Journal articles on the topic 'Sexual dimorphism'
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Sumarto, Bayu K. A., Hirozumi Kobayashi, Ryo Kakioka, Rieko Tanaka, Ken Maeda, Hau D. Tran, Noriyuki Koizumi, et al. "Latitudinal variation in sexual dimorphism in a freshwater fish group." Biological Journal of the Linnean Society 131, no. 4 (November 6, 2020): 898–908. http://dx.doi.org/10.1093/biolinnean/blaa166.
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Abstract Tropical animals are characterized by showy ornaments and conspicuous body colours as compared with their temperate relatives. Some recent studies have hypothesized that sexual selection pressures are stronger in the tropics than in the temperate zone. Although negative correlations between latitude and the degree of sexual dimorphism would support this hypothesis, phylogeny should be taken into account in such comparative studies. Comparisons of the degree of sexual dimorphism in body size and fin lengths among species of the Adrianichthyidae, a freshwater fish family having a wide geographical range throughout Southeast and East Asia, revealed that lower latitude species are sexually more dimorphic in all characters than higher latitude species. Phylogenetic generalized least squares analyses using a mitochondrial DNA phylogeny demonstrated that the negative correlations between latitude and the degree of sexual dimorphism become non-significant when phylogeny is considered, but that the variance in the degree of sexual dimorphism is explained not only by phylogeny but also almost equally by latitude. Ancestral state reconstruction indicated that sexual dimorphisms have evolved independently even within major clades. These findings are consistent with the view that tropical species are exposed to stronger sexual selection pressures than temperate species. We discuss possible causes of the latitudinal variation in sexual selection pressure.
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Lofeu, Leandro, Renata Brandt, and Tiana Kohlsdorf. "Digit identity matters: origin and evolution of sexual dimorphism in the digit lengths of tropidurid lizards." Biological Journal of the Linnean Society 131, no. 1 (July 31, 2020): 109–21. http://dx.doi.org/10.1093/biolinnean/blaa088.
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Abstract Sexual dimorphism in digit lengths reflects phenotypic evolution mediated by developmental steroids. Differences in the identity of the sexually-dimorphic digit may evolve if the concentrations of sex-steroid receptors in the digit are easily modified and the initial changes have low impact on fitness. Accordingly, sexual dimorphism in digit lengths might initially originate under neutral selective regimes, being subsequently co-opted by embryonic hormonal effects on sensitive traits that are more likely to be targeted by selection. Correlated variation among sexually-dimorphic traits might therefore reflect pleiotropic hormonal modulation during development. Moreover, the identity and trend of the sexually-dimorphic digit might be evolutionarily labile even among closely-related species. We evaluated this model by assessing the identity of sexually-dimorphic digits among 11 Tropiduridae lizard species and inferring evolutionary patterns of sexual dimorphism. Assuming that digit lengths can be used as a proxy for hormonal modulation of steroid-sensitive traits during development, we tested for evolutionary associations among sexual dimorphism of digit lengths, body size and other traits that may be direct targets of sexual selection in the Tropiduridae. Sexual dimorphism in digit lengths is evolutionarily labile in the Tropiduridae, and diversity, instead of conservatism, seems to rule developmental mechanisms underlying the evolution of sexual dimorphism in digit ratios.
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Herring, Peter J. "REVIEW. Sex with the lights on? A review of bioluminescent sexual dimorphism in the sea." Journal of the Marine Biological Association of the United Kingdom 87, no. 4 (July 30, 2007): 829–42. http://dx.doi.org/10.1017/s0025315407056433.
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The reflected patterns and colours of terrestrial animals often show a sexual dimorphism associated with visual display, mate recognition and selection. In the sea the structures associated with bioluminescence may also show a marked sexual dimorphism. Some apparent bioluminescent dimorphisms (e.g. differences in photophore numbers) are probably secondary functions of sexual differences in size. A role in sexual communication is much more likely where specific photophores are developed or enlarged in mature specimens of one sex only but the presence of light organs in female anglerfishes (but not in males) is complicated by a significant size dimorphism. Dimorphisms in dragonfishes and lanternfishes primarily involve the relative enlargement of particular photophores in the males. A sexual role is assumed, but the morphological differences are often small. Most male ponyfishes have enlarged light organs; behavioural observations of free-swimming animals have clearly demonstrated that the males use them to generate bioluminescent sexual signals.
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Oliver, Jeffrey C., and Antónia Monteiro. "On the origins of sexual dimorphism in butterflies." Proceedings of the Royal Society B: Biological Sciences 278, no. 1714 (December 2010): 1981–88. http://dx.doi.org/10.1098/rspb.2010.2220.
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The processes governing the evolution of sexual dimorphism provided a foundation for sexual selection theory. Two alternative processes, originally proposed by Darwin and Wallace, differ primarily in the timing of events creating the dimorphism. In the process advocated by Darwin, a novel ornament arises in a single sex, with no temporal separation in the origin and sex-limitation of the novel trait. By contrast, Wallace proposed a process where novel ornaments appear simultaneously in both sexes, but are then converted into sex-limited expression by natural selection acting against showy coloration in one sex. Here, we investigate these alternative modes of sexual dimorphism evolution in a phylogenetic framework and demonstrate that both processes contribute to dimorphic wing patterns in the butterfly genera Bicyclus and Junonia . In some lineages, eyespots and bands arise in a single sex, whereas in other lineages they appear in both sexes but are then lost in one of the sexes. In addition, lineages displaying sexual dimorphism were more likely to become sexually monomorphic than they were to remain dimorphic. This derived monomorphism was either owing to a loss of the ornament (‘drab monomorphism’) or owing to a gain of the same ornament by the opposite sex (‘mutual ornamentation’). Our results demonstrate the necessity of a plurality in theories explaining the evolution of sexual dimorphism within and across taxa. The origins and evolutionary fate of sexual dimorphism are probably influenced by underlying genetic architecture responsible for sex-limited expression and the degree of intralocus sexual conflict. Future comparative and developmental work on sexual dimorphism within and among taxa will provide a better understanding of the biases and constraints governing the evolution of animal sexual dimorphism.
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Hodge, J. R., F. Santini, and P. C. Wainwright. "Colour dimorphism in labrid fishes as an adaptation to life on coral reefs." Proceedings of the Royal Society B: Biological Sciences 287, no. 1923 (March 18, 2020): 20200167. http://dx.doi.org/10.1098/rspb.2020.0167.
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Conspicuous coloration displayed by animals that express sexual colour dimorphism is generally explained as an adaptation to sexual selection, yet the interactions and relative effects of selective forces influencing colour dimorphism are largely unknown. Qualitatively, colour dimorphism appears more pronounced in marine fishes that live on coral reefs where traits associated with strong sexual selection are purportedly more common. Using phylogenetic comparative analysis, we show that wrasses and parrotfishes exclusive to coral reefs are the most colour dimorphic, but surprisingly, the effect of habitat is not influenced by traits associated with strong sexual selection. Rather, habitat-specific selective forces, including clear water and structural refuge, promote the evolution of pronounced colour dimorphism that manifests colours less likely to be displayed in other habitats. Our results demonstrate that environmental context ultimately determines the evolution of conspicuous coloration in colour-dimorphic labrid fishes, despite other influential selective forces.
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Mallon, Jordan C. "Recognizing sexual dimorphism in the fossil record: lessons from nonavian dinosaurs." Paleobiology 43, no. 3 (March 27, 2017): 495–507. http://dx.doi.org/10.1017/pab.2016.51.
