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.

scholarly journals GENETIC CHANGE OF RECOMBINATION VALUE IN DROSOPHILA MELANOGASTER. I. ARTIFICIAL SELECTION FOR HIGH AND LOW RECOMBINATION AND SOME PROPERTIES OF RECOMBINATION-MODIFYING GENES

Genetics ◽  
1972 ◽  
Vol 70 (3) ◽  
pp. 419-432
Author(s):  
Margaret Gale Kidwell
Keyword(s):  
Genetic Change ◽  
Selection Line ◽  
Realized Heritability ◽  
Selected Lines ◽  
Gene Frequencies ◽  
Random Drift ◽  
High Line ◽  
Selection For ◽  
Recombination Value ◽  
Selection Of

ABSTRACT A high and low selection line were formed by individual selection of females on the basis of their recombination. In the high line, recombination between Gl and Sb was increased from 14.8 percent to about 30 percent in twelve generations, when a plateau was apparently reached. Realized heritability was 0.12. The absence of a response to selection for low recombination is attributed mainly to genetic random drift, and partially to directional dominance and directional gene frequencies. Natural selection was found to act against increases of recombination above a level of about twenty percent in the measured interval. High recombination tended to be recessive to low recombination. In both selected lines and unselected stocks, intervals proximal to the centromere tended to have a higher recombination variance than distal intervals.

scholarly journals SELECTION FOR BLOOD PRESSURE LEVELS IN MICE

Genetics ◽  
1974 ◽  
Vol 76 (3) ◽  
pp. 537-549
Author(s):  
Gunther Schlager
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Population Bottleneck ◽  
Control Line ◽  
Selected Lines ◽  
High Line ◽  
Selection For ◽  
Random Control

ABSTRACT Response to two-way selection for systolic blood pressure was immediate and continuous for about eight generations. In the twelfth generation, the High males differed from the Low males by 38 mmHG; the females differed by 39 mmHg. There was little overlap between the two lines and they were statistically significant from each other and from the Random control line. There appeared to be no more additive genetic variance in the eleventh and twelfth generations. Causes for the cessation of response are explored. This is probably due to a combination of natural selection acting to reduce litter sizes in the Low line, a higher incidence of sudden deaths in the High line, and loss of favorable alleles as both selection lines went through a population bottleneck in the ninth generation.—In the eleventh generation, the selected lines were used to produce F1, F2, and backcross generations. A genetic analysis yielded significant additive and dominance components in the inheritance of systolic blood pressure.

Sexual size dimorphism in the viviparous caecilian amphibian Geotrypetes seraphini seraphini (Gymnophiona: Dermophiidae) including an updated overview of sexual dimorphism in caecilian amphibians

2016 ◽  
Vol 37 (3) ◽  
pp. 291-299 ◽  
Author(s):  
Markus Maerker ◽  
Sandy Reinhard ◽  
Peter Pogoda ◽  
Alexander Kupfer
Keyword(s):  
Sexual Dimorphism ◽  
Body Length ◽  
Sexual Size Dimorphism ◽  
Molecular Ecology ◽  
Female Size ◽  
Sexually Dimorphic ◽  
Size Dimorphism ◽  
Mating System Evolution ◽  
Accurate Comparison ◽  
Widespread Phenomenon

Sexual size dimorphism (SSD) describing intersexual size differences of a given taxon is a widespread phenomenon in the animal kingdom. SSD plays a significant role in understanding life history and mating system evolution. The snakelike morphology of limbless caecilian amphibians lacking obvious secondary sexual characters (in contrast to frogs and salamanders) impedes an accurate comparison between sexes.Here, the phylogenetically derived teresomatan and viviparous caecilianGeotrypetes seraphini seraphiniwas analysed for patterns of sexual dimorphism. In terms of body size females were the larger sex, but when body length was adjusted male-biased intersexual differences in cloacal shape appeared. The larger female size is likely explained by fecundity selection as clutch size was positively correlated to female body length. Unexpectedly a cryptic, ontogeny related variation of the nuchal collars was found. An overview of SSD in caecilians including data for 27 species of nine out of ten existing families revealed a quite high number of taxa showing sexually dimorphic head size dimensions exclusively present among phylogenetically derived teresomatan caecilians. Still further research including insights into the behavioural ecology and molecular ecology of mating systems is warranted to better understand the evolution of sexual size dimorphism of caecilian amphibians.

scholarly journals Sexual size dimorphism and sexual selection in artiodactyls

2020 ◽  
Vol 31 (3) ◽  
pp. 792-797
Author(s):  
Marcelo H Cassini
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Group Size ◽  
Sexual Size Dimorphism ◽  
Alternative Hypothesis ◽  
Mammalian Species ◽  
Generalized Least Squares ◽  
Size Dimorphism ◽  
Selection For

