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The role of fecundity and sexual selection in the evolution of size and sexual size dimorphism in New World and Old World voles (Rodentia: Arvicolinae)


Garcia-Navas, Vicente; Bonnet, Timothée; Bonal, Raul; Postma, Erik (2016). The role of fecundity and sexual selection in the evolution of size and sexual size dimorphism in New World and Old World voles (Rodentia: Arvicolinae). Oikos, 125(9):1250-1260.

Abstract

Evolutionary ecologists dating back to Darwin (1871) have sought to understand why males are larger than females in some species, and why females are the larger sex in others. Although the former is widespread in mammals, rodents and other small mammals usually exhibit low levels of sexual size dimorphism (SSD). Here, we investigate patterns of sexual dimorphism in 34 vole species belonging to the subfamily Arvicolinae in a phylogenetic comparative framework. We address the potential role of sexual selection and fecundity selection in creating sex diffrences in body size. No support was found for hyperallometric scaling of male body size to female body size. We observed a marginally signifiant relationship between SSD and the ratio of male to female home range size, with the latter being positively related to the level of intrasexual competition for mates. Ths suggests that sexual selection favours larger males. Interestingly, we also found that habitat type, but not mating system, constitutes a strong predictor of SSD. Species inhabiting open habitats – where males have extensive home ranges in order to gain access to as many females as possible – exhibit a higher mean dimorphism than species inhabiting closed habitats, where females show strong territoriality and an uniform distribution preventing males to adopt a territorial strategy for gaining copulations. Nonetheless, variation in the strength of sexual selection is not the only selective force shaping SSD in voles; we also found a positive association between female size and litter size across lineages. Assuming this relationship also exists within lineages (i.e. fecundity selection on female size), this suggests an additional role for variation in the strength of fecundity selection shaping interspecifi diffrences in female size, and indirectly in SSD. Threfore our results suggest that diffrent selective processes act on the sizes of males and females, but because larger size is favoured in both sexes, SSD is on average relatively small.

Abstract

Evolutionary ecologists dating back to Darwin (1871) have sought to understand why males are larger than females in some species, and why females are the larger sex in others. Although the former is widespread in mammals, rodents and other small mammals usually exhibit low levels of sexual size dimorphism (SSD). Here, we investigate patterns of sexual dimorphism in 34 vole species belonging to the subfamily Arvicolinae in a phylogenetic comparative framework. We address the potential role of sexual selection and fecundity selection in creating sex diffrences in body size. No support was found for hyperallometric scaling of male body size to female body size. We observed a marginally signifiant relationship between SSD and the ratio of male to female home range size, with the latter being positively related to the level of intrasexual competition for mates. Ths suggests that sexual selection favours larger males. Interestingly, we also found that habitat type, but not mating system, constitutes a strong predictor of SSD. Species inhabiting open habitats – where males have extensive home ranges in order to gain access to as many females as possible – exhibit a higher mean dimorphism than species inhabiting closed habitats, where females show strong territoriality and an uniform distribution preventing males to adopt a territorial strategy for gaining copulations. Nonetheless, variation in the strength of sexual selection is not the only selective force shaping SSD in voles; we also found a positive association between female size and litter size across lineages. Assuming this relationship also exists within lineages (i.e. fecundity selection on female size), this suggests an additional role for variation in the strength of fecundity selection shaping interspecifi diffrences in female size, and indirectly in SSD. Threfore our results suggest that diffrent selective processes act on the sizes of males and females, but because larger size is favoured in both sexes, SSD is on average relatively small.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2016
Deposited On:14 Jan 2016 10:13
Last Modified:30 Dec 2016 01:00
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0030-1299
Additional Information:This is the peer reviewed version of the following article: [García-Navas, V., Bonnet, T., Bonal, R. and Postma, E. (2015), The role of fecundity and sexual selection in the evolution of size and sexual size dimorphism in New World and Old World voles (Rodentia: Arvicolinae). Oikos. doi: 10.1111/oik.03026]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving (http://olabout.wiley.com/WileyCDA/Section/id-820227.html#terms). Data deposited at Dryad: doi:10.5061/dryad.q42b2
Publisher DOI:https://doi.org/10.1111/oik.03026

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