Characterizing the recruitment nature of weed species

我的研究计划的核心目标是确定杂草是如何以及为什么出现的。幼苗出苗的时间是物种成功的主要决定因素，对于杂草来说，从种子到幼苗的过渡代表了植物生命周期中从最脆弱的阶段到最脆弱的阶段的过渡。杂草幼苗的相对出苗时间（相对于作物植物）和出苗成功与否也决定了杂草侵害的竞争力、杂草逃脱管理的可能性，以及留下的杂草种子的数量和质量，以形成持久的种子库。此外，出现时间也是物种地理范围和入侵潜力的关键决定因素。最后，出现的时间极大地影响了杂草物种（包括逃逸的作物植物）在无人管理的栖息地（包括路边）的生存能力。这对景观尺度上的基因流动以及转基因作物与非转基因作物的有效分离和共存具有重要意义。尽管它具有根本的重要性，但我们对杂草为什么会出现的理解仍然很差。到目前为止，在我的项目中，我们一直在努力记录杂草的出现时间，并对出现时间的机制有更深入的了解。最近，我们已经证明，开花和种子脱落的时间可以在决定种子经历的条件（包括它们是否和在多大程度上被埋）方面发挥非常重要的作用，而这反过来又可以决定发芽的时间。我们使用兼性冬季一年生植物（FWA）作为这项工作的模式物种，并使用FWA，加拿大fleabane，我们首次记录了这些因素（开花和种子棚时间以及种子深度）对出苗时间的影响。目前尚不清楚的是，对一种杂草的观察结果在多大程度上适用于其他杂草，以及这些影响在多大程度上增加了某些个体的适应性，从而影响了后代的种群表现（和杂草）。在接下来的5年里，我们的方法将是展望杂草的生命周期（开花时间和种子棚），以获得回顾生命周期（招募和出苗时间）的洞察力，并使用冬季一年生杂草作为试验物种。这一研究将有助于更好地理解杂草萌发时间的机制，从而有助于杂草管理、杂草风险评估以及转基因和非转基因作物的共存。

The core goal of my research program is to determine how and why weeds emerge when they do. The timing of seedling emergence is a prime determinant of species success and for weeds, the transition from seed to seedling represents a transition from the least to the most vulnerable stage in a plant’s lifecycle. The relative timing (versus crop plants) and the success of weed seedling emergence also determines the competitiveness of weed infestations, the potential for weeds to escape management, and the quantity and quality of weed seeds left to form persistent seed banks. In addition, emergence timing is also a key determinant of the geographic range of species and their invasive potential. Finally, time of emergence greatly impacts the ability of weed species (including escaped crop plants) to survive in unmanaged habitats including roadsides. This has implications for gene flow at the landscape scale and the effective segregation and coexistence of genetically modified (GM) from non-GM crops. Despite its fundamental importance, our understanding of why weeds emerge when they do remains poor. To-date in my program we have been working to document weed emergence timing and to gain deeper insight into the mechanics of emergence timing. Most recently we have shown that timing of flowering and seed shed can play a very significant role in determining what conditions seeds experience (including whether and to what extent they are buried) and that this, in turn, can determine timing of emergence. We use facultative winter annuals (FWA) as model species for this work and with the FWA, Canada fleabane, we were the first to document the effects of these factors (flowering and seed shed timing, and seed depth) on emergence timing. What is not clear is the extent to which observations on one weed species apply to other weed species and to what extent these effects increase fitness of certain individuals thereby impacting population performance (and weediness) in future generations. Our approach over the next 5 years will be to look forward in the life cycle of weeds (flowering timing and seed shed) in order to gain insight looking backward in the life cycle (recruitment and emergence timing) using facultative winter annual weeds as test species. This research will lead to a better understanding of the mechanics of weed emergence timing which in turn will aid weed management, weed risk assessment and the coexistence of GM and non-GM crops.