scholarly journals The canine counts! Significance of a craniodental measure to describe sexual dimorphism in canids: Golden jackals (Canis aureus) and African wolves (Canis lupaster)

2021 ◽  
Author(s):  
Jennifer Hatlauf ◽  
Lisa Maria Krendl ◽  
Johannes Tintner ◽  
Paul Griesberger ◽  
Miklós Heltai ◽  
...  
Keyword(s):  
Logistic Regression ◽  
Sexual Dimorphism ◽  
Sexual Size Dimorphism ◽  
Conditional Inference ◽  
Canis Aureus ◽  
Size Dimorphism ◽  
Conditional Inference Trees ◽  
Dental Measurements ◽  
Widespread Phenomenon ◽  
The Difference

AbstractSexual dimorphism is a widespread phenomenon among mammals, including carnivorans. While sexual dimorphism in golden jackals (Canis aureus) has been analysed in the past, in the related and apparently convergent canid, the African wolf (Canis lupaster), it is poorly studied and showed to be relatively small. Previously, sexual size dimorphism (SSD) research in these species was mostly based on skull and body measurements. In our study, we also included dental measurements, namely the diameter of the canine. We used 11 measured sections of 104 adult specimens, comprising 61 golden jackal and 43 African wolf skulls. Data analyses were carried out through logistic regression and conditional inference trees (CIT). To compare the results of SSD to other species, sexual dimorphism indices (SDI) were calculated. Golden jackals and African wolves show significant sexual size dimorphism, both in cranial and dental size. The logistic regression revealed that the mesiodistal diameter of the upper canine is most effective in discerning the sexes. The difference in the calculated SDI of the canine diameter between the sexes amounted to 8.71 in golden jackals and 14.11 in African wolves, respectively—with regional diversity. Thus, the canine diameter is an important measure to investigate SSD as well as an easy tool to apply in the field.

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.

The evolution of sexual dimorphism in the lizard Anolis polylepis (Iguania): evidence from intraspecific variation in foraging behavior and diet

1996 ◽  
Vol 74 (7) ◽  
pp. 1238-1245 ◽  
Author(s):  
Gad Perry
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Feeding Behavior ◽  
Rain Forest ◽  
Sexual Size Dimorphism ◽  
Costa Rican ◽  
Agonistic Interactions ◽  
Size Dimorphism ◽  
Food Items ◽  
Competing Hypotheses

Two main explanations, intraspecific niche divergence and sexual selection, have been proposed to explain the origin of sexual size dimorphism. To test these competing hypotheses I studied the ecology, feeding behavior, and diet of the lizard Anolis polylepis in a Costa Rican rain forest. Male A. polylepis were significantly larger and heavier than females but ate smaller food items and had lower stomach volumes, despite possessing longer and wider heads. Males were more sedentary than females or juveniles, chose higher perches, and were more likely to be involved in agonistic interactions. Diets of males, females, and juveniles were also significantly different taxonomically. These data are consistent with the sexual selection origin theory but not with an ecological one. Thus, observed dietary differences probably evolved once dimorphism had been attained through sexual selection.

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.

Growth, maturity, and sexual dimorphism in the wood turtle, Clemmys insculpta

1990 ◽  
Vol 68 (4) ◽  
pp. 672-677 ◽  
Author(s):  
Jeffrey E. Lovich ◽  
Carl H. Ernst ◽  
John F. McBreen
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Carapace Length ◽  
Sexual Size Dimorphism ◽  
Von Bertalanffy ◽  
Size Dimorphism ◽  
Adult Females ◽  
Body Sizes ◽  
Von Bertalanffy Growth Model ◽  
Wood Turtle

Growth in the wood turtle (Clemmys insculpta) is described using the von Bertalanffy growth model and nonlinear regression. Growth in both sexes is similar until about 160 mm plastron length. Males grew at a faster rate after this size. Males appear to mature at a larger size and later age than females, although age-specific body size is highly variable. Sexual size dimorphism, in carapace length, is pronounced, with males attaining mean body sizes significantly larger (1.07–1.10 times) than those of adult females. Plastron length is an inappropriate measure of sexual size dimorphism because of the development of plastral concavity in males. Females tend to predominate in samples, possibly owing to differential maturity of the sexes. The direction of sexual size dimorphism may be maintained by intrasexual competition among males for access to females. Data for several adults captured at intervals of from 9 to 20 years support the concept of indeterminate growth.

scholarly journals Sex-specific microhabitat use is associated with sex-biased thermal physiology in Anolis lizards