Abstract Sexual size dimorphism is biased toward males in most mammalian species. The most common explanation is precopulatory intramale sexual selection. Large males win fights and mate more frequently. In artiodactyls, previous tests of this hypothesis consisted of interspecific correlations of sexual dimorphism with group size as a surrogate for the intensity of sexual selection (Is). However, group size is not a proper measure of sexual selection for several reasons as is largely recognized in other mammalian taxa. I conducted an interspecific test on the role of sexual selection in the evolution of sexual dimorphism using the variance in genetic paternity as a proxy for the Is. I reviewed the literature and found 17 studies that allowed estimating Is= V/(W2), where V and W are the variance and mean number of offspring per male, respectively. A phylogenetic generalized least squares analysis indicated that dimorphism (Wm/Wf) showed a significant positive regression with the intensity of sexual selection but not group size (multiple r2= 0.40; F3,17= 12.78, P = 0.002). This result suggests that sexual selection may have played a role in the evolution of sexual size dimorphism in Artiodactyla. An alternative hypothesis based on natural selection is discussed.

Sexual dimorphism in two savannah sparrow populations

1980 ◽  
Vol 58 (3) ◽  
pp. 412-415 ◽  
Author(s):  
Patrick J. Weatherhead
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Stabilizing Selection ◽  
Sexually Dimorphic ◽  
Mainland Population ◽  
Savannah Sparrow ◽  
Savannah Sparrows ◽  
Insular Population

Contrary to predictions, a monogamous, mainland population of savannah sparrows was found to be more sexually dimorphic than a polygynous, insular population. When only trophic characters were considered, the insular population fit the prediction of greater sexual dimorphism. Several explanations for increased sexual selection or decreased stabilizing selection in the more dimorphic population are considered. While none of the explanations seem readily applicable from the available evidence, further avenues of investigation are suggested.

scholarly journals How and why patterns of sexual dimorphism in human faces vary across the world

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Karel Kleisner ◽  
Petr Tureček ◽  
S. Craig Roberts ◽  
Jan Havlíček ◽  
Jaroslava Varella Valentova ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Mate Choice ◽  
Body Height ◽  
Human Populations ◽  
Sexually Dimorphic ◽  
Shape Variation ◽  
Cross Cultural Differences ◽  
Facial Shape ◽  
Human Faces

AbstractSexual selection, including mate choice and intrasexual competition, is responsible for the evolution of some of the most elaborated and sexually dimorphic traits in animals. Although there is sexual dimorphism in the shape of human faces, it is not clear whether this is similarly due to mate choice, or whether mate choice affects only part of the facial shape difference between men and women. Here we explore these questions by investigating patterns of both facial shape and facial preference across a diverse set of human populations. We find evidence that human populations vary substantially and unexpectedly in both the magnitude and direction of facial sexually dimorphic traits. In particular, European and South American populations display larger levels of facial sexual dimorphism than African populations. Neither cross-cultural differences in facial shape variation, sex differences in body height, nor differing preferences for facial femininity and masculinity across countries, explain the observed patterns of facial dimorphism. Altogether, the association between sexual shape dimorphism and attractiveness is moderate for women and weak (or absent) for men. Analysis that distinguishes between allometric and non-allometric components reveals that non-allometric facial dimorphism is preferred in women’s faces but not in faces of men. This might be due to different regimes of ongoing sexual selection acting on men, such as stronger intersexual selection for body height and more intense intrasexual physical competition, compared with women.

Sexual dimorphism and sex pheromone detection in Aphidoletes aphidimyza

2020 ◽  
Vol 70 (1) ◽  
pp. 13-25
Author(s):  
Aurore Nicolas ◽  
Julie Pourtois ◽  
Pol Karier ◽  
István Markó ◽  
Thierry Hance
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Sex Pheromone ◽  
Choice Experiments ◽  
Morphometric Study ◽  
Sexually Dimorphic ◽  
Aphidoletes Aphidimyza ◽  
Long Distance ◽  
The Right ◽  
The Relationship

Abstract Sexual dimorphism, particularly at the level of sensory and locomotor organs, is usually attributed to sexual selection. Antennae are notably developed in males of species that need to detect a sex pheromone at low concentration or at long distance. In addition to their role in intrasexual selection, antennae can be seen as important ornaments in intersexual selection. Antennae of Aphidoletes aphidimyza are clearly sexually dimorphic (males have longer antennae than females, with highly developed sensilla) while females emit a sex pheromone for mating. Males with longer and more symmetrical antennae than others could be more successful in reaching the source of sex pheromone, especially if they can fly properly. A morphometric study was first conducted, to apprehend the variability of antennae, wings and tibias in lab conditions. The length of the antennae of male A. aphidimyza is impressive and the right antenna is longer than the left antenna. Secondly, choice experiments were conducted in a Y-shaped olfactometer with males of A. aphidimyza facing the sex pheromone. The relationship between choice patterns and morphology of males was then studied, but no link was found between the morphology of males and their behaviour while exposed to the sex pheromone, although males were indeed attracted by the olfactometer arm containing the sex pheromone.

