Selection Response in Natural Populations

2018 ◽  
Author(s):  
Bruce Walsh ◽  
Michael Lynch
Keyword(s):  
Natural Populations ◽  
Selection Response ◽  
Correlated Response ◽  
Sources Of Error ◽  
True Target ◽  
Change In The Mean ◽  
The Mean ◽  
Actual Target ◽  
Long Term Studies

The breeder's equation often fails when applied to natural populations. In large part, this likely occurs because the assumed trait is not the actual target of selection. A within-generation change in the mean of a suggested target trait can arise as a correlated response from selection acting elsewhere. This chapter examines sources of error in the breeder's equation and approaches that attempt to determine if an assumed trait is actually the true target of selection. It also reviews a number of long-term studies from natural populations and examines possible sources for the failure of most of these studies to conform to the expectations of the breeder's equation.

scholarly journals Distribution of natal dispersal distances and the genetic structure of Spruce Grouse (Falcipennis canadensis) populations

2016 ◽  
Vol 94 (6) ◽  
pp. 421-425 ◽  
Author(s):  
G.F. Barrowclough ◽  
M.A. Schroeder
Keyword(s):  
Genetic Structure ◽  
Natural Populations ◽  
Natal Dispersal ◽  
Term Study ◽  
Long Term Study ◽  
The Mean ◽  
Dispersal Distances ◽  
Breeding Seasons ◽  
Long Term Studies

Natal dispersal distances are difficult to measure, yet important for estimating the genetic structure and demographic connectedness of natural populations. Here we provide estimates of the distributions of male and female natal dispersal distances from a long-term study of Spruce Grouse (Falcipennis canadensis (L., 1758)) in southwestern Alberta, Canada, based on individuals marked as brood chicks and re-observed as adults during subsequent breeding seasons. The mean distance dispersed by females (2.33 km) was twice that of males (1.13 km), and both dispersal distributions were leptokurtic. Given estimates of population density and survivorship, we estimated the genetic effective neighborhood size of this population as approximately 541 individuals. We computed equivalent estimates for two additional long-term studies of this species, based on data available in the literature; mean natal dispersal distances, averaged across sexes, ranged from 1.73 to 2.73 km for the three populations; effective deme sizes ranged from 541 to 890. Consequently, three widespread populations of Spruce Grouse yielded roughly similar estimates of demographic and genetic structure.

scholarly journals LONG-TERM SELECTION RESPONSE FOR 12-DAY LITTER WEIGHT IN MICE

Genetics ◽  
1972 ◽  
Vol 72 (1) ◽  
pp. 129-142
Author(s):  
E J Eisen
Keyword(s):  
Body Weight ◽  
Genetic Correlation ◽  
Half Life ◽  
Selection Process ◽  
Selection Response ◽  
Exponential Model ◽  
Correlated Response ◽  
Term Selection ◽  
Litter Weight

ABSTRACT Long-term selection for increased 12-day litter weight in two replicate lines (W2, W3) of mice resulted in an apparent selection limit at about 17 generations. Quadratic polynomial and exponential models were fitted to the data in order to estimate the plateaued response and half-life of the selection process. Using the polynomial results, the half-life estimates were 4.5 and 8.6 generations for W2 and W3, respectively. The plateaued responses were 5.1 and 5.8 g which, when expressed in phenotypic standard deviation units, became 1.1 and 1.3. The exponential model provides similar estimates. A negative association between 12-day litter weight and fitness was not considered to be an adequate explanation for the plateau since there was no decrease in fertility of the selected lines. Evidence that exhaustion of genetic variability was not the cause of the plateau came from the immediate response to reverse selection. It was proposed that the plateau may be due to a negative genetic correlation between direct and maternal genetic effects, which would be expected to occur after many generations of selection. There were positive correlated responses in both replicates for adult body weight, which was in agreement with the positive genetic correlation between preweaning and postweaning body weight. The expected positive correlated response for number born was realized in only one of the replicates.

