Genetic Correlation Of Flowering Time And Pollen To Ovule Ratio In Clarkia

We test whether a genetic correlation exists between life history and sexual allocation traits.  More specifically through a greenhouse selection experiment, we determine if date of first flower and the ratio of pollen to ovules (P:O) within a flower are genetically correlated. Across taxa, P:O ratio tends to be lower in those that flower early. We use a California native, wild herbaceous, flowering plant, C. xantiana ssp xantiana.  In a greenhouse selection experiment, we selectively bred for early flowering from field collected (population H99) maternal families of C. xantiana ssp xantiana.  We then compared the P:O ratio between maternal families of the early flowering line and a control line (randomly mated). Based on across taxon comparisons, we predict that there is a genetic correlation between flowering time and P:O ratio.  If this is the case, then the P:O ratio will be lower for early flowering lines when compared to the controls. A contrasting prediction (i.e. no genetic correlation between the two traits) that would not conflict with cross-taxon comparisons would show no difference in P:O ratio between the early flowering and control lines, indicating that the two traits must evolve independently. Our data support the latter prediction, that flowering time and P:O ratio are not genetically correlated.  This suggests that selection has acted independently on flowering time and the P:O ratio such that conditions that favor early flowering also favor lower P:O ratios.