scholarly journals The evolution of derived monomorphism from sexual dimorphism: A case study on salamanders

2020 ◽  
Author(s):  
Nancy L Staub
Keyword(s):  
Sexual Dimorphism ◽  
The Other ◽  
Head Width ◽  
Social Selection ◽  
Sexually Dimorphic ◽  
Ecological Significance ◽  
Selective Forces ◽  
Males And Females ◽  
Shed Light

Abstract While sexual dimorphism has long received special attention from biologists, derived monomorphism, the condition in which both males and females express similar derived features, has been less well studied. Historically, the appearance of “male-like” features in females has been explained by the genetic correlation between the sexes. Recent work emphasizes the importance of studying the independent selective forces on both females and males to understand sexual dimorphism. Sexual dimorphism and derived monomorphism in the genus Aneides are examined in light of predictions of social selection. Aneides hardii shows the greatest degree of sexual dimorphism in snout-vent length and head width, with the other species of Aneides less sexually dimorphic. This reduced dimorphism, however, is not a return to an ancestral monomorphic state, but rather exemplifies derived monomorphism because females express traits that were limited in expression to males of ancestral species. Instead of calling these “male-typical” traits in females, I suggest the term “derived monomorphic” traits, as these traits are typical in these females and “derived monomorphic” can apply to both sexes. Increased attention to studying the patterns and ecological significance of derived monomorphism will shed light on the underlying selective forces, including sexual selection, on both females and males.

scholarly journals Digit ratio in three species of tropidurid lizards

Herpetozoa ◽  
2021 ◽  
Vol 34 ◽  
pp. 67-70
Author(s):  
Kelton Gonçalves Miranda ◽  
Marcella Junqueira Goulart ◽  
Conrado Barbosa Galdino
Keyword(s):  
Sexual Dimorphism ◽  
Sex Hormones ◽  
Digit Ratio ◽  
Sexually Dimorphic ◽  
Lizard Species ◽  
Finger Length ◽  
Digit Ratios ◽  
Selective Forces ◽  
Males And Females ◽  
Interpopulation Variation

Proportions between pairs of digits are linked to fitness in tetrapods and they can be influenced by sex hormones through individuals’ ontogenies. Therefore, in many species, the proportions amongst finger length ratios (referred as digit ratio, i.e. 2D second and 4D fourth digits) can differ between males and females. We investigated whether the three most commonly used forelimb digit ratios are sexually dimorphic in three tropidurid species. In one of the three lizard species, Eurolophosaurus nanuzae, males and females differ for only 2D:4D digit ratio. Otherwise, our results on the studied Tropidurus species conform to previous studies showing no differences in digit ratios between males and females. Hence, it might be the case of local selective forces shaping interpopulation variation in the expression of sexual dimorphism for digit ratio.

scholarly journals Body size, female reproduction and sexual dimorphism in the lizard Ameiva ameiva (Teiidae) in a restinga of southeastern Brazil

2008 ◽  
Vol 25 (2) ◽  
pp. 370-372 ◽  
Author(s):  
Carlos Frederico Duarte Rocha
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Clutch Size ◽  
Reproductive Period ◽  
Southeastern Brazil ◽  
Head Width ◽  
Sexually Dimorphic ◽  
Female Reproduction ◽  
Female Body Size ◽  
Reproductive Body

In this study 57 specimens of the lizard Ameiva ameiva (Linnaeus, 1758) collected in the restinga at Barra de Maricá, in the state of Rio de Janeiro, southeastern Brazil, were analyzed to investigate size relations and reproduction (in females) and sexual dimorphism of this population. We answered the following questions: 1) what is the minimum reproductive body size in females? 2) what is the average clutch size and 3) how is clutch size related to body size? 4) Are body and head sizes sexually dimorphic? Mean clutch size was 6.7 ± 2.1 eggs and was positively correlated with female body size. Sexual dimorphism favoring males was found: adult mean snout-vent length was great in males (124.2 ± 17.8 mm) than females (96.5 ± 23.1 mm SVL), and males were larger with respect to head width and length, and body mass. Thus, despite the marked seasonality at Barra de Maricá, A. ameiva has an extended reproductive period. Also, intrasexual selection may have acted on females to produce larger clutches, and on males, favoring larger males.