2020 ◽  
pp. jeb.235697
Author(s):  
Michael L. Logan ◽  
Lauren K. Neel ◽  
Daniel J. Nicholson ◽  
Andrew J. Stokes ◽  
Christina L. Miller ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Habitat Use ◽  
Thermal Tolerance ◽  
Sexual Size Dimorphism ◽  
Microhabitat Use ◽  
Thermal Physiology ◽  
Male And Female ◽  
Size Dimorphism ◽  
Heterogeneous Habitats ◽  
Males And Females

If fitness optima for a given trait differ between males and females in a population, sexual dimorphism may evolve. Sex-biased trait variation may affect patterns of habitat use, and if the microhabitats used by each sex have dissimilar microclimates, this can drive sex-specific selection on thermal physiology. Nevertheless, tests of differences between the sexes in thermal physiology are uncommon, and studies linking these differences to microhabitat use or behavior are even rarer. We examined microhabitat use and thermal physiology in two ectothermic congeners that are ecologically similar but differ in their degree of sexual size dimorphism. Brown anoles (Anolis sagrei) exhibit male-biased sexual size dimorphism and live in thermally heterogeneous habitats, whereas slender anoles (Anolis apletophallus) are sexually monomorphic in body size and live in thermally homogeneous habitats. We hypothesized that differences in habitat use between the sexes would drive sexual divergence in thermal physiology in brown anoles, but not slender anoles, because male and female brown anoles may be exposed to divergent microclimates. We found that male and female brown anoles, but not slender anoles, used perches with different thermal characteristics and were sexually dimorphic in thermal tolerance traits. However, field-active body temperatures and behavior in a laboratory thermal arena did not differ between females and males in either species. Our results suggest that sexual dimorphism in thermal physiology can arise from phenotypic plasticity or sex-specific selection on traits that are linked to thermal tolerance, rather than from direct effects of thermal environments experienced by males and females.

Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach

Zootaxa ◽  
2016 ◽  
Vol 4196 (1) ◽  
pp. 120 ◽  
Author(s):  
DANIELA ELIANA SGANGA ◽  
LUCAS RAUL FERNANDEZ PIANA ◽  
LAURA SUSANA LÓPEZ GRECO
Keyword(s):  
Sexual Dimorphism ◽  
Geometric Morphometrics ◽  
Mating System ◽  
Abdominal Segment ◽  
Sexual Size Dimorphism ◽  
Centroid Size ◽  
Caridean Shrimp ◽  
Size Dimorphism ◽  
Adult Females ◽  
Ornamental Species

Neocaridina davidi is a caridean shrimp that has gained popularity in recent years as an ornamental species. Using geometric morphometrics, we investigated sexual dimorphism in carapace and second abdominal segment shape of N. davidi. Adult females displayed a more elongated carapace and a longer rostrum than males. However, male carapace shape was similar to that of juvenile females. The second abdominal pleura was more elongated and wider in adult females than in males. Significant differences were found in centroid size for the carapace and the second abdominal segment between sexes, which is consistent with sexual size dimorphism. These results support the hypothesis of a “pure search” mating system in N. davidi, where small males search actively for receptive females, and after insemination they continue searching. 

scholarly journals Sexual dimorphism of invasive knifefish (Chitala ornata) in Laguna de bay, Philippines

2020 ◽  
Vol 13 (1) ◽  
Keyword(s):  
Invasive Species ◽  
Sexual Dimorphism ◽  
Sexual Size Dimorphism ◽  
Management Strategies ◽  
Genital Papilla ◽  
Full Understanding ◽  
Morphometric Characters ◽  
Size Dimorphism ◽  
Size Dependent ◽  
Laguna De Bay

Chitala ornata (J.E. Gray) (Osteoglossiformes: Notopteridae) has since established abundant and nuisance populations in Laguna de Bay. A fundamental prerequisite for the development of management strategies for invasive species like C. ornata is a full understanding of its life history characteristics including sexual dimorphism. In the present study, we examined the sexual dimorphism of C. ornata. Sexes of C. ornata can be distinguished through the examination of its genital papilla wherein females show distinct morphological adaptions for effective oviposition on a spawning substrate. Comparison of means and multivariate analysis of several morphometric characters showed that sexual size dimorphism in C. ornata is female-biased which is mainly attributed to the disparity of resource expenditure between sexes for reproduction and size-dependent advantages of females in the production of more progenies with better chances of survival.

