Abstract
Flowering time divergence can be a crucial component of reproductive isolation between sympatric populations, but few studies have quantified its actual contribution to the reduction of gene flow. In this study, we aimed at estimating pollen-mediated gene flow between cultivated sunflower and a weedy conspecific sunflower population growing in the same field and at quantifying, how it is affected by the weeds' flowering time. For that purpose, we extended an existing mating model by including a temporal distance (i.e. flowering time difference between potential parents) effect on mating probabilities. Using phenological and genotypic data gathered on the crop and on a sample of the weedy population and its offspring, we estimated an average hybridization rate of approximately 10%. This rate varied strongly from 30% on average for weeds flowering at the crop flowering peak to 0% when the crop finished flowering and was affected by the local density of weeds. Our result also suggested the occurrence of other factors limiting crop-to-weed gene flow. This level of gene flow and its dependence on flowering time might influence the evolutionary fate of weedy sunflower populations sympatric to their crop relative.
Highlights
Flowering phenology is highly variable, both within and among plant populations (Hendry and Day 2005; Elzinga et al 2007)
Flowering time differences could act as a major barrier to gene flow between sympatric populations, thereby contributing to reproductive isolation
When cultivated and weedy forms grow in the same location, crop-to-weed gene flow could recurrently bring domesticated alleles into the weedy population and hinder its divergence from the crop
Summary
Flowering phenology is highly variable, both within and among plant populations (Hendry and Day 2005; Elzinga et al 2007). This variation, which is usually due to a combination of environmental and genetic effects, may strongly affect mating patterns: the more the flowering periods of two individuals overlap, the higher is their chance of mating with each other. This phenomenon is known as temporal assortative mating (Weis and Kossler 2004). To go deeper into the mechanisms underlying flowering time as a possible target for reinforcement, an important step is to test and quantify its actual contribution to the reduction of gene flow, which has rarely been carried out
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