scholarly journals Sexual dimorphism in species of Schistura (Teleostei: Nemacheilidae) from the Mae Khlong basin and peninsular Thailand

Zootaxa ◽  
2012 ◽  
Vol 3586 (1) ◽  
pp. 353 ◽  
Author(s):  
RUNGTHIP PLONGSESTHEE ◽  
F. WILLIAM H. BEAMISH ◽  
LAWRENCE M. PAGE
Keyword(s):  
Sexual Dimorphism ◽  
Environmental Factors ◽  
The Other ◽  
Sexually Dimorphic ◽  
Morphometric Characteristics ◽  
Pectoral Fin ◽  
Caudal Fin

Sexually dimorphic characteristics are described for four species of Schistura from the Mae Khlong basin and peninsularThailand. Males of S. mahnerti have a suborbital flap and rows of unculi on the upper surfaces of the pectoral-fin rays.Females of S. mahnerti have a suborbital groove. None of the morphological measurements differ significantly betweenmales and females of S. mahnerti. In the other three species, S. aurantiaca, S. cf. aurantiaca, and S. sexcauda, all indi-viduals lack the flap or groove, but most males have a conspicuous black botch on the procurrent rays of the upper lobeof the caudal fin, a feature absent in most females. Some morphometric characteristics vary between sexes of these spe-cies. Sexually dimorphic traits presumably have a function related to reproduction; however, little is known about reproduction in Schistura, and variation in morphology in relation to habitat or other environmental factors has not been studied.

Studying how to build peace and deal with stereotypes and discrimination in a period of terror and despair: A case study from Israel

2017 ◽  
Vol 12 (1) ◽  
pp. 64-75
Author(s):  
Zehavit Gross
Keyword(s):  
Middle East ◽  
Peace Education ◽  
Power Structure ◽  
Coping Mechanisms ◽  
Theory And Practice ◽  
The Other ◽  
Complex Emotions ◽  
The One ◽  
Shed Light

This paper aims to explore how Palestinian Arab and Jewish university students in Israel, attending a course on conflict resolution, deal with their stereotypical views of the Other and their prejudices, as well as their complex emotions of fear, hate, anxiety, and love during a period of tension and violence. On the one hand, they have a natural desire for professional partnership and friendship with their fellow students. On the other hand, they are attending this class in a Jewish university, in the heart of the Middle East, where acts of terrorism occur almost daily. This violence changes the power structure and the dynamics of their mutual relationships. Through an analysis of a specific case study the paper aims to shed light on how bridging theory and practice can generate a better understanding of complex situations, enabling reflection and developing signposts to improve coping mechanisms within peace education frameworks in times of terror.

Interpopulational variation in sexual dimorphism, reproductive output, and parasitism of Liophis miliaris (Colubridae) in the Atlantic forest of Brazil

2006 ◽  
Vol 27 (1) ◽  
pp. 37-46 ◽  
Author(s):  
Lígia Pizzatto ◽  
Otavio Marques
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Atlantic Forest ◽  
Reproductive Output ◽  
Sexual Size Dimorphism ◽  
The Other ◽  
Female Body Size ◽  
Body Sizes ◽  
Northern Atlantic ◽  
Males And Females

