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Lecture 7

EESC 3310 Lecture 7: Week 7 (10/11-10/13)

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Boston College
Earth & Environmental Sciences
EESC 3310

GMOs Transgene organisms do not pose a significant risk to organisms in the larger ecosystem. In other words there is little risk of gene escape to related organisms, developing super weeds, or killing non-target organisms or their food sources. (This statement explores the ecological interactions between transgene organisms and the larger ecosystem in which they would exist) *****The role of precaution in the regulation of transgenic organisms is highly contentious and, to some people, support for precaution symbolizes complete opposition to the use of transgenic organisms Biggest Points: do not know how it will affect outer ecosystems - super unclear on nontarget aspects, and adaptations can mutate and spread or affect other parts of the ecosystem Adaptation issues: ● Resistance occurs quickly when there is strong, uniform selection on a pest population for long periods of time ● More than 286 weed biotypes have evolved resistance to various herbicides during the past 30 years ● Viruses: Moreover, any changes in transmission characteristics resulting from recombination could allow the recombinant virus to colonize hosts that were previously unavailable to the parental virus. ● Because transgenes are inherited in the same way as naturally occurring genes, they have the potential to persist indefinitely in cultivated or free-living population ● Subsequently, these transgenes can continue to spread among other plants of the same species, especially if they confer traits that are favored by artificial or natural selection Nontarget issues: ● Transgenic pollen and seeds can disperse into seed nurseries, commercial fields, and local landraces ● Currently, it is not possible to prevent gene flow between sexually compatible species that inhabit the same region because pollen and seeds disperse too easily and too far to make complete reproductive confinement practical ● A second reason that ecological monitoring may be needed after commercialization is that ecosystems are complex. This complexity stems from year-to-year variation, spatial variation, and indirect biotic effects. Because laboratory and small-scale field experiments do not adequately replicate all of the interactions that occur in an ecosystem ● Nontarget effects of transgenic crops with insecticidal properties (i.e., Bt corn, Bt cotton) have received the greatest attention for obvious reasons: if a Bt toxin kills pest insects, it also has the potential to kill other insects. ● In the United Kingdom, the indirect effects of using herbicide-tolerant crops were examined experimentally in the Farm Scale Evaluations Project. Researchers reported significant changes in abundances and diversity of invertebrates associated with the management of genetically engineered herbicide-tolerant beets, oilseed rape, and corn, both within cropland and in habitats adjacent to fields ● The design of the Farm Scale Evaluations most likely underestimated ecological effects because cumulative effects were not included and because a split-plot design could reduce the possibility of detecting scale effects ● In summary, ecological studies can provide information to assess the significance and relative impacts of nontarget effects on communities and ecosystems if they are designed to compare transgenic and relevant alternatives. ● but these short- term studies often involve sample sizes that are too small for meaningful statistical analysis ● Plot-level studies detected no significant effects of Bt corn on the abundance of green lacewings, although the authors point out the need for studies on larger fields because of high between-year variability and small plot sizes (Pilcher et al. 1997). Prey insects vary in how much Bt toxin they as
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