Chapter 25, Problem 28ESP

Floral traits in plants often play key roles in diversification, in that slight modifications of those traits, if genetically determined, may quickly lead to reproductive restrictions and evolution. Insight into genetic involvement in flower formation is often acquired through selection experiments that expose realized heritability. Lendvai and Levin (2003) conducted a series of artificial selection experiments on flower size (diameter) in Phlox drummondii. Data from their selection experiments are presented in the following table in modified form and content.

1. (a) Considering that differences in control values represent year-to-year differences in greenhouse conditions, calculate (in mm) the average response to selection over the three-year period.
2. (b) Calculate the realized heritability for each year and the overall realized heritability.
3. (c) Assuming that the realized heritability in phlox is relatively high, what factors might account for such a high response?
4. (d) In terms of evolutionary potential, is a population with high heritability likely to be favored compared to one with a low realized heritability?