AbstractSexual maturity, sexual dimorphism, reproductive output, and parasitism of the colubrid snake Liophis miliaris were compared among populations inhabiting four regions of Brazil: (1) northern coastal Atlantic forest, (2) southern coastal Atlantic forest, (3) northern inland Atlantic forest (4) southern inland Atlantic forest. Females delayed maturity and attained larger body sizes than males in all regions. Males and females from northern Atlantic forest were smaller and attained maturity with a smaller body size than males of other regions. The sexual size dimorphism index ranged from 0.19 to 0.23 and was lowest in the northern Atlantic forest. There was no sexual dimorphism in head length in any of the populations studied. Clutch size was similar in all populations and increased with maternal body size. The reproductive frequency was lower in the northern coastal Atlantic forest and in contrast to the other regions, tended to increase with female body size. The nematoda Ophidiascaris sp. and cystacanths of Oligacanthorynchus spira (Acanthocephala) occurred equally in both sexes. Fewer snakes from the northern coastal Atlantic forest were infested by parasites compared to the other regions and parasitism apparently did not influence reproduction.

scholarly journals First Case of Dual Size Asymmetry in an Identical Arthropod Organ: Different Asymmetries of the Combative (Sexual) and Cutting (Non-Sexual) Parts of Mandibles in the Horned Stored-Product Beetle Gnatocerus cornutus (Fabricius, 1798)

Insects ◽  
2018 ◽  
Vol 9 (4) ◽  
pp. 151 ◽  
Author(s):  
Tomas Vendl ◽  
Vaclav Stejskal ◽  
Radek Aulicky
Keyword(s):  
Sexual Dimorphism ◽  
Regulatory Mechanisms ◽  
Directional Asymmetry ◽  
Sexually Dimorphic ◽  
First Case ◽  
Males And Females ◽  
Long Life ◽  
High Degree ◽  
Size Asymmetry ◽  
Single Organ

Although it is known that separate insect body structures may be asymmetrical within one species, the different functional asymmetries within a single organ as a result of differential selective regimes have not been described. Based on microscopic measurements and SEM photography, we examined the size, shape and asymmetry of the mandibular structures of males and females of the sexually dimorphic broad-horned flour beetle, Gnatocerus cornutus (Tenebrionidae, Coleoptera). It was found that sexual dimorphism only manifests in certain outgrowth parts (horns) of male mandibles, while the remaining cutting parts of the mandibles hold identical morphologies for both sexes. A more interesting finding—since this is the first published case of dual functionally selected asymmetry in an identical arthropod organ—was that the cutting part of the male mandible exhibited directional asymmetry, whereas the outgrowth horn part of the mandible showed a high degree of symmetry. Moreover, there was no relationship between the size and asymmetry of horns. The results indicate different regulatory mechanisms of sexually selected combative horns and the food-functional, more conservative (constrained by hard food and adult long life) cutting parts of mandibles.

Diet differences between males and females in sexually dimorphic ungulates: a case study on Siberian ibex

2020 ◽  
Vol 66 (4) ◽  
Author(s):  
Lei Han ◽  
David Blank ◽  
Muyang Wang ◽  
António Alves da Silva ◽  
Weikang Yang ◽  
...  
Keyword(s):  
Sexually Dimorphic ◽  
Males And Females

scholarly journals Differences in Pelvic Fin Length Represent Sexual Dimorphism in Utah Chub (Gila atraria)

2014 ◽  
Vol 7 (1) ◽  
pp. 42-45 ◽  
Author(s):  
Mark C. Belk ◽  
Scott Bird ◽  
Mehmet Cemal Oguz ◽  
Jerald B. Johnson
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Cyprinid Fish ◽  
Sexually Dimorphic ◽  
Adaptive Function ◽  
Males And Females ◽  
The Difference ◽  
Sexually Mature ◽  
Fin Length ◽  
Pelvic Fin

The cyprinid fish Gila atraria Girard (Utah chub) is generally considered a sexually monomorphic species. However, prior observations revealed variation in pelvic fin length within populations that appears sexually dimorphic. We measured the relative pelvic fin length of 419 sexually mature Utah chub from 8 different locations to determine the magnitude and generality of this apparent dimorphism. Pelvic fin length in G. atraria differs between sexes by about 10% on average; males have longer pelvic fins than females. The dimorphism is general across all locations, but it is not related to body size. Magnitude of the dimorphism varies by predation environment – the difference between males and females is slightly greater in low predation environments. We find no evidence for an adaptive function for this dimorphism; however, it does provide an efficient mechanism for determining sex without dissection.