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AbstractThe demonstration of sexual dimorphism in the fossil record can provide vital information about the role that sexual selection has played in the evolution of life. However, statistically robust inferences of sexual dimorphism in fossil organisms are exceedingly difficult to establish, owing to issues of sample size, experimental control, and methodology. This is particularly so in the case of dinosaurs, for which sexual dimorphism has been posited in many species, yet quantifiable data are often lacking. This study presents the first statistical investigation of sexual dimorphism across Dinosauria. It revisits prior analyses that purport to find quantitative evidence for sexual dimorphism in nine dinosaur species. After the available morphological data were subjected to a suite of statistical tests (normality and unimodality tests and mixture modeling), no evidence for sexual dimorphism was found in any of the examined taxa, contrary to conventional wisdom. This is not to say that dinosaurs were not sexually dimorphic (phylogenetic inference suggests they may well have been), only that the available evidence precludes its detection. A priori knowledge of the sexes would greatly facilitate the assessment of sexual dimorphism in the fossil record, and it is suggested that unambiguous indicators of sex (e.g., presence of eggs, embryos, medullary bone) be used to this end.
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Sanger, Thomas J., Susan M. Seav, Masayoshi Tokita, R. Brian Langerhans, Lela M. Ross, Jonathan B. Losos, and Arhat Abzhanov. "The oestrogen pathway underlies the evolution of exaggerated male cranial shapes in Anolis lizards." Proceedings of the Royal Society B: Biological Sciences 281, no. 1784 (June 7, 2014): 20140329. http://dx.doi.org/10.1098/rspb.2014.0329.
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Sexual dimorphisms vary widely among species. This variation must arise through sex-specific evolutionary modifications to developmental processes. Anolis lizards vary extensively in their expression of cranial dimorphism. Compared with other Anolis species, members of the carolinensis clade have evolved relatively high levels of cranial dimorphism; males of this clade have exceptionally long faces relative to conspecific females. Developmentally, this facial length dimorphism arises through an evolutionarily novel, clade-specific strategy. Our analyses herein reveal that sex-specific regulation of the oestrogen pathway underlies evolution of this exaggerated male phenotype, rather than the androgen or insulin growth factor pathways that have long been considered the primary regulators of male-biased dimorphism among vertebrates. Our results suggest greater intricacy in the genetic mechanisms that underlie sexual dimorphisms than previously appreciated.
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Frayer, D. W., and M. H. Wolpoff. "Sexual Dimorphism." Annual Review of Anthropology 14, no. 1 (October 1985): 429–73. http://dx.doi.org/10.1146/annurev.an.14.100185.002241.
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Prabhakar, Manoj, and B. Sivapathasundharam. "Sexual dimorphism." Journal of Oral and Maxillofacial Pathology 23, no. 1 (2019): 152. http://dx.doi.org/10.4103/jomfp.jomfp_68_19.
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Saino, Nicola, and Fiorenza De Bernardi. "Geographic variation in size and sexual dimorphism across a hybrid zone between Carrion Crows (Corvus corone corone) and Hooded Crows (C. c. cornix)." Canadian Journal of Zoology 72, no. 9 (September 1, 1994): 1543–50. http://dx.doi.org/10.1139/z94-205.
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Sexual size dimorphism was analysed across a hybrid zone existing between allopatric populations of Carrion Crows and Hooded Crows (Corvus corone corone and C. c. cornix) in northwestern Italy. Twenty-five morphological (osteological and plumage) variables were measured in a sample of 1599 specimens obtained from allopatric parental areas and from the hybrid zone. For each morphological variable considered, sexual size dimorphism was measured as the ratio of males/females or the absolute difference between mean sizes of males and females within each subpopulation studied. Overall sexual size dimorphism was described by discriminant function analysis. All the sexual size dimorphism measures adopted showed variation across the hybrid zone according to elevation. Male/female ratios and male–female differences significantly differed between the parental allopatric "operational taxonomic units," Carrion Crows being more dimorphic than Hooded Crows. Across the hybrid zone, sexual size dimorphism was correlated with the phenotypic composition of the crow subpopulations and with size of males but not size of females. The data presented show that sexual size dimorphism is correlated with an ecological gradient and that its geographical variation is determined by variation in size of males only.
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Cunningham, Peter, Martin Plath, Torsten Wronski, and Mohamed Sandouka. "Differences in sexual dimorphism among four gazelle taxa (Gazella spp.) in the Middle East." Animal Biology 60, no. 4 (2010): 395–412. http://dx.doi.org/10.1163/157075610x523279.
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AbstractSexual selection can lead to sexual dimorphism, where elaborated traits used in mate attraction or weaponry are more expressed in the male sex. The degree of sexual dimorphism, however, is known to vary even among closely related taxa. Here we examined sexual dimorphism in horn length and three measures related to body size (body weight, shoulder height, and neck circumference) in four gazelle taxa, representing at least three species, i.e. Dorcas gazelle (G. dorcas), Sand gazelle (G. subgutturosa marica) and Mountain gazelle (G. gazella). The latter is represented by two distinctive phenotypes maintained and bred at the King Khalid Wildlife Research Centre in Saudi Arabia. We describe marked differences in sexual dimorphism among taxa. For example, the difference in sexually dimorphic horn development was driven primarily by females exhibiting pronounced differences in horn development. We discuss how divergent mating systems, and group sizes affect these differences among the examined taxa, with more competition in larger groups probably promoting the evolution of larger horns in females, thereby leading to less sexual dimorphism.
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Tarnawski, B. A., G. H. Cassini, and D. A. Flores. "Skull allometry and sexual dimorphism in the ontogeny of the southern elephant seal (Mirounga leonina)." Canadian Journal of Zoology 92, no. 1 (January 2014): 19–31. http://dx.doi.org/10.1139/cjz-2013-0106.
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The southern elephant seal (Mirounga leonina (L., 1758)) is one of the most dimorphic mammals, but sexual dimorphism in its skull ontogeny is poorly known. We study ontogeny of sexual dimorphism by the allometric relationships between 21 measurements and its geometric mean. Based on 66 specimens (36 females, 30 males), the bivariate and multivariate analyses indicated that both approaches were congruent in most variables. We detected that sexual dimorphism was reached mostly by sexual shape differences in the ontogenetic trajectories of males and females. Twenty-four percent of variables were associated with intercept differences (pup size proportions), while 57% of variables were associated with slope intersexual differences (relative growth rates). Contrarily, sexual dimorphism was also achieved by size differences in adult stages (19% of variables), as males exhibited an extension of their common ontogenetic trajectories. Secondary growth spurt in males was detected for few variables. Our comparison with analogous data collected from southern sea lions (Otaria byronia (de Blainville, 1820)) indicated that in both species, sexual dimorphism was mostly associated with an enhanced ability to defend territories, which was linked to the polygynic behavior. However, discrepancies between both ontogenetic patterns of dimorphism were associated with interspecific differences in their life cycles.
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Lewis, Rebecca J., E. Christopher Kirk, and Ashley D. Gosselin-Ildari. "Evolutionary Patterns of Intersexual Power." Animals 13, no. 23 (November 29, 2023): 3695. http://dx.doi.org/10.3390/ani13233695.
