scholarly journals Can Cumulative Selection Explain Adaptation?

2005 ◽  
Vol 72 (5) ◽  
pp. 1099-1112 ◽  
Author(s):  
Bence Nanay
Keyword(s):  
Cumulative Selection

scholarly journals Artificial sexual selection alters allometry in the stalk-eyed fly Cyrtodiopsis dalmanni (Diptera: Diopsidae)

1993 ◽  
Vol 62 (3) ◽  
pp. 213-222 ◽  
Author(s):  
Gerald S. Wilkinson
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Body Length ◽  
Sexually Dimorphic ◽  
Selected Lines ◽  
Variable Intensity ◽  
High Line ◽  
Cumulative Selection ◽  
Selection For ◽  
Selection Of

SummarySelection for increased and decreased ratio of eye span to body length was exerted on male stalk-eyed flies (Cyrtodiopsis dalmanni) from Malaysia using replicate selected and unselected lines. Response to selection was symmetrical. After 10 generations high line male eye span increased to 1·3 body lengths while low line male eye span declined to 1·1 body lengths. Realized heritabilities for eye span to body length ratio, estimated using regressions of deviations from unselected controls on cumulative selection differentials, were greater than zero for all four selected lines with average h2 = 0·35 + 0·06. The static linear allometric relationship between eye span and body length diverged between selected lines and rotated among selected line males in the same direction as among males in other sexually dimorphic diopsid species. Crosses between lines after 13 generations of selection indicate that the genes which influence relative eye span combine additively and do not exhibit sex linkage or maternal effects. The genetic correlation between the sexes, 0·29 + 0·05 as estimated by the regression of female on male change in eye span, did not prevent sexual dimorphism in eye span from diverging between lines. These results suggest that the exaggerated eye span of male C. dalmanni is maintained by natural selection opposing sexual selection rather than by lack of or asymmetry in additive genetic variation. Furthermore, the variation in sexual dimorphism for eye span-body length allometry observed among extant diopsid species is consistent with sexual selection of variable intensity acting on relative eye span.

CORRELATED RESPONSE IN BIRTH WEIGHT, GROWTH RATE AND CARCASS MERIT UNDER SINGLE-TRAIT SELECTION FOR YEARLING WEIGHT IN BEEF SHORTHORN CATTLE

1974 ◽  
Vol 54 (2) ◽  
pp. 117-125 ◽  
Author(s):  
B. BECH ANDERSEN ◽  
H. T. FREDEEN ◽  
G. M. WEISS
Keyword(s):  
Birth Weight ◽  
Selection Response ◽  
Correlated Response ◽  
Weight Growth ◽  
Cumulative Selection ◽  
Selection For ◽  
Carcass Merit ◽  
Least Squares Estimates ◽  
Daily Gain

Data for male calves from the most recent 5 yr of a long-term (11 yr) selection experiment with beef Shorthorn cattle were analyzed to calculate the direct and correlated response of intensive selection for yearling weight on growth and carcass characteristics. Least squares estimates of line differences (select vs. control) for the final year indicated cumulative selection responses [Formula: see text] of 41.5 and 46.2 kg in yearling weight for the two herds. Associated with this selection response in the two herds were increases in birth weight (3.6 and 3.0 kg; [Formula: see text]) in weaning weight (16.2 and 7.8 kg; [Formula: see text] and NS) and daily gain from birth to 10 mo of age (104 and 118; [Formula: see text]). The indirect effects on carcass merit were higher percentage of bone (0.6 and 0.7; [Formula: see text]), and a reduced lean/bone ratio (−0.19 and −0.11; [Formula: see text] and NS). Other differences were not statistically meaningful. The heritabilities for growth characters calculated as son/sire regressions were: birth wt 0.30 ± 0.13; weaning wt 0.34 ± 0.22; yearling wt 0.47 ± 0.23; weaning wt/yearling 0.38 ± 0.21; and daily gain 0.22 ± 0.16. For the most important carcass merit measurements the heritabilities, calculated as half-sib correlations, were: % lean 0.03 ± 0.21; % bone 0.86 ± 0.29; % fat (ext.) 0.01 ± 0.21; % fat (int.) 0.19 ± 0.23; lean/bone 0.72 ± 0.28; and hindquarter wt/forequarter wt 0.24 ± 0.24.

Surrogate resources, cumulative selection, and fertility

1986 ◽  
Vol 9 (1) ◽  
pp. 209-209 ◽  
Author(s):  
Leigh M. Van Valen ◽  
Virginia C. Maiorana
Keyword(s):  
Cumulative Selection

scholarly journals P element transposition contributes substantial new variation for a quantitative trait in Drosophila melanogaster.

