Effects of disruptive selection

Thoday, J. M.

doi:10.1038/hdy.1960.3

Cited by 55 publications

(28 citation statements)

References 9 publications

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“…Barnes (1968) showed that sternopleural bristle number was subjected to stabilising selection in cage populations maintained at two temperatures, the optimum phenotype depending on the temperature. Evidence for the adaptive significance of sternopleural bristle number in populations maintained at different temperatures was previously obtained by Beardmore (in Thoday, 1959). However, it is not obvious why the mean bristle number in both of the present control lines first increased and then decreased.…”

Section: Discussionmentioning

confidence: 45%

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Stabilising selection in constant and fluctuating environments

Gibson

Bradley

1974

Heredity

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SUMMARYSelection in both constant and fluctuating temperature environments for a constant bristle number in Drosophila melanogaster resulted in the maintenance of that number and in a decrease of both genetic and environmental variance. Although mean bristle number in the control lines increased over the early generations there was a significant net decrease. Phenotypic variance decreased significantly, especially in later generations. In both control lines and in the line selected at 20-29° C. there was a significant decrease in asymmetry of bristle number. There was also a decrease in environmental variance in these three lines. Transplant experiments showed that when the lines were cultured in alien environments phenotypic variance tended to increase in the fluctuating and decrease in the constant temperature environment. However at generation 39, the phenotypic variance of lines selected in the fluctuating environment increased when samples of the lines were cultured in the constant temperature environment. The results indicate that stabilising selection can be effective in both fluctuating and constant temperature environments.

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Section: Discussionmentioning

confidence: 45%

“…Such selection has been investigated theoretically (Wright, 1935;Robertson, 1956;Latter, 1960;Curnow, 1964;Singh and Lewontin, 1966;Gale and Kearsey, 1968) and experimentally (Falconer, 1957;Thoday, 1959;Prout, 1962;Scharloo, 1964;Barnes, 1968). All of these studies assumed or were carried out in a constant environment.…”

Section: Introductionmentioning

confidence: 99%

Stabilising selection in constant and fluctuating environments

Gibson

Bradley

1974

Heredity

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“…The Drosophila data are derived from Roff and Mousseau (1987) and is based upon the median by study data set There are many factors which may be responsible for the maintenance of genetic variance of fitness characters, The rate of origin of variation by mutation alone may be sufficient to maintain substantial additive genetic variance within natural populations (Lande, 1976;Turelli, 1984). Heterozygote advantage (Falconer, 1981), frequency dependent selection (Bulmer, 1980), variable selection in heterogeneous environments (Ewing, 1979), diversifying selection (Thoday, 1972), and migration (Felsenstein, 1976) have been proposed as possible mechanisms for the sustenance of genetic variation. Also, significant heritabilities for fitness characters are not inconsistent with zero additive genetic variance in fitness given negative genetic correlations between fitness components (the antagonistic pleiotropy hypothesis).…”

Section: Discussionmentioning

confidence: 99%

Natural selection and the heritability of fitness components

1987

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The hypothesis that traits closely associated with fitness will generally possess lower heritabilities than traits more loosely connected with fitness is tested using 1120 narrow sense heritability estimates for wild, outbred animal populations, collected from the published record. Our results indicate that life history traits generally possess lower heritabilities than morphological traits, and that the means, medians, and cumulative frequency distributions of behavioural and physiological traits are intermediate between life history and morphological traits. These findings are consistent with popular interpretations of Fisher's (1930Fisher's ( , 1958 Fundamental Theorem of Natural Selection, and Falconer (1960, 1981), but also indicate that high heritabilities are maintained within natural populations even for traits believed to he under strong selection. It is also found that the heritability of morphological traits is significantly lower for ectotherms than it is for endotherms which may in part be a result of the strong correlation between life history and body size for many ectotherms. INTRODUCTIONThe fundamental theorem of natural selection states: "The rate of increase in fitness of any organism at any time is equal to its genetic variance in fitness at that time" (Fisher, 1930). Fisher's theorem is axiomatic to much of current evolutionary research. It has been variously interpreted but is generally construed to imply that traits that have been closely and consistently associated with fitness will exhibit low additive genetic variances as a result of natural selection (e.g., Hegmann and Dingle, 1982; Lynch and Sulzbach, 1984; Riddel et cii., 1981). However, the validity of the fundamental theorem is dependent upon many assumptions that may not usually be met by natural populations (e.g., population equilibrium, weak selection, constancy of genotypic fitnesses over time, and independence of genotypic frequencies) (Charlesworth, 1987). The maintenance of low additive genetic variance has also been inferred to imply low heritability (in the narrow sense); "On the whole, characters with the lowest heritabilities are those most closely connected with fitness, while characters with the highest heritabilities are those that might be judged on biological grounds to be the least important as determinants of natural selection." (Falconer, 1960(Falconer, , 1981.) The most extensive compilation of data in support of this view is that presented in table 10.1 of Falconer (1981). However, these data are rather few and derived primarily from domestic animals, which may be partly inbred. Extension to wild, outbred organisms may be erroneous.It is possible that some significant amount of additive genetic variance can be maintained within natural populations, even for characters tightly connected to fitness; possible mechanisms include mutation (Lande, 1976; Turelli, 1984), heterozygote advantage (Falconer, 1981), frequency dependence (Bulmer, 1980), fluctuating environments (Ewing, 1979) and migration (Felsenstein, 197...

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“…This paper describes an attempt to increase the response to directional selection for increased sternopleural chaetae number in Drosophila melanogaster by artifically increasing the genetic variance and heritability through the use of disruptive selection. The definition of disruptive selection used here is that given by Thoday (1972) as selection for more than one value on a phenotypic scale within any one generation. Disruptive selection on continuous characters has been shown repeatedly in laboratory experiments to be capable of increasing genetic variance (for example; Gibson Scharloo, 1964).…”

Section: Introductionmentioning

confidence: 99%

Directional-disruptive selection in Drosophila melanogaster

Yousif

Skibinski

1982

Heredity

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SUMMARYArtificial directional selection for increased sternopleural chaetae number in Drosophila ,nelanogaster is compared with a mode of directional selection which incorporates an element of disruptive selection. Compared with directional selection, this directional-disruptive selection results in a similar response but with a lower selection differential, and higher realised heritability. The differences might be attributed to a higher genetic variance maintained by the directional-disruptive selection.

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Effects of disruptive selection

Cited by 55 publications

References 9 publications

Stabilising selection in constant and fluctuating environments

Stabilising selection in constant and fluctuating environments

Natural selection and the heritability of fitness components

Directional-disruptive selection in Drosophila melanogaster

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