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Dominance and leverage are both possible causes of social inequality. If sexual dimorphism influences patterns of intersexual dominance, we predicted that highly dimorphic species are constrained to exhibit male-biased power (MP), but species with low sexual dimorphism are free to demonstrate a broader range of intersexual power relationships. If market effects influence intersexual leverage, we predicted that females have more power when group composition is more male-biased and estrus is asynchronous. We analyzed data on intersexual power, sexual dimorphism, expected estrous overlap, and sex ratio for 79 extant primate species using phylogenetic logistic regression and ancestral state reconstructions. Although MP is more common, every major primate clade includes non-MP species. MP was associated with greater body mass and canine length dimorphism and with female-biased sex-ratios. Low estrous overlap was associated with non-MP. Although MP was reconstructed as likely ancestral for anthropoids, the last common ancestor of this clade probably did not exhibit high sexual dimorphism. The last common ancestor of catarrhines was probably highly dimorphic, potentially constraining intersexual power relationships. Non-MP probably evolved multiple times in primates and may be less common because multiple traits are linked to MP while fewer traits are associated with female-biased power or equality.
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Behan-Pelletier, Valerie M., and Barbara Eamer. "Zachvatkinibates (Acari: Oribatida: Mycobatidae) of North America, with descriptions of sexually dimorphic species." Canadian Entomologist 137, no. 6 (December 2005): 631–47. http://dx.doi.org/10.4039/n05-055.
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AbstractThe oribatid mite genus Zachvatkinibates, found in littoral, forest canopy, and forest litter habitats, includes some species showing distinct sexual dimorphism in the octotaxic system of dermal glands, and others lacking this dimorphism. Three new species in this genus are described on the basis of adults, each of which shows species-specific sexual dimorphism: Z. nortonisp. nov. and Z. schatzisp. nov. from beach debris in British Columbia, Canada, and Z. shaldybinaesp. nov. from the littoral in eastern and northeastern Canada. We discuss the association of sexual dimorphism with the littoral habitat of species in this genus and, more generally, the expression of sexually dimorphic porose areas in Ceratozetoidea. We revise the diagnosis for the genus Zachvatkinibates and present a revised key for adults of Zachvatkinibates species of North America north of Mexico.
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Liu, Miao, Helena Korpelainen, and Chunyang Li. "Sexual differences and sex ratios of dioecious plants under stressful environments." Journal of Plant Ecology 14, no. 5 (April 20, 2021): 920–33. http://dx.doi.org/10.1093/jpe/rtab038.
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Abstract Dioecious plants exhibit sexual dimorphism in both sexual features (reproductive organs) and secondary sex characteristics (vegetative traits). Sexual differences in secondary traits, including morphological, physiological and ecological characters, have been commonly associated with trade-offs between the cost of reproduction and other plant functions. Such trade-offs may be modified by environmental stressors, although there is evidence that sexually dimorphic responses to stress do not always exist in all plant species. When sexual dimorphism exists, sexually different responses appear to depend on the species and stress types. Yet, further studies on dioecious plant species are needed to allow the generalization of stress effects on males and females. Additionally, sexual dimorphism may influence the frequency and distribution of the sexes along environmental gradients, likely causing niche differentiation and spatial segregation of sexes. At the present, the causes and mechanisms governing sex ratio biases are poorly understood. This review aims to discuss sex-specific responses and sex ratio biases occurring under adverse conditions, which will advance our knowledge of sexually dimorphic responses to environmental stressors.
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Fryxell, David C., Heather A. Arnett, Travis M. Apgar, Michael T. Kinnison, and Eric P. Palkovacs. "Sex ratio variation shapes the ecological effects of a globally introduced freshwater fish." Proceedings of the Royal Society B: Biological Sciences 282, no. 1817 (October 22, 2015): 20151970. http://dx.doi.org/10.1098/rspb.2015.1970.
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Sex ratio and sexual dimorphism have long been of interest in population and evolutionary ecology, but consequences for communities and ecosystems remain untested. Sex ratio could influence ecological conditions whenever sexual dimorphism is associated with ecological dimorphism in species with strong ecological interactions. We tested for ecological implications of sex ratio variation in the sexually dimorphic western mosquitofish, Gambusia affinis . This species causes strong pelagic trophic cascades and exhibits substantial variation in adult sex ratios. We found that female-biased populations induced stronger pelagic trophic cascades compared with male-biased populations, causing larger changes to key community and ecosystem responses, including zooplankton abundance, phytoplankton abundance, productivity, pH and temperature. The magnitude of such effects indicates that sex ratio is important for mediating the ecological role of mosquitofish. Because both sex ratio variation and sexual dimorphism are common features of natural populations, our findings should encourage broader consideration of the ecological significance of sex ratio variation in nature, including the relative contributions of various sexually dimorphic traits to these effects.
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Barrett, Spencer C. H., and Andrea L. Case. "The ecology and evolution of gender strategies in plants: the example of Australian Wurmbea (Colchicaceae)." Australian Journal of Botany 54, no. 5 (2006): 417. http://dx.doi.org/10.1071/bt05151.
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Angiosperms possess diverse sexual systems, often with different combinations of hermaphroditic, pistillate and staminate flowers. Despite this sexual diversity, most populations are either monomorphic or dimorphic with respect to gender strategy, where gender refers to the relative contribution that individuals make to fitness through female and male function. An important problem in evolutionary biology is to determine how and why variation in gender strategies originates and is maintained. Wurmbea (Colchicaceae), a genus of insect-pollinated geophytes, has recently become the focus of ecological and evolutionary studies aimed at understanding these issues. Phylogenetic reconstructions suggest dispersal from Africa to Australia, then New Zealand, and multiple transitions between monomorphic and dimorphic sexual systems within Australia. Microevolutionary studies of W. dioica and W. biglandulosa, two wide-ranging taxa with monomorphic and dimorphic populations, provide insights into the selective mechanisms governing transitions between sexual systems. Dimorphic populations of these taxa likely comprise independent origins of dimorphism via the gynodioecious pathway by invasion of females into monomorphic populations. Shifts in pollination biology and flower size, and their consequent effects on mating patterns, may have contributed to the evolution of gender dimorphism. Pollinator-mediated selfing and inbreeding depression provide a sufficient fertility advantage for females to be maintained in dimorphic populations. Once dimorphism establishes, increasing gender specialisation is associated with invasion of more arid environments. Inbreeding avoidance, particularly under stressful ecological conditions, is the most likely selective mechanism maintaining gender dimorphism in Wurmbea. We conclude our review by suggesting avenues for future research that might provide a more comprehensive picture of the evolution of gender strategies in Wurmbea.
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Yamaguchi, Tatsuhiko, Rie Honda, Hiroki Matsui, and Hiroshi Nishi. "Sexual shape dimorphism and selection pressure on males in fossil ostracodes." Paleobiology 43, no. 3 (May 22, 2017): 407–24. http://dx.doi.org/10.1017/pab.2016.57.
