GENETIC VARIATION IN ALLELOCHEMISTRY OF GARLIC MUSTARD (ALLIARIA PETIOLATA): ITS ROLE IN DEMOGRAPHY AND IMPLICATIONS FOR MANAGEMENT

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: NRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 0211281
• Grant No.: 2008-35320-18702
• Proposal No.: 2007-02894
• Project Start Date: Nov 15, 2007
• Project End Date: Nov 14, 2009
• Grant Year: 2008
• Program Code: [51.9]- (N/A)

Recipient Organization
UNIVERSITY OF ILLINOIS
2001 S. Lincoln Ave.
URBANA,IL 61801

Performing Department
NATURAL HISTORY

Non Technical Summary
Garlic mustard is one of the most problematic invaders of North American forests. The European species has spread to 36 states, where it can form dense stands, displacing native understory plants and tree seedlings. Garlic mustard's success as an invader may be due in part to its production of toxic chemicals, which inhibit the growth of native plants and the soil microbes which many native plants need to grow properly. While it is known that many invasive species produce toxic chemicals, further research is needed to develop improved control and restoration practices that utilize this knowledge effectively. In this project, I will determine whether the amount of toxic chemicals produced by garlic mustard differs from place to place, due to differences in the sites or the genetics of the garlic mustard population. I will also develop cost-effective ways to measure the amount of toxic chemicals produced at a given site. Secondly, I will determine how these differences in chemistry among sites affect the rate of spread of the species. Finally, I will compare the efficacy of garlic mustard removal and efforts to restore native plants in sites with produce high or low levels of the toxic chemicals. I will use these results to develop guidelines that managers can use to assign restoration priorities to their specific populations. This research will increase our basic knowledge of species invasions while also providing information directly applicable to managers attempting to control the spread of garlic mustard and restore invaded areas.

Animal Health Component

20%

Research Effort Categories

Basic

80%

Applied

20%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
123	0620	1070	50%
136	0620	1070	50%

Knowledge Area
136 - Conservation of Biological Diversity; 123 - Management and Sustainability of Forest Resources;

Subject Of Investigation
0620 - Broadleaf forests of the North;

Field Of Science
1070 - Ecology;

Keywords

invasive species

garlic mustard

alliaria petiolata

allelopathy

glucosinolate

genetic variation

population dynamics

restoration

Goals / Objectives
For knowledge of allelopathy (the ability of a plant species to inhibit other organisms through the production of toxic chemicals) to result in improved control of invasive species and restoration of invaded habitats, research must extend beyond simply demonstrating the existence of allelopathy to investigate: 1) Quantitative variation in allelopathy across an invasion front; 2) The effects of allelopathy on population dynamics of the invader; and 3) Whether data on site-level variation in allelopathic activity can target and improve the success of management and restoration efforts. To these ends, this project will address four major objectives: Objective 1. Quantify variation in soil quality and allelopathic potential within and among A. petiolata populations, and determine cost-effective assays of allelopathic activity. I hypothesize that sites with extensive, dense, and old A. petiolata populations will have lower allelopathic activities than those with young, small, and/or sparse populations, and that allelopathic activity will correlate strongly with glucosinolate concentrations, although soil quality may reflect past allelopathic activities more than current ones. Objective 2. Determine how variation in allelopathy affects population growth and demography. I hypothesize that rates of population growth and spatial spread will be positively correlated with allelopathic activity and glucosinolate concentration and that allelopathic activity will primarily affect the seedling to rosette transition, when plant competition is strongest. Objective 3. Compare the efficacy of alternative restoration and management practices in A. petiolata populations with high or low allelochemical concentrations. I hypothesize that native soil and plant restoration will be more effective in populations with lower allelochemical concentrations, due to greater survival of soil inoculums. However, in highly allelopathic populations, A. petiolata removal will be necessary (perhaps for several years) before native plant and soil restoration will be successful. Objective 4. Develop guidelines for prioritizing control and restoration efforts based on allelopathic activities and/or glucosinolate concentrations of specific populations. Specific ranges of glucosinolate concentration will be identified in which restoration efforts have a high or low probability of success

