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William E. Rogers
Faculty Fellow
Faculty Fellow in Ecology and Evolutionary Biology
e-mail:[email protected]
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B.A.(1991) Gustavus Adolphus College
Ph.D.(1998) Kansas State University
Research Areas
Exotic plant invasions; plant-animal interactions; biodiversity
Research Statement
In collaboration with Evan Siemann, I am seeking to understand how local environmental
factors (e.g., herbivores, fungal pathogens, resources, mycorrhizal symbionts, disturbance
regime and recruitment limitation) interact with post-invasion evolutionary adaptations to
determine the effects of Chinese Tallow Tree (Sapium sebiferum) invasions into various
habitats along the East Texas Gulf Coast. In addition to advancing basic scientific knowledge
of alien species invasions, we are working on several applied research projects related to
controlling exotic plant and animal (e.g., feral hogs) invasions into Texas ecosystems that
should contribute to better informed land management decisions.
Exotic plant Invasions
In collaboration with Evan Siemann, I am seeking to understand how local environmental
factors (e.g., herbivores, fungal pathogens, resources, mycorrhizal symbionts, disturbance
regime and recruitment limitation) interact with post-invasion evolutionary adaptations to
determine the effects of Chinese Tallow Tree (Sapium sebiferum) invasions into various
habitats along the East Texas Gulf Coast. In addition to advancing basic scientific knowledge
of alien species invasions, we are working on several applied research projects related to
controlling exotic plant and animal (e.g., feral hogs) invasions into Texas ecosystems that
should contribute to better informed land management decisions.
Understanding the Causes and Consequences of Exotic Plant Invasions and the
Importance of Post-introduction Evolutionary Adaptations
Looking back, I think it was more difficult to see what the problems were than to solve them.
- Charles Darwin
Correctly identifying the essential problems in ecology is imperative not only for advancing the
conceptual foundations of the disciplines, but also for addressing environmental concerns that
increasingly have tremendous societal, political and economic impacts. I believe that my
research program is poised to provide novel insights into ecological and evolutionary
processes that will contribute to better management and restoration of a variety of imperiled
ecosystems.
Causes and Consequences of Exotic Plant Invasions
Invasions by exotic plant species are considered one of the greatest contemporary and future
environmental threats. Understanding the mechanisms of invasion is critically important to
society with increasing impacts of exotic species and to ecologists because invasion plays a
key role in community assembly and ecosystem function. Presently, I am working at Rice
University in collaboration with Dr. Evan Siemann on a series of studies seeking to understand
the causes and consequences of invasion by the non-indigenous Chinese tallow tree (Sapium
sebiferum) into a variety of habitats along the Texas Gulf Coast. We are examining how the
interaction between local ecological processes and regional patterns of Sapium abundance
contribute to the reduction of plant and animal diversity through the conversion of speciesrich native ecosystems into a species-poor woodland. Using a combination of field,
greenhouse, and laboratory experiments we are testing leading ecological theories concerning
determinants of plant invasions. We are addressing these hypotheses by experimentally
manipulating seed recruitment, resources (light, nutrients, mycorrhizal fungi, and water) and
enemies (herbivores and fungal pathogens) at both the population and community-levels in
order to assess their roles in facilitating Sapium invasion.
In an EPA funded collaboration with Dr. James Grace (USGS), we initiated experiments
examining how management strategies involving fire, flooding, drought, soil nutrients, and
vertebrate and invertebrate enemies interact to determine the fate of Sapium seed
germination and seedling establishment into coastal prairie. Additionally, Evan Siemann and I
have recently completed the 5th year in a long-term collaboration with the National Park
Service by monitoring an experimental removal of Sapium (16 400m2 plots) in a heavily
invaded bottomland forest of the Big Thicket National Preserve. This study will allow us to
answer both basic scientific questions about community responses to large-scale species
removals and applied questions related to the feasibility of controlling the spread of Sapium
and restoration of heavily invaded forests We also have a study examining feral hog impacts
on regeneration growth dynamics of an oak-pine forest in the Big Thicket. These non-native
mammals cause considerable damage to forest understories and potentially promote the
establishment of invasive plants while negatively impacting native tree species recruitment.
Comparative studies have become an important component of invasive species research and
addressing ecological questions across environmental gradients is useful for testing the
generality of empirical data. Moreover, generality and predictability are essential for basic
scientific findings to contribute to conservation goals like managing against exotic invaders.
