Brian J. Wilsey

Brian J. Wilsey

B.S. 1986 Henderson State University
M.S. 1988 Louisiana State University
Ph.D. 1995 Syracuse University

Title and Mailing Address:
  Associate Professor, Department of Ecology, Evolution, and Organismal Biology,
  253 Bessey Hall,
  Iowa State University, Ames, IA 50011-1020
Office: 131 Bessey Hall
Lab:     40 Bessey Hall
Phone: (515)294-0232
Fax:     (515)294-1337
E-mail: bwilsey@iastate.edu

RESEARCH INTERESTS

In the Wilsey lab, we are interested in the ecology of prairie grasslands. Tallgrass prairies are among the most species-diverse ecosystems. We commonly count 20-30 plant species in Iowa within small quadrats (0.4 m2), and most small prairies (< 10 ha) support more than one hundred species ( Martin et al. 2005, Wilsey et al. 2005a). It is still largely unknown how this very high species diversity develops and is maintained over time. Developing a better understanding of mechanisms behind diversity maintenance is a central focus of work in the lab (e.g. Wilsey et al. 2005, Polley et al. 2005, Martin and Wilsey 2006, Isbell et al. 2009, Wilsey et al. 2009). Furthermore, we are studying how changes in species diversity influence community stability and ecosystem process rates (i.e. ecosystem services). Information from our studies will be useful in the management and restoration of grassland ecosystems.

Loess Hills Loess Hills, Iowa (Sylvan Runkel Preserve)

Is plant diversity an important predictor of ecosystem process rates?

Biodiversity is declining worldwide from human activities. In recent years, ecologists have focused on how species composition and diversity may impact community and ecosystem processes. Species composition and diversity may influence processes independently of, or interactively with, the abiotic components of the environment. Species diversity has two components, 1) richness, or the number of species in a given area, and 2) evenness, or how evenly distributed biomass or abundance is among species. Several high profile studies in the 1990's found that net primary productivity and resistance to invasions declined as species richness was reduced in experimental plots (Naeem et al. 1994, Tilman et al. 1997, Hector et al. 1999). However, since high and low richness plots had different species compositions, it was not easy to differentiate between the "sampling effect", i.e. having high productivity because there was a greater probability of selecting productive species in high richness plots, and complementarity effects that are based on more efficient resource use by a complement of species. Since 1997, we have been experimentally varying the other component of diversity, evenness, in experimental grassland plots. By varying evenness instead of richness, plots with different levels of diversity are created, but without the variability caused by different species compositions. In the first experiment, which was done in an old field, we found that total primary productivity decreased linearly as community diversity (evenness) was reduced, and that it was largely invariant to changes in species composition. (Wilsey and Potvin 2000). A second experiment found that communities with lowered evenness were less resistant to invasion by plants and spittle bugs (Wilsey and Polley 2002). In more recent experiments, we found that species richness and evenness have additive effects on primary productivity and ecosystem C exchange (Wilsey and Polley 2004), and that invasion resistance (Losure et al. 2007) and NPP (Isbell et al. 2008) can vary between extinction scenarios in prairie communities. Species that green-up early in the growing season were especially important in preventing invasion because their growth period matched the period of maximum invasion pressure (Losure et al. 2007).

Species diversity partioning

What should we be measuring in biodiversity studies? Are species abundances related to local extinction risk? Do changes in rarity (quantified with evenness measures) occur before local extinctions? Under what conditions is seed limitation important and how do they alter diversity components? Species diversity has multiple components, and we are attempting to develop a better understanding of how components are related and whether they respond similarly to ecological processes. We have found that a diversity partitioning approach provides us with a more complete understanding of diversity compared to using single measures alone. Studies have looked at relationships between richness, evenness (inverse of dominance), and heterogeneity measures (Stirling and Wilsey 2001, Wilsey et al. 2005b) and between local (alpha) and regional scale (beta) measures (Martin et al. 2005, Wilsey 2009). We have looked at relationships between evenness and richness in a literature survey (Stirling and Wilsey 2001) and with across-grassland data (Wilsey et al. 2005b) at the local scale. Surprisingly, we found that richness and evenness can be negatively correlated in plant communities (Stirling and Wilsey 2001, Wilsey et al. 2005b), and that evenness accounts for much more of the variation in plant diversity (H') than does richness (Stirling and Wilsey 2001). Evidence from plant communities suggested that evenness and richness are acting as diversity components (Stirling and Wilsey 2001) each responding in their own way to changes in the environment, with richness responding more to migration during seed dispersal events and evenness responding more to competition intensity and ungulate grazing (Martin and Wilsey 2006, Wilsey and Stirling 2007). Changes in evenness often precede (and predict) changes in richness (Wilsey and Polley 2004, Wilsey and Stirling 2007, Wilsey et al. 2009). Thus, species richness alone seems to be an incomplete indicator of diversity in plant communities, and studies of both dimensions of diversity (evenness and richness) can be more informative than studies with richness alone. Current research is testing various mechanisms of biodiversity maintenance in native vs. exotic communities (Wilsey et al. 2009).

Past Interests:

In the past, we studied how herbivores affect plant responses to changes in the environment; for example, are responses to global change larger or smaller in areas where plants are defoliated by herbivores? In studies that grew grasses under both elevated and ambient levels of atmospheric CO2, we found that defoliation had little affect on the response of many species to elevated CO2 >(Wilsey et al. 1997), but that in some species, defoliation led to a smaller increase in growth under elevated CO2 (Wilsey 1996, 2001). Another study found that patches in tropical pastures that had been grazed by cattle had lower ecosystem respiration and net CO2 release than did ungrazed patches (Wilsey et al. 2002). bison

Selected Current and Past Projects

  1. MEND: Maintenance of Exotic vs. Native Diversity
  2. Effects of Dominant Species on Loess Hill Prairie Restorations
  3. Grazing Effects on Plant and Ecosystem Processes
  4. Quantifying Prairie Restoration Success

GRADUATE STUDENTS AND POSTDOCS

  • Leanne Martin, M.S. May 2005, Ph.D. student
  • David Losure, M.S., May 2006
  • Andrea Blong, M.S., May 2007
  • Kathryn Yurkonis, Ph.D. candidate
  • Forest Isbell, Ph.D. candidate
  • Tim Dickson, Postdoc
  • Pedram Daneshgar, Postdoc



    SELECTED RECENT PUBLICATIONS AND DATASETS FROM THE WILSEY LAB:(Complete List).

    Date Last Modified: June 2, 2009
    Copyright 2000 Brian J Wilsey