Professor Geddes
College of Arts and Sciences
(773) 442-5737
Ecology/Environmental Science
Courses Taught
The Changing Natural Environment (BIO 104)
Alien Invasions of Chicago (First Year Experience BIO 109A)
Essential Skills for Biologists (BIO 150)
General Biology II (BIO 202)
General Ecology (Writing Intensive Program BIO 305)
Biology Senior Seminar (Capstone BIO 390)
Independent Research in Biology (BIO 392, BIO 393)
Community Ecology (BIO 357*)
Conservation Biology (BIO 453)
Restoration Ecology (BIO 455)
Independent Investigations (BIO 481X)
Research Interests
My research interests focus on two broader themes: 1) Invasive plant species and the mechanisms that underlie successful invasions in wetlands, and 2) Ecological interactions in freshwater aquatic communities. Under theme #1, I’m interested in how plant invasive species’ traits (such as rapid growth, large biomass, large litter deposition, and even genotype) trigger a cascade of effects that span from their interaction with co-occurring native species all the way up to ecosystem-level processes. Within this topic, I am exploring two important wetland plant invaders: cattails (Typha spp.) and common reed (Phragmites spp.). I also combine molecular tools (microsatellite markers) to answer ecological questions, mostly related to the identification of hybridizing invasive plant species. Under theme #2, I’m interested in: a) how aquatic communities are fueled, either via primary production, detritus, or external inputs (i.e., spatial subsidies), and b) how emerging contaminants affect those aquatic communities.

Miami-Dade Community College                    Biology                                    A.A. 1994

Florida International University                        Biology                                    B.S. 1996

Florida International University                        Biology                                    M.S. 1999

University of Chicago                                           Ecology                                   Ph.D. 2004

Loyola University Chicago                                  Ecology                                   Post-doc 2004-2009


Selected Publications

Geddes, P., T. Grancharova, J. J. Kelly, D. Treering, and N. C. Tuchman. In review. Effects of invasive Typha x glauca on wetland ecosystem properties are influenced by time since invasion. Submitted to Aquatic Ecology.

Lishawa, S.C., K.J. Jankowski, P. Geddes, D.J. Larkin, A.M. Monks, and N.C. Tuchman. 2014. Denitrification in a Laurentian Great Lakes coastal wetland invaded by hybrid cattail (Typha × glauca). Aquatic Sciences DOI 10.1007/s00027-014-0348-5.

Larkin, D. M. Freyman, S. Lishawa, P. Geddes and N.C. Tuchman. 2011. Mechanisms of dominance by the invasive hybrid cattail Typha X glauca. Biological Invasions 14(1):65-77.

Mitchell, M.M, S. Lishawa , P. Geddes, D. Larkin, D. Treering, and N.C. Tuchman. 2011. Time-dependent impacts of cattail invasion in Great Lakes coastal wetlands. Wetlands 31:1143-1149.

Geddes, P. 2009. Decoupling carbon effects and UV protection from terrestrial subsidies on pond zooplankton. Hydrobiologia 628:47-66.

Tuchman, N. C., D. Larkin, P. Geddes, R. Wildova, K. Jankowski, and D. E. Goldberg. 2009. Patterns of environmental change associated with Typha x glauca invasion in a Great Lakes coastal wetland. Wetlands 29(3):964-975.

Chick, J. H., Geddes, P. and Trexler, J. C. 2008. Periphyton mat structure mediates trophic interactions in a subtropical marsh. Wetlands 28(2):378-389.

Leibold, M. A. and P. Geddes. 2005. El concepto de nicho en las metacomunidades. Ecología Austral 15:117-129.

Geddes, P. and J. C. Trexler. 2003. Uncoupling of omnivore-mediated positive and negative effects on periphyton mats. Oecologia 136:585-595.

Hermann, P. M., A. C. Curino, and P. Geddes. 2002. Comparative vegetative anatomy of Neosparton darwinii and N. ephedroides (Verbenaceae). Boletín de la Sociedad Argentina de Botánica 36:63-70.

Turner, A. M., Trexler, J. C., Jordan, F., Slack, S. J., Geddes, P., J. H. Chick, and W. F. Loftus. 1999. Targeting ecosystem features for conservation: Standing crops in the Florida Everglades. Conservation Biology 13:898-911.


Additional Information

Undergraduate Mentor:

Sarah Whidden (Fall 2013 – present), Luis Allende (Fall 2013 – present), Courtney Moran (Summer 2013 – present), Daniel Arrecis (Summer 2013 – present), Michelle Guy (Summer 2013 – present), Tracia Spence (Summer 2013), Dayvis Blasini (Spring 2012 – Fall 2013), María Jazmín Ríos (Summer 2012 – Fall 2013), Nancy Salgado (Summer 2013), Chris Sferra (Fall 2012), Christopher Craddock (Summer 2012), Yaiyr Astudillo-Scalia (Spring 2011 – Summer 2012), Jennifer Shaier (Summer 2011), Salina Wunderle (Summer 2011 – Fall 2011), Jeny Semoon (Summer 2010), Sumitra Gurung (Summer 2010), JJ Mulliken (Summer 2010), Kristen Veldman (Summer 2010), Steve Ryan (Summer 2010), Matthew Deisinger (Summer 2010).


Thesis Advisor or Committee Member:

Paul Hartzog, Northwestern University / Chicago Botanic Garden (PhD Committee Member, current)

Andrea Erber, Northeastern Illinois University (Master’s Research Thesis Advisor; defended Spring 2013)

Lisa Volesky, Northeastern Illinois University (Master’s Research Thesis Advisor; defended Fall 2012)

Justin Chappelle, Northeastern Illinois University, Dept. of Geography and Environmental Studies (Master’s Research Thesis Committee Member; defended Fall 2012)

Mark Mitchell, Loyola University Chicago (Master’s Research Thesis Committee Member; defended Fall 2010)

Sara Rose, Northeastern Illinois University (Master’s Research Thesis Committee Member; defended Fall 2009)

BBH 340H
5500 N. St. Louis Ave.
Chicago, IL 60625
United States

(773) 442-5737
Office Hours
M 2:00-3:00 p.m. T 5:30-6:30 p.m. W 2:00-4:00 p.m. and by appointment
Main Campus