Temporal population genetic structure in the pollen pool for flowering time: a field experiment with Brassica rapa (Brassicaceae)

Premise of the study: Assortative mating by flowering time can cause temporal genetic structure in species with heritable flowering times. A strong temporal structure, when coupled with a seasonal shift in selection, may lead to adaptive temporal clines. We implemented a
prospective and retrospective method to estimate the temporal genetic structure in the pollen pool of Brassica rapa.
Methods: The prospective method uses flowering schedules to estimate the seasonal shift in the pollen donors’ phenotype. By examining the offspring generation, we can get a direct estimate of temporal genetic structure, i.e., a retrospective estimate. However, this estimate is problematic because of the phenotypic correlation of the trait of interest, flowering time, between dam and sire. We developed a novel retrospective method that isolates flowering time by holding the maternal contribution constant and sampled the pollen pool in eight open-pollinated field plots throughout the flowering season.
Ke...