RAPID COMMUNICATION/COMMUNICATION RAPIDE Invasion of transgenes from salmon or other genetically modified organisms into natural populations

In recent years, there has been widespread concern about the ecological and genetic effects of genetically modified organisms. In salmon and other fishes, transgenic growth hormone genes have been shown to have large effects on size and various traits related to fitness. In this paper, I have shown by using a deterministic model that if such a transgene has a male-mating advantage and a general viability disadvantage, then the conditions for its invasion in a natural population are very broad. More specifically, for 66.7% of the possible combinations of the possible mating and viability parameters, the transgene increases in frequency, and for 50% of the combinations, it goes to fixation. In addition, by this increase in the frequency of the transgene, the viability of the natural population is reduced, increasing the probability of extinction of the natural population. These findings provide independent confirmation of previous concerns about the inherent risks of transgenic organisms, especially for native salmon populations potentially affected by commercial salmon production using transgenic stocks. Résumé : Depuis quelques années, les effets écologiques et génétiques des organismes génétiquement modifiés sont devenus l’objet de préoccupations universelles. Chez le saumon et d’autres poissons, les gènes transgéniques de l’hormone de croissance ont des effets importants sur la taille et sur d’autres caractéristiques reliées au fitness. L’utilisation d’un modèle déterministe a permis de démontrer que si un tel transgène procure un avantage aux mâles lors de l’accouplement et un désavantage pour la viabilité générale, les conditions qui permettent son insertion dans la population sont très larges. En particulier, dans 66,7% des combinaisons des valeurs possibles des variables reliées à l’accouplement et à la viabilité, la fréquence du transgène augmente et, dans 50% des combinaisons, il y a fixation du transgène. De plus, l’augmentation de la fréquence du transgène entraîne une réduction de la viabilité de la population naturelle et augmente la probabilité de son extinction. Ces résultats confirment de façon indépendante la pertinence des préoccupations concernant les risques inhérents aux organismes transgéniques, particulièrement pour les populations de saumons indigènes qui risquent d’être affectées par une production commerciale qui utilise des stocks transgéniques. [Traduit par la Rédaction] 844 Rapid communication / Communication rapide Many genetically modified (GM) animals and plants utilize genes from other organisms, transgenes, to increase yield or change other economically important traits. Recently, Losey et al. (1999) showed that corn transformed with the bacterium Bacillus thuringiensis has detrimental effects on nontarget monarch butterflies (however, see Wraight et al. 2000), a report that raised great concern about the risks associated with GM organisms. In addition, if transgenes can spread by gene flow and selective advantage from GM organisms into natural opulations of the same or related species, then issues about GM organisms are further amplified. Fish of several species transgenic for growth hormone genes are much larger than non-transgenic fish, and the muscular and molecular bases of this size increase has been documented in coho salmon, Oncorhynchus kisutch (Hill et al. 2000). Because larger males have increased mating success (Howard et al. 1998), these transgenes, once introduced by gene flow, may invade (increase in frequency) in a natural population because of this selective mating advantage. Transgenes may also potentially increase male mating success by changing factors such as mating behavior, color, etc. (W. Muir, personal communication). However, if the transgene also reduces viability, it may result in the extinction of the natural population because of reduced population fitness (Muir and Howard 1999). In this paper, I show that the conditions for invasion of transgenes and a consequent reduction in fitness are broad, raising great concerns about the Can. J. Fish. Aquat. Sci. 58: 841–844 (2001) © 2001 NRC Canada 841 DOI: 10.1139/cjfas-58-5-841 Received February 23, 2001. Accepted March 29, 2001. Published on the NRC Research Press Web site on April 12, 2001. J16235 P.W. Hedrick. Department of Biology, Arizona State University, Tempe, AZ 85287, U.S.A. (e-mail: [email protected]). J:\cjfas\cjfas58\cjfas-05\F01-064.vp Wednesday, April 11, 2001 11:48:42 AM Color profile: Generic CMYK printer profile Composite Default screen