53 research outputs found
Sperm sociality: Cooperation, altruism, and spite
No full textCitation: Pizzari, T & Foster, K. R. (2008). 'Sperm sociality: cooperation, altruism, and spite', PLoS Biology, 6(5), e130. [Available at http://biology.plosjournals.org]. Copyright 2008 Pizzari and Foster. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Sexual conflict and sexual selection: Measuring antagonistic coevolution
No full textArnqvist (2004) raises some concerns with several of the points made by Pizzari and Snook (2003) on the study of sexually antagonistic coevolution (SAC) generated by sexual conflict, arguing that: (1) sexual conflict cannot be expressed in terms of average male and female fitness; (2) our criticism of current experimental approaches, particularly interpopulation crosses, is unjustified; and (3) the alternative experimental approach we proposed is problematic. Here we discuss and respond to these criticisms by: (1) clarifying that we can distinguish between SAC and mutualistic sexual coevolution by measuring changes in the average fitness of the reproducing subsamples of males and females of a population across generations, (2) maintaining that testing SAC using interpopulation crosses is undermined by the lack of a priori knowledge of what traits mediate SAC across isolated populations, and (3) reinforcing the advantages of our experimental approach to distinguish between sexually mutualistic and antagonistic selection
Post-insemination sexual selection in birds.
No full textIn many avian species females obtain sperm from multiple males during a single reproductive event, setting the scene for post-insemination sexual selection through the competition of the ejaculates of different males over fertilisation (sperm competition) and female biased utilisation of sperm (cryptic female choice). The use of poultry techniques in combination with molecular tools is catalysing an interest in birds as vertebrate model systems to study the mechanisms of post-insemination sexual selection. This chapter: (i) outlines the main mechanisms of avian sperm competition, (ii) introduces methodological approaches to study post-insemination sexual selection in birds, (iii) reviews recent evidence of multiple mechanisms of strategic sperm allocation by males, and (iv) discusses mechanisms of cryptic female choice. Post-insemination variance in paternity in birds, appears to be determined by the interactions between complex male and female strategies of differential sperm utilisation. It is argued that a better understanding of the operation of post-insemination sexual selection in birds may be achieved through a two-pronged approach which, on the one hand, investigates behavioural and physiological mechanisms applying poultry techniques and molecular tools to domestic model species, and on the other, verifies these mechanisms and tests their adaptive significance in more natural populations
Evolution: the paradox of sperm leviathans.
No full textSexual selection theory predicts that sperm competition will push males to produce more, smaller sperm. Paradoxically, in the fruitfly Drosophila bifurca sperm competition is rife but males produce few, giant sperm--the largest known. A recent study reconciles the evolution of giant sperm with theory
Food, vigilance, and sperm: the role of male direct benefits in the evolution of female preference in a polygamous bird
No full textThe adaptive significance of female selection of copulation partners remains unresolved, particularly in polygamous species where males do not provide paternal care. In these species the possibility that direct benefits other than paternal care may play an important role in the evolution of female choice has received little attention. I tested whether direct benefits are associated with female choice in the polygamous feral fowl, Gallus g. domesticus, where females prefer socially dominant copulation partners and males do not care for the young but do provide females with three commodities: food, vigilance, and sperm. I used a combination of empirical and experimental data to show that male propensity to offer food and vigilance, but not sperm, was positively associated with male social status, suggesting that the provision of these resources may be costly and condition dependent in males. Copulation success was correlated with male status but not with the number of feedings a female received from a male, indicating that a female preferred dominant partners that in general provided any female with more food, rather than partners that provided only her with more food, consistent with the idea that females may use male resource provisioning as a proximate mechanism to assess male condition. Together, these results indicate that male resources provisioning is (1) tightly linked to male social status, (2) a potential indicator of male condition and possibly genetic quality, and (3) a potential criterion for females to select dominant partners, thus playing an important role in the evolution of partner choice even in polygamous species lacking paternal care. Copyright 2003.
Indirect partner choice through manipulation of male behaviour by female fowl, Gallus gallus domesticus.
No full textThe direct and indirect consequences of female copulatory behaviour for copulation success have seldom been quantified. In feral fowl, most copulations were forced by males and copulation success was determined by two factors. First, female differential resistance and solicitation directly affected copulation success and were displayed non-randomly with respect to male social status. Second, another female copulatory behaviour, the distress call, had an indirect effect on both copulation success and the quality of copulation partners. Distress calls triggered male attention to a copulation, which increased the probability of higher-ranking males than the copulating male disrupting the copulation and inseminating the calling female. Females preferentially uttered distress calls when mounted by low-ranking males. Both copulation resistance and distress calling influenced copulation success, but only distress calling increased the probability of copulation disruption by other males. Consistent with the effect of direct selection, differential distress calling indirectly biased copulation success in favour of dominant males. Female fowl may thus ameliorate the effect of male sexual coercion by manipulating male behaviour
Evolution: sperm ejection near and far.
No full textIn promiscuous fruit flies, the last male to inseminate a female has a fertilising advantage. Recent evidence indicates that this happens because females eject previously stored semen after a new copulation, revealing female bias in sperm use and the resulting battle of the sexes over fertilisation
Sexual selection: sperm in the fast lane.
No full textSperm competition has led to spectacular adaptations in males and their ejaculates. A recent study of Tanganykan cichlids provides compelling evidence that sperm competition can drive the evolution of faster, longer sperm
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