Sexual selection and the rodent baculum: an intraspecific study in the house mouse (Mus musculus domesticus)

Ramm, Steven A.; Khoo, Lin; Stockley, Paula

doi:10.1007/s10709-009-9385-8

Cited by 27 publications

(25 citation statements)

References 57 publications

(111 reference statements)

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“…In addition, comparative analyses indicate that baculum size may be subject to sexual selection in rodents and carnivores, with increased baculum length favoured under high levels of sperm competition [10]. In the present study however, we find baculum width to be a more important predictor of reproductive success for male house mice under conditions of intense postcopulatory sexual selection, which is consistent with relatively high intraspecific variation [16,17] and positive allometry [17,18] in this aspect of penile morphology.…”

Section: Discussionsupporting

confidence: 80%

Baculum morphology predicts reproductive success of male house mice under sexual selection

et al. 2013

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BackgroundDiversity in penile morphology is characterised by extraordinary variation in the size and shape of the baculum (penis bone) found in many mammals. Although functionally enigmatic, diversity in baculum form is hypothesised to result from sexual selection. According to this hypothesis, the baculum should influence the outcome of reproductive competition among males within promiscuous mating systems. However, a test of this key prediction is currently lacking.ResultsHere we show that baculum size explains significant variation in the reproductive success of male house mice under competitive conditions. After controlling for body size and other reproductive traits, the width (but not length) of the house mouse baculum predicts both the mean number of offspring sired per litter and total number of offspring sired.ConclusionsBy providing the first evidence linking baculum morphology to male reproductive success, our results support the hypothesis that evolutionary diversity in baculum form is driven by sexual selection.

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Section: Discussionsupporting

confidence: 80%

Baculum morphology predicts reproductive success of male house mice under sexual selection

et al. 2013

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“…The allometry of genitalia has been of recent interest because of the realization that variation in the size and shape of genitalia may be heavily influenced by sexual selection (Hosken & Stockley, 2004). Traits under sexual selection are predicted to exhibit positive allometry (Green, 1992; Petrie, 1992; Pomiankowski & Møller, 1995; Kodric‐Brown, Sibly & Brown, 2006; but see Bonduriansky, 2007), and there is substantial evidence that the mammalian baculum exhibits positive allometry in a variety of species, ostensibly because of the baculum's importance in post‐copulatory selection (Miller & Burton, 2001; Lüpold et al ., 2004; Kinahan et al ., 2007; Ramm, 2007; Tasikas et al ., 2009; but see Kinahan et al ., 2008; Manjerovic et al ., 2008; Ramm et al ., 2010). These studies have focused on mammals that do not exhibit the male‐biased sexual size dimorphism typical in mammals (Andersson, 1994).…”

Section: Discussionmentioning

confidence: 99%

Allometry of the baculum and sexual size dimorphism in American martens and fishers (Mammalia: Mustelidae)

Schulte‐Hostedde

Bowman

Middel

2011

Biological Journal of the Linnean Society

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Genitalia are among the most variable of morphological traits, and recent research suggests that this variability may be the result of sexual selection. For example, large bacula may undergo post-copulatory selection by females as a signal of male size and age. This should lead to positive allometry in baculum size. In addition to hyperallometry, sexually selected traits that undergo strong directional selection should exhibit high phenotypic variation. Nonetheless, in species in which pre-copulatory selection predominates over post-copulatory selection (such as those with male-biased sexual size dimorphism), baculum allometry may be isometric or exhibit negative allometry. We tested this hypothesis using data collected from two highly dimorphic species of the Mustelidae, the American marten (Martes americana) and the fisher (Martes pennanti). Allometric relationships were weak, with only 4.5-10.1% of the variation in baculum length explained by body length. Because of this weak relationship, there was a large discrepancy in slope estimates derived from ordinary least squares and reduced major axis regression models. We conclude that stabilizing selection rather than sexual selection is the evolutionary force shaping variation in baculum length because allometric slopes were less than one (using the ordinary least squares regression model), a very low proportion of variance in baculum length was explained by body length, and there was low phenotypic variability in baculum length relative to other traits. We hypothesize that this pattern occurs because post-copulatory selection plays a smaller role than pre-copulatory selection (manifested as male-biased sexual size dimorphism). We suggest a broader analysis of baculum allometry and sexual size dimorphism in the Mustelidae, and other taxonomic groups, coupled with a comparative analysis and with phylogenetic contrasts to test our hypothesis.

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“…Mice were thawed and bacula prepared following established protocols (Ramm et al ). Digital images were captured using a binocular microscope at ×25 magnification.…”

Section: Methodsmentioning

confidence: 99%

“…Under the assumption that traits subject to sexual selection should exhibit positive allometry, the scaling relationships between baculum length and body size have been explored, but have produced conflicting results (Patterson ; Lüpold et al ; Miller and Nagorsen ; Ramm et al ; Schulte‐Hostedde et al ). The conceptual premise on which these studies have been based has also been questioned (Bonduriansky ).…”

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confidence: 99%

Experimental Evidence for the Evolution of the Mammalian Baculum by Sexual Selection

Simmons

Firman

2013

Evolution

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Male genitalia exhibit a taxonomically widespread pattern of rapid and divergent evolution. Sexual selection is generally believed to be responsible for these patterns of evolutionary divergence, although empirical support for the sexual selection hypothesis comes mainly from studies of insects. Here we show that sexual selection is responsible for an evolutionary divergence in baculum morphology among populations of house mice Mus domesticus. We sourced mice from three isolated populations known to be subject to differing strengths of postcopulatory sexual selection and bred them under common-garden conditions. Mice from populations with strong postcopulatory sexual selection had bacula that were relatively thicker compared with mice from populations with weak selection. We used experimental evolution to determine whether these patterns of divergence could be ascribed to postcopulatory sexual selection. After 27 generations of experimental evolution, populations of mice subjected to postcopulatory sexual selection evolved bacula that were relatively thicker than populations subjected to enforced monogamy.Our data thereby provide evidence that postcopulatory sexual selection underlies an evolutionary divergence in the mammalian baculum and supports the hypothesis that sexual selection plays a general role in the evolution of male genital morphology across evolutionary diverse taxonomic groups.

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Sexual selection and the rodent baculum: an intraspecific study in the house mouse (Mus musculus domesticus)

Cited by 27 publications

References 57 publications

Baculum morphology predicts reproductive success of male house mice under sexual selection

Baculum morphology predicts reproductive success of male house mice under sexual selection

Allometry of the baculum and sexual size dimorphism in American martens and fishers (Mammalia: Mustelidae)

Experimental Evidence for the Evolution of the Mammalian Baculum by Sexual Selection

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