Project Methods
This research will combine several approaches to quantify the variation in allelopathic activity among A. petiolata populations, and the impact of that variation on population dynamics and management strategies. Objective 1: Quantify variation in soil quality and allelopathic activity within and among A. petiolata populations, and determine cost-effective assays of allelopathic activity. I will collect A. petiolata seeds from 10 individuals, as well as soil samples, from 40 populations across a gradient of invasion age (5 in New York, 30 in Illinois and Michigan, 5 in Arkansas). Three native tree species will be grown in soil from each population to determine the current soil quality of each site. I will measure the glucosinolate concentrations (a likely allelochemical of A. petiolata) of greenhouse grown plants from each population. Additionally, I will grow the natives in soil cultured for one generation by A. petiolata individuals from each population to asses the current soil killing ability of each population, and will correlate this metric with the mean glucosinolate concentration of the population. Finally, I will use extracts of the A. petiolata plants from each population in a series of bioassays to determine cost-effective measures of allelopathic ability that managers could perform on specific populations. Objective 2: Determine how variation in allelopathy affects population growth and demography. Among the A. petiolata populations sampled for Objective 1 will be 13 populations (8 MI, 5 IL) in which detailed demographic data have been collected for the last 3 years. I will correlate my measures of allelopathic activity with measures of population growth and spatial spread for each population. I will additionally correlate allelopathic data with each transition rate to determine where in the lifecycle allelopathy is having the strongest effect, and to determine how allelopathic effects on demographic rates influence overall population growth rate. Objective 3: Compare the efficacy of alternative restoration and management practices in A. petiolata populations with high or low allelochemical concentrations. Using the data from Objective 1, I will select 5 high and 5 low glucosinolate populations. In each site, I will perform a 2x2 factorial experiment, crossing A. petiolata removal with soil restoration. Each site will include 16 1 square meter plots, half of which will have A. petiolata removed in the early spring. Six tree seedlings (two of each species) will be planted in each plot; in half of the plots, one individual per species will have been grown in live soil for four months prior to planting, while all others will have been grown in sterile soil. These seedlings will be followed for two growing seasons. Objective 4: Develop guidelines for prioritizing control and restoration efforts based on allelopathic activities and/or glucosinolate concentrations of specific populations. Decision tree analysis will be used to determine ranges of allelopathic activity/glucosinolate concentrations in which particular management strategies (A. petiolata removal and native plant/soil restoration) will be most successful.

