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141
Sperm length variation as a predictor of extrapair paternity in passerine birds.
Published 2010-10-01“…The rate of extrapair paternity is a commonly used index for the risk of sperm competition in birds, but paternity data exist for only a few percent of the approximately 10400 extant species. …”
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142
Ejaculate depletion patterns evolve in response to experimental manipulation of sex ratio in Drosophila melanogaster.
Published 2007“…Measures of ejaculate investment were made in males that had been maintained at male-biased (MB) and female-biased (FB) adult sex ratios, in which levels of sperm competition were high and low, respectively. Theory predicts that when the risk of sperm competition is high and mating opportunities are rare (as they are for males in the MB populations), males should increase investment in their few matings. …”
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143
Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in <i>Peromyscus</i> Mice
Published 2021-09-01“…The function of the sperm hook remains largely unknown, but it has been hypothesized to have evolved as an adaptation to inter-male sperm competition and thus has been implicated in increased swimming efficiency or in the formation of collective sperm movements. …”
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144
Sexual development and reproductive pattern of the Mutton hamlet, Alphestes afer (Teleostei: Epinephelidae): a dyandric, hermaphroditic reef fish
“…Males showed a high sperm competition rank (3.8), suggesting intense sperm competition. …”
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145
Masturbation in a male Phayre's langur, <i>Trachypithecus phayrei</i>
Published 2021-11-01“…The lack of sexual opportunity could result in masturbation and sperm competition among males. However, sperm competition is reported to be low in such non-seasonal breeders. …”
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146
Postcopulatory sexual selection is associated with reduced variation in sperm morphology.
Published 2007-05-01“…However, previous studies have focused almost exclusively on the influence of sperm competition on variation among species. In this study we tested the hypothesis that intraspecific variation in sperm morphology is driven by the level of postcopulatory sexual selection in passerine birds.Using two proxy measures of sperm competition level, (i) relative testes size and (ii) extrapair paternity level, we found strong evidence that intermale variation in sperm morphology is negatively associated with the degree of postcopulatory sexual selection, independently of phylogeny.Our results show that the role of postcopulatory sexual selection in the evolution of sperm morphology extends to an intraspecific level, reducing the variation towards what might be a species-specific 'optimum' sperm phenotype. …”
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147
The bold and the sperm: positive association between boldness and sperm number in the guppy
Published 2019-07-01“…Our work highlights the importance of considering post-copulatory traits when investigating fitness consequences of personality traits, especially in species with high levels of female multiple matings and hence sperm competition.…”
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148
The evolution of continuous variation in ejaculate expenditure strategy.
Published 2009“…Sperm competition theory has largely focused on the evolution of ejaculate expenditure strategies across different species or populations or across discrete mating roles on which sperm competition operates differentially. …”
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149
Male mounting alone reduces female promiscuity in the fowl.
Published 2005“…The fertilization success of an insemination is at risk when a female has the possibility to copulate with multiple males, generating sperm competition and sexual conflict over remating. Female propensity to remate is often reduced after copulation, and a staggering diversity of highly derived male traits that discourage female promiscuity have been investigated. …”
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150
Sexual selection and the adaptive evolution of mammalian ejaculate proteins.
Published 2008“…One of these, the seminal vesicle-derived protein Svs2, also shows some evidence for a concentration of positive selection in those lineages in which sperm competition is common. However, this was not a general trend among all the rodent genes we examined. …”
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151
Body size correlates with fertilization success but not gonad size in grass goby territorial males.
Published 2012-01-01“…In fish species with alternative male mating tactics, sperm competition typically occurs when small males that are unsuccessful in direct contests steal fertilization opportunities from large dominant males. …”
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152
Oral Sex, Semen Displacement, and Sexual Arousal: Testing the Ejaculate Adjustment Hypothesis
Published 2013-12-01“…We discuss limitations to the current research and highlight the heuristic value of sperm competition theory for understanding human sexual behaviors.…”
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153
Post-insemination sexual selection in birds.
Published 2007“…In 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). …”
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154
Effects of sperm storage and male colour on probability of paternity in a polychromatic lizard
Published 2009“…Sexual selection may take place before or after mating and may involve a large number of different mechanisms, for example, overt male aggression, mate choice, sperm competition and cryptic female choice. In most species, males show similar reproductive tactics and, hence, achieve their reproductive success in the same or a similar way. …”
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155
Male fecundity stimulation: conflict and cooperation within and between the sexes: model analyses and coevolutionary dynamics.
Published 2010“…Female promiscuity forces the ejaculates of different males to compete for fertilization through sperm competition. In turn, competing ejaculates often influence female promiscuity and fitness, for example, when ejaculate products increase female fecundity. …”
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156
Experiments confirm a dispersive phenotype associated with a natural gene drive system
Published 2021-05-01“…This could help the t avoid detrimental sperm competition, because density is associated with the frequency of polyandry. …”
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157
Context-dependent behavioural plasticity compromises disruptive selection of sperm traits in squid.
Published 2021-01-01“…Therefore, polyandry that intensifies post-mating sperm competition should constrain intraspecific sperm polymorphism. …”
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158
Spermathecal structure data
Published 2019“…These data are for the bioRxiv publication entitled: Structural variation in Drosophila melanogaster spermathecal ducts and its association with sperm competition dynamics.…”
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159
Male mating rate is constrained by seminal fluid availability in bedbugs, Cimex lectularius.
Published 2011-01-01“…Sexual selection, differences in reproductive success between individuals, continues beyond acquiring a mating partner and affects ejaculate size and composition (sperm competition). Sperm and seminal fluid have very different roles in sperm competition but both components encompass production costs for the male. …”
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160
The effect of female quality on male ejaculatory expenditure and reproductive success in a praying mantid.
Published 2015-01-01“…Strategic ejaculation is a behavioural strategy shown by many animals as a response to sperm competition and/or as a potential mechanism of cryptic male choice. …”
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