The influence of mixtures of Stylosanthes spp. accessions on the occurrence of anthracnose caused by Colletotrichum gloeosporioides

1994 ◽  
Vol 45 (1) ◽  
pp. 203 ◽  
Author(s):  
RD Davis ◽  
S Chakraborty ◽  
DF Cameron ◽  
JAG Irwin ◽  
RM Boland
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Resistant Cultivar ◽  
Pure Stand ◽  
Northern Australia ◽  
Short Term ◽  
Mixed Stands ◽  
The Mean ◽  
Moderately Resistant ◽  
Long Term Studies

The effectiveness of using accession mixtures of Stylosanthes spp. to manage anthracnose (Colletotrichum gloeosporioides) in pastures in northern Australia was examined during three consecutive years. Two mixtures containing six accessions were compared with the components grown as pure stands. No significant differences in anthracnose incidence (proportion of infected plants/plot) were indicated between the two mixtures and the mean incidence of their respective components grown in pure swards. Areas under the disease progress curves for the accessions were not significantly different between pure and mixed stands of the cultivars other than Seca and Verano. Resistant cultivar Seca developed more disease in a mixture than in a pure stand, and moderately resistant Verano had less disease in a mixture than in a pure stand. In the short term, no apparent anthracnose control advantage is achieved in highly susceptible accessions of Stylosanthes spp. when they are included in mixtures with less susceptible accessions. Long term studies involving grazing animals are necessary to adequately evaluate control of this disease through the use of mixtures.

scholarly journals A complex multi-locus, multi-allelic genetic architecture underlying the long-term selection-response in the Virginia body weight line of chickens

2017 ◽  
Author(s):  
Yanjun Zan ◽  
Zheya Sheng ◽  
Lars Rönnegård ◽  
Christa F. Honaker ◽  
Paul B. Siegel ◽  
...  
Keyword(s):  
Body Weight ◽  
Additive Genetic Variance ◽  
Natural Populations ◽  
Selection Response ◽  
Multiple Alleles ◽  
Term Selection ◽  
Selection Responses ◽  
Genome Wide ◽  
Genetic Mechanisms

AbstractThe ability of a population to adapt to changes in their living conditions, whether in nature or captivity, often depends on polymorphisms in multiple genes across the genome. In-depth studies of such polygenic adaptations are difficult in natural populations, but can be approached using the resources provided by artificial selection experiments. Here, we dissect the genetic mechanisms involved in long-term selection responses of the Virginia chicken lines, populations that after 40 generations of divergent selection for 56-day body weight display a nine-fold difference in the selected trait. In the F15 generation of an intercross between the divergent lines, 20 loci explained more than 60% of the additive genetic variance for the selected trait. We focused particularly on seven major QTL and found that only two fine-mapped to single, bi-allelic loci; the other five contained linked loci, multiple alleles or were epistatic. This detailed dissection of the polygenic adaptations in the Virginia lines provides a deeper understanding of genome-wide mechanisms involved in the long-term selection responses. The results illustrate that long-term selection responses, even from populations with a limited genetic diversity, can be polygenic and influenced by a range of genetic mechanisms.

Long-term animal research in genetic improvement of livestock and poultry

1996 ◽  
Vol 76 (4) ◽  
pp. 581-585
Author(s):  
E. B. Burnside
Keyword(s):  
Animal Species ◽  
Genetic Variance ◽  
Genetic Selection ◽  
Selection Response ◽  
Animal Experimentation ◽  
Private Industry ◽  
Animal Products ◽  
Selection Experiments ◽  
Long Term Studies

In animal experimentation, long-term studies have contributed substantially to our knowledge of genetics in particular, and of nutrition, physiology, and reproduction, to lesser extents. Long-term genetic selection experiments have yielded information on selection limits, dissipation of genetic variance over time, and created unique lines which may be utilized as consumer demands shift. Costs of long-term experimentation are not inordinately high in comparison to other experimentation, if economic animal species are used and returns from animal products are recovered to help finance the experiment. Government finance is, however, required for long-term experimentation, as private industry has little motivation for this work. The paper outlines recent significant contributions of long-term experimentation, and provides guidelines for planning experiments. Key words: Selection response, animal genetics, long-term experimentation, experimental design

