Title

Adaptive plasticity and the nature of environmental variation

Date of Completion

January 2005

Keywords

Biology, Botany|Biology, Ecology

Degree

Ph.D.

Abstract

We studied the effects of both coarse versus fine grained variation and novel versus common environmental variation in water regime on accessions of Arabidopsis thaliana. Variation in water regime was tested by exposing plants to both fine- and coarse-grained variation (i.e. mean and variance) in water availability. A novel environment was created by adding 100 mM NaCl to the water. We found that the scale and frequency of environmental variation can lead to differences in which traits are affected and the magnitude of effects. The effects of fine-grained variation were distinct from those of coarse-grained variation, and typically more subtle. Both affected seed production and therefore fitness. There was little evidence of strain specific variation in plastic response. Brackish water affected all genotypes, most traits, the relationship between traits, and fitnesses, consistently for the worse. The effect of varying exposure to brackish water varied among traits and among genotypes. Overall, we found that the response to changing environments depends as much on the combination of environmental variables and the scale of the variation as much as it depends on the variables themselves. Altering the scale and nature of the variation in water availability resulted in changes in which traits and which genotypes responded. Furthermore, the scale and nature of environmental variation also affected the overall genetic architecture: the relationships of traits with each other and their relationships with fitness. ^