The application of self-limiting transgenic insects in managing resistance in experimental metapopulations
Zhou, L; Alphey, N; Travers, L; et al.Walker, A; Morrison, N; Bonsall, M; Raymond, BD
Date: 29 October 2018
Article
Journal
Journal of Applied Ecology
Publisher
Wiley for British Ecological Society
Publisher DOI
Abstract
1. The mass release of transgenic insects carrying female lethal self-limiting genes can
reduce pest insect populations. Theoretically, substantial releases can be a novel
resistance management tool, since wild type alleles conferring susceptibility to
pesticides can dilute resistance alleles in target populations. A potential ...
1. The mass release of transgenic insects carrying female lethal self-limiting genes can
reduce pest insect populations. Theoretically, substantial releases can be a novel
resistance management tool, since wild type alleles conferring susceptibility to
pesticides can dilute resistance alleles in target populations. A potential barrier to the
deployment of this technology is the need for large-scale area wide releases. Here we
address whether localized releases of transgenic insects could provide an alternative,
means of population suppression and resistance management, without serious loss of
efficacy.
2. We used experimental mesocosms constituting insect metapopulations to explore the
evolution of resistance to the Bacillus thuringiensis toxin Cry1Ac in a high-dose/refugia
landscape in the insect Plutella xylostella. We ran two selection experiments, the first
compared the efficacy of ‘everywhere’ releases and negative controls to a spatially
density-dependent or ‘whack-a-mole’ strategy that concentrated release of transgenic
insects in sub-populations with high levels of resistance. The second experiment tested
the relative efficacy of whack-a-mole and everywhere releases under spatially
homogenous and heterogeneous selection pressure.
3. The whack-a-mole releases were less effective than everywhere releases in terms of
slowing the evolution of resistance, which in the first experiment, largely prevented the
evolution of resistance. In contrast to predictions, heterogeneous whack-a-mole releases
were not more effective under heterogeneous selection pressure. Heterogeneous
selection pressure did, however, reduce total insect population sizes
4. Whack-a-mole releases provided early population suppression that was
indistinguishable from homogeneous everywhere releases. However, insect population
densities tracked the evolution of resistance in this system, as phenotypic resistance
provides access to the 90% of experimental diet containing the toxin Cry1Ac. Thus, as
resistance levels diverged between treatments, carrying capacities diverged and
population sizes increased under the whack- a-mole approach.
Synthesis and Applications Spatially density-dependent releases of transgenic insects,
particularly those targeting source populations at landscape level, could suppress pest
populations in the absence of blanket area-wide management. The resistance
management benefits of self-limiting transgenic insects are, however, reduced in
spatially localized releases, suggesting that they are not best suited for spatially
restricted ‘spot’ treatment of problematic resistance. Nevertheless, area-wide and
spatially heterogeneous releases could be used to support other resistance management
interventions.
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