CALLAHAN, HS; PIGLIUCCI, M; KURASHIGE, NS; Barnard College, Columbia University; University of Tennessee; Barnard College: Artificial Correlational Selection in Arabidopsis thaliana: What Else Changes When Shade-Avoidance Responses Are Altered

In many plants, the timing of flowering responds sensitively to seasonal environmental variation, including changes in photoperiod or shifts in light quality, particularly shifts in the ratio of red to far:red (R:FR) light. Molecular genetic studies of lab strains of Arabidopsis thaliana have demonstrated that the photoreceptory and transduction systems regulating response to distinct seasonal stimuli overlap considerably. Does such overlap constrain not only developmental but also evolutionary responses to complex environments? Answering this question requires information about the quantitative genetic architecture of a population, which we investigated in a short-term artificial selection experiment. Starting with a sample of 68 genotypes derived from an Arabidopsis wild population, we imposed selection to either increase or decrease R:FR-mediated plasticity of a focal flowering time trait: number of rosette leaves at bolting. There were significant responses to selection for increased plasticity and limited responses to selection for decreased plasticity. In a series of follow-up experiments, we examined several indirect responses to selection. Indirect responses were generally modest. Some were uniform and linear, others were non-linear, and others were non-significant. Results of these studies underscore the difficulty of making generalizations about the quantitative genetic architecture of multiple trait means and plasticities. This talk will also discuss the extent to which results may reflect: (1) the model organism used, (2) the particular population chosen, and (3) details of the selection protocol.