Measuring sexual size dimorphism in the yellow-pine chipmunk (Tamias amoenus)

2000 ◽  
Vol 78 (5) ◽  
pp. 728-733 ◽  
Author(s):  
Albrecht I Schulte-Hostedde ◽  
John S Millar
Keyword(s):  
Functional Analysis ◽  
Body Size ◽  
Sexual Size Dimorphism ◽  
Multivariate Methods ◽  
Size Dimorphism ◽  
Skeletal Tissue ◽  
Tamias Amoenus ◽  
Males And Females ◽  
Yellow Pine ◽  
The Difference

Body size was examined in the yellow-pine chipmunk (Tamias amoenus), which is reported to have female-biased sexual size dimorphism. Our objective was to determine if yellow-pine chipmunks from the Kananaskis Valley were dimorphic. Three methods were used. We compared body mass, 5 univariate components of body size, and multivariate centroids between males and females, and quantified measurement error. Females were significantly heavier (10-20%) and had a longer body (4%) and a longer (0.9%) and wider (2.2%) skull than male chipmunks, as well as being larger in overall size of skeletal tissue (structural body size). Multivariate methods such as discriminant functional analysis can robustly determine whether the sexes are significantly different in overall structural body size. However, univariate measures of body size provide an intuitively clear index of the magnitude of the difference in size of a particular character between the sexes.

scholarly journals Rensching cats and dogs: feeding ecology and fecundity trends explain variation in the allometry of sexual size dimorphism

2017 ◽  
Vol 4 (6) ◽  
pp. 170453 ◽  
Author(s):  
P. J. Johnson ◽  
M. J. Noonan ◽  
A. C. Kitchener ◽  
L. A. Harrington ◽  
C. Newman ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Body Mass ◽  
Feeding Ecology ◽  
Sexual Size Dimorphism ◽  
Allometric Scaling ◽  
Sexually Dimorphic ◽  
Size Dimorphism ◽  
Dietary Variation ◽  
The Difference ◽  
Familial Differences

The tendency for sexual size dimorphism (SSD) to increase with body mass in taxa where males are larger, and to decrease when females are larger, is known as Rensch's rule. In mammals, where the trend occurs, it is believed to be the result of a competitive advantage for larger males, while female mass is constrained by the energetics of reproduction. Here, we examine the allometry of SSD within the Felidae and Canidae, demonstrating distinctly different patterns: in felids, there is positive allometric scaling, while there is no trend in canids. We hypothesize that feeding ecology, via its effect on female spacing patterns, is responsible for the difference; larger male mass may be advantageous only where females are dispersed such that males can defend access to them. This is supported by the observation that felids are predominately solitary, and all are obligate carnivores. Similarly, carnivorous canids are more sexually dimorphic than insectivores and omnivores, but carnivory does not contribute to a Rensch effect as dietary variation occurs across the mass spectrum. The observed inter-familial differences are also consistent with reduced constraints on female mass in the canids, where litter size increases with body mass, versus no observable allometry in the felids.

scholarly journals Life history of a basal bird: morphometrics of the Early Cretaceous Confuciusornis

2008 ◽  
Vol 4 (6) ◽  
pp. 719-723 ◽  
Author(s):  
Luis M Chiappe ◽  
Jesús Marugán-Lobón ◽  
Shu'an Ji ◽  
Zhonghe Zhou
Keyword(s):  
Life History ◽  
Sexual Dimorphism ◽  
Exponential Growth ◽  
Growth Stage ◽  
Sexual Size Dimorphism ◽  
Growth Patterns ◽  
Morphometric Study ◽  
Size Dimorphism ◽  
Caudal Vertebrae ◽  
History Of

Confuciusornis sanctus stands out among the remarkable diversity of Mesozoic birds recently unearthed from China. Not only is this primitive beaked pygostylian (birds with abbreviated caudal vertebrae fused into a pygostyle) much more abundant than other avian taxa of this age but differences in plumage between specimens—some having a pair of long stiff tail feathers—have been interpreted as evidence for the earliest example of sexual dimorphism in birds. We report the results of a multivariate morphometric study involving measurements of more than 100 skeletons of C. sanctus . Our analyses do not show any correlation between size distribution and the presence or absence of blade-like rectrices (tail feathers), thus implying, that if these feathers are sexual characters, they are not correlated with sexual size dimorphism. Our results also provide insights into the taxonomy and life history of confuciusornithids, suggesting that these birds may have retained ancestral dinosaurian growth patterns characterized by a midlife exponential growth stage.

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