Data from: How to escape from crop-to-weed gene flow: phenological variation and isolation-by-time within weedy sunflower populations

The evolution of crop-related weeds may be constrained by recurrent gene flow from the crop. However, flowering time variation within weedy populations may open the way for weed adaptation by allowing some weeds to escape from this constraint. We investigated this link between phenology, gene flow and adaptation in weedy sunflower populations recently emerged in Europe from crop-wild hybridization. We studied jointly flowering phenology and genetic diversity for 15 microsatellite loci in six cultivated sunflower fields infested by weedy sunflower populations. The flowering overlap of cultivated and weedy sunflowers varied between and within populations: some weedy individuals were found completely isolated from the crop, the frequency of these plants being higher in populations from highly infested fields. Within weedy populations, we detected a pattern of isolation-by-time: the genetic divergence between individuals was positively correlated with their divergence in flowering period. Additionally, earlier weeds, which flowered synchronously with the crop, were genetically more similar to the cultivated varieties than late-flowering weeds. Overall our results suggest that crop-to-weed gene flow did occur but was limited by divergent phenologies. We discuss the roles of weed adaptation and population history in generating this partial reproductive isolation.

作物相关杂草的演化可能受到作物持续基因流的约束。然而，杂草种群内的开花时间变异，可通过使部分杂草摆脱该约束，为杂草的适应性演化开辟路径。我们针对欧洲新近由作物-野生杂交起源的杂草向日葵种群，探究了物候、基因流与适应性三者间的关联。我们对6个滋生有杂草向日葵的栽培向日葵田，开展了15个微卫星（microsatellite）位点的开花物候与遗传多样性联合分析。栽培与杂草向日葵的开花重叠度在种群间及种群内均存在差异：部分杂草个体完全与作物产生生殖隔离，这类植株在重度滋生的种群中出现频率更高。在杂草种群内部，我们检测到了时间隔离模式：个体间的遗传分化与其开花期分化呈正相关。此外，与作物同期开花的早花杂草，相较于晚花杂草，与栽培品种的遗传相似性更高。总体而言，我们的研究结果表明，作物向杂草的基因流确实发生，但受物候分化的限制。我们还讨论了杂草适应性与种群历史在形成该部分生殖隔离过程中的作用。