BE/CNH: Spatiotemporal Dynamics of Engineered Crop Genes: Natural and Human Constraints and Consequences

基因流动是指基因成功地从一个种群转移到另一个种群。作物基因流动是自然过程的结果，如花粉的风传播和人类过程，如在田地里播种。理论和实证研究主要集中在局部和景观尺度上的基因流动，而忽视了全球尺度上的基因流动。围绕工程基因（转基因）的意外移动的争议提高了人们的认识，即新的等位基因可以快速和远距离移动。目前还没有模型来评估作物转基因在时间和空间上通过自然和人类过程的传播，也没有研究人类对基因流动的影响。这个跨学科的研究项目将集中于开发一个综合模型来描述一种新的作物转基因在空间和时间上的传播动态。关注转基因流动的一个好处是，它提供了已知年龄和起源的等位基因的例子。该模型将随着三个研究团队之间的反复互动而发展。最初的模型将使用美国和墨西哥的玉米（Zea mays，玉米）作为模型系统，但该模型最终将适用于其他作物系统，如油菜籽。此外，该项目将超越最初的两国重点，探索转基因在全球范围内的传播。一个研究小组将把模型的构建作为其主要任务。该模型将从简单的自然扩散过程的结构开始。另外两个团队将为完善模型做出概念上的贡献，例如：(1)影响传播模式的自然过程，如风向、植物开花时间和交叉兼容的野生亲缘物种的空间分布；(2)影响传播模式的人类过程，如农民管理和选择重新种植的种子或通过当地和国际贸易运输种子。这些团队还将从文献中提供新的数据和已有的数据，以修改和测试模型。然后，研究小组将评估这个改进后的模型，包括：(1)自然影响，例如杂草的演变或野生亲缘种生物多样性的丧失；(2)人类影响，例如贸易政策的演变，以应对食品供应中的意外转基因，或当地品种中转基因的存在引发的传统农业系统的变化。由这些后果产生的新的基因流影响将被纳入模型。例如：(1)转基因在不断扩大的杂草种群中的空间传播；(2)国际贸易壁垒或劳动力迁移模式的改变。该模型的进化结果将与墨西哥玉米转基因频率的真实时空变化进行比较。研究小组的定期会议将有助于改进综合模式，同时提供新的机会来审查分散的限制和后果。最终的结果将是一个全球性的模型，可以概括地描述任何受人类和自然过程限制的植物等位基因的传播。该项目将对预测植物基因在自然和人类传播下的传播具有重要意义。因此，它将对入侵生物的传播以及转基因流动的焦点产生影响。转基因流动的话题是基因工程更广泛的公众讨论的一部分。该项目的结果将直接关系到解决一些关键问题，如工程基因的意外传播，这些问题已被报道在非工程作物品种中偶然发生，在墨西哥玉米中，尽管该国多年来一直禁止种植转基因玉米，以及在自然种群中。因此，这项研究的结果将提供科学投入，为国家和国际两级的外行听众和决策者提供信息。该项目得到了2004年度环境生物复杂性特别竞赛的支持，该竞赛侧重于自然和人类系统耦合动力学。

Gene flow is the successful movement of genes from one population to another. Crop gene flow is the result of both natural processes like wind dispersal of pollen and human processes like the planting of seeds in fields. Theoretical and empirical studies have focused on gene flow at the local and landscape scale, but they generally have neglected gene flow on the global scale. The controversy surrounding the unintended movement of engineered genes (transgenes) has raised awareness that new alleles can move rapidly and over great distances. No models have emerged to evaluate the spread of crop transgenes through both natural and human processes over time and space, nor have human impacts on gene flow been explored yet. This interdisciplinary research project will focus on the development of an integrated model to describe the dynamics of dispersal of a new crop transgene in space and time. A benefit of focusing on transgene flow is that it affords examples of alleles whose age and origins are known. The model will evolve with iterative interactions between three research teams. The initial model will use corn (Zea mays, maize) in the U.S. and Mexico as a model system, but the model eventually will be adapted for other crop systems, such as canola. Furthermore, the project will move beyond the initial two-nation focus to explore transgene spread at the global scale. One research team will have the construction of the model as its primary assignment. The model will start with a structure of simple natural dispersal processes. The other two teams will make conceptual contributions for refining the model, such as (1) natural processes that affect dispersal patterns like wind directionality, timing of plant flowering, and the spatial distribution of cross-compatible wild relatives, and (2) human processes that affect dispersal patterns like farmer management and choice of seeds for replanting or transport of seed through local and international trade. Those teams will also contribute novel data and pre-existing data from the literature for modifying and testing the model. The teams then will evaluate the refined model for (1) natural impacts, such as the evolution of weediness or the loss of biodiversity in wild relatives, and (2) human impacts, such as evolution of trade policy in response to unintended transgenes in the food supply or changes in traditionally based agricultural systems precipitated by the presence of transgenes in local varieties. New gene-flow influences resulting from these consequences will then be incorporated into the model. Examples include (1) the spatial spread of the transgene into expanding weed populations and (2) international trade barriers or changing labor migration patterns. The evolutionary results from the model will be compared with real spatial and temporal changes in corn transgene frequencies in Mexico. Regular meetings of the research teams will serve to improve the integrative model while providing new opportunities to scrutinize the constraints and consequences of dispersal. The final product will be a global model that can be generalized to describe for the spread of any plant allele as constrained by human and natural processes.The project will have significant implications for predicting plant gene dispersal under natural and human dispersal. It will thus have implications for the spread of invasive organisms as well as for its focus of transgene flow. The topic of transgene flow is a part of the greater public discussion of genetic engineering. The results of the project will have direct relevance to addressing critical issues like the unintended spread of engineered genes that have been reported occurring adventitiously in non-engineered crop varieties, in Mexican corn despite a multiyear moratorium against planting transgenic corn in that country, and in natural populations. The results of this study therefore will provide that scientific input to inform both lay audiences and policy makers at both the national and international levels. The project is supported by an award resulting from the FY 2004 special competition in Biocomplexity in the Environment focusing on the Dynamics of Coupled Natural and Human Systems.