For these reasons, my current research examines the influence of herbivores on postintroduction evolutionary adaptations in Sapium in its native range of China, its North
American introduced range, and sites of recent introduction on the Hawaiian Islands. Our fully
funded NSF renewal has enabled us to initiate these cross-continental comparative studies
while our recently funded USDA grant has allowed us to explore similar issues along a
biogeographical gradient in southeastern United States that includes Georgia, Florida,
Louisiana and Texas. We have previously demonstrated genetic differences in growth and
defense between native and invasive genotypes of Sapium. Decoupling defense and herbivory
has seemingly allowed this invasive species, and possibly many others, to escape the ?to grow
or defend? trade-off of plants. As a result, evolutionary-based increases in the competitive
ability of introduced plant species potentially contributes to an invasive life-history. The
newest member of our research team, Dr. Saara DeWalt, is analyzing molecular markers of
Sapium genotypes so that we will be able to better identify ecological and evolutionary
differences promoting invasion success. In total, these studies will have profound implications
for the field of biological control by changing the underlying assumptions that are used to
predict future invaders and may aid in the development of new control strategies for existing
invaders.
Selected Publications
Refereed articles
Bossdorf, Oliver, Lucile LaFuma, William E. Rogers, Evan Siemann, Harald Auge, Daniel Prati
"Phenotypic and genetic differentiation in native versus introduced plant
populations." Oecologia (2005) In Press
Rogers, William E., & Evan Siemann "Herbivory tolerance and compensatory differences in
native and invasive ecotypes of Chinese tallow tree (Sapium sebiferum)." Plant Ecology
(2005) In Press
Roma?ach, Stephanie S., Eric W. Seabloom, O. James Reichman, William E. Rogers & Guy N.
Cameron "Effects of species, gender, age, and habitat on pocket gopher burrow
geometry." Journal of Mammalogy (2005) In Press
Siemann, Evan, & William E. Rogers "Recruitment limitation, seedling performance and
persistence of exotic tree monocultures." Biological Invasions (2005) In Press
Butterfield, Bradley J., William E. Rogers & Evan Siemann "Growth and allometry of an
invasive tree and four native species along a water gradient: avoidance of stress tradeoffs." Texas Journal of Science, 56 (2004) : 335-346.
Donahue, Candace, William E. Rogers, & Evan Siemann "Effects of Sapium sebiferum (Chinese
tallow tree) mulch on seed germination: restoring an invaded prairie." Texas Journal of
Science, 56 (2004) : 347-356.
Hartley, Maria K., Saara DeWalt, William E. Rogers, & Evan Siemann "A comparison of
arthropod assemblages on native trees versus the introduced Chinese tallow tree (Sapium
sebiferum)." Texas Journal of Science, 56 (2004) : 369-382.
Lankau, Richard A., William E. Rogers & Evan Siemann "Constraints on the utilization of the
invasive Chinese Tallow Tree (Sapium sebiferum) by generalist native herbivores in coastal
prairies." Ecological Entomology, 29 (2004) : 66-75.
Nijjer, Somereet, William E. Rogers, & Evan Siemann "The effect of mycorrhizal inoculum on
the growth of five native tree species and the invasive Chinese Tallow Tree (Sapium
sebiferum)." Texas Journal of Science, 56 (2004) : 357-368.
Rogers, William E., & Evan Siemann "Invasive ecotypes tolerate herbivory more effectively
than native ecotypes of the Chinese tallow tree." Journal of Applied Ecology, 41 (2004) : 561570.
Rogers, W., Siemann, E. "Effects of simulated herbivory and resources on Chinese tallow tree
(Sapium sebiferum, Euphorbiaceae) invasion of native coastal prairie." American Journal of
Botany, 90 (2003) : 241-247.
Rogers, W., Siemann, E., Lankau, Richard "Damage induced production of extrafloral nectaries
in native and introduced seedlings of Chinese tallow tree (Sapium sebiferum)." American
Midland Naturalist, 149 (2003) : 413-417.
Siemann, E., Rogers, W. "Changes in light and nitrogen availability under pioneer trees may
indirectly facilitate tree invasions of grasslands." Journal of Ecology, 91 (2003) : 923-931.
Siemann, E., Rogers, W. "Herbivory, disease, recruitment limitation and the success of alien
and native tree species." Ecology, 84 (2003) : 1489-1505.
