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
253 Bessey Hall,
Iowa State University, Ames, IA 50011-1020
Office: 131 Bessey Hall
Lab: 40 Bessey Hall
RESEARCH INTERESTS OF THE WILSEY LAB
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
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
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).
are studying how changes in
species diversity influence community stability and ecosystem process rates
(i.e. ecosystem services).
our studies will be useful in the management and
Loess Hills, Iowa (Sylvan
Biodiversity and ecosystem process rates in native and exotic
communities (MEND - Maintenance of Exotic vs. Native Diversity). Funded by the
U.S. National Science Foundation
The homogenization of the earth's biota is affecting nearly every region of the
earth, and is expected to increase due to increased movement
of people and goods between regions. Grasslands, which cover roughly 25% of
the planet, contain perhaps the most homogenized communities. Many exotic (i.e. non-native or "invasive") species have been
introduced or have escaped into grasslands where they form 'novel ecosystems' (Hobbs et al. 2006) of species with
a very recent history of interacting with each other. This has led to a patchwork of exotic- and native-dominated
fields on modern landscapes. Species interactions, biodiversity, niche overlap, and ecosystem functioning could
all differ between these novel ecosystems and the native systems that they replaced. We are testing whether there are fundamental differences
in biodiversity maintenance mechanisms and ecosystem functioning between
exotic- and native-dominated grasslands with large numbers species (e.g. 40 native and exotic species in Wilsey et al
. 2009). Hypotheses are being tested by comparing paired exotic and native
species in planted mixtures and monocultures in common garden experiments and with observational studies of intact grasslands.
Treatments also include summer precipitation that mimics increased
tropical storm activity predicted by global climate change models in one study (Wilsey et al. in press)
and cattle grazing in a study with my former graduate student Forest Isbell (Isbell and Wilsey 2011). Summer
precipition treatments are either no precipitation or 128 mm added from July 15-August 15
(or 15% increase in annual precipitation). The most important findings so far are:
1) species diversity and richness was consistently much lower
in exotic communities than in native communities, even when communities were compared in a common environment,
2) species interactions were fundamentally different, with complementary resource use occurring in native but not exotic communities,
3) niche overlap was much higher in exotic than in native communities, and this was related to temporal (Wilsey et al.
in press) or canopy overlap (Isbell and Wilsey 2011),
4) spring green-up was consistently about four weeks earlier in exotic communities and three
and a half weeks earlier in exotic monocultures than natives, and
5) intercorrelations among phenology measures (green-up, flowering date,
senescence date) were highly altered in exotic communities,
and 6) all these effects were similar between irrigation treatments.
The earlier green-up by exotic species suggests that some of the earlier green-up attributed to
climate change may be a result of an increase in abundance of exotics, and this deserves further study. Thus, our
our results suggest that there are key differences between novel ecosystems and the native ones that they replaced.
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 diversity can impact community and ecosystem processes.
Species 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
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
productivity because there was a greater probability of selecting productive
species in high richness plots, and complementarity effects that are based on
efficient resource use by a complement of species. We have been
varying the other component of diversity, evenness, in experimental grassland
plots. By varying evenness instead of (and in addition to) 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 in 1997, we
found that total primary productivity decreased linearly as community
diversity (evenness) was reduced, and that it was largely invariant to changes
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). Others found that species richness-productivity relationship were similar between communities
planted with equal relative abundances and communities with realistically unequal abundances across species (Wilsey
and Polley 2004, Isbell et al. 2009a,b), and that invasion resistance and NPP
can vary between extinction scenarios in prairie communities (Losure et al. 2007, Isbell et al. 2008).
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). Studies with litter decomposition found that higher evenness, but not
richness, resulted in higher decomposition rates, and that diversity effects were smaller than microtopographic
effects (Dickson and Wilsey 2009).
Species diversity partioning
What should we be measuring in biodiversity studies? Are species relative abundances
related to local extinction risk? Do changes in rarity (quantified with
evenness measures) occur before local extinctions (quantified with richness) or is rarity unrelated to extinction risk?
Under what conditions is seed limitation important and how do they alter these biodiversity 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 2010). We have looked at
between evenness and richness in a literature survey (Stirling and Wilsey
2001) and with across-grassland data (Wilsey et al. 2005b).
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
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.
We have studied how native ungulates (bison and a few elk) affect tallgrass prairie restoration success at Neal
Smith National Wildlife Refuge. Exlosures were erected and maintained for five years to study
how grazing has altered tallgrass prairies community development (Martin et al. 2005, Martin and Wilsey 2006).
The recruitment of rare prairie species into grass-dominated stands was higher with grazing than without
grazing, but an important finding was that rare species were not recruited without seed additions.
Selected Current and Past Projects
Maintenance of Exotic vs. Native Diversity
Effects of Dominant Species on Loess Hill Prairie Restorations
Effects on Plant and Ecosystem Processes
Prairie Restoration Success
GRADUATE STUDENTS AND RECENT POSTDOCS
Kaitlin Barber, Ph.D. student
Leanne Martin, M.S., May 2005, Ph.D. candidate
Yue Huang, Visiting student from Northeast Normal University, Changchun, China
David Losure, M.S., May 2006
Andrea Blong, M.S., May 2007
Kathryn Yurkonis, Ph.D., Jan. 2010, now Univ. North Dakota
Forest Isbell, Ph.D., May 2010, now at Univ. Minnesota
Tim Dickson, Postdoc, now at Michigan State Univ.
Pedram Daneshgar, Postdoc, now at Monmouth University, N.J.
