Sex Allocation Theory for Birds and Mammals

Frank, Steven A.

doi:10.1146/annurev.es.21.110190.000305

Cited by 407 publications

(214 citation statements)

References 103 publications

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“…Previous studies have not detected genetic variation for sexual proportion in a variety of species with sex-chromosomes (Toro & Charlesworth, 1982; and references cited therein; but see Frank, 1990). Curtsinger (1981) found a significant heritability (10 per cent) in non-SR strains of D. pseudoobscura, but this study did not exclude X-or Y-linked inheritance.…”

Section: Discussioncontrasting

confidence: 71%

“…The type of variation is also very relevant: Y-linked control of sexual proportion may lead to male bias, whereas female bias may result from cytoplasmic and X-linked control. Fisher's Principle -and hence, the 50 per cent equilibrium -applies strictly only to autosomal genes (Shaw, 1958;Hamilton, 1967;Bull & Charnov, 1988;Frank, 1990). Finally, it should be noted that the evolutionary explanation for autosomal suppressors of sex-ratio relies entirely on Fisher's Principle. This theory is the most accepted explanation for the commonness of the 1:1 sexual proportion but it has undergone few direct tests (Bull & Charnov, 1988;Conover & Voorhees, 1990;Basolo, 1994), none of them in a system with clear autosomal variation for sexual proportion (Carvalho et al, in preparation).…”

Section: Because Of This Meiotic Drive Advantage Srmentioning

confidence: 99%

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Heritability of sexual proportion in experimental sex-ratio populations of Drosophila mediopunctata

1997

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Sex-linked meiotic drive genes are expected to spread quickly in populations and may cause their extinction because of the lack of one sex. Theoretically, the most general evolutionary response to these genes is the spread of autosomal suppressors of meiotic drive because of Fisher's Principle, a mechanism of natural selection that would correct uneven sexual proportions. Such adaptive response depends on heritable autosomal variation for sexual proportion, which seems to be lacking in most species with chromosomal sex-determination. Natural populations of Drosophila mediopunctata bear sex-ratio X chromosomes ('SR'), an X-Y meiotic drive system that leads to female bias. In this paper we show that sexual proportion is highly heritable (h2 = 41 per cent) in experimental populations of this species because of autosomal genes, thus fulfilling the conditions for adaptive evolution of sexual proportion. The spread of autosomal suppressors is expected to have a dual effect on sexual proportion, reducing both the female excess in the progenies of SR/Y males and the frequency of SR chromosomes. Hence, prior to the spread of their suppressors, SR chromosomes presumably attained a high frequency in natural populations of D. mediopunctata, causing a strong female bias.

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Section: Discussioncontrasting

confidence: 71%

Section: Because Of This Meiotic Drive Advantage Srmentioning

confidence: 99%

Heritability of sexual proportion in experimental sex-ratio populations of Drosophila mediopunctata

1997

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“…Evolutionary theory of sex allocation predicts that mothers should adjust the sex of their offspring according to the fitness return (Trivers & Willard 1973;Maynard Smith 1980;Charnov 1981;Frank 1990;Leimar 1996;Hewison & Gaillard 1999). While empirical studies on many insect taxa have clearly supported sex allocation theory, for large mammals this is still a contentious issue (Sheldon & West 2004).…”

Section: Introductionmentioning

confidence: 99%

Male phenotypic quality influences offspring sex ratio in a polygynous ungulate

et al. 2006

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Evolutionary models of sex ratio adjustment applied to mammals have ignored that females may gain indirect genetic benefits from their mates. The differential allocation hypothesis (DAH) predicts that females bias the sex ratio of their offspring towards (more costly) males when breeding with an attractive male. We manipulated the number of available males during rut in a polygynous ungulate species, the reindeer (Rangifer tarandus), and found that a doubling of average male mass (and thus male attractiveness) in the breeding herd increased the proportion of male offspring from approximately 40 to 60%. Paternity analysis revealed indeed that males of high phenotypic quality sired more males, consistent with the DAH. This insight has consequences for proper management of large mammal populations. Our study suggests that harvesting, by generating a high proportion of young, small and unattractive mates, affects the secondary sex ratio due to differential allocation effects in females. Sustainable management needs to consider not only the direct demographic changes due to harvest mortality and selection, but also the components related to behavioural ecology and opportunities for female choice.

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“…The hypothesis of Trivers & Willard (1973) predicts that in these circumstances females in good condition should allocate relatively more to male offspring than females in poor condition. Although the literature reporting sex-allocation patterns in mammals is abundant (reviewed in Williams 1979;Clutton-Brock & Iason 1986;Frank 1990), controversy still surrounds these predictions and no general conclusions have emerged (e.g. Brown 2001;Cameron & Linklater 2002;Krackow 2002; but see Sheldon & West 2004).…”

Section: Introductionmentioning

confidence: 99%

Sex–biased maternal investment in voles: importance of environmental conditions

Koskela

Huitu

Koivula

et al. 2004

Proc. R. Soc. Lond. B

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Adaptive bias in sex allocation is traditionally proposed to be related to the condition of mothers as well as to the unequal fitness values of produced sexes. A positive relationship between mother condition and investment into male offspring is often predicted. This relationship was also recently found to depend on environmental conditions. We studied these causalities experimentally using a design where winter food supply was manipulated in eight outdoor-enclosed populations of field voles Microtus agrestis. At the beginning of the breeding season in spring, food-supplemented mothers seemed to be in a similar condition, measured as body mass, head width, body condition index and parasite load (blood parasite Trypanosoma), to non-supplemented mothers. Food supplements affected neither the litter size, the reproductive effort of mothers, nor the litter sex ratios at birth. However, food supplementation significantly increased the birth size of male offspring and improved their condition, as indicated by reduced parasite loads (intestinal Eimeria). Interestingly, mothers in good body condition produced larger male offspring only when environmental conditions were improved by food supplements. Although the adaptiveness of variation in mammalian sex ratios is still questionable, our study indicates that mothers in good condition bias their investment towards male offspring, but only when environmental conditions are favourable.

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Sex Allocation Theory for Birds and Mammals

Cited by 407 publications

References 103 publications

Heritability of sexual proportion in experimental sex-ratio populations of Drosophila mediopunctata

Heritability of sexual proportion in experimental sex-ratio populations of Drosophila mediopunctata

Male phenotypic quality influences offspring sex ratio in a polygynous ungulate

Sex–biased maternal investment in voles: importance of environmental conditions

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