Schliekelman P, Gould F
Department of Statistics, North Carolina State University, Raleigh 27695-8203, USA.
J Econ Entomol. 2000 Dec;93(6):1543-65. doi: 10.1603/0022-0493-93.6.1543.
Advances in genetics have made it feasible to genetically engineer insect strains carrying a conditional lethal trait on multiple loci. We model the release into a target pest population of insects carrying a dominant and fully penetrant conditional lethal trait on 1-20 loci. Delaying the lethality for several generations after release allows the trait to become widely spread in the target population before being activated. To determine effectiveness and optimal strategies for such releases, we vary release size, number of generations until the conditional lethality, nonconditional fitness cost resulting from gene insertions, and fitness reduction associated with laboratory rearing. We show that conditional lethal releases are potentially orders of magnitude more effective than sterile male releases of equal size, and that far smaller release sizes may be required for this approach than necessary with sterile males. For example, a release of male insects carrying a conditional lethal allele that is activated in the F4 generation on 10 loci reduces the target populatioin to 10(-4) of no-release size if there are initially two released males for every wild male. We show how the effectiveness of conditional lethal releases decreases as the nonconditional fitness reduction (i.e., fitness reduction before the trait becomes lethal) associated with the conditional lethal genes increases. For example, if there is a 5% nonconditional fitness cost per conditional lethal allele, then a 2:1 (released male:wild male) release with conditional lethal alleles that are activated in the F4 generation reduces the population to 2-5% (depending on the degree of density dependence) of the no-release size. If there is a per-allele reduction in fitness, then as the number of loci is increased there is a trade-off between the fraction of offspring carrying at least one conditional lethal allele and the fitness of the released insects. We calculate the optimal number of loci on which to insert the conditional lethal gene given various conditions. In addition, we show how laboratory-rearing fitness costs, density-dependence, and all-male versus male-female releases affect the efficiency of conditional lethal releases.
遗传学的进展使得对携带多个位点条件致死性状的昆虫品系进行基因工程改造成为可能。我们建立了一个模型，用于模拟携带1至20个位点上显性且完全显性的条件致死性状的昆虫释放到目标害虫种群中的情况。释放后将致死性延迟几代，可使该性状在被激活之前在目标种群中广泛传播。为了确定此类释放的有效性和最佳策略，我们改变释放规模、直到条件致死的代数、基因插入导致的非条件适合度成本以及与实验室饲养相关的适合度降低。我们表明，条件致死释放可能比同等规模的不育雄虫释放有效几个数量级，并且与不育雄虫相比，这种方法所需的释放规模可能小得多。例如，如果最初每只野生雄虫有两只携带在第4代激活的条件致死等位基因的雄虫被释放，那么在10个位点上携带条件致死等位基因的雄虫释放会将目标种群减少到无释放规模时的10^(-4)。我们展示了随着与条件致死基因相关的非条件适合度降低（即性状致死之前的适合度降低）增加，条件致死释放的有效性如何降低。例如，如果每个条件致死等位基因存在5%的非条件适合度成本，那么在第4代激活条件致死等位基因的2:1（释放雄虫:野生雄虫）释放会将种群减少到无释放规模时的2 - 5%（取决于密度依赖程度）。如果每个等位基因的适合度降低，那么随着位点数量增加，携带至少一个条件致死等位基因的后代比例与释放昆虫的适合度之间存在权衡。我们计算了在各种条件下插入条件致死基因的最佳位点数量。此外，我们展示了实验室饲养适合度成本、密度依赖以及全雄虫释放与雌雄混合释放如何影响条件致死释放的效率。
