PARENT SESSION
Contributed Oral Session 86: Herbivory: Genetic Variability in Insect - Plant Interactions
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal
Fitness impacts of transgenes in wild relatives of transgenic crops: Modeling population-level changes in invasiveness.
Hagen, Joy*,1, Satterthwaite, Will1, Letourneau, Deborah1, 1 University of California, Santa Cruz, Santa Cruz, CA
ABSTRACT- Genetically engineered crops with novel forms of pest resistance are under scrutiny for risks associated with increased fitness, competitive ability, and invasiveness of wild crop relatives that may obtain the trait through gene flow. To assess whether reduced herbivory increases fitness and enhances population spread in weedy wild crop relatives, we protected wild radish and wild mustard plants at various sites in each of three growing conditions (agricultural fields, field margins, and natural areas) from herbivory by Bt-susceptible lepidopteran herbivores. Seedling mortality was significantly reduced in lepidopteran exclusion plots of mustard, but not of radish. Lepidopteran exclusion resulted in an average 16% reduction in plant damage by herbivores for both radish and mustard in 2004-2005. We use annual periodic matrix models to assess (1) the population level effect of Bt-based protection from herbivores, (2) the uncertainty associated with single-year field trials, and (3) the difference in predictions for agricultural and natural habitats. The contribution of lepidopteran herbivory reduction at each stage of the life cycle to the overall increase in population growth is explored using Life Table Response Experiments (LTRE). The model shows whether effects of lepidopteran exclusion on population growth are significant in the face of the environmental variation of our two-year study in different habitats and whether the effect of insect-resistance can convert stable or decreasing population trajectories into increasing ones, thereby leading to local expansion of wild radish and mustard populations.
Key words: genetically engineered crops, invasive species, matrix model, LTRE