Sexual dimorphism in Carnivorans

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Sexual dimorphism in pinnipeds particularly elephant seals is the most pronounced among Carnivorans.
Sexual dimorphism in lions is the most prominent among felids

Sexual dimorphism is the condition where sexes of the same species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction.[1] Sexual dimorphism in carnivorans, in which males are larger than females, is common. Sexual selection is frequently cited as the cause of the intraspecific divergence in body proportions and craniomandibular morphology between the sexes within the Carnivora order.[2][3] It is anticipated that animals with polygynous mating systems and high levels of territoriality and solitary behavior will exhibit the highest levels of sexual size dimorphism. Pinnipeds offer an illustration for this.

Different types

Body size

Sexual size dimorphism is the difference in body size between the sexes within a group of some sort or another. Carnivorans exhibit high levels of sexual size dimorphism with males generally being larger than females.[4]

Canine tooth

Males have larger, longer and more powerful canines than their female counterparts. A study of skull and tooth size in 45 species of Carnivorans showed that sexual dimorphism was most pronounced in the size of the canine tooth.[2] Breeding systems seems to be the most reasonable explanation for the finding. Social species like lions, in which males have a canine teeth 25% larger than females are the most sexual dimorphic of felids.

Skeletal structure

In terms of skeletal structure, Carnivorans are highly sexually dimorphic. Males have more robust and larger skulls which promotes a stronger biteforce, larger necks to permit more powerful neck muscles that work to prevent torsional loading of the neck and improve the ability to rend with the teeth and jerk the skull. Males also have larger scapulae that enable more muscle to transmit force from the trunk to the forelimbs and stabilize the shoulder joint and stronger limbs with better mechanical advantages due to anatomy.[5][6][7]

Mechanisms

A secondary factor that propels the evolution of sexual dimorphism might be provided by niche divergence and resource partitioning. For instance, the evidence for the divergence of the intersexual niche is found in the size and structure of the craniomandibular bones. The ecological difference between the sexes and even a decline in intersexual rivalry for resources and habitat usage is reflected in the skull's phenotypic variation.[8][9] It is well known that many carnivoran species' males and females use different dietary resources. This is frequently manifested in prey size, with males frequently consuming larger prey than their female counterparts.[10][11] Moreover, there is a correlation between sexual dimorphism and carnivory in carnivorans, meaning that species that are more carnivorous have larger size differences between males and females.[2][12] Hence, increased sexual dimorphism in obligate carnivores lessens intraspecific nutritional competition by minimizing conflict between males and females.[13]

Because they have an evolutionary impact on body size in both males and females, or both, sexual selection and natural selection are frequently seen as the main mechanisms behind sexual size dimorphism. It has long been assumed that sexual selection is the main cause of sexual size dimorphism in the majority of endothermic vertebrates (including mammals and birds), where the larger sex directly boosts its reproductive success through intrasexual competition.[14][15][16][17] The evolution of sexual size dimorphism has been theorized to be influenced or maintained by natural selection.[18] It is also possible that sexual selection has influenced the evolution of sexual size dimorphism, as suggested by the hyperallometric patterns found in both mammals and birds.

