| 1. |
- Keeling, Linda, et al.
(författare)
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Chicken genomics : feather-pecking and victim pigmentation.
- 2004
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 431:7009
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Tidskriftsartikel (refereegranskat)abstract
- Feather-pecking in domestic birds is associated with cannibalism and severe welfare problems. It is a dramatic example of a spiteful behaviour in which the victim's fitness is reduced for no immediate direct benefit to the perpetrator and its evolution is unexplained. Here we show that the plumage pigmentation of a chicken may predispose it to become a victim: birds suffer more drastic feather-pecking when the colour of their plumage is due to the expression of a wild recessive allele at PMEL17, a gene that controls plumage melanization, and when these birds are relatively common in a flock. These findings, obtained using an intercross between a domestic fowl and its wild ancestor, have implications for the welfare of domestic species and offer insight into the genetic changes associated with the evolution of feather-pecking during the early stages of domestication.
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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. |
- Pizzari, Tommaso, et al.
(författare)
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Sex-specific, counteracting responses to inbreeding in a bird
- 2004
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Ingår i: Proceedings of the Royal Society of London B. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 271:1553, s. 2115-2121
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Tidskriftsartikel (refereegranskat)abstract
- Inbreeding often depresses offspring fitness. Because females invest more than males in a reproductive event, inbreeding is expected to be more costly to mothers than fathers, creating a divergence between the reproductive interests of each sex and promoting sex-specific inbreeding strategies. Males and females may bias the probability of inbreeding by selecting copulation partners, and, in sexually promiscuous species, through male strategic sperm investment in different females and female selection of the sperm of different males. However, these processes are often difficult to study, and the way that different male and female strategies interact to determine inbreeding remains poorly understood. Here we demonstrate sex-specific, counteracting responses to inbreeding in the promiscuous red junglefowl, Gallus gallus. First, a male was just as likely to copulate with his full-sib sister as with an unrelated female. In addition, males displayed a tendency to: (i) initiate copulation faster when exposed to an unrelated female than when exposed to a sister, and (ii) inseminate more sperm into sisters than into unrelated females. Second, females retained fewer sperm following insemination by brothers, thus reducing the risk of inbreeding and counteracting male inbreeding strategies.
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| 4. |
- Pizzari, Tommaso, et al.
(författare)
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Sophisticated sperm allocation in male fowl
- 2003
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 426:6962, s. 70-74
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Tidskriftsartikel (refereegranskat)abstract
- When a female is sexually promiscuous, the ejaculates of different males compete for the fertilization of her eggs; the more sperm a male inseminates into a female, the more likely he is to fertilize her eggs. Because sperm production is limited and costly, theory predicts that males will strategically allocate sperm (1) according to female promiscuity, (2) saving some for copulations with new females, and (3) to females producing more and/or better offspring. Whether males allocate sperm in all of these ways is not known, particularly in birds where the collection of natural ejaculates only recently became possible. Here we demonstrate male sperm allocation of unprecedented sophistication in the fowl Gallus gallus. Males show status-dependent sperm investment in females according to the level of female promiscuity; they progressively reduce sperm investment in a particular female but, on encountering a new female, instantaneously increase their sperm investment; and they preferentially allocate sperm to females with large sexual ornaments signalling superior maternal investment. Our results indicate that female promiscuity leads to the evolution of sophisticated male sexual behaviour.
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