The Evolutionary Consequences of Gmo Escape

Topics: Gene, DNA, Horizontal gene transfer Pages: 5 (1677 words) Published: December 18, 2012
The Evolutionary Consequences of GMO Escape
Hybridization between genetically modified plants and populations of crop plants is a major hazard to be avoided in conducting field trials of genetically modified plants. The reason to avoid this is that gene flow from the transgenic plants into the crop population results in the creation of unwanted and potentially devastating hybrids. This essay explores some of the mechanisms behind gene flow between species, and their evolutionary consequences. The main mechanism for gene flow between species is a hybrid population, either able to reproduce with parental species and thus forming a bridge for gene flow, or reproductively isolated from the parental species and undergoing hybrid speciation to form a new species. Research in this area seems to indicate that the crops most at risk of significant transgenic invasion are those with a fixed genetic load, thus the best preventative measure would be to increase genetic variability in crop populations. Introduction

What if? It’s the question that everyone is asking. What if the stock market collapses completely? What if we have to sell our house? What if Transgenic Organisms escape and initiate gene flow between themselves and a population of crop plants? Well, perhaps the latter is not on quite everyone’s lips, but it is the question which this essay sets out to address. The regulations set out by the New Zealand Environmental Risk Management Authority regarding field trials with transgenic plants are there for a reason; gene flow between transgenic plants and crop plant populations is a very real possibility. It occurs mainly via the creation of hybrids between the species. These hybrids may then act as a sort of genetic bridge for gene flow from one species to the other, or they may be reproductively isolated from both of the parental species and become a new species through hybrid speciation. Whether the genetic recombination occurs via a hybrid genetic bridge or through the evolution of a hybrid species, each scenario has differing strengths and weaknesses, the potency of which are often dependent on environmental factors as much as genetics. Hybrids as a Genetic Bridge between Species

A major mechanism for the transfer of genetic material between species is introgression (Ellstrand, 2001). Introgression occurs through the formation of hybrids between species, which then back-cross with one or both of the parental populations, introducing some of the traits from one species into the other species and possibly vice-versa. In other words, the hybrids act as a bridging factor for gene flow between the species (Hails & Morely, 2005). An example of introgression between genetically modified plants and a pre-existing species is shown in a study by A. A. Snow and P. M. Palma, which explored the introgression of herbicide resistance from transgenic crop plants into weeds. The result of this introgression was that the weeds gained an increased level of fitness due to no longer being susceptible to that particular type of herbicide and thus able to produce more offspring in a greater life span (Snow & Palma, 1997). Another example of introgression conferring herbicide resistance, this time between two pre-existing species, is in a study by Devos et al. This study investigated introgression between domesticated Oil Seed Rape and its wild relatives and found that the trait of herbicide resistance in domesticated Oil Seed Rape was present, through introgression, in the wild relatives of the Oil Seed Rape (Devos et al., 2008). Results such as those recorded in the study by A. A. Snow and P. M. Palma mentioned above, in which introgression of positive fitness traits occurs from transgenic crop plants into a population of weeds, are particularly worrying when we examine the probability of the escape of modified genetic material from crops into other, unwanted, plant species. While these repercussions must be taken seriously,...
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