See also

References

  1. ^ Encyclopedia of Animal Behaviour. Vol. 2. Academic Press. 21 January 2019. p. 7. ISBN 978-0-12-813252-4.
  2. ^ a b c Gittleman, J. L.; Valkenburgh, B. Van (May 1997). "Sexual dimorphism in the canines and skulls of carnivores: effects of size, phylogency, and behavioural ecology". Journal of Zoology. 242 (1): 97–117. doi:10.1111/j.1469-7998.1997.tb02932.x. ISSN 0952-8369.
  3. ^ Sylvia Brunner, Michael M Bryden, Peter D. Shaughnessy (September 2004). "Cranial ontogeny of otariid seals". Systematics and Biodiversity. 2 (1): 83–110. Bibcode:2004SyBio...2...83B. doi:10.1017/S1477200004001367. S2CID 83737300.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ "Sexual Size Dimorphism". obo. Retrieved 2023-03-21.
  5. ^ Radinsky, Leonard B. (1982). "Evolution of Skull Shape in Carnivores. 3. The Origin and Early Radiation of the Modern Carnivore Families". Paleobiology. 8 (3): 177–195. Bibcode:1982Pbio....8..177R. doi:10.1017/S0094837300006928. ISSN 0094-8373. JSTOR 2400405. S2CID 89207900.
  6. ^ Goslow, G. E.; Seeherman, H. J.; Taylor, C. R.; McCutchin, M. N.; Heglund, N. C. (October 1981). "Electrical activity and relative length changes of dog limb muscles as a function of speed and gait". The Journal of Experimental Biology. 94: 15–42. doi:10.1242/jeb.94.1.15. ISSN 0022-0949. PMID 7310312.
  7. ^ Meltzer, S. J. (1907). "The Factors of Safety in Animal Structure and Animal Economy". Science. 25 (639): 481–498. Bibcode:1907Sci....25..481M. doi:10.1126/science.25.639.481. ISSN 0036-8075. JSTOR 1633836. PMID 17781693.
  8. ^ Thom, Michael D.; Harrington, Lauren A.; Macdonald, David W. (June 2004). "Why are American mink sexually dimorphic? A role for niche separation". Oikos. 105 (3): 525–535. Bibcode:2004Oikos.105..525T. doi:10.1111/j.0030-1299.2004.12830.x.
  9. ^ Christiansen, Per; Harris, John M. (2012-10-26). "Variation in Craniomandibular Morphology and Sexual Dimorphism in Pantherines and the Sabercat Smilodon fatalis". PLOS ONE. 7 (10): e48352. Bibcode:2012PLoSO...748352C. doi:10.1371/journal.pone.0048352. ISSN 1932-6203. PMC 3482211. PMID 23110232.
  10. ^ Birks, J. D. S.; Dunstone, N. (1985). "Sex-Related Differences in the Diet of the Mink Mustela vison". Holarctic Ecology. 8 (4): 245–252. Bibcode:1985Ecogr...8..245B. doi:10.1111/j.1600-0587.1985.tb01175.x. ISSN 0105-9327. JSTOR 3682351.
  11. ^ Macdonald, D. W.; Johnson, D. D. P. (February 2015). "Patchwork planet: the resource dispersion hypothesis, society, and the ecology of life". Journal of Zoology. 295 (2): 75–107. doi:10.1111/jzo.12202. ISSN 0952-8369.
  12. ^ Noonan, Michael J.; Johnson, Paul J.; Kitchener, Andrew C.; Harrington, Lauren A.; Newman, Chris; Macdonald, David W. (2016-10-29). "Sexual size dimorphism in musteloids: An anomalous allometric pattern is explained by feeding ecology". Ecology and Evolution. 6 (23): 8495–8501. Bibcode:2016EcoEv...6.8495N. doi:10.1002/ece3.2480. ISSN 2045-7758. PMC 5167046. PMID 28031801.
  13. ^ Murdoch, William W. (1966). ""Community Structure, Population Control, and Competition"-A Critique" (PDF). The American Naturalist. 100 (912): 219–226. doi:10.1086/282415. ISSN 0003-0147. S2CID 84354616.
  14. ^ Clutton-Brock, Tim (2007-12-21). "Sexual selection in males and females". Science. 318 (5858): 1882–1885. Bibcode:2007Sci...318.1882C. doi:10.1126/science.1133311. ISSN 1095-9203. PMID 18096798. S2CID 6883765.
  15. ^ Fairbairn, Daphne J.; Blanckenhorn, Wolf U.; Székely, Tamás (2007-07-05). Sex, Size and Gender Roles: Evolutionary Studies of Sexual Size Dimorphism. OUP Oxford. ISBN 978-0-19-152608-4.
  16. ^ Lindenfors, Patrik; Tullberg, Birgitta S.; Biuw, Martin (2002-08-01). "Phylogenetic analyses of sexual selection and sexual size dimorphism in pinnipeds". Behavioral Ecology and Sociobiology. 52 (3): 188–193. doi:10.1007/s00265-002-0507-x. ISSN 1432-0762. S2CID 46546173.
  17. ^ Fitzpatrick, John L.; Almbro, Maria; Gonzalez-Voyer, Alejandro; Kolm, Niclas; Simmons, Leigh W. (November 2012). "Male contest competition and the coevolution of weaponry and testes in pinnipeds". Evolution; International Journal of Organic Evolution. 66 (11): 3595–3604. doi:10.1111/j.1558-5646.2012.01713.x. hdl:10261/61082. ISSN 1558-5646. PMID 23106721. S2CID 19287881.
  18. ^ Pincheira-Donoso, Daniel; Hunt, John (February 2017). "Fecundity selection theory: concepts and evidence". Biological Reviews of the Cambridge Philosophical Society. 92 (1): 341–356. doi:10.1111/brv.12232. ISSN 1469-185X. PMID 26526765. S2CID 3033879.
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