The effects of mating systems and selection on pupa weight inTribolium

Abstract

An experimental evaluation of the effect of mating systems and selection upon an additive trait thought to be highly heritable was made. There were two similar replications. Each consisted of a mass selected and randomly selected group, with five mating systems within each group.Realized heritabilities in the mass selected lines were considerably less than was expected prior to the initiation of the experiment, and averaged approximately fourteen percentage points less than heritability estimated from the zero generation. This in turn resulted in smaller correlations between the genotypes of mates than had been previously expected in the assortatively and disassortatively mated lines.The average response of the mass selected, assortatively mated lines was slightly more than the mass selected, randomly mated lines, though not statistically significant. This result seems to conform to theoretical expectations.In the mass selected lines, estimates of phenotypic and genetic variance declined regardless of mating systems. There was a tendency for phenotypic variances to decrease in the randomly selected lines, but this was not the case for estimates of genetic variance.As an aid to selection, it seems that assortative mating would be of little value with traits of low or intermediate heritability but might be useful if the trait is highly heritable.

Selection under assortative mating in mice

“…The present results, obtained on a character of moderate heritability in mammals, complement those previously obtained with Drosophila by McBride & Robertson (1963) and by Wilson et al (1965) with Tribolium. These workers found a very slight and statistically insignificant advantage for assortative mating over random mating and concluded that only in cases of selection for characters of very high heritability would there be any economic advantage in using assortative mating.…”

“…The results were thus nicely in accord with the theory, although the advantages of selecting under assortative mating were not striking. Wilson, Kyle & Bell (1965) studied the effects of mating system on selection in Tribolium. Assortative mating afforded slightly more progress than did random mating in increasing 19-day pupa weight, but the difference was not statistically significant.…”

A deterministic multi-tier model of assortative mating following selection

“…This has been demonstrated in experimental studies with Drosophila (McBride and Robertson, 1963) and Tribolium (Wilson et al, 1965), in stochastic computer simulations (De Lange, 1974) and in deterministic computer simulations (Fernando and Gianola, 1986;Smith and Hammond, 1987;Tallis and Leppard, 1987). Smith and Hammond (1987) (Fernando and Gianola, 1986;Smith and Hammond, 1987).…”

INBREEDING: ITS EFFECT ON RESPONSE TO SELECTION FOR PUPAL WEIGHT AND THE HERITABLE VARIANCE IN FITNESS IN THE FLOUR BEETLE,TRIBOLIUM CASTANEUM

“…This is relevant to our study because inbreeding, bottlenecks and mating systems all can be used to address the relationship between the loss of heterozygosity and changes in genetic variance. Under certain genetic circumstances, non-random mating systems have been shown to increase the response to selection by changing levels of homozygosity (Wright 1921(Wright , 1952Haldane 1937;Fisher 1949;Breese 1956;McBride and Robertson 1963;Wilson et al 1965). Furthermore, different mating systems acquire homozygosity at different rates (Wright 1921).…”

“…Numerous experimental studies have examined the effects of mating system or inbreeding on selection for continuously varying traits in a variety of organisms (Tantawy and Reeve 1956;Wilson et al 1965;reviews in Rathie and Nicholas 1980;Weir et al 1980). Other empirical studies (Bowman and Falconer 1960;Madalena and Robertson 1975;Enfield 1976;Katz and Enfield 1977;Rathie and Nicholas 1980) have investigated the effects of population subdivision on the response to selection.…”