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AbstractSexual dimorphism is thought to have evolved via selection on both sexes. Ostracodes display sexual shape dimorphism in adult valves; however, no previous studies have addressed temporal changes on evolutionary timescales or examined the relationships between sexual shape dimorphism and selection pressure and between sexual shape dimorphism and juvenile shape. Temporal changes in sexually dimorphic traits result from responses of these traits to selection pressure. Using the Gaussian mixture model for the height/length ratio, a valve-shape parameter, we identified sexual differences in the valve shape of Krithe dolichodeira s.l. from deep-sea sediments of the Paleocene (62.6–57.6 Ma) and estimated the proportion of females in the fossil populations at 11 time intervals. Because the proportion of females in a population is altered by the mortality rate of adult males, it is reflective of selection pressure on males. We attempted to correlate the height/length ratios between the sexes with the proportion of females, taking into consideration that the valve shape was not linked with the selection pressure on males. In time-series data of the height/length ratio, both sexes indicate no significant changes on evolutionary timescales, even though the sex ratio of the population changed from female skewed to male skewed during the late Paleocene. The sexual shape dimorphism was not driven by sexual selection. The static allometry between the height/length ratio and length indicates that the sexual shape dimorphism did not function for sexual display. The absence of change over time in the female allometric slope suggests that the evolution of valve shape was constrained by stasis.
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Marino, Thomas. "Sexual Dimorphism and Sexual Intermediaries." American Journal of Bioethics 10, no. 7 (June 30, 2010): 24–25. http://dx.doi.org/10.1080/15265161.2010.482636.
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Ibor, Oju Richard, George Eni, Andem Bassey Andem, Akanimo Joseph, and Azubuike Victor Chukwuka. "Sexual dimorphism in black jaw tiliapia (Sarotherodon melanotheron) and banded jewelfish (Hemichromis fasciatus) from the Great Kwa River, Calabar, Nigeria." Croatian Journal of Fisheries 75, no. 4 (December 1, 2017): 122–31. http://dx.doi.org/10.1515/cjf-2017-0016.
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AbstractIn this study, the pattern and magnitude of sexual dimorphic differences have been investigated in black jaw tilapia (Sarotherodon melanotheron) (n = 160; 74 males and 86 females) and banded jewelfish (Hemichromis fasciatus) (n = 120; 42 males and 78 females) from the Great Kwa River, Calabar, Nigeria. Fish samples were collected between July and December 2015. Fourteen morphometric variables, including body weight, total length, standard length, body depth, cheek depth, pre-orbital length, postorbital length, pectoral fin length (right and left), pelvic fin length (right and left), head length, gonad weight, eye diameter and four meristic variables, including number of pectoral fins (right and left) and number of pelvic fins (right and left), were taken using standard methods. Size-adjusted morphometric measurements subjected to step-wise discriminant function analysis were used to determine predictor variables to morphologically differentiate sexes for both species; magnitude of dimorphism between sexes was estimated using percentage classification accuracy of the discriminant function analysis. From the discriminant function analysis, the pectoral fin length and gonad weight positively contributed significantly to morphometric dimorphism (magnitude=69.2%) in male and femaleS. melanotheronsuggesting adaptation for reproductive function; while forH. fasciatusthe body depth and standard length were important contributors to sexual dimorphism (magnitude=84.2%) suggesting size dimorphism for aggressiveness, territorial behavior and improving swimming performance. Overall, our results indicate that the different magnitude of sexual dimorphism between the two species could be attributable to the type and functional role of sexual dimorphic traits.
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Sharma, Manisha, Sameer Gupta, Avdesh Sharma, Vandana Bhardwaj, Pooja Sharma, and Pradeep Kumar. "Dental Sexual Dimorphism." Dental Journal of Advance Studies 03, no. 03 (December 2015): 135–39. http://dx.doi.org/10.1055/s-0038-1672028.
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Abstract Objective : Forensic odontology is a lineage that deals in relation to jaws and teeth as evidence to law and justice. Tooth serves as a prime importance in the context of sex identification. (1) To investigate whether there exists any correlation between odontometric measures and sexual dimorphism. (2) To compare the inter-canine arch width of mandible. (3) To evaluate the mean value of standard mandibular canine index. Method: This study is an odontometric analysis performed intra-orally with a sample of 150 teeth (75male:75 female) on students of Kanti Devi Dental college, Mathura. Mesiodistal dimensions of mandibular right and left canine with a caliper device and statistical analysis for significance of sexual dimorphism was done with student’s t test. Result: The result showed that sexual dimorphism is significant in relation to mesiodistal diameter of canine. Furthermore, there was statistical significant difference in tooth crown dimension between males and females where the males showed higher mean values. Conclusion: The study show definite statistically significant sexual dimorphism hence they can play significant role in providing expertise in civil & criminal proceedings to ensure that forensic dentistry will remain viable component of forensic medicine.
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McPherson, F. J., and P. J. Chenoweth. "Mammalian sexual dimorphism." Animal Reproduction Science 131, no. 3-4 (April 2012): 109–22. http://dx.doi.org/10.1016/j.anireprosci.2012.02.007.
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Lenarz, William H., and Tina Wyllie Echeverria. "Sexual dimorphism inSebastes." Environmental Biology of Fishes 30, no. 1-2 (January 1991): 71–80. http://dx.doi.org/10.1007/bf02296878.
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BEHAN-PELLETIER, VALERIE M., and BARBARA EAMER. "The first sexually dimorphic species of Oribatella (Acari, Oribatida, Oribatellidae) and a review of sexual dimorphism in the Brachypylina." Zootaxa 2332, no. 1 (January 11, 2010): 1. http://dx.doi.org/10.11646/zootaxa.2332.1.1.
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The oribatid mite genus Oribatella includes over 100 named species, none of which shows distinct sexual dimorphism in the octotaxic system of dermal glands. We propose a new species of this genus, Oribatella canadensis sp, nov., collected from dry soil habitats in western Canada, that shows distinct dimorphism in these dermal glands, the first record of this dimorphism in the Oribatelloidea. The posterior pair of glands in males, but not females, is enlarged and associated with a shallow, medial pit-tubercle complex, and is generally similar to convergent dimorphisms in some genera of Mochlozetidae (Oripodoidea), Mycobatidae (Ceratozetoidea) and Galumnidae (Galumnoidea). We describe this species based on adult and nymphal stages, and expand the diagnosis of the genus to accommodate the newly described immatures. We review the expression of sexual dimorphism in brachypyline oribatid mites and discuss its association with periodically dry habitats.
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Macías Garcia, C., G. Smith, C. González Zuarth, J. A. Graves, and M. G. Ritchie. "Variation in sexual dimorphism and assortative mating do not predict genetic divergence in the sexually dimorphic Goodeid fish Girardinichthys multiradiatus." Current Zoology 58, no. 3 (June 1, 2012): 440–52. http://dx.doi.org/10.1093/czoolo/58.3.440.
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Abstract Sexual dimorphism is often used as a proxy for the intensity of sexual selection in comparative studies of sexual selection and diversification. The Mexican Goodeinae are a group of livebearing freshwater fishes with large variation between species in sexual dimorphism in body shape. Previously we found an association between variation in morphological sexual dimorphism between species and the amount of gene flow within populations in the Goodeinae. Here we have examined if morphological differentiation within a single dimorphic species is related to assortative mating or gene flow between populations. In the Amarillo fish Girardinichthys multiradiatus studies have shown that exaggerated male fins are targets of female preferences. We find that populations of the species differ in the level of sexual dimorphism displayed due to faster evolution of differences in male than female morphology. However, this does not predict variation in assortative mating tests in the laboratory; in fact differences in male morphology are negatively correlated with assortative mating. Microsatellite markers reveal significant genetic differences between populations. However, gene flow is not predicted by either morphological differences or assortative mating. Rather, it demonstrates a pattern of isolation by distance with greater differentiation between watersheds. We discuss the caveats of predicting behavioural and genetic divergence from so-called proxies of sexual selection.
