Is body shape of mangrove-dwelling monitor lizards (Varanus indicus; Varanidae) sexually dimorphic?

2011 ◽  
Vol 32 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Jan Hnízdo ◽  
Veronika Cikánová ◽  
Olga Šimková ◽  
Daniel Frynta ◽  
Petr Velenský ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Body Shape ◽  
Sexually Dimorphic ◽  
Evolutionary Explanation ◽  
Body Measurements ◽  
Male And Female ◽  
Fecundity Selection ◽  
Selective Forces ◽  
Monitor Lizards

AbstractIn monitor lizards, males are typically larger than conspecific females, but body shape is usually quite similar in both sexes. This not only represents a puzzle worthy of evolutionary explanation, but also makes field sex determination of monitor lizards difficult. We asked whether subtle differences in body shape follow the same pattern as in other sexually dimorphic lizard taxa and thus can be explained by the same selective forces. We tested the hypotheses that (1) females have a longer abdomen due to fecundity selection and (2) males possess bigger heads due to intrasexual selection. We also hypothesised that (3) male monitors show a wider chests and longer upper fore-limbs to win male-male wrestling matches. We monitored ontogeny in 35 mangrove-dwelling monitors (Varanus indicus). Seventeen body measurements were taken every three months up to the age of 24-34 months. Sex was determined by an ultrasonographic imaging. We employed multiple approaches to remove the effect of size and used both confirmation and exploratory statistics. The results revealed that sexual differences in body shape were small and emerged after maturity. Females have a relatively longer abdomen while males wider chest and longer upper fore-limbs. Thus, the differences in body shape between male and female varanid lizards may be attributed to both fecundity and sexual selection.

scholarly journals Objective Assessment of Sexual Plumage Dichromatism in the Picui Dove

The Condor ◽  
2002 ◽  
Vol 104 (2) ◽  
pp. 248-254
Author(s):  
Bettina Mahler ◽  
Bart Kempenaers
Keyword(s):  
Sexual Selection ◽  
Objective Assessment ◽  
Spectral Shape ◽  
Sexual Dichromatism ◽  
Sexually Dimorphic ◽  
Near Ultraviolet ◽  
Body Regions ◽  
Color Differences ◽  
Objective Determination

Abstract The Picui Dove (Columbina picui) has been considered sexually monochromatic, with females slightly duller than males. This assessment has been based on colors perceived by the human eye. However, birds possess an additional, near-ultraviolet photoreceptor and thus are sensitive to wavelengths humans are not. Measurements of reflectance using spectroradiometry permit an objective determination of the coloration of the birds' plumage and of color differences between the sexes. We here show that the plumage coloration of the Picui Dove is clearly sexually dimorphic. Males were overall brighter than females, and several body regions showed a significant sex difference in spectral shape. These results imply that studies of sexual selection in this and related species should measure sexual dichromatism objectively, and should not rely on human color perception. Determinación Objetiva del Dicromatismo Sexual del Plumaje en Columbina picui Resumen. La especie Columbina picui ha sido considerada sexualmente monocromática, siendo las hembras levemente más opacas que los machos. Esta conclusión ha sido basada en la percepción humana del color. Sin embargo, las aves poseen un fotorreceptor adicional en el ultravioleta cercano y son, por lo tanto, sensibles a longitudes de onda que los humanos no perciben. La medición de la reflectancia por medio de la técnica de espectrofotometría permite una determinación objetiva del color del plumaje y de las diferencias de color entre los sexos. En este estudio mostramos que C. picui es claramente sexualmente dicromática, siendo los machos más brillantes que las hembras y presentando en algunas regiones del cuerpo diferencias en el espectro de las longitudes de onda reflejadas. Estos resultados demuestran que la determinación de dicromatismo sexual no debería basarse en la percepción humana y tiene, además, implicancias para los estudios de selección sexual en esta especie y especies relacionadas.

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

Evolution ◽  
2002 ◽  
Vol 56 (7) ◽  
pp. 1538 ◽  
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 in hermaphrodites, sperm and broadcast spawners, plants and fungi

2016 ◽  
Vol 371 (1706) ◽  
pp. 20150541 ◽  
Author(s):  
Madeleine Beekman ◽  
Bart Nieuwenhuis ◽  
Daniel Ortiz-Barrientos ◽  
Jonathan P. Evans
Keyword(s):  
Sexual Selection ◽  
Direct Contact ◽  
Sexually Dimorphic ◽  
Reproductive Competition ◽  
Mate Quality ◽  
Male And Female ◽  
Evolutionary Force ◽  
Simultaneous Hermaphrodites ◽  
Relative Quality

Darwin was the first to recognize that sexual selection is a strong evolutionary force. Exaggerated traits allow same-sex individuals to compete over access to mates and provide a mechanism by which mates are selected. It is relatively easy to appreciate how inter- and intrasexual selection work in organisms with the sensory capabilities to perceive physical or behavioural traits that signal mate quality or mate compatibility, and to assess the relative quality of competitors. It is therefore not surprising that most studies of sexual selection have focused on animals with separate sexes and obvious adaptations that function in the context of reproductive competition. Yet, many sexual organisms are both male and female at the same time, often lack sexual dimorphism and never come into direct contact at mating. How does sexual selection act in such species, and what can we learn from them? Here, we address these questions by exploring the potential for sexual selection in simultaneous hermaphrodites, sperm- and broadcast spawners, plants and fungi. Our review reveals a range of mechanisms of sexual selection, operating primarily after gametes have been released, which are common in many of these groups and also quite possibly in more familiar (internally fertilizing and sexually dimorphic) organisms. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.

