Grantee Research Project Results
Evolution of Defense Chemistry in Alliaria petiolata Since Introduction Into North AmericaEPA Grant Number: U915981
Title: Evolution of Defense Chemistry in Alliaria petiolata Since Introduction Into North America
Investigators: Lewis, Kristin C.
Institution: Harvard University
EPA Project Officer: Just, Theodore J.
Project Period: January 1, 2001 through January 1, 2004
Project Amount: $80,792
RFA: STAR Graduate Fellowships (2001)
Research Category: Academic Fellowships , Fellowship - Terrestrial Ecology and Ecosystems , Ecological Indicators/Assessment/Restoration
Invasive species threaten the integrity and function of ecosystems across the globe. However, prediction of and prevention of invasion have thus far proved elusive because of the dearth of commonalities among invasive species that might predict invasiveness. One of the characteristics common among invasive plant species is escape from specialist herbivores in their new range. It has been predicted that plants released from herbivory will adjust their resource allocation to reduce investment in defense, particularly when defenses are costly. Such a change in allocation could result in increased availability of resources for other activities such as growth and reproduction. In invasive plant species, this may contribute to strong competitive ability and rapid spread. Alternatively, release from specialists and continued selection pressure from generalists in the new range could increase investment in defenses if they are mainly effective against generalists. The objective of this research project is to investigate whether and how the cruciferous invasive species Alliaria petiolata, which has costly defenses (glucosinolates), might shift resource allocation between chemical defenses and other fitness-related traits.Approach:
Using field populations of these plants in New England and in Hungary, I have been measuring growth, herbivory, defense chemistry, and reproductive capacity to determine whether invasive U.S. populations differ significantly from native-range European populations. Using herbivore exclusions, I have been able to distinguish between constitutive (inflexible) defense expression and defenses induced by herbivore damage. These data will provide insight into the changes that have occurred since introduction in these plants and the role of defense chemistry in competitive ability and invasiveness. If this is an important contributing factor to invasiveness, then potential for release from or sustained generalist herbivory and response flexibility in resource allocation could become important screening tools to predict which species may become invasive when introduced outside their home range.Supplemental Keywords:
fellowship, Alliaria petiolata, invasive species, resource allocation, chemical defenses, fitness-related traits, generalist herbivory.