title: Population-level effects of fitness costs associated with repressible female-lethal transgene insertions in two pest insects.
abstract: Genetic control strategies offer great potential for the sustainable and effective control of insect pests. These strategies involve the field release of transgenic insects with the aim of introducing engineered alleles into wild populations, either permanently or transiently. Their efficacy can therefore be reduced if transgene-associated fitness costs reduce the relative performance of released insects. We describe a method of measuring the fitness costs associated with transgenes by analyzing their evolutionary trajectories when placed in competition with wild-type alleles in replicated cage populations. Using this method, we estimated lifetime fitness costs associated with two repressible female-lethal transgenes in the diamondback moth and olive fly as being acceptable for field suppression programs. Furthermore, using these estimates of genotype-level fitness costs, we were able to project longer-term evolutionary trajectories for the transgenes investigated. Results from these projections demonstrate that although transgene-associated fitness costs will ultimately cause these transgenes to become extinct, even when engineered lethality is repressed, they may persist for varying periods of time before doing so. This implies that tetracycline-mediated transgene field persistence in these strains is unlikely and suggests that realistic estimates of transgene-associated fitness costs may be useful in trialing 'uncoupled' gene drive system components in the field.
authors.affiliation: Department of Zoology, University of Oxford Oxford, UK ; Oxitec Ltd, Milton Park Oxford, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Harvey-Samuel
authors.affiliation: Department of Zoology, University of Oxford Oxford, UK ; Oxitec Ltd, Milton Park Oxford, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ant
authors.affiliation: Oxitec Ltd, Milton Park Oxford, UK.
authors.forename: Hongfei
authors.initials: H
authors.lastname: Gong
authors.affiliation: Oxitec Ltd, Milton Park Oxford, UK.
authors.forename: Neil I
authors.initials: NI
authors.lastname: Morrison
authors.affiliation: Department of Zoology, University of Oxford Oxford, UK ; Oxitec Ltd, Milton Park Oxford, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Alphey
keywords: fitness costs; genetic engineering; insect; integrated pest management; release of insects carrying a dominant lethal; transgenic