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.

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.

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. 

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.

scholarly journals Morphometric characteristics of crayfish, Cherax gherardiae, from Maybrat, West Papua, Indonesia

2018 ◽  
Vol 26 (4) ◽  
pp. 223-230
Author(s):  
Yulianus Sedik ◽  
Dominggus Rumahlatu ◽  
Bambang Irawan ◽  
Agoes Soegianto
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Carapace Length ◽  
Condition Factor ◽  
Carapace Width ◽  
Allometric Growth ◽  
Morphometric Characteristics ◽  
Significant Difference ◽  
West Papua ◽  
Males And Females

Abstract The objectives of this study were to determine the length-weight relationships (LWRs), chelae length (ChL)-width (ChW) relationships, carapace length (CL)-width (CW) relationships, sexual dimorphism, and condition factor (K) of Cherax gherardiae from Maybrat, West Papua Indonesia. The sex ratio of C. gherardiae was found to be 1.04:1. The LWRs for males, females, and all individuals were W = 0.225L1.96, W = 0.181L2.02, and W = 0.187L2.03, respectively. Males and females exhibited negative allometric growth (b<3). There was no significant difference in lengths between males and females; however, the weight of males was greater than that of females. The K values for males, females, and all individuals were 3.17, 3.09, and 3.13, respectively. The ChL of the crayfish ranged from 1.0 to 7.5 cm, and the ChW ranged from 0.4 to 2.5 cm. The CL of crayfish ranged from 1.6 to 6.0 cm, and the CW ranged from 0.6 to 4.1 cm. Males had longer chelae and carapaces than did females. There was no significant difference in chelae width or carapace width between males and females. The ChL-ChW relationships for males, females, and all individuals were ChW = 0.312ChL + 0.260, ChW = 0.397ChL - 0.050, and ChW = 0.345ChL + 0.119, respectively. The CL-CW relationships for males, females, and all individuals were CW = 0.750CL-0.955, CW = 0.526CL - 0.178, and CW = 0.635CL-0.543, respectively.

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 Allometric shell growth in infaunal burrowing bivalves: examples of the archiheterodonts Claibornicardia paleopatagonica (Ihering, 1903) and Crassatella kokeni Ihering, 1899

2018 ◽  
Author(s):  
Damián Eduardo Perez ◽  
María Belén Santelli
Keyword(s):  
Shell Growth ◽  
Late Oligocene ◽  
Allometric Growth ◽  
Ontogenetic Changes ◽  
Elliptic Fourier Analysis ◽  
Geometric Morphometric ◽  
Positive Allometry ◽  
Ontogenetic Trajectories ◽  
Early Paleocene ◽  
Ontogenetic Allometry

We present two cases of study of ontogenetic allometry in outlines of bivalves using longitudinal data, a rarity among fossils, based on the preserved post-larval record of shells. The examples are two infaunal burrowing bivalves of the southern South America, Claibornicardia paleopatagonica (Archiheterodonta: Carditidae) (early Paleocene) and Crassatella kokeni (Archiheterodonta: Crassatellidae) (late Oligocene–late Miocene). Outline analyses were conducted using a geometric morphometric approach (Elliptic Fourier Analysis), obtaining successive outlines from shells’ growth lines, which were used to reconstruct ontogenetic trajectories. In both taxa, ontogenetic changes are characterized by the presence of positive allometry in the extension of posterior end, resulting in elongated adult shells. This particular allometric growth is known in others infaunal burrowing bivalves (Claibornicardia alticostata and some Spissatella species) and the resulting adult morphology is present in representatives of several groups (e.g. Carditidae, Crassatellidae, Veneridae, Trigoniidae). Taxonomic, ecological and evolutionary implications of this allometric growth pattern are discussed.