scholarly journals Masculinity and the mechanisms of human self-domestication

2017 ◽  
Author(s):  
Ben Thomas Gleeson
Keyword(s):  
Sexual Selection ◽  
Androgen Receptor ◽  
Sexual Dimorphism ◽  
Technological Development ◽  
Human Adaptation ◽  
Physiological Mechanisms ◽  
Related Literature ◽  
Wide Range ◽  
Selection For ◽  
Potential Interactions

AbstractObjectivesPre-historic decline in human craniofacial masculinity has been proposed as evidence of selection for elevated sociability and a process of ‘human self-domestication’ thought to have promoted complex capacities including language, culture, and cumulative technological development. This follows experimental observation of similar changes in non-human animals under selection for reduced aggression. Two distinct domestication hypotheses posit developmental explanations, involving hypoplasia of embryonic neural crest cells (NCCs), and declining androgen influence, respectively. Here, I assess the operation and potential interactions between these two mechanisms and consider their role in enhanced human adaptation to a cooperative sociocultural niche.MethodsI provide a review and synthesis of related literature with a focus on physiological mechanisms effecting domesticated reductions in masculinity and sexual dimorphism. Further, I examine pre-historic modes of socio-sexual selection likely to drive human self-domestication via reduced aggression and masculinity.ResultsI find pluripotent NCCs provide progenitors for a wide range of vertebrate masculine features, acting as regular targets for sexually driven evolutionary change; suggesting domesticated hypoplasia of NCC-derived tissues would be sufficient to explain declines in masculine traits and features. However, lineage specific androgen receptor variability likely moderates these NCC-based effects.ConclusionsThese findings extend theorised mechanisms driving noted physiological, morphological, and behavioural changes thought to indicate enhanced sociability and human and self-domestication. Multiple current explanations for human sociability are consistent with physiological domestication under socio-sexual selection favouring dampened masculine physiology and behaviour as adaptations to an enhanced sociocultural niche. The analysis highlights multiple avenues for further investigation.

scholarly journals Sexual dimorphism in the mandible of the armadillo Chaetophractus villosus (Desmarest, 1804) (Dasypodidae) from northern Patagonia, Argentina

2009 ◽  
Vol 69 (2) ◽  
pp. 347-352 ◽  
Author(s):  
SM. Squarcia ◽  
NS. Sidorkewicj ◽  
R. Camina ◽  
EB. Casanave
Keyword(s):  
Sexual Dimorphism ◽  
Body Length ◽  
Morphometric Analysis ◽  
Sex Discrimination ◽  
Important Variable ◽  
Sexually Dimorphic ◽  
Data Set ◽  
Northern Patagonia ◽  
Chaetophractus Villosus ◽  
Stable Shape

The aim of this study was to study the sexual dimorphism in adult Chaetophractus villosus (Desmarest, 1804), from northern Patagonia, Argentina. Eight mandibular traits were measured in 37 males and 34 females. Univariate and multivariate morphometric analysis were applied to the data set. Results showed that C. villosus was sexually dimorphic, with higher absolute values corresponding to females. The total length of the mandible was the most important variable to discriminate sexes, followed by the height at the level of the last tooth and body length. The percentages of sex discrimination were high, as they were when a new sample (17 males, 13 females) was tested. Females have larger mandibles than males independently of their larger cranial size. They also showed a higher degree of correlation between variables, suggesting a more stable shape for the mandible than in males.

Differences in sexual dimorphism among four gazelle taxa (Gazella spp.) in the Middle East

2010 ◽  
Vol 60 (4) ◽  
pp. 395-412 ◽  
Author(s):  
Peter Cunningham ◽  
Martin Plath ◽  
Torsten Wronski ◽  
Mohamed Sandouka
Keyword(s):  
Body Weight ◽  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Mating Systems ◽  
Research Centre ◽  
Sexually Dimorphic ◽  
Male Sex ◽  
The Difference ◽  
Horn Development

AbstractSexual selection can lead to sexual dimorphism, where elaborated traits used in mate attraction or weaponry are more expressed in the male sex. The degree of sexual dimorphism, however, is known to vary even among closely related taxa. Here we examined sexual dimorphism in horn length and three measures related to body size (body weight, shoulder height, and neck circumference) in four gazelle taxa, representing at least three species, i.e. Dorcas gazelle (G. dorcas), Sand gazelle (G. subgutturosa marica) and Mountain gazelle (G. gazella). The latter is represented by two distinctive phenotypes maintained and bred at the King Khalid Wildlife Research Centre in Saudi Arabia. We describe marked differences in sexual dimorphism among taxa. For example, the difference in sexually dimorphic horn development was driven primarily by females exhibiting pronounced differences in horn development. We discuss how divergent mating systems, and group sizes affect these differences among the examined taxa, with more competition in larger groups probably promoting the evolution of larger horns in females, thereby leading to less sexual dimorphism.

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