PARENT SESSION
Poster Session #4: Invasions.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Do introduced plants reduce their allocation to defense? An experimental test with goldenrod (Solidago gigantea).

Meyer, Gretchen¹, Weber, Ewald², Egan, Todd¹, Clare, Robert¹, ^{1 2}

ABSTRACT- When plants are introduced to new areas, they leave their specialized herbivores and pathogens behind. The evolution of increased competitive ability (EICA) hypothesis holds that this escape from natural enemies allows introduced plants to reduce their investment in defense, thereby freeing resources for growth and reproduction and increasing their potential for invasiveness. We tested whether or not introduced plants show reduced allocation to defense using Solidago gigantea, which is native to North America and invasive in Europe. Plants derived from 10 North American and 20 European populations were grown in a common garden at the University of Wisconsin-Milwaukee Field Station. Plants were exposed to insect herbivores and pathogens that colonized the garden from nearby goldenrod fields. Insects and diseases were censused at regular intervals, and plant performance was assessed by measuring plant heights, number of flowering stems, and flower mass. Results indicate that European populations were more susceptible to at least some insects and diseases. Population-to-population variation in plant performance was high. Even so, European populations were overall less likely to flower than North American populations, perhaps because they sustained higher levels of damage. These results support the idea that introduced plants reduce their allocation towards defense compared to plants growing in the native range.

KEY WORDS: Solidago gigantea, introduced species, invasive species, EICA hypothesis