Title

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

Document Type

Article

Publication Date

2017

Keywords

assortative mating, Brassica rapa, flowering phenology, gamete pool, gene traps, isolation by time, temporal cline

Abstract

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.

KEY RESULTS:

We found temporal genetic structure for flowering time in seven of the eight field plots. Interestingly, the direct (retrospective) temporal structure estimate was 35% larger than the prospective estimate based on flowering schedules. Spatial clumping of pollen donors did not affect temporal structure, but structure intensified when heritability was experimentally enhanced.

CONCLUSIONS:

Temporal genetic structure, especially for flowering time, likely occurs in many plant populations and may be underestimated using a prospective method. We discuss the genome‐wide consequences of temporal genetic structure and the potential for adaptive temporal clines in plant populations.

Department

Biology

Volume

104

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