SELECTED RECENT PUBLICATIONS AND DATASETS FROM THE WILSEY LAB:(Complete List).
* denotes a graduate student; ** a postdoctoral fellow
*Martin, L.M., and B.J. Wilsey. 2012. Assembly history alters alpha and beta diversity, exotic-native
proportions, and ecosystem functioning of restored prairie plant communities.
Journal of Applied Ecology 49:1436-1445
*Yurkonis, K.A., Wilsey, B.J. and K.A. Moloney. 2012. Initial plant arrangement affects invasion resistance in experimental grassland plots. Journal of Vegetation Science 23:4-12
*Isbell, F., Calcagno, V., Hector, A., Connolly, J., Harpole, W.S., Reich, P.B., Scherer-Lorenzen, M.,
Schmid, B., Tilman, D., van Ruijven, J., Weigelt, A., Wilsey, B.J., Zavaleta, E.S. and M. Loreau. 2011.
High plant diversity is needed to maintain ecosystem services.Nature 477:199-202
Wilsey, B.J., **Daneshgar, P.P., and H.W. Polley. 2011. Biodiversity, phenology and temporal niche differences
between native and novel exotic-dominated grasslands. Perspectives in Plant Ecology, Evolution and Systematics13:265-276
*Isbell, F.I. and B.J. Wilsey. 2011. Increasing native, but not exotic, biodiversity increases aboveground
productivity in ungrazed and intensely grazed grasslands. Oecologia
Dornbush, M.E. and B.J. Wilsey. 2010. Experimental manipulation of soil depth alters species richness and co-occurrence in restored tallgrass prairie. Journal of Ecology 98:117-125
Wilsey, B.J. 2010. An empirical comparison of beta diversity indices in
establishing prairies. Ecology
**Dickson, T.L., Wilsey, B.J., Busby, R.R. and D.L. Gebhart. 2010. A non-native
legume causes large community and ecosystem changes in both the presence and
absence of a cover crop. Biological Invasions12:65-76
*Yurkonis, K.A., B.J. Wilsey, K.E. Moloney, and A. van der Valk. 2010. Paired
drilled and broadcast grassland reconstructions have similar diversity but
differ in dominant plant distributions. Restoration Ecology 18:311-321
Wilsey, B.J. 2010. Productivity and subordinate species response to dominant
grass species and seed source during restoration.Restoration Ecology
Wilsey, B.J., **Teaschner, T.B., **Daneshgar, P.P., *Isbell, F.I. and H.W. Polley.
2009. Biodiversity maintenance mechanisms differ between native and novel
exotic-dominated communities. Ecology Letters
*Isbell, F.I., Polley, H.W. and B.J. Wilsey. 2009a. Species interaction
mechanisms maintain grassland plant species diversity. Ecology90:1821-
*Isbell, F.I., Polley, H.W. and B.J. Wilsey. 2009b. Biodiversity, productivity,
and the temporal stability of productivity: patterns and processes. Ecology
**Dickson, T.L. and B.J. Wilsey. 2009. Biodiversity and tallgrass prairie
decomposition: the relative importance of species identity, evenness, richness
and microtopography.Plant Ecology201:639-649
*Isbell, F.I., *Losure, D.A., *Yurkonis, K.A. and B.J. Wilsey. 2008. Diversity-
productivity relationships in two realistic rarity-extinction
*Losure, D.A., Wilsey, B.J. and K.A. Moloney. 2007. Evenness-invasibility
relationships differ between two extinction scenarios in tallgrass
Wilsey, B. and G. Stirling. 2007. Species richness and evenness respond in a
different manner to propabule density in developing prairie microcosm
communities. Plant Ecology.
Polley, H.W., Wilsey, B.J. and J.D. Derner. 2007. Dominant species constrain
effects of species diversity on temporal variability in biomass production of
tallgrass prairie. Oikos.
Wilsey, B.J. and H.W. Polley. 2006.
Aboveground productivity and root-shoot allocation differ between native and
introduced grass species. Oecologia.
*Martin, L.M. and B.J. Wilsey. 2006. Assessing grassland restoration success:
relative roles of seed additions and native ungulate activities. Journal of
Wilsey, B.J., *Martin, L.M. and H.W. Polley. 2005a.
Predicting plant extinction based on species-area curves in prairie fragments
with high beta richness. Conservation Biology.
Wilsey, B.J. Chalcraft, D.R., Bowles, C.M., and M.R. Willig. 2005b.
Relationships among indices suggest that richness is an incomplete surrogate
for grassland biodiversity. Ecology
*Martin, L.M., Moloney, K.A. and B.J. Wilsey. 2005. An assessment of grassland
restoration success using species diversity components. J. Applied Ecology
Wilsey, B.J. and H.W. Polley. 2004. Realistically low species evenness does
not alter grassland species-richness-productivity relationships. Ecology
Wilsey, B.J. and H.W. Polley. 2003. Effects of seed additions and grazing
history on species diversity and aboveground productivity of sub-humid Texas
grasslands. Ecology 84:920-932.[PDF]
- Wilsey, B.J. and H.W. Polley. 2002. Reductions in grassland species
evenness increase dicot seedling invasion and spittle bug infestation.
- Stirling, G. and B. Wilsey. 2001. Empirical relationships between
richness, evenness and proportional diversity.
American Naturalist 158:286-300.[PDF]
- Wilsey, B.J. and C. Potvin. 2000. Biodiversity and ecosystem functioning:
the importance of species evenness in an old field. Ecology
Date Last Modified: February 29, 2012
Copyright 2000 Brian J Wilsey