Poster Session #50: Evolutionary Ecology.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall


Drought effects on Lupinus perennis: Implications for prairie plants in future climates.

Halpern, Stacey1, 1

ABSTRACT- Climate models for the 21st century predict that drought, an important plant stressor, will increase in magnitude or frequency in the Upper Midwest. To investigate the potential effects of increased drought on native plants, I have conducted field and greenhouse experiments with the perennial legume, Lupinus perennis. In the greenhouse, more stressed L. perennis seedlings had significantly lower biomass and number of N-fixing nodules, higher root:shoot, and thicker leaves. Drought effects in a field experiment in Wisconsin were more variable. I mimicked drought using temporary rain-out shelters. Shelters reduced soil water content but did not lead to differences among treatments in adult plant water potential, size, or flowering phenology. Rapid root growth may permit adults to escape drought by reaching subsurface water, which may have been shallower due to an extremely wet summer. To test whether drought affected germination and juvenile survivorship in the field, I followed the fate of seeds from known maternal families. Family and family x treatment interactions significantly affected germination rates and seedling survivorship, which suggests genetic variation in juvenile drought tolerance. In conjunction with adult drought tolerance, these results suggest that juveniles are more sensitive to environmental stress, and that heritable differences in stress-resistance exist during this stage. Studies that neglect germination and seedling establishment may underestimate ecological and fitness effects of stress events, as well as the potential for evolutionary responses to climate change.

KEY WORDS: seedling establishment, water stress, genotype by environment interactions, germination