Sexual Selection in Dung Beetles .1. A Multivariate Study of the Morphological Variation in 2 Species of Onthophagus (Scarabaeidae, Onthophagini)

1987 ◽  
Vol 35 (2) ◽  
pp. 123 ◽  
Author(s):  
D Cook
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Morphometric Analysis ◽  
Body Shape ◽  
Dung Beetles ◽  
Structural Polymorphism ◽  
Multivariate Study ◽  
History Of ◽  
Males And Females ◽  
Horned Beetles

Sexual dimorphism in horned beetles reflects a history of different selection pressures operating on males and females. A multivariate morphometric analysis was carried out on two scarabaeine dung beetles, Onthophagus binodis Thunberg and O. ferox Harold. There is clear structural polymorphism within O. binodis; horned males, females and hornless males were separated on the basis of body shape. Sexual dimorphism within O. ferox was established; sexes were separated according to the size of pronotal and cephalic horns. The effect of differential selection is discussed within the context of sexual selection.

Differences in male and female cognitive abilities: Sexual selection or division of labor?

1996 ◽  
Vol 19 (2) ◽  
pp. 254-255
Author(s):  
Michael T. Ghiselin
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Sexual Dimorphism ◽  
Division Of Labor ◽  
Cognitive Abilities ◽  
Reproductive Competition ◽  
Male And Female ◽  
Males And Females

AbstractIn Darwinian terminology, “sexual selection” refers to purely reproductive competition and is conceptually distinct from natural selection as it affects reproduction generally. As natural selection may favor the evolution of sexual dimorphism by virtue of the division of labor between males and females, this possibility needs to be taken very seriously.

scholarly journals Sexual dimorphism in steppe tortoises (Testudo horsfieldii): influence of the environment and sexual selection on body shape and mobility

2001 ◽  
Vol 72 (3) ◽  
pp. 357-372 ◽  
Author(s):  
X. BONNET ◽  
F. LAGARDE ◽  
B. T. HENEN ◽  
J. CORBIN ◽  
K. A. NAGY ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Body Shape

Sexual dimorphism in the claws of the European terrapin (Emys orbicularis): potential implications for the reproductive fitness of the species.

2019 ◽  
Author(s):  
Gonzalo Alarcos ◽  
Jaime Madrigal-González ◽  
Miguel Lizana ◽  
Fabio Flechoso
Keyword(s):  
Sexual Selection ◽  
Comparative Analysis ◽  
Sexual Dimorphism ◽  
Reproductive Success ◽  
Sexual Maturity ◽  
Reproductive Fitness ◽  
Emys Orbicularis ◽  
Future Studies ◽  
Different Populations ◽  
Males And Females

There are many biometric differences between the males and females of the European pond turtle (Emys orbicularis) as regards their size, colouring, the shape of the plastron, tail, etc. The males use their claws to grasp the female during copulation and hence sexual selection should favour the males that have larger claws, which allow them to grasp the female better. Here, we address this type of sexual dimorphism in a comparative analysis of indices obtained from claw length, the length of the carapace and the locality where individuals were sampled. The results show that the curvature of the claws differs between the two sexes, being longer in males and increasing with age, size, and hence, the state of sexual maturity, than in females. Greater claw length could confer advantages for males when grasping the carapace of females, and hence, improve their reproductive fitness. Importance in the reproductive success that might have this feature in males could originate future studies that will relate the shape, thickness, length and other measures of the claws in males with their reproductive success in different populations, genetic variety, and most importantly, viability of populations. 

scholarly journals Ontogenetic allometry in the foot size of Oligoryzomys flavescens (Waterhouse, 1837) (Rodentia, Sigmodontinae)

2015 ◽  
Vol 75 (2) ◽  
pp. 435-441 ◽  
Author(s):  
R. Maestri ◽  
R. Fornel ◽  
TRO. Freitas ◽  
JR. Marinho
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Sexual Dimorphism ◽  
Encounter Rate ◽  
Allometric Growth ◽  
Positive Allometry ◽  
Rate Of Growth ◽  
Ontogenetic Allometry ◽  
Males And Females ◽  
Oligoryzomys Flavescens

Ontogenetic allometry is the study of how the size or shape of certain structures changes over the course of an animal’s development. In this study, using Huxley's formula of allometric growth (1932), we assessed the changes in the rate of growth of the feet size of the sigmodontine rodent Oligoryzomys flavescens during its ontogeny and compared differences between males and females. We find evidence of a change of polarity during the ontogenetic development of the species, with the presence of positive allometry during pregnancy and negative allometry in adulthood. Moreover, we note the presence of sexual dimorphism in the size of the feet, in which males of the species have a higher rate of growth than females. This growth pattern is positively related to escape from predators in childhood in both sexes and, in adulthood, provides a higher encounter rate of females by males, due to the larger displacement of the latter. We suggest that both the forces of natural selection and sexual selection have acted to shape the evolution of foot size in this species.

