| 1. |
- Gillingham, Mark, et al.
(författare)
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Cryptic preference for MHC-dissimilar females in male red junglefowl, Gallus gallus
- 2009
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : Royal Society. - 0962-8452 .- 1471-2954. ; 276:1659, s. 1083-1092
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Tidskriftsartikel (refereegranskat)abstract
- An increasing number of studies test the idea that females increase offspring fitness by biasing fertilization in favour of genetically compatible partners; however, few have investigated or controlled for corresponding preferences in males. Here, we experimentally test whether male red junglefowl, Gallus gallus, prefer genetically compatible females, measured by similarity at the major histocompatibility complex (MHC), a key gene complex in vertebrate immune function. Theory predicts that because some degree of MHC heterozygosity favours viability, individuals should prefer partners that carry MHC alleles different from their own. While male fowl showed no preference when simultaneously presented with an MHC-similar and an MHC-dissimilar female, they showed a 'cryptic' preference, by allocating more sperm to the most MHC-dissimilar of two sequentially presented females. These results provide the first experimental evidence that males might respond to the MHC similarity of a female through differential ejaculate expenditure. By revealing that cryptic male behaviours may bias fertilization success in favour of genetically compatible partners, this study demonstrates the need to experimentally disentangle male and female effects when studying preferences for genetically compatible partners.
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| 2. |
- Løvlie, Hanne, et al.
(författare)
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Male mounting alone reduces female promiscuity in the fowl
- 2005
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Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 15:13, s. 1222-1227
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Tidskriftsartikel (refereegranskat)abstract
- 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. However, it is difficult to separate the effect of such specialized traits and insemination products from the more basic effect that the act of mounting per se may have on female remating. Here, we use a novel approach that separates the influence of mounting from that of insemination on female remating in the promiscuous feral fowl. Mounting alone caused a transient but drastic reduction in female propensity to remate, and-crucially-the number of sperm that a female obtained from a new male. Therefore, like other taxa, female fowl show a reduction in promiscuity after copulation, but this is entirely due to mounting alone. This effect of mounting, independent of insemination and fertilization, indicates that even copulations that deliver little or no semen, a puzzling behavior common in many species including the fowl, may play a crucial role in sperm competition.
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| 3. |
- Løvlie, Hanne, 1977-
(författare)
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Pre- and post-copulatory sexual selection in the fowl, Gallus gallus
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The evolutionary goal of individuals is reproduction and sexual selection favours traits improving reproductive success. When males invest less than females in offspring, males have potentially a higher reproductive rate than females. This typically results in sex-specific reproductive strategies of male-male competition and female choice of mating partner. Under polyandry, sexual selection can continue after copulation as sperm competition and cryptic female choice. This thesis focuses on male and female pre- and post-copulatory reproductive strategies in the promiscuous red junglefowl, Gallus gallus ssp., and its domestic subspecies the domestic fowl, Gallus gallus domesticus. Males impose high re-mating rates on females, which triggers female resistance in copulations. In addition, when sexual harassment increases, females re-mate at times of day when male mating propensity is lower, to avoid intense sexual harassment. Males allocate sperm supplies differentially according to (i) variation in female polyandry and own competitive ability, (ii) earlier sperm investment in a female, and (iii) female reproductive quality, signalled by female comb size. Males also perform ‘aspermic’ copulations (i.e. copulations with no semen transfer), which inhibit polyandry and in turn reduce sperm competition. In mating opportunities with relatives, males do not avoid inbreeding. However, females avoid inbreeding before copulation through kin recognition and after copulation by selecting against related males’ sperm. These results show that selection on males to re-mate at higher rates than females and copulate indiscriminately according to partner relatedness, trigger counteracting female responses, creating the potential for sexual conflict over fertilisation. Teasing apart pre- and post-copulatory strategies and the contribution of each sex therefore becomes crucial in order to understand the evolution of reproductive strategies and the mechanisms affecting paternity.
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