Arthur R. Marshall, Jr., Ecological Sciences Laboratory

Mail: Department of Biology
111 Bartram Hall, PO Box 118525
Gainesville, FL 32611-8525

Robert D. Holt

Professor and Arthur R. Marshall, Jr., Chair in Ecology
Ph.D., Harvard University

111 Bartram Hall



My core personal research focuses on theoretical and conceptual issues at the population and community levels of ecological organization, and on the task of linking ecology with evolutionary biology. In addition to basic research, I am interested in bringing modern ecological theory to bear on significant applied problems, particularly in conservation biology. I have also carried out large-scale experiments on habitat fragmentation. My students include both theoreticians and empirical, experimental ecologists. I have historically collaborated with many faculty at a wide range of institutions, both inside and outside the USA.  Web page with links to publications.


Mary Christman

Courtesy Associate Professor
Ph.D., George Washington University

110 Bartram Hall



My background and interests are at the intersection of statistical methodology and environmental and ecological research. My current interests include development and application of statistical methods for spatial modeling of community structure and species abundances; accounting for uncertainty and sampling error in models of population dynamics; analyses when data are zero-inflated; developing sampling designs and estimators for rare and elusive species; linear and non-linear mixed models; hierarchical modeling; and sampling strategies for spatial data analysis. I collaborate and consult with scientists across many disciplines, including agriculture and natural resources, zoology, ecology, human nutrition, fisheries, and wildlife conservation. Curriculum vitae.


Robert Ulanowicz

Professor Emeritus of Theoretical Ecology, University of Maryland
Ph.D., Johns Hopkins University

110 Bartram Hall


I have spent my career on Chesapeake Bay creating quantitative methods to analyze networks of trophic transfers. I have developed methods that quantify indirect effects, trophic hierarchies, domains of recycling and whole system indexes of ecosystem organization and flexibility. In the process, I have reached the conclusion that the dynamics of ecosystems are hardly mechanical, but rather dual and dialectic-like. Consequently, I have proposed a perspective on nature that is predicated on processes rather than on objects and laws. My current interest is in promulgating the necessity of indeterminacy for ecosystem sustainability. In economic terms, the implication is that parallel, alternative currencies are likely required to impart sustainability to local and national economies. More than anyone ever wanted to know about me can be found at


Michael Barfield

Assistant Scientist
Ph.D., University of Kansas

111 Bartram Hall



I have worked at the Ecological Sciences Laboratory doing research on theoretical population biology since 2001. Publications are available through the link below, and include research on adaptation in source-sink systems (Holt et al. 2003, 2004a, 2004b, 2005; Holt and Barfield 2008, 2009b; Peniston et al. 2019), infectious disease ecology (Orive et al. 2005; Holt and Barfield 2006; Wayne et al. 2011; Smith et al. 2015; Barfield et al. 2015; Tuncer et al. 2016; Levi et al. 2016; Barfield et al. 2018), effects of temporal variation on populations (Holt and Barfield 2003; Holt et al. 2003, 2004b; Roy et al. 2005), evolution (Knight et al. 2008; Barfield et al. 2011), species ranges (Holt et al. in 2011; Holt and Barfield 2011; Filin et al. 2008), phenotypic plasticity (Scheiner et al. 2017, 2020), evolutionary rescue (Barfield and Holt 2016; Orive et al. 2017; Peniston et al. 2020), habitat connectivity (Fletcher et al. 2019), tropical forest diversity (Levi et al. 2019a, 2019b) and aquatic ecology (O’Brien et al. 2004, 2005; Mestre et al. 2019; Branco et al. 2020).  Web page with links to publications.


James Peniston

Ph.D. Student, Biology
B.A., U. of California-
Santa Barbara

110 Bartram Hall



I am very broadly interested in ecology and evolution. My dissertation work focuses on how the interplay between ecological and evolutionary processes affects adaptation to harsh environments. The majority of my work involves the use of mathematical models or computer simulations, but I strive to combine theoretical predictions with experimental tests whenever possible. Thus, I am using experimental evolution in yeast systems to test some of my theoretical predictions regarding adaptation to harsh environments. I am a strong proponent of the importance of theoretical work in biology and I believe that theoretical and empirical biologists must work together in order to advance our understanding of natural systems.


