Two-trait Selection and the Genetic Correlation I. Prediction of Responses in Single-trait and in Two-trait Selection

Sheridan, A. K.; Js, Barker

doi:10.1071/bi9740075

Cited by 8 publications

(8 citation statements)

References 13 publications

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“…The two-trait selection lines of Sheridan and Barker (1974) comprised four replicates of each of the following four treatments: UU Both traits selected upwards DD Both traits selected downwards UD Coxals selected upwards, sternopleurals downwards DU Coxals selected downwards, sternopleurals upwards At generations 10 and 22 of these lines, flies were taken to set up single-trait selection lines for estimation of realized genetic correlations. At generation 10 random samples of flies were taken separately from all replicate lines of treatments UU and UD, and from two replicate lines of each of DD and DU.…”

Section: Methodsmentioning

confidence: 99%

“…Ten pairs of parents were selected from 50 pairs scored, and selection continued for 10 generations. All experimental procedures and the calculation of realized heritabilities and genetic correlations were as described for the single-trait lines from the base population (Sheridan and Barker 1974), except that in calculating realized genetic correlations the heritability of the unselected trait was taken as that estimated from the single-trait line drawn from the same replicate of the same two-trait selection treatment and selected in the same direction as the selected trait.…”

Section: Methodsmentioning

confidence: 99%

“…In the experiment reported here, D. melanogaster populations were selected, using independent culling levels, for each of the four combinations of high or low third coxal bristle number with high or low sternopleural bristle number. The selection in each of these four types of two-trait lines was continued for 22 generations (Sheridan and Barker 1974). In order to estimate changes in the genetic correlation resulting from the different types of two-trait selection, realized genetic parameters…”

Section: Introductionmentioning

confidence: 99%

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Two-trait Selection and the Genetic Correlation II. Changes in the Genetic Correlation During Two-trait Selection

Sheridan¹,

Js²

1974

Aust. Jnl. Of Bio. Sci.

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Although there is little experimental information on the effect of simultaneous selection for two quantitative characters on the magnitude of the genetic correlation between them, it is apparently generally expected that such selection for the two characters in the same direction will cause a negative change in the genetic correlation, and selection in opposite directions a positive change. Selection using independent culling levels was done for each of the four combinations of high or low third coxal bristle number with high or low sternopleural bristle number in Drosophila melanogaster for 22 generations. To estimate changes in the genetic correlation, realized genetic parameters were estimated from single-trait lines started from the base population, and from the two-trait lines after 10 and 22 generations of selection. Changes in the genetic correlation in individual two-trait selection lines were variable and unpredictable. At generation 22 concurrent two-trait selection had resulted in significantly larger realized genetic correlations than divergent two-trait selection, so that results were contrary to the generally accepted expectation.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Two-trait Selection and the Genetic Correlation II. Changes in the Genetic Correlation During Two-trait Selection

Sheridan¹,

Js²

1974

Aust. Jnl. Of Bio. Sci.

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“…where i r is approximately equal to i 0 √[(1 + r P /4)(1 + r P )], and i 0 is the expected selection when r P = 0 (Sheridan & Barker, 1974). More generally, for any type of directional selection (G. de Jong, personal communication) the change in trait means is given by: …”

Section: The Effect Of Directional Selection On Trade‐offsmentioning

confidence: 99%

The evolution of trade‐offs: where are we?

Roff

Fairbairn

2006

J of Evolutionary Biology

560

559

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Trade‐offs are a core component of many evolutionary models, particularly those dealing with the evolution of life histories. In the present paper, we identify four topics of key importance for studies of the evolutionary biology of trade‐offs. First, we consider the underlying concept of ‘constraint’. We conclude that this term is typically used too vaguely and suggest that ‘constraint’ in the sense of a bias should be clearly distinguished from ‘constraint’ in the sense of proscribed combinations of traits or evolutionary trajectories. Secondly, we address the utility of the acquisition–allocation model (the ‘Y‐model’). We find that, whereas this model and its derivatives have provided new insights, a misunderstanding of the pivotal equation has led to incorrect predictions and faulty tests. Thirdly, we ask how trade‐offs are expected to evolve under directional selection. A quantitative genetic model predicts that, under weak or short‐term selection, the intercept will change but the slope will remain constant. Two empirical tests support this prediction but these are based on comparisons of geographic populations: more direct tests will come from artificial selection experiments. Finally, we discuss what maintains variation in trade‐offs noting that at present little attention has been given to this question. We distinguish between phenotypic and genetic variation and suggest that the latter is most in need of explanation. We suggest that four factors deserving investigation are mutation‐selection balance, antagonistic pleiotropy, correlational selection and spatio‐temporal variation, but as in the other areas of research on trade‐offs, empirical generalizations are impeded by lack of data. Although this lack is discouraging, we suggest that it provides a rich ground for further study and the integration of many disciplines, including the emerging field of genomics.

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“…In spite of a large variability in observed responses between replicates, the selection methods based on restricted indices or independent culling levels prove generally to be effective as attested especially by results of S HERIDAN and BARKER ( 1974 ) in Drosophila, OKADA and HARDIN ( 19 67) in Tribolium castaneum and M CCARTHY ( 1971 ) in mice. However, in such antagonistic selection « genetic correlation may be more powerful in impeding component responses than predicted from presently available theory » as concluded by RuTLEDGr: et al ( 1973 ) from data of a selection experiment in mice on tail length and body weight.…”

Section: -Discussionmentioning

confidence: 99%

Some Considerations on Selection Criteria and Optimization for Terminal Sire Breeds

FOULLEY¹

1976

Genet. Sel. Evol.

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SUMMARYThe efficiency of selection of beef breeds for terminal crossing has been analysed in terms of selection criteria for growth and methods for selection of sires, notably with reference to the situation and research in France. With respect to selection of specialized beef lines, the advantage of control of the individual feed intake and of carcass performances as compared to control of growth only is shortly discussed. For this purpose, not only the favourable indirect response but also the resulting increment of feed intake and changes in body composition according to the reference system used (weight, duration, age) should be taken into account.Because of the increase in birth weight due to the intensification of selection for muscle growth within the beef breeds and the strong genetic correlation between this weight and the paternal component of calving difficulties, it seems advisable to use restricted indices for selection on birth weight, at least for terminal sire lines used in heifers.In the French situation of terminal crossing practised on suckling cows of dual purpose or hardy breeds with the aim of producing veal calves, a special attention has been paid to the genetic and economic advantage of two stage selection for choosing bull sires : selection on a station performance test ( 12 -month-weight), selection on a field progeny test ( 3 -month-weight). Although progeny testing is absolutely required for this type of selection, it has not necessarily to be applied to AI bulls before their commercial use ; it might be sufficient to choose the bulls after performance testing provided the latter is realized on sons of elite bulls.

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Two-trait Selection and the Genetic Correlation I. Prediction of Responses in Single-trait and in Two-trait Selection

Cited by 8 publications

References 13 publications

Two-trait Selection and the Genetic Correlation II. Changes in the Genetic Correlation During Two-trait Selection

Two-trait Selection and the Genetic Correlation II. Changes in the Genetic Correlation During Two-trait Selection

The evolution of trade‐offs: where are we?

Some Considerations on Selection Criteria and Optimization for Terminal Sire Breeds

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