scholarly journals Hydraulic constraints of reproduction do not explain sexual dimorphism in the genus Leucadendron (Proteaceae)

2017 ◽  
Author(s):  
Adam B. Roddy ◽  
Justin van Blerk ◽  
Jeremy J. Midgley ◽  
Adam G. West
Keyword(s):  
Sexual Dimorphism ◽  
Fire Frequency ◽  
Sexually Dimorphic ◽  
Hydraulic Efficiency ◽  
Costs Of Reproduction ◽  
Dioecious Species ◽  
Shoot Architecture ◽  
Males And Females ◽  
And Function ◽  
In Fire

AbstractBecause of the importance of reproduction in plant life history, the physiological costs of reproduction often influence vegetative structure and function. In dioecious species, these effects can be quite obvious, as different costs of male and female reproductive functions are entirely separated among different individuals in a population. In fire-prone ecosystems, in which recruitment is driven by fire frequency, many plants will maintain their seeds in the canopy, only to be released after a fire. The dioecious genus Leucadendron is a notable case of this, as females can maintain their seed cones for years, and, even more interestingly, species in the genus differ substantially in the degree to which males and females are sexually dimorphic. A recent study (Harris and Pannell 2010) argued that the hydraulic costs of maintaining seed cones for many years would effect the degree of sexual dimorphism among species. However, this assumed that shoot hydraulic architecture would be related to traits exhibiting sexual dimorphism. Here we explicitly test this hypothesis on two Leucadendron species. We found (1) that metrics of branch ramification used in the previous study to characterize dimorphism do not conform to known scaling relationships and (2) that sexual dimorphism in shoot architecture has no effect on hydraulic efficiency. Both of these results seriously question the pattern described by Harris and Pannell (2010) and suggest that the hydraulic costs of prolonged seed retention in Leucadendron do not significantly affect branch architecture.

scholarly journals A revision of the genus Teleopsis Rondani (Diptera, Diopsidae) in Sri Lanka with descriptions of two new species and a review of the other stalk-eyed flies from the island

ZooKeys ◽  
2020 ◽  
Vol 946 ◽  
pp. 113-151
Author(s):  
Hans R. Feijen ◽  
Cobi Feijen
Keyword(s):  
New Species ◽  
Sexual Dimorphism ◽  
Sri Lanka ◽  
Species Group ◽  
The Other ◽  
Sister Species ◽  
Sri Lankan ◽  
Sexually Dimorphic ◽  
Two New Species

The literature on Sri Lankan Diopsidae is reviewed. Eight Diopsidae are now known to occur in Sri Lanka, five species in the genus Teleopsis and one species each in the genera Sphyracephala, Diopsis, and Cyrtodiopsis. The presence of Cyrtodiopsis requires confirmation to exclude the possibility of mislabelling. All five Teleopsis species are endemic, as are the Diopsis species and probably the Cyrtodiopsis species. Only Sphyracephala bipunctipennis Senior-White has a larger distribution as it also occurs in India. A key is presented for the Diopsidae of Sri Lanka. Three Teleopsis species were already known to occur in Sri Lanka: T. ferruginea Röder, T. krombeini Feijen and T. maculata Feijen. These species form the T. ferruginea species group. Two new species are now described for this group: Teleopsis neglectasp. nov. and Teleopsis sororasp. nov.Teleopsis ferruginea is redescribed, as an earlier redescription turned out to be based on a series of specimens of its sister species T. sororasp. nov. The other three Diopsidae of Sri Lanka are listed and illustrated. Allometric aspects of the five Teleopsis species are discussed. Three Teleopsis species are sexually dimorphic with regard to eye span, while two species are monomorphic. It is assumed that sexual dimorphism developed independently in the T. ferruginea species group. This brings the number of known cases of independent development of sexual dimorphism in the Diopsidae to ten.

Sign in / Sign up

Export Citation Format

Share Document