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

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.

Lead Investigator: 
Other Investigator(s): 
dispersal of a new crop transgene
US and Mexico
Temporal Scope: 
Spatial Scope: 
Natural System: 
temperate terrestrial gene flow
Human System: 
agriculture, crop choice, trade policy