Sex, Difference, and Desire

2020 ◽  
pp. 177-232
Author(s):  
Ben Bradley
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Evolutionary Psychology ◽  
Evolutionary Biology ◽  
Racial Politics ◽  
Sexual Agency ◽  
Human History ◽  
Male And Female ◽  
Males And Females ◽  
Descent Of Man

The parts of The Descent of Man dealing with sexual desire and difference have sparked more controversy and misrepresentation than any of Darwin’s other publications. Crucial to Descent’s arguments is the derivation of sexual selection from the dramas of display and desire observed among animals. The book describes four plotlines structuring the theatre of sexual agency in animals, each having different implications for the roles played by males and females. When Descent extends these plotlines to humans, they alter and modulate into an even more varied array of scenarios, again, each with its own distinctive roles for women and men. A mirror-dynamic figures centrally in both animal and human sex—the need to recognize or predict others’ desires so as to act in a way to arouse them. However, several nodes of concern disturb Darwin’s presentation of human sex: tensions between his three epochs of human history; Victorian racial politics; Victorian ideas about male and female superiority; and the imperatives of propriety. The chapter illustrates some of the muddles that result from these concerns, including: confirmation bias; aporia in argument; grammatical kinks; and overlap between sexual and natural selection. Finally, the chapter instances some of the main resonances in more recent scholarship of Darwin’s discussion of sex, instancing debates in feminism, about anthropomorphism, in evolutionary biology, and evolutionary psychology.

scholarly journals Allometric shell growth in infaunal burrowing bivalves: examples of the archiheterodonts Claibornicardia paleopatagonica (Ihering, 1903) and Crassatella kokeni Ihering, 1899

2018 ◽  
Author(s):  
Damián Eduardo Perez ◽  
María Belén Santelli
Keyword(s):  
Shell Growth ◽  
Late Oligocene ◽  
Allometric Growth ◽  
Ontogenetic Changes ◽  
Elliptic Fourier Analysis ◽  
Geometric Morphometric ◽  
Positive Allometry ◽  
Ontogenetic Trajectories ◽  
Early Paleocene ◽  
Ontogenetic Allometry

We present two cases of study of ontogenetic allometry in outlines of bivalves using longitudinal data, a rarity among fossils, based on the preserved post-larval record of shells. The examples are two infaunal burrowing bivalves of the southern South America, Claibornicardia paleopatagonica (Archiheterodonta: Carditidae) (early Paleocene) and Crassatella kokeni (Archiheterodonta: Crassatellidae) (late Oligocene–late Miocene). Outline analyses were conducted using a geometric morphometric approach (Elliptic Fourier Analysis), obtaining successive outlines from shells’ growth lines, which were used to reconstruct ontogenetic trajectories. In both taxa, ontogenetic changes are characterized by the presence of positive allometry in the extension of posterior end, resulting in elongated adult shells. This particular allometric growth is known in others infaunal burrowing bivalves (Claibornicardia alticostata and some Spissatella species) and the resulting adult morphology is present in representatives of several groups (e.g. Carditidae, Crassatellidae, Veneridae, Trigoniidae). Taxonomic, ecological and evolutionary implications of this allometric growth pattern are discussed.

Mating Strategy and Reproductive Success in the Teiid Lizard, Ameiva Plei

Behaviour ◽  
1995 ◽  
Vol 132 (7-8) ◽  
pp. 529-557 ◽  
Author(s):  
Ellen J. Censky
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Reproductive Success ◽  
Sexual Size Dimorphism ◽  
Size Dimorphism ◽  
Large Size ◽  
Trade Offs ◽  
Males And Females ◽  
Current Selection ◽  
Growth And Reproduction

AbstractCurrent selection on sexual size dimorphism was studied in a widely foraging non-territorial lizard, Ameiva plei. Males were significantly larger than females. Large males won intrasexual agonistic encounters and guarded females during their entire receptive period (1-4 days). Guarding males spent significantly less time foraging than males who were alone. Only males that guarded females were observed to mate. Mating success was highly skewed with only six of 21 mature males in the study site observed mating. All six males who mated were 141 mm SVL (males mature at 62 mm SVL). The four largest males obtained 84% of all observed matings and were estimated to have fertilized 88% of the eggs. Sexual selection appears to favor large size in males due to competition among males to guard females. Large females on Anguilla also had higher reproductive success bccause SVL was positively correlated with clutch size and number of clutches in a season. It appears that natural selection has favored different trade-offs between growth and reproduction in males and females.

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