A Novel Extended Deep Plane Facelift Technique for Jawline Rejuvenation and Volumization

2018 ◽  
Vol 39 (12) ◽  
pp. 1265-1281 ◽  
Author(s):  
Andrew A Jacono ◽  
Lucas M Bryant ◽  
Nigar N Ahmedli
Keyword(s):  
Fat Grafting ◽  
Visual Perspective ◽  
Volume Depletion ◽  
Level Of Evidence ◽  
Gonial Angle ◽  
Change In The Mean ◽  
Rotational Flap ◽  
Mandibular Region ◽  
The Mean

Abstract Background Jawline aging is a complex process. We believe loss of posterior jawline definition and volume depletion is an underappreciated factor in the aging face. Objectives The aim of this study was to describe a novel composite, rotational flap modification of an extended deep-plane rhytidectomy. We evaluated long-term efficacy on improving jawline contour and volumization of the posterior mandibular region overlying the gonial angle. Methods We performed a prospective study on patients who underwent our modification of extended deep-plane rhytidectomy. We define and introduce the mandibular defining line, a new anatomic metric in evaluating the mandibular contour. We define the area of the posterior lower face overlying the gonion and mandibular angle as the gonial area. Using 3-dimensional photography, we quantify contour changes along the mandibular border and volume change along the gonial area. Results Eighty-nine patients (178 hemifaces) were analyzed. The mean gonial area volume gained was 3.5 cc. Average follow-up was 19 months. There was a statistically significant change in the mean mandibular defining line from 7.1 cm preoperatively to 9.8 cm postoperatively. This represents a lengthening of the visual perspective of the mandibular contour of 2.7 cm. Conclusions Composite, rotational flap modification of extended deep-plane rhytidectomy provides significant long-term augmentation of volume to the posterior mandibular region and lengthens the visual perspective of the inferior mandibular contour, creating a more youthful jawline. In selected cases, this may obviate the need for other volumization procedures used to improve jawline contour, such as autologous fat grafting. Level of Evidence: 4

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.

Sagittal spinopelvic parameters in children with achondroplasia: identification of 2 distinct groups

2012 ◽  
Vol 17 (1) ◽  
pp. 57-60 ◽  
Author(s):  
Isaac O. Karikari ◽  
Ankit I. Mehta ◽  
Can Solakoglu ◽  
Carlos A. Bagley ◽  
Michael C. Ain ◽  
...  
Keyword(s):  
Sacral Slope ◽  
Spinopelvic Parameters ◽  
Significant Difference ◽  
Pediatric Patient Population ◽  
Unpaired Student ◽  
The Mean ◽  
Age Range ◽  
Radiographic Data ◽  
Long Term Studies

Object Spinopelvic parameters in children with achondroplasia have not been described. Because they observed a unique sagittal spinopelvic phenotype in some achondroplastic children with very horizontal sacrums, the authors sought to quantify the spinopelvic parameters in a pediatric patient population. Methods A retrospective review was performed to identify all children (age range 1 month–10 years) with a diagnosis of achondroplasia between 2004 and 2009. Clinical and radiographic data were analyzed for age, sex, lumbar lordosis (LL), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). Differences among these variables were analyzed using a 2-tailed, unpaired Student t-test. Results Forty children, 23 males and 17 females, with achondroplasia were identified during the study period. The mean age was 2.6 years. Two groups of patients were identified based on PT (that is, negative or positive tilt and horizontal or not horizontal sacrum). A negative PT was identified in all children with an extremely horizontal sacrum. Seventeen children had a negative PT (mean −16.6°), and the mean parameters in this group were 65.4° for LL, 31.7° for TLK, 18.5° for TK, 43.3° for SS, and 26.4° for PI. Twenty-three children had a positive PT (mean 17.9°), and the mean parameters in this group were 53.4° for LL, 41.5° for TLK, 9.6° for TK, 30.8° for SS, and 43.8° for PI. A statistically significant difference was observed for LL (p = 0.01), TLK (p = 0.05), SS (p = 0.006), PT (p = 0.006), and PI (0.0002). Conclusions Spinopelvic parameters in achondroplasia are potentially dichotomous. The future implications of this observation are not known and will need to be explored in future long-term studies that follow pediatric patients with achondroplasia through adulthood.

