As invasive species evolve in their new ranges, will this worsen or ameliorate their impacts on natives? Garlic mustard (Alliaria petiolata) is one of the most problematic invaders of forest understories in the Northeast and Midwest United States, in part due to novel allelochemicals that negatively affect native plants and soil communities.  I sampled the major allelochemicals of garlic mustard, glucosinolates and flavanoids, in populations spanning the invasive range from New York to Illinois.

Results/Conclusions

Garlic mustard density increased with increasing allelochemical concentrations, supporting their role in driving invasions. Older populations, as determined by herbarium records, had significantly lower allelochemical levels, suggesting the negative impact of garlic mustard on native plants may decrease over time. Common garden experiments will determine if these results reflect genetic differences between populations, and if they translate into differential effects on native plants and soil communities.