scholarly journals SEXUAL DIMORPHISM IN LIZARD BODY SHAPE: THE ROLES OF SEXUAL SELECTION AND FECUNDITY SELECTION

Evolution ◽  
2002 ◽  
Vol 56 (7) ◽  
pp. 1538-1542 ◽  
Author(s):  
Mats Olsson ◽  
Richard Shine ◽  
Erik Wapstra ◽  
Beata Ujvari ◽  
Thomas Madsen
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Body Shape ◽  
Fecundity Selection

scholarly journals Sexual selection on male vocal fundamental frequency in humans and other anthropoids

2016 ◽  
Vol 283 (1829) ◽  
pp. 20152830 ◽  
Author(s):  
David A. Puts ◽  
Alexander K. Hill ◽  
Drew H. Bailey ◽  
Robert S. Walker ◽  
Drew Rendall ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Immune Function ◽  
Fundamental Frequency ◽  
Low Frequency ◽  
Evolutionary Transitions ◽  
Mating Competition ◽  
Males And Females ◽  
Low Cortisol

In many primates, including humans, the vocalizations of males and females differ dramatically, with male vocalizations and vocal anatomy often seeming to exaggerate apparent body size. These traits may be favoured by sexual selection because low-frequency male vocalizations intimidate rivals and/or attract females, but this hypothesis has not been systematically tested across primates, nor is it clear why competitors and potential mates should attend to vocalization frequencies. Here we show across anthropoids that sexual dimorphism in fundamental frequency ( F 0 ) increased during evolutionary transitions towards polygyny, and decreased during transitions towards monogamy. Surprisingly, humans exhibit greater F 0 sexual dimorphism than any other ape. We also show that low- F 0 vocalizations predict perceptions of men's dominance and attractiveness, and predict hormone profiles (low cortisol and high testosterone) related to immune function. These results suggest that low male F 0 signals condition to competitors and mates, and evolved in male anthropoids in response to the intensity of mating competition.

scholarly journals Evaluation of fluctuating asymmetry and sexual dimorphism of Channa striata using landmark-based geometric morphometric analysis from Agusan Marsh and Lake Mainit in Caraga Region, Philippines

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Rex Bomvet Saura ◽  
Geneveve Falcasantos ◽  
Rex Jr. Andante ◽  
Luna Munda ◽  
Marycris Alimorong ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Chemical Analysis ◽  
Morphometric Analysis ◽  
Fluctuating Asymmetry ◽  
Low Oxygen ◽  
Geometric Morphometric ◽  
Physico Chemical ◽  
Geometric Morphometric Analysis ◽  
Channa Striata ◽  
Males And Females

Abstract. Saura EBD, Falcasantos GC, Andante RJM, Munda LC, Alimorong MM, Hernando BJ. 2021. Evaluation of fluctuating asymmetry and sexual dimorphism of Channa striata using landmark-based geometric morphometric analysis from Agusan Marsh and Lake Mainit in Caraga Region, Philippines. Nusantara Bioscience 13: 100-110. Evaluation was conducted to determine the impact of ecological condition to Channa striata using fluctuating asymmetry (FA) employing the landmark-based geometric morphometric analysis, using TPS software, SAGE, PAST-Hotellings Test, including Physico-chemical analysis, cyanide and four base metals. Results of Physico-chemical analysis of the two habitats showed Agusan marsh with low oxygen level (3.37-4.55) and high in Iron and TDS as compared to DENR Standards. The statistical results showed high variations (p < 0.0001) on left and right-side having percentage of 79.22% in Agusan Marsh and 72.35% in Lake Mainit which is relatively high Fluctuating Asymmetry. In terms of sex, Agusan marsh had 84.27% and 85.41% FA in males and females while Lake Mainit having 85.12% and 80.89% in males and females. The fairly similar percentage of Fluctuating Asymmetry confirms no sexual dimorphism and no shape differences between male and female, and no peculiar characters to distinguished between sexes based on the 17 landmark points. Present study concluded that FA observed in the snout tip was due to breeding behavior, the landmark points in cephalic, pectoral, and caudal region were associated with burrowing and mobility factors within the lateral line system in these fishes which thrive in high turbid habitat and low oxygen. Furthermore, it was found that the level of FA tends to increase in disturbed environs.