Study of Dosage Compensation in Drosophila

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1167-1181
Author(s):  
Pei-Wen Chiang ◽  
David M Kurnit
Keyword(s):  
Gene Expression ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Qpcr Assay ◽  
Male And Female ◽  
Multiple Genes ◽  
Chromosomal Changes ◽  
Regulatory Effects

Abstract Using a sensitive RT-QPCR assay, we analyzed the regulatory effects of sex and different dosage compensation mutations in Drosophila. To validate the assay, we showed that regulation for several genes indeed varied with the number of functional copies of that gene. We then confirmed that dosage compensation occurred for most genes we examined in male and female flies. Finally, we examined the effects on regulation of several genes in the MSL pathway, presumed to be involved in sex-dependent determination of regulation. Rather than seeing global alterations of either X chromosomal or autosomal genes, regulation of genes on either the X chromosome or the autosomes could be elevated, depressed, or unaltered between sexes in unpredictable ways for the various MSL mutations. Relative dosage for a given gene between the sexes could vary at different developmental times. Autosomal genes often showed deranged regulatory levels, indicating they were in pathways perturbed by X chromosomal changes. As exemplified by the BR-C locus and its dependent Sgs genes, multiple genes in a given pathway could exhibit coordinate regulatory modulation. The variegated pattern shown for expression of both X chromosomal and autosomal loci underscores the complexity of gene expression so that the phenotype of MSL mutations does not reflect only simple perturbations of genes on the X chromosome.

scholarly journals Possibility of Human Gender Recognition Using Raman Spectra of Teeth

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3983
Author(s):  
Ozren Gamulin ◽  
Marko Škrabić ◽  
Kristina Serec ◽  
Matej Par ◽  
Marija Baković ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Principal Component ◽  
Support Vector ◽  
Gender Recognition ◽  
Proof Of Concept ◽  
Male And Female ◽  
Tooth Type ◽  
Tooth Apex ◽  
The Difference

Gender determination of the human remains can be very challenging, especially in the case of incomplete ones. Herein, we report a proof-of-concept experiment where the possibility of gender recognition using Raman spectroscopy of teeth is investigated. Raman spectra were recorded from male and female molars and premolars on two distinct sites, tooth apex and anatomical neck. Recorded spectra were sorted into suitable datasets and initially analyzed with principal component analysis, which showed a distinction between spectra of male and female teeth. Then, reduced datasets with scores of the first 20 principal components were formed and two classification algorithms, support vector machine and artificial neural networks, were applied to form classification models for gender recognition. The obtained results showed that gender recognition with Raman spectra of teeth is possible but strongly depends both on the tooth type and spectrum recording site. The difference in classification accuracy between different tooth types and recording sites are discussed in terms of the molecular structure difference caused by the influence of masticatory loading or gender-dependent life events.

A Cuticle Collagen Encoded by the lon-3 Gene May Be a Target of TGF-β Signaling in Determining Caenorhabditis elegans Body Shape

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1631-1639
Author(s):  
Yo Suzuki ◽  
Gail A Morris ◽  
Min Han ◽  
William B Wood
Keyword(s):  
Caenorhabditis Elegans ◽  
Body Shape ◽  
Small Body ◽  
Dependent Manner ◽  
Loss Of Function ◽  
Cellular Mechanisms ◽  
C Elegans ◽  
Gene Expression Analyses ◽  
Dose Dependent

Abstract The signaling pathway initiated by the TGF-β family member DBL-1 in Caenorhabditis elegans controls body shape in a dose-dependent manner. Loss-of-function (lf) mutations in the dbl-1 gene cause a short, small body (Sma phenotype), whereas overexpression of dbl-1 causes a long body (Lon phenotype). To understand the cellular mechanisms underlying these phenotypes, we have isolated suppressors of the Sma phenotype resulting from a dbl-1(lf) mutation. Two of these suppressors are mutations in the lon-3 gene, of which four additional alleles are known. We show that lon-3 encodes a collagen that is a component of the C. elegans cuticle. Genetic and reporter-gene expression analyses suggest that lon-3 is involved in determination of body shape and is post-transcriptionally regulated by the dbl-1 pathway. These results support the possibility that TGF-β signaling controls C. elegans body shape by regulating cuticle composition.

scholarly journals Effect of Self-reported Height on Occupational Rank Among Police Officers: Especially for Women it Pays to be Tall

2021 ◽  
Author(s):  
Abraham P. Buunk ◽  
Gert Stulp ◽  
Wilmar B. Schaufeli
Keyword(s):  
Sexual Selection ◽  
The Netherlands ◽  
Police Officers ◽  
Educational Level ◽  
Leadership Positions ◽  
Male And Female ◽  
Similar Percentage ◽  
Average Population ◽  
Female Police Officers

AbstractThis study among 725 male and 247 female police officers from The Netherlands examined the association between self-reported height and occupational rank from the perspective of sexual selection. Male and female police officers were taller than the average population. A larger percentage of women than of men was found in the lowest ranks, but in the leadership positions, there was a similar percentage of women as of men. Overall, but especially among women, height was linearly associated with occupational rank: the taller one was, the higher one’s rank. These effects were independent of educational level and age. The implications for evolutionary theorizing from the perspective of sexual selection on the effect of tallness on status and dominance among women are discussed.

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