scholarly journals Spatio-Temporal Ecological and Evolutionary Dynamics in Natural Butterfly Populations (2015 Field Season)

2015 ◽  
Vol 38 ◽  
pp. 29-32
Author(s):  
Zachariah Gompert ◽  
Lauren Lucas
Keyword(s):  
Genetic Variation ◽  
Natural Selection ◽  
Molecular Evolution ◽  
Natural Populations ◽  
Spatial And Temporal Variation ◽  
Long Term Study ◽  
Genome Wide ◽  
In The Wild ◽  
Long Term Studies

The study of evolution in natural populations has advanced our understanding of the origin and maintenance of biological diversity. For example, long term studies of wild populations indicate that natural selection can cause rapid and dramatic changes in traits, but that in some cases these evolutionary changes are quickly reversed when periodic variation in weather patterns or the biotic environment cause the optimal trait value to change (e.g., Reznick et al. 1997, Grant and Grant 2002). In fact, spatial and temporal variation in the strength and nature of natural selection could explain the high levels of genetic variation found in many natural populations (Gillespie 1994, Siepielski et al. 2009). Long term studies of evolution in the wild could also be informative for biodiversity conservation and resource management, because, for example, data on short term evolutionary responses to annual fluctuations in temperature or rainfall could be used to predict longer term evolution in response to directional climate change. Most previous research on evolution in the wild has considered one or a few observable traits or genes (e.g., Kapan 2001, Grant and Grant 2002, Barrett et al. 2008). We believe that more general conclusions regarding the rate and causes of evolutionary change in the wild and selection’s contribution to the maintenance of genetic variation could be obtained by studying genome-wide molecular evolution in a suite of natural populations. Thus, in 2012 we began a long term study of genome-wide molecular evolution in a series of natural butterfly populations in the Greater Yellowstone Area (GYA). This study will allow us to quantify the contribution of environment-dependent natural selection to evolution in these butterfly populations and determine whether selection consistently favors the same alleles across space and through time.

scholarly journals Spatio-Temporal Evolutionary Dynamics in Natural Butterfly Populations (2012 Field Season)

2012 ◽  
Vol 35 ◽  
pp. 73-76
Author(s):  
Zachariah Gompert ◽  
Lauren Lucas
Keyword(s):  
Genetic Variation ◽  
Natural Selection ◽  
Molecular Evolution ◽  
Natural Populations ◽  
Spatial And Temporal Variation ◽  
Long Term Study ◽  
Genome Wide ◽  
In The Wild ◽  
Long Term Studies

The study of evolution in natural populations has advanced our understanding of the origin and maintenance of biological diversity. For example, long term studies of wild populations indicate that natural selection can cause rapid and dramatic changes in traits, but that in some cases these evolutionary changes are quickly reversed when periodic variation in weather patterns or the biotic environment cause the optimal trait value to change (e.g., Reznick et al. 1997; Grant and Grant 2002). In fact, spatial and temporal variation in the strength and nature of natural selection could explain the high levels of genetic variation found in many natural populations (Gillespie 1994; Siepielski et al. 2009). Long term studies of evolution in the wild could also be informative for biodiversity conservation and resource management, because, for example, data on short term evolutionary responses to annual fluctuations in temperature or rainfall could be used to predict longer term evolution in response to directional climate change. Most previous research on evolution in the wild has considered one or a few observable traits or genes (Kapan 2001; Grant and Grant 2002; Barrett et al. 2008). We believe that more general conclusions regarding the rate and causes of evolutionary change in the wild and selection’s contribution to the maintenance of genetic variation could be obtained by studying genome-wide molecular evolution in a suite of natural populations. Thus, we have begun a long term study of genome-wide molecular evolution in a series of natural butterfly populations in the Greater Yellowstone Area (GYA). This study will allow us to quantify the contribution of environment-dependent natural selection to evolution in these butterfly populations and determine whether selection consistently favors the same alleles across space and through time.

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