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Djurakíc, Marko, Sonja Djordjevíc, Xavier Bonnet, Ljiljana Tomovíc, Rastko Ajtíc, and Ana Golubovíc. "Sexual body size and body shape dimorphism of Testudo hermanni in central and eastern Serbia." Amphibia-Reptilia 32, no. 4 (2011): 445–58. http://dx.doi.org/10.1163/156853811x598479.
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AbstractHermann's tortoise (Testudo hermanni) is widely distributed in western and southern Europe. Most populations in the western part of the distribution range (e.g. Spain, France, Italy) are severely reduced, and relatively well studied, whilst the species is still abundant in eastern areas (i.e. the Balkans). However, essential biological information (e.g. main morphological, ecological, and behavioural characteristics) for the Balkans are still extremely limited. As reptiles exhibit strong geographic variation in most morphological, as well as life history traits, gathering data from distant areas is important. We present data from two populations of T. hermanni in Serbia, focusing on sexual dimorphism in body size and body shape. We found that almost all of the 43 morphological traits analysed were significantly different between sexes and that sexual size and sexual shape dimorphisms were not expressed in similar ways. Notably, sexual size dimorphism (SSD) was more pronounced than sexual shape dimorphism (SShD). Our analyses suggested that SShD is more stable than SSD, and that the scale of the focus (i.e. whole body proportions versus morphological details) is a key factor to test this notion. When general measurements were considered, the expected consistency of SShD between populations was verified; nevertheless, when more specific morphological attributes were considered, substantial variations were observed. These results provide a baseline for comparisons between populations to further examine geographic variation of sexual dimorphism.
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BAYARTOGTOKH, BADAMDORJ, SERGEY G. ERMILOV, and ALEXANDER A. KHAUSTOV. "An interesting sexually dimorphic species, Chamobates callipygis Pavlichenko, 1991 (Acari, Oribatida, Chamobatidae), with remarks on sexual dimorphism <br>in Ceratozetoidea." Zootaxa 5115, no. 1 (March 11, 2022): 91–102. http://dx.doi.org/10.11646/zootaxa.5115.1.6.
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Based on materials from the leaf litter of a mixed forest in Crimea, a new diagnosis for the sexually dimorphic species, Chamobates callipygis Pavlichenko, 1991, is presented to accommodate its previously unreported females. This is the only species in Chamobatidae showing a distinct sexual dimorphism, which is expressed by the posterior porose region on the notogaster, such that males only have a large protuberance on the posterior part of notogaster bearing a pair of fused porose areas A3, and a densely striated region behind them. The specific function of this structure is not yet known, but the sexual dimorphism is presumably involved in pheromonal communication facilitating sperm transfer. Also, the males of this species have a few transverse striations in the dorsomedial part of notogaster (at level of porose areas A1 and A2). Further, we discuss all cases of sexual dimorphism in the superfamily Ceratozetoidea, and the possible function of this dimorphism.
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Barve, Sahas, Soham Dixit, André A. Dhondt, and Farah Ishtiaq. "Sexual Dimorphism in Breast Stripe Width and Beak Eco-Morphology in Himalayan Green-Backed Tits (Parus Monticolus)." Avian Biology Research 10, no. 4 (November 2017): 259–63. http://dx.doi.org/10.3184/175815617x15063340995374.
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Quantitative field data on sexual dimorphism is scant for most bird species. In this first field study of a western Himalayan population of Green-backed Tits ( Parus monticolus), we demonstrate that breast stripe width is a dimorphic trait that is a reliable measure to sex this species in the wild. Based on our ability to sex the birds in hand, we describe the sexual dimorphism in eco-morphological variables in our study population. Sexual dimorphism in beak morphology changed from winter to summer due to males having shorter beaks (4.5%) in summer; however, there was little change in female beak measurements. Our study on this Himalayan congener of a widely studied European species can be used to inform studies of the evolutionary ecology of morphological traits in closely-related species inhabiting vastly different habitats.
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Kimball, Rebecca T., Colette M. St Mary, and Edward L. Braun. "A Macroevolutionary Perspective on Multiple Sexual Traits in the Phasianidae (Galliformes)." International Journal of Evolutionary Biology 2011 (May 2, 2011): 1–16. http://dx.doi.org/10.4061/2011/423938.
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Traits involved in sexual signaling are ubiquitous among animals. Although a single trait appears sufficient to convey information, many sexually dimorphic species exhibit multiple sexual signals, which may be costly to signalers and receivers. Given that one signal may be enough, there are many microevolutionary hypotheses to explain the evolution of multiple signals. Here we extend these hypotheses to a macroevolutionary scale and compare those predictions to the patterns of gains and losses of sexual dimorphism in pheasants and partridges. Among nine dimorphic characters, including six intersexual signals and three indicators of competitive ability, all exhibited both gains and losses of dimorphism within the group. Although theories of intersexual selection emphasize gain and elaboration, those six characters exhibited greater rates of loss than gain; in contrast, the competitive traits showed a slight bias towards gains. The available models, when examined in a macroevolutionary framework, did not yield unique predictions, making it difficult to distinguish among them. Even with this limitation, when the predictions of these alternative models were compared with the heterogeneous patterns of evolution of dimorphism in phasianids, it is clear that many different selective processes have been involved in the evolution of sexual signals in this group.
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Mallon, Jordan C., and Robert B. Holmes. "A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia)." Canadian Field-Naturalist 120, no. 4 (October 1, 2006): 403. http://dx.doi.org/10.22621/cfn.v120i4.347.
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The sexual dimorphism attributed to Chasmosaurus belli by Sternberg (1927) is revisited and reevaluated. A reexamination of the two specimens originally considered by Sternberg reveals that they are less complete than first suggested, with only a moderate amount of overlapping material between them. Only a few of the postcranial elements (humeri, sternal plates, and presacral vertebrae) show evidence of dimorphism, the significance of which is either doubtful or equivocal. Instead of representing sexual dimorphs, it is likely that the two specimens belong to separate species, C. belli and C. russelli, as evidenced by their distinct frill morphologies and by their stratigraphic segregation within the Dinosaur Park Formation of Alberta. These findings emphasize the need to remain sceptical about claims advocating sexual dimorphism in the fossil record in the absence of statistical significance or stratigraphic control.
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Wright, David B. "Evolution of sexually dimorphic characters in peccaries (Mammalia, Tayassuidae)." Paleobiology 19, no. 1 (1993): 52–70. http://dx.doi.org/10.1017/s0094837300012318.
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Cladistic analysis of osteological and dental characters in a monophyletic group of Miocene and younger tayassuids demonstrates a pattern of changes in the degree of sexual dimorphism in canine tooth diameter and zygomatic arch width, and in phenotypic correlations between these characters. Primitively, tayassuids have canine teeth that are sexually dimorphic and discretely bimodal in size, and zygomatic arches that are narrow in both sexes. Many late Miocene and Pliocene tayassuids have broad, winglike zygomatic processes. In some species, these processes are large in both sexes, but in others, those of females are much smaller than those of males. The presence of large processes in both sexes is primitive relative to the condition of strong sexual dimorphism. In five separate clades, the zygomatic processes of both sexes become reduced in size, and the degree of sexual dimorphism in canine size becomes reduced as well. The pattern is congruent with predictions derived from a theoretical model of the evolution of sexual dimorphism, and it further indicates the emergence of a new phenotypic correlation between two previously uncorrelated characters, canine size and zygoma size. The advent of this new correlation coincides with the advent of pronounced sexual dimorphism in zygomatic processes. Although such a pattern could be explained by genetically modifying phenotypic expression of homologous characters in one sex or the other, an epigenetic modification of expression is equally plausible: the evolution of sexual dimorphism in homologous characters could be accomplished by placing phenotypic expression of an originally monomorphic character under the control of steroid sex hormones. This hypothesis is consistent with evidence from many vertebrate groups, and it provides testable predictions.