Siemann, E., Rogers, W. "Increased competitive ability of an invasive tree may be limited by
an invasive beetle." Ecological Applications, 13(6) (2003) : 1503-1507.
Siemann, E., Rogers, W. "Reduced resistance of invasive varieties of the alien tree Sapium
sebiferum to a generalist herbivore." Oecologia, 135 (2003) : 451-457.
Rogers, William E. & Evan Siemann "Effects of simulated herbivory and resource availability on
native and invasive exotic tree seedlings." Basic and Applied Ecology, 4 (2002) : 297-307.
Somereet Nijjer, Richard A. Lankau, Rogers, W. E. & Evan Siemann "Effects of temperature
and heat on Chinese tallow (Sapium sebiferum)and Texas Sugarberry (Celtis laevigata) seed
germination." Texas Journal of Science, 54 (2002) : 63-68.
Rogers, William E. and David C. Hartnett "Vegetation responses to different spatial patterns of
soil disturbance in burned and unburned tallgrass prairie." Plant Ecology, 155 (2001) : 99109.
Rogers, William E. and David C. Hartnett "Temporal vegetation dynamics and recolonization
mechanisms on different-sized soil disturbances in tallgrass prairie." American Journal of
Botany, 88 (2001) : 1634-1642.
Rogers, William E., David C. Hartnett and Bradley Elder "Effects of plains pocket gopher
(Geomys bursaris) disturbances on tallgrass-prairie." American Midland Naturalist, 145 (2001)
: 344-357.
Siemann, Evan & William E. Rogers "Genetic differences in growth of an invasive tree
species." Ecology Letters, 4 (2001) : 514-518.
Keay, J, William E. Rogers, R. Lankau and Evan Siemann "The role of allelopathy in the
invasion of Chinese Tallow tree." Texas Journal of Science, 52 (2000) : 57-64.
Rogers, William E., S. Nijjer, C. L. Smith and E. Siemann "Effects of resources and herbivory
on leaf morphology and physiology of Chinese Tallow (Sapium sebiferum)." Texas Journal of
Science, 52 (2000) : 43-56.
Book chapters
Rogers, William E., & Evan Siemann "The role of herbivores in alien plant invasions: insights
using a combination of methods to enhance or reduce herbivory." Insects and Ecosystem
Function (2004) : 329-355.
Siemann, Evan, Walter P. Carson, William E. Rogers & Wolfgang W. Weisser "Reducing
herbivory using insecticides." Insects and Ecosystem Function (2004) : 303-327.
Presentations
Invited Papers
Co-advisor. "A comparison of arthropod assemblages on native trees versus the introduced
Chinese tallow (Sapium sebiferum)." Ecological Society of America meeting, Portland, OR.
(August 2004) With Maria Hartley & Evan Siemann
"Chinese tallow tree invasions of Texas coastal prairie: effects of fire, fertility and herbivores."
Ecological Society of America meeting, Portland, OR. (August 2004) With Evan Siemann
"Do genetic differences in growth and defense contribute to the success of an invasive plant
species: Intra- and inter-continental comparisons." Ecological Society of America meeting,
Portland, OR. (August 2004) With Evan Siemann
Co-advisor. "Restoring an invaded prairie: Effects of Sapium sebiferum (Chinese tallow tree)
mulch on seed germination." Texas Society for Ecological Restoration meeting, Clear Lake, TX.
(July 2004) With Candice Donahue & Evan Siemann
"A comparison of arthropod assemblages on native trees versus the introduced Chinese tallow
tree (Sapium sebiferum)." Society for Ecological Restoration, Austin, Texas. (November 2003)
With Maria Hartley & Evan Siemann
October 2003. "Growth of Chinese tallow and four native species along a water gradient." Big
Thicket Science Conference, Beaumont, Texas.
"Large-scale experimental tests of recruitment limitation and Chinese tallow tree invasions."
