IBYME   02675
INSTITUTO DE BIOLOGIA Y MEDICINA EXPERIMENTAL
Unidad Ejecutora - UE
artículos
Título:
Variance in male reproductive success and sexual size dimorphism in pinnipeds: testing an assumption of sexual selection theory
Autor/es:
GONZALEZ M, CASSINI MH
Revista:
MAMMAL REVIEW
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2013 vol. 161 p. 481 - 487
ISSN:
0305-1838
Resumen:
1. 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.
2. 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.
3. 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.
4. 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.