Genetics ◽  
1992 ◽  
Vol 131 (1) ◽  
pp. 73-78
Author(s):  
A Torkamanzehi ◽  
C Moran ◽  
F W Nicholas
Keyword(s):  
Drosophila Melanogaster ◽  
Quantitative Trait ◽  
Spontaneous Mutation ◽  
Additive Genetic Variance ◽  
P Element ◽  
Response To Selection ◽  
Stock Selection ◽  
Bristle Number ◽  
Cumulative Response ◽  
Cumulative Selection

Abstract The P-M system of transposition in Drosophila melanogaster is a powerful mutator for many visible and lethal loci. Experiments using crosses between unrelated P and M stocks to assess the importance of transposition-mediated mutations affecting quantitative loci and response to selection have yielded unrepeatable or ambiguous results. In a different approach, we have used a P stock produced by microinjection of the ry506 M stock. Selection responses were compared between transposition lines that were initiated by crossing M strain females with males from the "co-isogenic" P strain, and ry506 M control lines. Unlike previous attempts to quantify the effects of P element transposition, there is no possibility of P transposition in the controls. During 10 generations of selection for the quantitative trait abdominal bristle number, none of the four control lines showed any response to selection, indicative of isogenicity for those loci affecting abdominal bristle number. In contrast, three of the four transposition lines showed substantial response, with regression of cumulative response on cumulative selection differential ranging from 15% to 25%. Transposition of P elements has produced new additive genetic variance at a rate which is more than 30 times greater than the rate expected from spontaneous mutation.

A note on short term selection for birth weight in mice

1976 ◽  
Vol 22 (1) ◽  
pp. 127-130 ◽  
Author(s):  
J. Eklund ◽  
G. E. Bradford
Keyword(s):  
Birth Weight ◽  
Realized Heritability ◽  
Base Population ◽  
Short Term ◽  
Individual Values ◽  
Term Selection ◽  
Cumulative Response ◽  
Cumulative Selection ◽  
Line Selection ◽  
Selection For

SummaryA short-term selection experiment was undertaken to estimate the realized heritability for birth weight in mice.A cross of two strains was used as a base population, from which heaviest and lightest birth weight individuals were selected to initiate an up (JU) and a down (JD) selected line. Selection was applied on a within-litter basis for six generations. By the end of the experiment, the two lines differed by 0·20 ± 0·01 g. The heritability, estimated from the regression of cumulative response on cumulative selection differentials and adjusted to that of individual values, was 0·14 ± 0·02. Six-week body weight, averaged over both sexes, was higher in line JU than in JD by 1·0 ± 0·3 g at generation 6. Litter size was higher in line JU in every generation, the regression of the divergence between JU and JD on generation number being 0·13 ± 0·03.

Selection for carcass lean content in a terminal sire breed of sheep

1992 ◽  
Vol 54 (3) ◽  
pp. 367-377 ◽  
Author(s):  
N. D. Cameron ◽  
J. Bracken
Keyword(s):  
Selection Index ◽  
Selection Criterion ◽  
Live Weight ◽  
Residual Maximum Likelihood ◽  
Cumulative Response ◽  
Cumulative Selection ◽  
Selection For ◽  
The Difference ◽  
Terminal Sire ◽  
Sire Breed

AbstractA divergent selection experiment for carcass leanness in Texel-Oxford sheep was established to examine the differences between genetically lean and fat animals derived from the same base population. The selection criterion was designed to change body composition without a corresponding change in live weight, using an index of ultrasonic backfat depth and live weight at 20 weeks of age. The index was constructed using estimates of genetic and phenotypic parameters, which were available at the start of the experiment in 1985. The difference between the high and low lines, after 3 years of selection, for the selection index, live weight at 20 weeks of age, ultrasonic backfat and muscle depths was 0·59,1·30 kg, -0·76 mm and 0·88 mm respectively. The estimated difference for carcass lean and fat weight was 0·72 kg and -0·04 kg respectively with 13·5 g/kg and -13·8 g/kg for carcass lean and fat proportion. The realized heritability for the selection index, estimated from the regression of cumulative response on cumulative selection differential was 0·42, with a standard error of 0·25, after taking account of genetic drift. The selection index heritability, estimated with residual maximum likelihood (REML) methodology, was 0·46 (s.e. 0·14). REML heritability estimates for live weight at 20 weeks of age, ultrasonic backfat and muscle depths were 0·20 (s.e. 0·13), 0·35 (s.e. 0·14) and 0·43 (s.e. 0·14) respectively.

scholarly journals INHERITANCE OF PLASMA CHOLESTEROL LEVELS IN MICE

Genetics ◽  
1973 ◽  
Vol 73 (2) ◽  
pp. 303-312
Author(s):  
Robert S Weibust
Keyword(s):  
Age Differences ◽  
Plasma Cholesterol ◽  
Inbred Strains ◽  
Genetic Determination ◽  
Cholesterol Levels ◽  
Strain Data ◽  
Cumulative Selection ◽  
Selection For ◽  
Sex And Age Differences

ABSTRACT Mean plasma cholesterol levels were determined at two ages in mice from eight unrelated inbred strains (BALB/cJ, BDP/J, CBA/J, C57BL/6J, LP/J, RF/J, SJL/J, and 129/J). Significant strain, sex, and age differences were observed. Estimates of the degree of genetic determination of the trait obtained from an analysis of the strain data averaged 58 ± 4% for the males and 54 ± 8% for the females.—Selection for high and low plasma cholesterol levels produced two significantly different and distinct lines. Selection was initiated in a genetically heterogeneous population derived from an eight-way cross of the inbred strains listed above. After five generations of selection the divergence of the high and low lines amounted to 4 phenotypic standard deviations of the foundation population. Realized heritability estimated from the regression of divergence on the combined cumulative selection differential was 51 ± 5% for the males and 50 ± 3% for the females. The results indicate that genetic factors are important in controlling plasma cholesterol levels in the mouse and that the majority of these factors act additively.

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