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Cassini, Marcelo H. "Sexual size dimorphism and sexual selection in artiodactyls." Behavioral Ecology 31, no. 3 (March 29, 2020): 792–97. http://dx.doi.org/10.1093/beheco/araa017.
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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.
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Costa Mendes, Leonor, Julien Delrieu, Claudia Gillet, Norbert Telmon, Delphine Maret, and Frédéric Savall. "Sexual dimorphism of the mandibular conformational changes in aging human adults: A multislice computed tomographic study by geometric morphometrics." PLOS ONE 16, no. 6 (June 22, 2021): e0253564. http://dx.doi.org/10.1371/journal.pone.0253564.
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The aging process has an impact on mandibular bone morphology and can therefore affect shape sexual dimorphism. Understanding the effect of senescence on mandibular shape changes is particularly important to correctly estimate the sex of an individual and predict age-related conformational modifications. The purpose of this study was to assess age-related changes in mandibular shape and sexual dimorphism. The study sample comprised 160 Multi Slice Computed Tomography examinations of individuals aged 40 to 79 years. Geometric morphometric analysis of fourteen osteometric landmarks was used to examine sexual dimorphism and patterns of mandibular shape variation with age. Results showed that mandibular sexual dimorphism of shape remained significant with aging. Conformational changes occurred between 50 and 70 years and were different for male and female individuals. Females presented earlier and more marked age-related shape changes than males. These observations suggest that mandibular senescence is a sexually dimorphic process since its onset, rate, and the areas subjected to conformational changes differ from male to female individuals. Senescence-related changes present substantial variability, and further investigation is required to determine precisely the age that marks their onset.
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Mizumoto, Nobuaki, Masato S. Abe, and Shigeto Dobata. "Optimizing mating encounters by sexually dimorphic movements." Journal of The Royal Society Interface 14, no. 130 (May 2017): 20170086. http://dx.doi.org/10.1098/rsif.2017.0086.
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All organisms with sexual reproduction undergo a process of mating, which essentially involves the encounter of two individuals belonging to different sexes. During mate search, both sexes should mutually optimize their encounters, thus raising a question of how they achieve this. Here, we show that a population with sexually dimorphic movement patterns achieves the highest individual mating success under a limited lifespan. Extensive simulations found and analytical approximations corroborated the existence of conditions under which sexual dimorphism in the movement patterns (i.e. how diffusively they move) is advantageous over sexual monomorphism. Mutual searchers with limited lifespans need to balance the speed and accuracy of finding their mates, and dimorphic movements can solve this trade-off. We further demonstrate that the sexual dimorphism can evolve from an initial sexually monomorphic population. Our results emphasize the importance of considering mutual optimization in problems of random search.
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Barcelon, Ellane, Seohyun Chung, Jaesung Lee, and Sung Joong Lee. "Sexual Dimorphism in the Mechanism of Pain Central Sensitization." Cells 12, no. 16 (August 9, 2023): 2028. http://dx.doi.org/10.3390/cells12162028.
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It has long been recognized that men and women have different degrees of susceptibility to chronic pain. Greater recognition of the sexual dimorphism in chronic pain has resulted in increasing numbers of both clinical and preclinical studies that have identified factors and mechanisms underlying sex differences in pain sensitization. Here, we review sexually dimorphic pain phenotypes in various research animal models and factors involved in the sex difference in pain phenotypes. We further discuss putative mechanisms for the sexual dimorphism in pain sensitization, which involves sex hormones, spinal cord microglia, and peripheral immune cells. Elucidating the sexually dimorphic mechanism of pain sensitization may provide important clinical implications and aid the development of sex-specific therapeutic strategies to treat chronic pain.
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Forero, M. G., J. L. Tella, J. A. Donázar, G. Blanco, M. Bertellotti, and O. Ceballos. "Phenotypic assortative mating and within-pair sexual dimorphism and its influence on breeding success and offspring quality in Magellanic penguins." Canadian Journal of Zoology 79, no. 8 (August 1, 2001): 1414–22. http://dx.doi.org/10.1139/z01-088.
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We examined within-pair sexual dimorphism and phenotypic assortative mating in Magellanic penguins (Spheniscus magellanicus) breeding in six colonies located on the Patagonian coast (Argentina). All measured phenotypic traits except the number of pectoral spots differed between the sexes; bill depth and flipper length were the most and least dimorphic traits, respectively. We found assortative mating by bill depth and body mass. The similarity in body condition within pairs was close to significant. When we performed separate correlations for birds that bred successfully, i.e., raised one or two offsprings, and birds that did not attempt to breed or bred unsuccessfully, only the successful breeders showed assortative mating by body mass. In addition, we attempted to relate the body size of each member of the pair and the degree of sexual dimorphism within pairs to the breeding performance of individuals, which was measured as brood size, and body condition and immunocompetence of offspring. We found that pairs that were less dimorphic in flipper length raised more offspring. This effect was due to female flipper length per se and not to the relative difference in flipper length between members of the pair. Females with larger flippers had a higher probability of raising two chicks. No effects of body measurements or degree of sexual dimorphism on body condition or T-cell-mediated immune response of offspring were found. We discuss these results in the context of potential factors responsible for the maintenance of sexual size dimorphism in this species.
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Vohra, Poonam, and Pratima Kulkarni. "SEXUAL DIMORPHISM OF HUMAN HYOID BONE." International Journal of Anatomy and Research 5, no. 1.3 (March 31, 2017): 3607–10. http://dx.doi.org/10.16965/ijar.2017.118.
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Luthringer, R., A. Cormier, S. Ahmed, A. F. Peters, J. M. Cock, and S. M. Coelho. "Sexual dimorphism in the brown algae." Perspectives in Phycology 1, no. 1 (June 1, 2014): 11–25. http://dx.doi.org/10.1127/2198-011x/2014/0002.
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Amores-Ampuero, Anabel. "Sexual dimorphism in base of skull." Anthropologischer Anzeiger 74, no. 1 (April 1, 2017): 9–14. http://dx.doi.org/10.1127/anthranz/2017/0603.
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Polcz, Valerie E., Evan L. Barrios, Benjamin Chapin, Catherine C. Price, Ravinder Nagpal, Paramita Chakrabarty, Gemma Casadesus, Thomas Foster, Lyle L. Moldawer, and Philip A. Efron. "Sex, sepsis and the brain: defining the role of sexual dimorphism on neurocognitive outcomes after infection." Clinical Science 137, no. 12 (June 2023): 963–78. http://dx.doi.org/10.1042/cs20220555.