scholarly journals The evolution of female ornaments and weaponry: social selection, sexual selection and ecological competition

2012 ◽  
Vol 367 (1600) ◽  
pp. 2274-2293 ◽  
Author(s):  
Joseph A. Tobias ◽  
Robert Montgomerie ◽  
Bruce E. Lyon
Keyword(s):  
Sexual Selection ◽  
Social Selection ◽  
Ecological Resources ◽  
Female Ornaments ◽  
Wide Range ◽  
Sexual Selection Theory ◽  
Mating Opportunities ◽  
History Of ◽  
Mate Acquisition ◽  
Males And Females

Ornaments, weapons and aggressive behaviours may evolve in female animals by mate choice and intrasexual competition for mating opportunities—the standard forms of sexual selection in males. However, a growing body of evidence suggests that selection tends to operate in different ways in males and females, with female traits more often mediating competition for ecological resources, rather than mate acquisition. Two main solutions have been proposed to accommodate this disparity. One is to expand the concept of sexual selection to include all mechanisms related to fecundity; another is to adopt an alternative conceptual framework—the theory of social selection—in which sexual selection is one component of a more general form of selection resulting from all social interactions. In this study, we summarize the history of the debate about female ornaments and weapons, and discuss potential resolutions. We review the components of fitness driving ornamentation in a wide range of systems, and show that selection often falls outside the limits of traditional sexual selection theory, particularly in females. We conclude that the evolution of these traits in both sexes is best understood within the unifying framework of social selection.

scholarly journals Evolution of Sexual Dimorphism in Tube Blennies (Teleostei: Chaenopsidae)

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Philip A Hastings
Keyword(s):  
Sexual Dimorphism ◽  
Intermediate Level ◽  
Sexual Differences ◽  
Phylogenetic Hypothesis ◽  
Male Courtship ◽  
History Of Evolution ◽  
History Of ◽  
Time Of Breeding ◽  
Males And Females

Synopsis The study of sexual differences provides insights into selective factors operating on males and females, especially for clades exhibiting varied levels of dimorphism. Sexual differences in morphology and coloration (melanophores) were compiled for 66 of the 89 species of tube blennies (Blenniiformes, Chaenopsidae) from the systematic literature and examination of preserved specimens. Chaenopsids include essentially monomorphic species and those in which males and females differ in as many as 17 morphological and 14 coloration features. While the sexes of most species differ in coloration (at least at the time of breeding), they are morphologically similar in Acanthemblemaria, Hemiemblemaria, and Lucayablennius. While other genera exhibit an intermediate level of dimorphism, species of Coralliozetus, Cirriemblemaria, and Emblemaria are dramatically dimorphic. Character maps on a phylogenetic hypothesis indicate that this extreme level of dimorphism evolved independently in these genera. A complex history of evolution is implied by examination of jaw length with both increases and decreases in one or both sexes leading to either dimorphism or monomorphism. Several features related to shelter defense are monomorphic in species where both sexes inhabit shelters, but dimorphic where only males occupy shelters. Other dimorphic features increase the conspicuousness of male courtship and aggressive displays.

The Use of Geometric Morphometric Techniques to Identify Sexual Dimorphism in Gait

2016 ◽  
Vol 32 (5) ◽  
pp. 441-448 ◽  
Author(s):  
Claire Waldock ◽  
Nick Milne ◽  
Jonas Rubenson ◽  
Cyril Jon Donnelly
Keyword(s):  
Sexual Dimorphism ◽  
Principal Components Analysis ◽  
Principal Components ◽  
Body Shape ◽  
Stance Phase ◽  
Gait Cycle ◽  
Geometric Morphometric ◽  
Males And Females ◽  
Components Analysis ◽  
Shape And Size

This study attempts to apply geometric morphometric techniques for the analysis of 3D kinematic marker-based gait data. As a test, we attempted to identify sexual dimorphism during the stance phase of the gait cycle. Two techniques were used to try to identify differences in the way males and females walk without the results being affected by individual differences in body shape and size. Twenty-eight kinematic markers were placed on the torso and legs of 6 male and 8 female subjects, and the 3D time varying coordinates of the kinematic markers were recorded. The gait cycle trials were time-normalized to 61 frames representing the stance phase of gait, and the change in the shape of the configuration of kinematic markers was analyzed using principal components analysis to produce ‘gait signatures’ that characterize the kinematics of each individual. The variation in the gait signatures was analyzed with a further principal components analysis. These methods were able to detect significant sexual dimorphism even after the effects of sexual body shape and size differences were factored out. We discuss insights gained from performing this study which may be of value to others attempting to apply geometric morphometric methods to motion analysis.

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