Review
Variance in male reproductive success and sexual size dimorphism in pinnipeds: testing an assumption of sexual selection theory
Editor: KH
Abstract
- The theory of evolution by sexual selection for sexual size dimorphism (SSD) postulates that SSD primarily reflects the adaptation of males and females to their different reproductive roles. For example, competition among males for access to females increases male body size because larger males are better able to maintain dominant status than smaller males. Larger dominant males sire most offspring while smaller subordinate males are unsuccessful, leading to skew in reproductive success. Therefore, species with male‐biased SSD are predicted to have greater variance in male reproductive success than those in which both sexes are similar in size.
- We tested this prediction among the Pinnipedia, a mammalian group with a great variation in SSD. From a literature review, we identified genetic estimates of male reproductive success for 10 pinniped taxa (eight unique species and two subspecies of a ninth species) that range from seals with similarly sized males and females to species in which males are more than four times as large as females.
- We found no support for a positive relationship between variance in reproductive success and SSD among pinnipeds after excluding the elephant seals Mirounga leonina and Mirounga angustirostris, which we discuss as distinctive cases.
- Several explanations for these results are presented, including the revival of one of Darwin's original ideas. Darwin proposed that natural selection may explain SSD based on differences in energetic requirements between sexes and the potential for sexual niche segregation. Males may develop larger bodies to exploit resources that remain unavailable to females due to the energetic constraints imposed on female mammals by gestation and lactation. The importance of this alternative explanation remains to be tested.
Citing Literature
Number of times cited: 14
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- M.G. Keevil, B.S. Hewitt, R.J. Brooks and J.D. Litzgus, Patterns of intraspecific aggression inferred from injuries in an aquatic turtle with male-biased size dimorphism, Canadian Journal of Zoology, 95, 6, (393), (2017).
- Amanda M. Bishop, James E. Stewart, Patrick Pomeroy and Sean D. Twiss, Intraseasonal temporal variation of reproductive effort for male grey seals, Animal Behaviour, 134, (167), (2017).
- Kristy L. Biolsi, Pinniped Life History, Encyclopedia of Animal Cognition and Behavior, 10.1007/978-3-319-47829-6_942-1, (1-16), (2017).
- Marcelo H. Cassini, Role of fecundity selection on the evolution of sexual size dimorphism in mammals, Animal Behaviour, 128, (1), (2017).
- Valentina Franco-Trecu, Massimiliano Drago, Diana Szteren and Federico Riet-Sapriza, Population Ecology and Conservation Status of the South American Sea Lion in Uruguay, Tropical Pinnipeds, 10.1201/9781315151588-12, (194-210), (2017).
- A Bishop, P Pomeroy and SD Twiss, Breeding male grey seals exhibit similar activity budgets across varying exposures to human activity, Marine Ecology Progress Series, 10.3354/meps11254, 527, (247-259), (2015).
- Annalisa Berta, James L. Sumich and Kit M. Kovacs, Reproductive Structures, Strategies, and Patterns, Marine Mammals, 10.1016/B978-0-12-397002-2.00013-2, (465-532), (2015).
- Valentina Franco-Trecu, Paula Costa-Urrutia, Yolanda Schramm, Bettina Tassino and Pablo Inchausti, Tide line versus internal pools: mating system and breeding success of South American sea lion males, Behavioral Ecology and Sociobiology, 69, 12, (1985), (2015).
- Oliver Krüger, Jochen B. W. Wolf, Rudy M. Jonker, Joseph I. Hoffman and Fritz Trillmich, DISENTANGLING THE CONTRIBUTION OF SEXUAL SELECTION AND ECOLOGY TO THE EVOLUTION OF SIZE DIMORPHISM IN PINNIPEDS, Evolution, 68, 5, (1485-1496), (2014).
- Klaus Hackländer, Mammal Reviewcontinues to shine, Mammal Review, 44, 3-4, (163), (2014).
- Valentina Franco-Trecu, Paula Costa, Yolanda Schramm, Bettina Tassino and Pablo Inchausti, Sex on the rocks: reproductive tactics and breeding success of South American fur seal males, Behavioral Ecology, 25, 6, (1513), (2014).
- Jimena Bohórquez-Herrera, Claudia Janetl Hernández-Camacho, David Aurioles-Gamboa and Víctor H. Cruz-Escalona, Plasticity in the agonistic behaviour of male California sea lions, Zalophus californianus, Animal Behaviour, 89, (31), (2014).