Margaret Simon

Posdoctoral Associate

Ph.D., University of California, Los Angeles

110 Bartram Hall




Nicholas Kortessis

Postdoctoral Associate

Ph.D., University of Arizona

110 Bartram Hall

I am a theoretical evolutionary ecologist. Much of what I try to understand is what factors cause differential fitness, which is the ecological force of evolutionary change. Evolutionary change often changes ecology, leading to dynamical feedbacks between ecology and evolution. I use mathematical tools to describe this feedback in order to understand ecological patterns in nature. My graduate work was on ecological character displacement in temporally variable environments. I currently work on movement of organisms in spatially fragmented environments, asking how landscape change may alter an organism’s ecology. I am also involved in a project understanding how plant pathogens influence plant communities. Pathogens generally evolve quickly relative to their hosts. Evolutionary change of the pathogen figures prominently in this work. You can read more about my work at my website,


Vitrell Sherif

Lab Manager

111 Bartram Hall


Vitrell is the administrative lab manager for the Arthur R. Marshall, Jr., Laboratory. She took the cover photograph for the March 2015 issue of the Israel Journal of Ecology and Evolution (shown below – click for larger version). This issue featured the essay “Inference to the best explanation: Reflections on the issue of climate change,” by Robert D. Holt, which used the metaphor of Easter egg baskets in discussing scientific inference.
IJEE cover March 2015

Previous Personnel

(Names link to old Marshall lab web pages.)

Visiting Faculty

Luiz Dos Anjos, here for 2008, Londrina State U., Londrina, Brazil.
Leticia Aviles, Spring 2011, University of British Columbia.
Mark Taper, September 2011-February 2012, Montana State U.

Visiting Scientists

Pitágoras da Conceição Bispo
Ciro C.Z. Branco


Tiffany Knight, postdoc 2003-4, now at German Centre for Integrative Biodiversity Research, Martin Luther University of Halle-Wittenberg and the Helmholtz Centre for Environmental Research (UFZ).
Nicholas Friendenberg, postdoc 2003. His website
Manojit Roy, postdoc 2004-2010, now at the University of Michigan.
Ricardo Holdo, postdoc 2005-2010, now at the University of Georgia.
Taal Levi, postdoc 2013-2014, now at Oregon State University.
Cristina Goncalves, postdoc 2014.

Graduate Students

Tristan Kimbrell, Ph.D. 2007.
Tania Kim, M.S. 2006.
Gabriela Blohm, M.S. 2008.
Connie Clark, Ph.D. 2009.
Cedric Worman, Ph.D. 2012.
Smriti Bhotika, Ph.D. 2012.
Kristen Sauby, Ph.D. 2017.

Student Assistants

David J. Hall
Vanessa Trujillo
Yaneke (Yani) Paulay

Recent Visitors
Colleen Webb, Colorado State University.
Richard Gomulkiewicz, Washington State University.
Jeannine Cavender-Bares, U. of Minnesota.
Carolina Murcia, Science Director for the Organization of Tropical Studies.
Jin Yao, New Mexico State U.
Ido Filin, U. of Helsinki.
James Estes, U. of California, Santa Cruz.
Michael Rosenzweig, U. of Arizona.
Sam Scheiner, Program Director, Division of Environmental Sciences, National Science Foundation.
Val Smith, U. of Kansas.
Michael Bonsall, U. of Oxford.
Per Lundberg, U. of Lund, Sweden.
Leticia Avilés, U. of British Columbia.
Lev Ginzburg, Stony Brook University.
Roger Arditi, Université Pierre et Marie Curie, Paris.
Maria Orive, University of Kansas.
William Godsoe, Lincoln University (New Zealand).
Xiao Song, Zhejiang University, China.
Shilu Zheng, Zhejiang University, China.
Owen Petchey, University of Zurich, Zurich, Switzerland.
Andy Gonzalez, McGill University, Montreal, Quebec.
Meghan Duffy, University of Michigan.
Joel Brown, Moffitt Cancer Center.
Tom Givnish, University of Wisconsin-Madison.
Shripad Tuljapurkar, Stanford University.
Joel Brown, Rockefeller and Columbia Universities.
Egbert Giles Leigh, Jr., Smithsonian Tropical Research Institute.