Author : Jordan, Nicholas

Summary : There are several summary points to emphasize. First, the ecology of weeds in contemporary cropping systems may facilitate transgene escape by permitting survival of weed-crop hybrids that are maladapted, relative to "wild-type" weeds, in a variety of fitness component. This most likely occurs when the hybrids and subsequent backcross progeny carry a transgene of sufficient adaptive value. Second, seed and dispersal ecology are major determinants of weed fitness and population growth rate, although this is not widely appreciated as such among non-weed scientists. Effects of crop-derived transgenes and all other crops genes on these traits will strongly affect the adaptation of weed-crop hybrids and backcross progeny. Third, most major weed species show extensive, seed and temporal variation on several scales. This variation has both genetic and environmental causes and may strongly affect processes involved in all phases of transgene escape. Finally, a landscape perspective may be important for proper assessment of prospects for transgene escape. Populations of agricultural weeds are distributed across agricultural landscapes, including many populations that occur outside of cropped fields. Particularities of the ecology of these populations may affect all three phases of transgene escape.