Possible ecological risks of transgenic organism release when transgenes affect mating success: Sexual selection and the Trojan gene hypothesis

摘要

Widespread interest in producing transgenic organisms is balancedby concern over ecological hazards, such as species extinction if suchorganisms were to be released into nature. An ecological riskassociated with the introduction of a transgenic organism is that thetransgene, though rare, can spread in a natural population. An increasein transgene frequency is often assumed to be unlikely becausetransgenic organisms typically have some viability disadvantage.Reduced viability is assumed to be common because transgenicindividuals are best viewed as macromutants that lack any history ofselection that could reduce negative fitness effects. However, thesearguments ignore the potential advantageous effects of transgenes onsome aspect of fitness such as mating success. Here, we examine therisk to a natural population after release of a few transgenicindividuals when the transgene trait simultaneously increasestransgenic male mating success and lowers the viability of transgenicoffspring. We obtained relevant life history data by using the smallcyprinodont fish, Japanese medaka (Oryzias latipes) as amodel. Our deterministic equations predict that a transgene introducedinto a natural population by a small number of transgenic fish willspread as a result of enhanced mating advantage, but the reducedviability of offspring will cause eventual local extinction of bothpopulations. Such risks should be evaluated with each new transgenicanimal before release.