makes it very challenging to identify the relative roles of competition, predation, parasitism, resource availability, etc. in structuring extant communities. However, with biological invasions, it is possible to observe these processes in real time as a novel organism invades, establishes, and dominates (in the case of strong invaders) a new assemblage. It is also possible to see how the assemblage finally settles into a new equilibrium state as the invader's dominance wanes through the ecological and evolutionary adaptation of the community to its presence. Newly hypothesized understandings of these processes can then be tested in the context of directed community assembly through the applied largescale natural experiments that are attempts to manage the invasion problem, for example, classical biological control - the intentional introduction of exotic organisms to manage invasions. Thus, biological invasions offer an opportunity to advance understandings of community ecology that can in turn be tested by applying these understandings to the management of the invasives problem.
Biological invasions present the second greatest threat to natural ecosystems and the services they provide next only to actual land transformation. Exotic species invasions cost the United States 120-140 billion dollars per year in revenue losses and mitigation costs. Magement of this problem has been particuarly challenging due to a lack of understanding of the fundamental processes underlying invasion. My research attempts to better understand the causes and consequences of invasion and the efficacy of current managmen tools in order to better guide management approaches toward more effective mitigation. Success in these efforts offers tremendous benefits in terms of US revenues and stability of ecosystem services.
Why This Research is Important
I have conducted research in wildlife habitat relationships pertaining to small mammals and America marten. I have conducted research related to a variety of methodological approaches in wildlife such as sampling forest carnivores using remote sensing cameras, smoked tracking plates and snowtracking, small mammal trapping techniques, and population estimation.
- University of Montana, Ph.D. Organismal Biology and Ecology, 2005
- University of Montana, MAS Zoology, 1995
- University of Montana, BS Wildlife Biology, 1992
Featured Publications & Products
- Ortega, Yvette K.; Pearson, Dean E. 2011. Long-term effects of weed control with picloram along a gradient of spotted knapweed invasion.
- Pearson, Dean E. 2010. Trait- and density-mediated indirect interactions initiated by an exotic invasive plant autogenic ecosystem engineer.
- Finch, Deborah M.; Pearson, Dean; Wunderle, Joseph; Arendt, Wayne. 2010. Terrestrial animals as invasive species and as species at risk from invasions.
- Bricker, Mary; Pearson, Dean; Maron, John. 2010. Small-mammal seed predation limits the recruitment and abundance of two perennial grassland forbs.
- Maron, John L.; Pearson, Dean E.; Hovick, Stephen M.; Carson, Walter P. 2010. Funding needed for assessments of weed biological control.
Publications & Products
- Pearson, Dean; Ortega, Yvette. 2013. Biogeography of plant invasions.
- Litt, Andrea R.; Pearson, Dean E. 2013. Non-native plants and wildlife in the Intermountain West.
- Ortega, Yvette; Pearson, Dean. 2013. Spotted knapweed: Effects of climate change on the invasiveness and biological control.
- Pearson, Dean E.; Potter, Teal; Maron, John L. 2012. Biotic resistance: Exclusion of native rodent consumers releases populations of a weak invader.
- Pearson, Dean E.; Ortega, Yvette K.; Sears, Samantha J. 2012. Darwin's naturalization hypothesis up-close: Intermountain grassland invaders differ morphologically and phenologically from native community dominants.
- Zwolak, R.; Pearson, D. E.; Ortega, Y. K.; Crone, E. E. 2012. Mechanisms driving postfire abundance of a generalist mammal.
- Ortega, Yvette K.; Pearson, Dean E.; Waller, Lauren P.; Sturdevant, Nancy J.; Maron, John L. 2012. Population-level compensation impedes biological control of an invasive forb and indirect release of a native grass.
- Maron, John L.; Pearson, Dean E.; Potter, Teal; Ortega, Yvette K. 2012. Seed size and provenance mediate the joint effects of disturbance and seed predation on community assembly.
- Pearson, Dean E.; Callaway, Ragan M.; Maron, John L. 2011. Biotic resistance via granivory: Establishment by invasive, naturalized, and native asters reflects generalist preference.
- Pearson, Dean; Sutherland, Steve; Butler, Jack; Smith, Jane; Sieg, Carolyn. 2011. I. Plants.
- Pearson, Dean; Ortega, Yvette. 2011. Invasive Species Science Update (No. 5).
- Pearson, D. E.; Kim, M.; Butler, J. 2011. Rocky Mountain Research Station invasive species visionary white paper.
- Pearson, Dean; Finch, Deborah. 2011. V. Terrestrial vertebrates.
- Maron, John L.; Pearson, Dean E. 2011. Vertebrate predators have minimal cascading effects on plant production or seed predation in an intact grassland ecosystem.
- Maron, John L; Pearson, Dean E.; Fletcher, Robert J., Jr. 2010. Counterintuitive effects of large-scale predator removal on a midlatitude rodent community.
- Ortega, Yvete K.; Pearson, Dean E. 2010. Effects of picloram application on community dominants vary with initial levels of spotted knapweed (Centaurea stoebe) invasion.
- Zwolak, Rafal; Pearson, Dean E.; Ortega, Yvette K.; Crone, Elizabeth E. 2010. Fire and mice: Seed predation moderates fire's influence on conifer recruitment.
- Pearson, Dean E. 2009. Biological invasions on oceanic islands: Implications for island ecosystems and avifauna.
- Butler, Jack; Pearson, Dean; Kim, Mee-Sook. 2009. Invasive Species Working Group: Research Summary and Expertise Directory.
- Pearson, Dean E. 2009. Invasive plant architecture alters trophic interactions by changing predator abundance and behavior.
- Pearson, Dean; Ortega, Yvette. 2009. Managing invasive plants in natural areas: Moving beyond weed control.
- Crone, Elizabeth E.; Marler, Marilyn; Pearson, Dean E. 2009. Non-target effects of broadleaf herbicide on a native perennial forb: a demographic framework for assessing and minimizing impacts.
- Zwolak, Rafal; Foresman, Kerry; Crone, Elizabeth; Pearson, Dean; Ortega, Yvette. 2008. Are mice eating up all the pine seeds?.
- Pearson, Dean E.; Fletcher, Robert J., Jr. 2008. Mitigating exotic impacts: restoring native deer mouse populations elevated by an exotic food subsidy.
- Pearson, Dean E.; Callaway, Ragan M. 2008. Weed biocontrol insects reduce native plant recruitment through second-order apparent competition.
- Pearson, Dean E.; Ortega, Yvette K.; Ruggiero, Leonard F. 2003. Trap-induced mass declines in small mammals: Mass as a population index.
- Pearson, Dean E.; Ortega, Yvette K. 2001. An indirect dispersal pathway for spotted knapweed seeds via deer mice and great-horned owls.
- Pearson, Dean E.; Ortega, Yvette K.; McKelvey, Kevin S.; Ruggiero, Leonard F. 2001. Small mammal communities and habitat selection in Northern Rocky Mountain bunchgrass: Implications for exotic plant invasions.
- Ruggiero, Len; Pearson, Dean. 2000. Presence/absence as a metric for monitoring vertebrate populations.
- Pearson, Dean E. 2000. Small mammals of the Bitterroot National Forest: Ecological significance and guidelines for management.
- Pearson, Dean E. 1999. Small mammals of the Bitterroot National Forest: A literature review and annotated bibliography.
|Why Do the Exotics Beat the Natives: Where Is the Home-Team Advantage|
New research sets forth a framework for understanding why exotic plants invade and how to fight the invasions