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Abstract Sexual dimorphisms exist in multiple domains, from learning and memory to neurocognitive disease, and even in the immune system. Male sex has been associated with increased susceptibility to infection, as well as increased risk of adverse outcomes. Sepsis remains a major source of morbidity and mortality globally, and over half of septic patients admitted to intensive care are believed to suffer some degree of sepsis-associated encephalopathy (SAE). In the short term, SAE is associated with an increased risk of in-hospital mortality, and in the long term, has the potential for significant impairment of cognition, memory, and acceleration of neurocognitive disease. Despite increasing information regarding sexual dimorphism in neurologic and immunologic systems, research into these dimorphisms in sepsis-associated encephalopathy remains critically understudied. In this narrative review, we discuss how sex has been associated with brain morphology, chemistry, and disease, sexual dimorphism in immunity, and existing research into the effects of sex on SAE.
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Sweitzer, Richard Alan, and Joel Berger. "Sexual dimorphism and evidence for intrasexual selection from quill impalements, injuries, and mate guarding in porcupines (Erethizon dorsatum)." Canadian Journal of Zoology 75, no. 6 (June 1, 1997): 847–54. http://dx.doi.org/10.1139/z97-107.
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Sexual selection is a commonly cited explanation for sexual size dimorphism. We examined patterns of sexual dimorphism in North American porcupines (Erethizon dorsatum) and used data on quill impalements, injuries, and guarding behavior to examine the intrasexual component of sexual selection among male porcupines. Results indicated that porcupines were sexually dimorphic for foot-pad length, body length, and body mass because males grew more rapidly and for longer periods than females. Quill impalements, injuries, and guarding episodes were restricted predominantly to older, larger males, intimating that only the largest porcupines were reproductively active. Regression analyses suggested that size was more important than age in predicting reproductive activity among males. Also, relatively few quill impalements and guarding episodes among younger, smaller animals suggest that there is a threshold size below which male porcupines do not attempt to compete for mate access. Although our data do not directly link larger body size in males with relatively high reproductive success, they suggest that sexual dimorphism in this species is at least partly the result of the intrasexual component of sexual selection. It is also possible that females select males on the basis of quill morphology or some other indicator of male quality. Thus, our understanding of sexual dimorphism in porcupines would benefit from additional research investigating the extent to which body size and patterns of quill number or size are advantageous to male porcupines in garnering mating opportunities and enhancing fitness.
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Yan, Chengzhi, Hui Ma, Yuejun Yang, and Zhiping Mi. "Sexual Dimorphism in the Limb Bones of Asiatic Toad (Bufo gargarizans) in Relation to Sexual Selection." Animals 13, no. 16 (August 16, 2023): 2638. http://dx.doi.org/10.3390/ani13162638.
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Sexual dimorphism is often considered to be the result of differences in the intensity of sexual selection between sexes. From this point of view, the sexual dimorphism of the limb bones of the Bufo gargarizans in southwest China was studied. Results showed that the fore- and hindlimb skeletons of this species were sexually dimorphic in anatomy. The humerus, radioulna, and total lengths of the forelimb skeleton of males were substantially longer than those of females, but the hand length of males was smaller than that of females. Several other features of males, such as deltoid and medial crest areas and humerus and radioulnar weights, were also significantly larger than those of females. The femoris, tibiofibula, talus–calcaneus, and foot lengths; total hindlimb skeleton length; and femoral upper crest areas of males were significantly greater than those of females. However, no significant intersexual difference in femoris and tibiofibular weights was observed. These findings suggested that robust forelimb bones and long hindlimb bones could contribute to the mating success of males; if so, sexual selection promotes the evolution of sexual size and shape dimorphism in the limb bones of the B. gargarizans.
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Silos, Rose Ann, Brent Joy Hernando, Juzavil Juario, Sheryl Patiño, Princess Angelie Casas, Jazzie D’Zeim Arreza, Angelo Responte, and Sonnie A. Vedra. "Sexual Dimorphism of Flathead Mullet (Mugil cephalus) from Northern Mindanao Rivers Using Geometric Morphometric Analysis." International Letters of Natural Sciences 45 (August 2015): 34–48. http://dx.doi.org/10.18052/www.scipress.com/ilns.45.34.
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Sexual dimorphism is biologically important for determining the morphological traits of marine species. Flathead mullet (Mugilcephalus) was examined based on the patterns of sexual dimorphism from the two rivers in Northern Mindanao. The samples were collected from Cagayan de Oro River and Mandulog River to investigate phenotypic divergence and sexual dimorphism in two different populations of wild-caught M. cephalus using geometric morphology based on landmark basis. A total of 17 landmarks were identified to describe the left and right body shapes of the specimen using the TpsRelw (version 1) to obtain the warp scores of each population. Results of the Relative Warp Analysis show no significant variation in the body shape within the sexes in the respective sampling sites. Results of the discriminant function analysis (DFA) show that in Cagayan de Oro River there is no significant variation in the body shape of mullets between sexes suggesting no sexual dimorphism in the flathead mullets in Cagayan de Oro River. In contrast , Discriminant Function Analysis show that there is significant variation in body shape between sexes in Mandulog River in Iligan City suggesting presence of sexual dimorphism in the area which can be due to the presence of abundant and highly diverse predator species in Mandulog River. Sexual dimorphosm can be used by fishes as an adaptive mechanism to maximize predator-escape performance and survival capacity. Furthermore, there is a significant shape variation between populations of mullets in Cagayan de Oro and Mandulog River which can be interpreted as due to geographic isolation which serves as physical barrier on the gene pool. In conclusion, many factors could account for variation in body shape of Mugilcephalus including predation and biogeographical barriers.
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Silos, Rose Ann, Brent Joy Hernando, Juzavil Juario, Sheryl Patiño, Princess Angelie Casas, Jazzie D’Zeim Arreza, Angelo Responte, and Sonnie A. Vedra. "Sexual Dimorphism of Flathead Mullet (<i>Mugil</i> c<i>ephalus</i>) from Northern Mindanao Rivers Using Geometric Morphometric Analysis." International Letters of Natural Sciences 45 (August 28, 2015): 34–48. http://dx.doi.org/10.56431/p-32f6t9.
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Sexual dimorphism is biologically important for determining the morphological traits of marine species. Flathead mullet (Mugilcephalus) was examined based on the patterns of sexual dimorphism from the two rivers in Northern Mindanao. The samples were collected from Cagayan de Oro River and Mandulog River to investigate phenotypic divergence and sexual dimorphism in two different populations of wild-caught M. cephalus using geometric morphology based on landmark basis. A total of 17 landmarks were identified to describe the left and right body shapes of the specimen using the TpsRelw (version 1) to obtain the warp scores of each population. Results of the Relative Warp Analysis show no significant variation in the body shape within the sexes in the respective sampling sites. Results of the discriminant function analysis (DFA) show that in Cagayan de Oro River there is no significant variation in the body shape of mullets between sexes suggesting no sexual dimorphism in the flathead mullets in Cagayan de Oro River. In contrast , Discriminant Function Analysis show that there is significant variation in body shape between sexes in Mandulog River in Iligan City suggesting presence of sexual dimorphism in the area which can be due to the presence of abundant and highly diverse predator species in Mandulog River. Sexual dimorphosm can be used by fishes as an adaptive mechanism to maximize predator-escape performance and survival capacity. Furthermore, there is a significant shape variation between populations of mullets in Cagayan de Oro and Mandulog River which can be interpreted as due to geographic isolation which serves as physical barrier on the gene pool. In conclusion, many factors could account for variation in body shape of Mugilcephalus including predation and biogeographical barriers.
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Caruso, Christina M. "Sexual dimorphism in floral traits of gynodioecious Lobelia siphilitica (Lobeliaceae) is consistent across populations." Botany 90, no. 12 (December 2012): 1245–51. http://dx.doi.org/10.1139/b2012-094.