Big Thicket Science Conference, Beaumont, Texas. (October 2003) With Evan Siemann
"Mycorrhizae's role in forest regeneration dynamics and the invasive success of Sapium
sebiferum (Chinese Tallow) in the Big Thicket National Preserve." Big Thicket Science
Conference, Beaumont, Texas. (October 2003) With Somerett Nijjer & Evan Siemann
"Escaping the 'to grow or defend' dilemma of plants: an explanation for the invasive success
of an exotic tree species." Ecological Society of America, Tucson, AZ. (August 2002) With
Evan Siemann
"Large-scale experimental tests of recruitment limitation and alien plant invasions." Ecological
Society of America, Tucson, AZ. (August 2002) With Evan Siemann
Invited Talks
"Ecological and evolutionary effects of enemies on an invasive tree species." Department of
Rangeland Ecology and Management, Texas A&M University, College Station. (November
2004)
"Invasion biology of an alien tree: ecological and evolutionary influences of enemies."
University of Richmond, Richmond, Virginia. (January 2003)
"Invasion biology of an alien tree: influence of enemies and conservation implications."
University of Central Florida, Orlando, Florida. (Feb 2003)
Other
"Burrow geometry of three species of pocket gophers: effects of habitat, body size and social
behaviour." International Theriological Congress, Sun City, South Africa. (July 2001) With S.
Romanach, E. Seabloom, G. Cameron & J. Reichman
"Chinese tallow tree (Sapium sebiferum) invasion of native coastal prairie: interactive effects
of herbivory and resources." Ecological Society of America, Madison, WI. (August 2001) With
Evan Siemann
"Evolution of increase competitive ability in an invasive tree species." Society for Conservation
Biology, Hilo, HI. (July 2001) With Evan Siemann
"Fire, fertility, and herbivore effects on Chinese tallow (Sapium sebiferum) invasion of coastal
prairie." Society for Conservation Biology, Hilo, HI. (July 2001) With Evan Siemann & James
Grace
"The role of native generalist herbivores in Chinese tallow tree (Sapium sebiferum) invasions
into coastal prairie." Ecological Society of America, Madison, WI. (August 2001) With Richard
Lankau & Evan Siemann
"Factors affecting Chinese tallow invasions: lessons from pot experiments." USGS, Wetland
Research Center, Lafayette, Louisiana. (March 2000)
"Interactive effects of resources and herbivory on tree growth: experimental tests using a
native and an invasive exotic species." Ecological Society of America, Snowbird, Utah. (August
2000)
"Chinese Tallow Tree (Sapium sebiferum) invasion into grasslands: the effects of resources."
Big Thicket Science Conference, Beaumont, Texas. (October 1999)
"Vegetation responses to various spatial patterns of disturbance." Ecological Society of
America, Spokane, Washington. (August 1999)
Posters
"Genetic reconstruction of the introduction of Chinese tallow tree to the United States."
Ecological Society of America meeting, Portland, OR. (August 2004) With Saara DeWalt &
Evan Siemann
Co-advisor. "Growth strategies and performance of five tree species along a water gradient."
Natural Sciences Undergraduate Research Symposium, Rice University, Houston, TX. (May
2004) With Bradley Butterfield & Evan Siemann
Co-advisor. "Mycorrhizal effects on the growth of five native tree species and the invasive
Sapium sebiferum." Ecological Society of America meeting, Portland, OR. (August 2004) With
Somereet Nijjer & Evan Siemann
Co-advisor. "Restoring an invaded prairie: effects of Sapium sebiferum (Chinese tallow tree)
mulch on seed germination." Ecological Society of America meeting, Portland, OR. (August
2004) With Candice Donahue & Evan Siemann
"Effects of Sapium sebiferum (Chinese tallow tree) Mulch on Seed Germination: Restoring an
Invaded Prairie." Society for Ecological Restoration, Austin, Texas. (November 2003) With
Candy Donahue & Evan Siemann
"Effects of light and flooding on the invasion of Sapium sebiferum into coastal prairies."
Ecological Society of America, Tucson, AZ. (August 2002) With Rick Lankau and Evan Siemann
"Responses of prairie arthropod communities to fire: balancing plant and arthropod
conservation." Ecological Society of America, Tucson, AZ. (August 2002) With Maria Hartley,
Larry Allain, Jim Grace and Evan Siemann.
Workshops
"Post-introduction evolutionary increases in the competitive ability of an invasive tree are
negated by herbivores from its native range." European Science Foundation/Center for
Environmental Research (Highlighted in Trends in Ecology and Evolution 17(12)), Halle,
Germany. (October 2002) With Evan Siemann
Awards, Prizes, & Fellowships
Member, American Institute of Biological Sciences
Member, American Society of Naturalists
Member, Ecological Society of America