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William E. Rogers Faculty Fellow Faculty Fellow in Ecology and Evolutionary Biology e-mail:[email protected] 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