Biology Department: Stacey L. Halpern

Dr. Stacey L. Halpern with pitcher plant




Stacey L. Halpern

Associate Professor of Biology

209/208 Strain
503-352-3109 (voice)
503-352-2933 (fax)




Plants and insects make up more than half of all known species, and their interactions play key roles in both natural and agricultural systems. Both plants and plant-insect interactions are also strongly affected by changes in the environment, including human-caused changes. I study the responses of plant populations and plant-insect interactions to this environmental variation. I aim to do research that not only addresses fundamental questions in ecology and evolution, but also contributes to understanding and perhaps mitigating the ecological effects of changes caused by human activities.

Ecology of invasive plants

Invasive plants may face novel environments in their introduced ranges, and some of these changes may contribute to invasion success. I am interested in how differences in plant-herbivore interactions may affect plant invasions. Currently, my collaborator (Nora Underwood) and I are exploring how density dependence in plant-herbivore interactions might influence plant invasions. In particular, we're interested in the potential effects of insect herbivores on population regulation in an invasive plant. This work occurs in Florida, and every summer I bring students with me to conduct research. This project is funded by the National Science Foundation through 2010, so I encourage interested students to contact me about participating.

Undergraduates who have participated in this research so far: Brian Bielfelt, Lauren Brothers, David Bednar, Maria Sardi, Joel Weekley, Amanda Chisholm, Katty Paulino, Kahaili Barrows, Jessica Swihart, Audry Hite 


Selected publications & presentations (* indicates undergraduate researcher):

Halpern, S. L., N. Underwood, and  D. Bednar*. 2007. ESA. Plant density affects interactions between Solanum carolinense and its insect herbivores: implications for plant population regulation. San Jose, CA.

Weekley, J.* and S. L. Halpern. 2007. Murdock Undergraduate Research Conference (MUR). The effect of host plant density on the growth rate of a specialist beetle. Willamette University, Salem, OR.

Bednar, D.* and S. L. Halpern. 2006. MUR. Density of Solanum carolinense affects oviposition of Leptinotarsa juncta. University of Portland, Portland, OR.

Halpern, S. L. and N. Underwood. 2006. Approaches for testing assumptions about the role of herbivores in plant population dynamics. Journal of Applied Ecology 43: 922-929.


In collaboration with Jean Burns and Alice Winn, I also investigated the traits that may be associated with plant invasiveness. In the group of Dayflowers we studied, invasive species are more opportunistic than non-invasive species—they can take advantage of good conditions (such as low competition or high light availability) with large improvements in performance.

Three high school students participated in this research at Florida State University as part of the Young Scholars Program.

Publications & presentations:

Burns, J. H., S. L. Halpern, and A. A. Winn. 2007. Do low-quality environments limit the advantages of opportunism in invasive species? Biological Invasions 9: 213-225.

Burns, J. H., A. A. Winn, S. L. Halpern, and T. E. Miller. 2006. The effect of environment on invasibility in the Commelinaceae. Ecological Society of America, Memphis, TN.

Adaptation to climate change

Changes in atmospheric composition are driving climate changes that have left an ecological "fingerprint" on species' phenologies and ranges. Despite the understanding that climate can also act as a strong selective agent, evolutionary responses to climate change have received little attention or have been discounted altogether. I evaluated the potential for adaptive evolution in an herbaceous perennial, Lupinus perennis. I found that although evolutionary responses to climate change may ameliorate the negative effects of changes in drought regimes, these changes may not keep pace with the rate of environmental change.

Undergraduates who participated in this research: Valerie Kurth, Zdana King, Bill Severud

Selected publications & presentations:

Halpern, S. L. 2005. Sources and consequences of variation in seed size in Lupinus perennis (Fabaceae): Adaptive and non-adaptive hypotheses. American Journal of Botany 92: 205-213.

Halpern, S. L. 2004. Selection on morphology and phenology across water environments: Possible responses to climate change in Lupinus perennis. ESA, Portland, OR.


Mentoring student research

I believe that participating in research is an important component of an undergraduate education in biology. I enjoy working closely with students on their projects, which make real contributions to my overall research program.

An ideal student research experience involves several components. First, I encourage students to develop their ideas during a semester-long independent study. During this time, students read literature, explore questions, and write a proposal for their project. Then I work closely with students (often over the summer) to carry out their project, including revising plans in the face of the inevitable monkey-wrenches that occur in research. Finally, I help students prepare their projects for formal oral, poster, or written presentation. Students typically present at local or regional conferences, and some participate in writing up results for publication in professional journals.

I encourage students to contact me early in their undergraduate career if they are interested in research. For independent studies during the semester, I ask students to complete a contract (link to this form) before registering for credit.


The impact I've seen teacher-scholars have on individuals and on society is the reason I'm passionate about education. To have that impact, I believe it's essential for teachers to foster student-directed learning and critical thinking. I do this by creating opportunities for students to practice problem-solving skills and the scientific process through case studies and experiential learning.