Despite a shared genetic architecture between males and females, sexual differences are widespread. The extent of this shared genetic architecture, reflected in the intersexual genetic correlation, has previously been correlated with the extent of phenotypic sexual dimorphism in shared traits. However, the magnitude of the difference in sex-specific additive genetic variances may also fuel sexu...

For centuries, biologists have asked "why are there so many species, and why do we see such magnificent biological diversity?" This dissertation addresses this question by examining sexual size and shape dimorphism hummingbird bills at both a micro and macroevolutionary scale. Specifically, I quantify sexual size and shape dimorphism of bill morphology of 269 species of hummingbirds and begin w...

Unambiguous examples of ecological causation of sexual dimorphism are rare, and the best evidence involves sexual differences in trophic morphology. We show that moderate female-biased sexual dimorphism in bill curvature is the ancestral condition in hermit hummingbirds (Phaethornithinae), and that it is greatly amplified in species such as Glaucis hirsutus and Phaethornis guy, where bills of f...

This study examined sexual dimorphism of head morphology in the ecologically diverse three-spined stickleback Gasterosteus aculeatus. Male G. aculeatus had longer heads than female G. aculeatus in all 10 anadromous, stream and lake populations examined, and head length growth rates were significantly higher in males in half of the populations sampled, indicating that differences in head size in...

Introduction: The existence of sexual dimorphism in human skeletons especially skull and its medico-legal importance had long been studied [3] [2,1]. This study has investigated the existence of sexual dimorphism in cranial dimensions of Nigerian population. Methods: A total of 100 adult dry skulls, (78 males, 22 females) free from damage and deformity fully ossified from Departments of Ana...

this study estimated the magnitude of sexual dimorphism in a relict sheep from catalunya (ne spain), called fardasca,using geometric morphometric techniques. for these analyses, a total of 18 skull specimens (2 adult males and 16 females) were studied. our results suggest that the breed is not cranially dimorphic, so sex determination using landmarks described here as criteria is likely to yiel...

the carob moth, ectomyelois ceratoniae (zeller), belongs to the family pyralidae and the subfamily phycitinae. in spite of some features of sexual dimorphism in size and shape in the order lepidoptera and the mentioned family, it has not been recorded in this species. in the current study, sexual dimorphism in the wing shape and size of carob moth on four hosts (pomegranate, fig, pistachio and ...

background: ratio of second and fourth digit (2d:4d) is known to be germane in analyzing utero concentrations of testosterone and estrogen in human and other vertebrates. 2d:4d had been linked several traits like athletes’ abilities, reproductive success, risk of cancer and cardiovascular disease (cvd). metabolic syndrome (mets) is a clustering of several cardiovascular risk factors. waist ci...

Sexual differences are often dramatic and widespread across taxa. Their extravagance and ubiquity can be puzzling because the common underlying genome of males and females is expected to impede rather than foster phenotypic divergence. Widespread dimorphism, despite a shared genome, may be more readily explained by considering the multivariate, rather than univariate, framework governing the ev...

The degree of sexual dimorphism found in mammals ranges from species in which females are larger than males (Rails 1976a) to those in which males are much larger than females and possess striking secondary sexual characteristics which females lack. Although some work has been done on mammals, principally pinnipeds (Bartholomew 1970; Stirling 1975) and primates (Crook 1972), current theories as ...