Dominant rams lose out by sperm depletion

Preston, Brian T.; Stevenson, Ian R.; Pemberton, Josephine M.; Wilson, Kenneth

doi:10.1038/35055617

Cited by 340 publications

(259 citation statements)

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“…As suggested above (examples 2, 7), some morphological traits may be subject to stabilizing sexual selection: for example, combat success may be maximized with a particular relative weapon size (Clutton-Brock 1982; Kitchener 2000; but see Preston et al 2001Preston et al , 2003, multiple mechanisms of sexual selection may exert conflicting selection on a trait (Moore and Moore 1999;Bonduriansky and Rowe 2003), or sexual and viability selection may balance (e.g., Wilkinson 1987). Our model suggests that selection on the trait size to body size ratio per se produces isometric scaling (example 2), while more complex functions that yield net stabilizing selection on trait size (example 7) may produce other allometric patterns.…”

Section: Discussionmentioning

confidence: 99%

The Evolution of Static Allometry in Sexually Selected Traits

2003

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Abstract. Although it has been the subject of verbal theory since Darwin, the evolution of morphological trait allometries remains poorly understood, especially in the context of sexual selection. Here we present an allocation trade-off model that predicts the optimal pattern of allometry under different selective regimes. We derive a general solution that has a simple and intuitive interpretation and use it to investigate several examples of fitness functions. Verbal arguments have suggested cost or benefit scenarios under which sexual selection on signal or weapon traits may favor larger individuals with disproportionately larger traits (i.e., positive allometry). However, our results suggest that this is necessarily true only under a precisely specified set of conditions: positive allometry will evolve when the marginal fitness gains from an increase in relative trait size are greater for large individuals than for small ones. Thus, the optimal allometric pattern depends on the precise nature of net selection, and simple examples readily yield isometry, positive or negative allometry, or polymorphisms corresponding to sigmoidal scaling. The variety of allometric patterns predicted by our model is consistent with the diversity of patterns observed in empirical studies on the allometries of sexually selected traits. More generally, our findings highlight the difficulty of inferring complex underlying processes from simple emergent patterns.Key words. Allometry, display traits, evolution, exaggerated traits, morphology, sexual selection, signaling, weapons.Received April 7, 2003. Accepted June 5, 2003 An organism's shape is defined by the sizes of its body parts (traits) in relation to the size of the whole (body size), with the scaling pattern relating trait size to body size known as the trait allometry. Although a great deal of work has been devoted to the mathematical analysis of observed allometric patterns (e.g., Brody 1945;Gould 1966;Sprent 1972;Eberhard and Gutiérrez 1991) and the effects of biomechanical constraints (e.g., McMahon 1975;Pennycuick 1992;Ravosa et al. 2000), much less is known about how allometry is shaped by selection. This last question is of particular interest in the context of sexually selected traits, which sometimes exhibit spectacular elaboration and enlargement (e.g., Darwin 1871;Gould 1974;Simmons and Tomkins 1996;Emlen and Nijhout 2000). In this paper, we use a resource allocation trade-off model to investigate how the form of selection acting on a trait and body size affects the evolution of static allometry, trait scaling with body size among conspecific individuals at the same developmental stage (Cock 1966). The model yields some intuitively appealing predictions as well as counterintuitive insights that challenge the validity or generality of verbal theories.Allometries are usually modeled using the allometric equation (Brody 1945), Y ϭ aX b . When log-transformed, this becomes the linear equation log(Y) ϭ log(a) ϩ blog(X), where b is the allometric slope. Although, in pra...

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Section: Discussionmentioning

confidence: 99%

The Evolution of Static Allometry in Sexually Selected Traits

2003

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“…Indeed, trade-offs between pre-and postcopulatory sexual selection are expected under sperm competition theory, where investment in obtaining matings is predicted to come at a cost to investment in ejaculates (Parker 1998). Such trade-offs may account for negative associations between fertilization success and mating success (Danielsson 2001;Preston et al 2001), and/or promote the evolution of alternative mating strategies in which males compensate for the inability to monopolize mates by investing relatively heavily in more competitive ejaculates (see reviews in Oliveira et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Quantitative genetic evidence that males trade attractiveness for ejaculate quality in guppies

2010

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Polyandry, where females mate with multiple males, means that a male's reproductive success will depend both on his ability to acquire mates and the ability of his sperm to compete effectively for fertilizations. But, how do males partition their reproductive investment between these two episodes of selection? Theory predicts that increases in ejaculate investment will come at a cost to investment in other reproductive traits. Although evidence revealing such trade-offs is accumulating, we know little about their genetic basis. Here, I report patterns of genetic (co)variation for a range of traits subject to pre-and postcopulatory sexual selection in the guppy Poecilia reticulata, a promiscuous livebearing fish in which males alternate between courtship and sneak matings to obtain copulations. The analyses of genetic variation and covariation for these behaviours revealed a strong genetic predisposition for one tactic over the other. Both mating tactics were also strongly genetically integrated with the level of sexual ornamentation and ejaculate quality. Males that predominantly performed sneak matings were less ornamented but had faster swimming sperm than those that predominantly used courtship. These patterns of genetic variation and covariation reveal potential evolutionary constraints on the direction of selection of pre-and postcopulatory traits, and support sperm competition theory by revealing a trade-off between sexual attractiveness and investment in ejaculates.

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“…It is now recognized that, counter to Bateman's principle [46], the reproductive success of a male is sometimes limited by the number of sperm that he can produce. Males who are successful in precopulatory sexual selection can have higher costs of sperm production and become sperm depleted, so that female fertility is sperm limited, and successful males can suffer reduced competitive fertilization success [62][63][64]. Moreover, one of the putative genetic benefits of postcopulatory female choice is the avoidance of genetic incompatibility between maternal and paternal haplotypes, so that the preferred sire of a female depends on her own genotype [65,66].…”

Section: Reviewmentioning

confidence: 99%