Progress 11/15/07 to 11/14/09

Outputs
OUTPUTS: This project has produced several outputs. Activities include four greenhouse experiments and one large scale field experiment. The first greenhouse experiment tested for evolutionary change in allelopathic properties of garlic mustard. The second tested whether the presence of living soil microbial communities affected the allelopathic effect of garlic mustard on sycamore seedlings. The third used soils from 16 sites with a range of invasion histories to test whether 1) soil quality for native plants increases or decreases with increasing length of invasion, and 2) whether soils with a longer history of association with garlic mustard develop functional or compositional resistance to the invader's effects. The final experiment is ongoing and will test whether garlic mustard genotypes from older populations are better or worse competitors with conspecifics from younger populations, and against two native species. The field experiment began in 2008 and was monitored throughout 2009. This experiment tested whether native tree seedlings performed better in older or less toxic garlic mustard populations, and whether the efficiency and efficacy of two restoration strategies (garlic mustard removal and soil restoration) depended on the age or toxicity of the population. This project also produced several events aimed at disseminating results to others. These results were presented at the Ecological Society of America conference in August 2008 and again in 2009. I also presented some of these results to undergraduates through a guest lecture for the Association of Chicagoland Colleges, and to the general public at the Illinois Natural History Survey 150th anniversary Jamboree. They were also presented to the Lake Forest Open Lands Association, a non-profit conservation group, in October 2009. News articles for the popular press were published in several online sources summarizing the results of the first peer-reviewed article from this project. PARTICIPANTS: Richard Lankau (PI) designed, performed, and analyzed the greenhouse and field experiments. Adam Davis (post-doctoral mentor) provided guidance on the design and analysis of data, as well as materials and equipment to perform the research. TARGET AUDIENCES: The target audiences for this project include other researchers, land managers, undergraduate students, and the general public. Efforts to address these target audiences to date include presenting data at the 2008 and 2009 Ecological Society of America annual meeting, numerous discussions with the land managers at the 10 field sites, guest lectures in undergraduate classrooms, serving as a mentor for underrepresented minorities through the ESA SEEDS program, providing information about invasive species to the general public at the Illinois Natural History Survey 150th Anniversary Jamboree, and presenting research findings to lay members of the Lake Forest Open Lands Association, a conservation non-profit group. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
This project resulted in a substantial change in knowledge in the last year. Important findings of the various greenhouse and field experiments include: 1) over many generations at a given site garlic mustard tends to reduces its investment in toxic allelochemicals. This genetic change toward reduced allelochemical concentrations led to weaker negative impacts on native tree seedling growth, 2) the allelopathic effects of garlic mustard on a native tree were eliminated by the activity of a healthy soil microbial community, 3) over time, soils associated with garlic mustard tend to improve in quality for some native species (as compared to soils associated with younger invader populations), implying a regaining of soil function, 4) soils with a longer history of garlic mustard show increasing compositional resistance for some microbial taxa, but increasing susceptibility for others, 5) soils with a longer history of garlic mustard show increasing functional resistance, as determined by their ability to support the growth of native plants, 6) in a field study, native tree seedlings survived and grew better in older and less toxic garlic mustard populations, 7) restoring healthy soil microbial communities imporved tree surivial and growth in the field, but only when the garlic mustard was also removed, and 8) restoration activities (garlic mustard removal and soil restoration) had the largest positive impacts on native tree seedling growth in younger, more toxic invader populations. Together, these findings suggest that 1) restoration of native plant species will be more successful in older and less toxic garlic mustard populations, and 2) the amount of restoration effort required for successful establishment of native species will depend on the invasion history and allelochemical concentration of the invader population.

Publications

• Lankau, R.A., Nuzzo, V., Spyreas, G. and Davis, A.S. 2009. Evolutionary limits ameliorate the negative impacts of an invasive plant. Proceedings of the National Academy of Sciences of the United States. 106:15362-15367.
• Lankau, R.A. 2009. Soil microbial communities alter allelopathic competition between Alliaria petiolata and a native species. DOI: 10.1007/s10530-009-9608-z.

Progress 11/15/07 to 11/14/08

Outputs
OUTPUTS: Although this project has been underway for only one year, it has already produced several important outputs. A large greenhouse experiment testing for evolutionary change in allelopathic properties of garlic mustard has been completed, and a large, multi-site field experiment testing the efficacy of different management and restoration strategies has been established and monitored for one growing season. Results from these studies were presented at the annual meeting of the Ecological Society of America. I also presented some of these results to undergraduates through a guest lecture for the Association of Chicagoland Colleges, and to the general public at the Illinois Natural History Survey 150th anniversery Jamboree. PARTICIPANTS: Richard Lankau (PI) designed and performed the greenhouse and field experiments. Adam Davis (post-doctoral mentor) provided guidance on the design and analysis of data, as well as materials and equipment to perform the research. TARGET AUDIENCES: The target audiences for this project include other researchers, land managers, undergraduate students, and the general public. Efforts to address these target audiences to date include presenting data at the 2008 Ecological Society of America annual meeting, numerous discussions with the land managers at the 10 field sites, guest lectures in undergraduate classrooms, serving as a mentor for underrepresented minorities through the ESA SEEDS program, and providing information about invasive species to the general public at the Illinois Natural History Survey 150th Anniversary Jamboree. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Results from this project to date have provided significant improvements in the understanding of garlic mustard invasions. We have demonstrated that over many generations at a given site garlic mustard tends to reduces its investment in toxic allelochemicals. This genetic change toward reduced allelochemical concentrations led to weaker negative impacts on native tree seedling growth. Additionally, in a multi-site field experiment, we have seen that native tree seedling growth is higher in sites with a longer history with garlic mustard, and that the relative benefit of management (hand-pulling garlic mustard) and restoration (providing inoculations of healthy soil microbial communities) increased with the concentration of toxic chemicals in the garlic mustard population.

Publications

• No publications reported this period