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1 February 2005 Pest Control by Genetic Manipulation of Sex Ratio
Paul Schliekelman, Stephen Ellner, Fred Gould
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We model the release of insects carrying an allele at multiple loci that shifts sex ratios in favor of males. We model two approaches to sex ratio alteration. In the first (denoted SD), meiotic segregation (or sperm fertility) is distorted in favor of gametes carrying the male-determining genetic element (e.g., Y-chromosome). It is assumed that any male carrying at least one copy of the SD allele produces only genotypically male offspring. In the second approach (denoted PM), the inserted allele alters sex ratio by causing genetically female individuals to become phenotypically male. It is assumed that any insect carrying at least one copy of the PM allele is phenotypically male. Both approaches reduce future population growth by reducing the number of phenotypic females. The models allow variation in the number of loci used in the release, the size of the release, and the negative fitness effect caused by insertion of each sex ratio altering allele. We show that such releases may be at least 2 orders of magnitude more effective than sterile male releases (SIT) in terms of numbers of surviving insects. For example, a single SD release with two released insects for every wild insect and a 5% fitness cost per inserted allele could reduce the target population to 1/1000th of the no-release population size, whereas a similar-sized SIT release would only reduce the population to one-fifth of its original size. We also compare these two sex ratio alteration approaches to a female-killing (FK) system and the sterile male technique when there are repeated releases over a number of generations. In these comparisons, the SD approach is the most efficient with equivalent pest suppression achieved by release of ≈1 SD, 1.5–20 PM, 2–70 FK, and 16–3,000 SIT insects, depending on conditions. We also calculate the optimal number of SD and PM allele insertions to be used under various conditions, assuming that there is an additional genetic load incurred for each allelic insertion.

Paul Schliekelman, Stephen Ellner, and Fred Gould "Pest Control by Genetic Manipulation of Sex Ratio," Journal of Economic Entomology 98(1), 18-34, (1 February 2005).
Received: 28 May 2004; Accepted: 1 October 2004; Published: 1 February 2005

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pest control
segregation distortion
sterile male
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