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In angiosperms, the evolution of gender dimorphism is often correlated with the evolution of sexual dimorphism in floral traits. The magnitude of sexual dimorphism will reflect both sex-specific selection and constraints on evolution in response to this selection. If the evolution of sexual dimorphism is constrained by genetic correlations, then trait means are predicted to evolve more quickly than the magnitude of sexual dimorphism in the same traits. To test whether mean floral traits evolve more quickly than sexual dimorphism in these traits, I measured flower size and flower number of gynodioecious Lobelia siphilitica L. from 10–14 populations across the species’ range. Females produced more flowers than hermaphrodites, but neither mean flower number nor the magnitude of dimorphism in flower number varied among populations. Pistillate flowers were smaller than perfect flowers, and mean flower size varied among populations. However, the magnitude of dimorphism in flower size did not vary. My results suggest that the evolution of sexual dimorphism in flower size, but not necessarily flower number, could be constrained by within- or between-sex genetic correlations in L. siphilitica.
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Robertson, Julia M., Barbara E. Kingsley, and Gina C. Ford. "Sexually Dimorphic Faciometrics in Humans From Early Adulthood to Late Middle Age: Dynamic, Declining, and Differentiated." Evolutionary Psychology 15, no. 3 (September 1, 2017): 147470491773064. http://dx.doi.org/10.1177/1474704917730640.
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Faciometrics have widely been used in contemporary studies on gender-related behavioral traits, for example, perceived and actual aggression, co-operation and trustworthiness, prejudicial beliefs, unethical behavior, and achievement drive, as well as, but to a lesser degree, in nonhuman primates. For the large part, these studies have focused primarily on “student-aged” populations with little empirical scrutiny regarding the efficacy of applying these measures with older participants. This study therefore investigated sexual dimorphism across four age-groups (20s, 30s, 40s, and 50s) in 444 participants (225 men). The expected sexual dimorphism was seen in the youngest age group in three of the four indices. The facial width to height ratio, however, although most commonly used empirically, was not found to be significantly different between men and women, consistent with more recent literature. Importantly, as age increased, sexual dimorphism decreased, but this was not consistent across all measures of it. Rather, it is evident that differing measures of sexual dimorphism follow distinct developmental trajectories. The only single marker which remained significantly different across all age-groups was cheekbone prominence. Sexual dimorphic faciometrics are therefore dynamic, declining, and differentiated through adulthood. Consequently, it is concluded that care should be taken in using faciometrics in studies involving older populations and that more research is needed to understand the impact of these distinct faciometric trajectories in gender- and masculinity-related studies.
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Dennison, Jessica L., Natalie R. Ricciardi, Ines Lohse, Claude-Henry Volmar, and Claes Wahlestedt. "Sexual Dimorphism in the 3xTg-AD Mouse Model and Its Impact on Pre-Clinical Research." Journal of Alzheimer's Disease 80, no. 1 (March 9, 2021): 41–52. http://dx.doi.org/10.3233/jad-201014.
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Female sex is a leading risk factor for developing Alzheimer’s disease (AD). Sexual dimorphism in AD is gaining attention as clinical data show that women are not only more likely to develop AD but also to experience worse pathology and faster cognitive decline. Pre-clinical AD research in animal models often neglects to address sexual dimorphism in evaluation of behavioral or molecular characteristics and outcomes. This can compromise its translation to a clinical setting. The triple-transgenic AD mouse model (3xTg-AD) is a commonly used but unique AD model because it exhibits both amyloid and tau pathology, essential features of the human AD phenotype. Mounting evidence has revealed important sexually dimorphic characteristics of this animal model that have yet to be reviewed and thus, are often overlooked in studies using the 3xTg-AD model. In this review we conduct a thorough analysis of reports of sexual dimorphism in the 3xTg-AD model including findings of molecular, behavioral, and longevity-related sex differences in original research articles through August 2020. Importantly, we find results to be inconsistent, and that strain source and differing methodologies are major contributors to lack of consensus regarding traits of each sex. We first touch on the nature of sexual dimorphism in clinical AD, followed by a brief summary of sexual dimorphism in other major AD murine models before discussing the 3xTg-AD model in depth. We conclude by offering four suggestions to help unify pre-clinical mouse model AD research inspired by the NIH expectations for considering sex as a biological variable.
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C. Belk, Mark, Scott Bird, Mehmet Cemal Oguz, and Jerald B. Johnson. "Differences in Pelvic Fin Length Represent Sexual Dimorphism in Utah Chub (Gila atraria)." Open Fish Science Journal 7, no. 1 (December 9, 2014): 42–45. http://dx.doi.org/10.2174/1874401x01407010042.
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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.
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Chapman, A., LS Hall, and MB Bennett. "Sexual Dimorphism in the Pelvic Girdle of Australian Flying Foxes." Australian Journal of Zoology 42, no. 2 (1994): 261. http://dx.doi.org/10.1071/zo9940261.
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Sexual dimorphism was observed in the pelvic girdle of all individuals and age classes of Pteropus alecto, P. poliocephalus and P. scapulatus. In females the pelvic girdle is open (V-shaped) whereas it is closed (O-shaped) in males. This striking dimorphism enabled the sex of any individual, including skeletal material alone, to be determined with 100% accuracy. In females the interpubic distance (i.e. the distance between the two pubic bones) is correlated with forearm length. The first comparative photographs of the dimorphic pelvis are presented and the usefulness of this new diagnostic character explored.
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Hernandez, Paula A., Miranda Moreno, Zahra Barati, Conner Hutcherson, Adwait A. Sathe, Chao Xing, Jamie Wright, Tre Welch, and Yasin Dhaher. "Sexual Dimorphism in the Extracellular and Pericellular Matrix of Articular Cartilage." CARTILAGE 13, no. 3 (July 2022): 194760352211217. http://dx.doi.org/10.1177/19476035221121792.
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Objective Women have a higher prevalence and burden of joint injuries and pathologies involving articular cartilage than men. Although knee injuries affecting young women are on the rise, most studies related to sexual dimorphism target postmenopausal women. We hypothesize that sexual dimorphism in cartilage structure and mechanics is present before menopause, which can contribute to sex disparities in cartilage pathologies. Design Bovine knee was used as a model to study healthy adult cartilage. We compared elastic moduli under compression, abundances of extracellular and pericellular matrix (PCM) proteins using proteomics, and PCM constituency with tissue immunofluorescence. The gene expression of matrix-related genes under basal, anabolic, and catabolic conditions was assessed by quantitative polymerase chain reaction (qPCR). Results The equilibrium modulus was higher in male cartilage compared with female cartilage. Proteoglycans were not associated with this biomechanical dimorphism. Proteomic and pathway analyses of tissue showed dimorphic enriched pathways in extracellular matrix (ECM)-related proteins in which male cartilage was enriched in matrix interconnectors and crosslinkers that strengthen the ECM network. Moreover, male and female tissue differed in enriched PCM components. Females had more abundance of collagen type VI and decorin, suggesting different PCM mechanics. Furthermore, the activation of regenerative and catabolic function in chondrocytes triggered sex-dependent signatures in gene expression, indicating dimorphic genetic regulation that is dependent on stimulation. Conclusions We provide evidence for sexual dimorphism in cartilage before menopause. Some differences are intrinsic to chondrocytes’ gene expression defined by their XX versus XY chromosomal constituency.