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Evolutionary Demography of a Bruchid Beetle. IV. Genetic Trade-Off, Stabilizing Selection and a Model of Optimal Body Size

R. M. Sibly, R. H. Smith and H. Moller
Functional Ecology
Vol. 5, No. 5 (1991), pp. 594-601
DOI: 10.2307/2389477
Stable URL: http://www.jstor.org/stable/2389477
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Evolutionary Demography of a Bruchid Beetle. IV. Genetic Trade-Off, Stabilizing Selection and a Model of Optimal Body Size
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Abstract

Body size is generally related to fecundity in arthropods, and in Callosobruchus maculatus (F.) fecundity and juvenile development rate are known to be genetically correlated, probably because both depend on body weight. Here we estimate the form of the genetic dependence on body weight from previously published breeding value plots, and we estimate physiological effects where necessary, to obtain a model of how natural selection affects body size in culture conditions. The genetic trade-off between fecundity and development rate leads to indirect stabilizing selection on female body weight at emergence. The model shows how optimal body weight increases with culture interval. Selection is shown to be weaker at longer culture intervals, so that genetic variation in body weight should there persist longer. Model predictions are shown to be robust by sensitivity analysis, and to fit the available data. Thus, predicted optimal body weights are intermediate, and observed body weights are close to those predicted on the basis of the culture history of the study population.

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