| 1. |
- Merilä, Juha, et al.
(författare)
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Antagonistic natural selection revealed by molecular sex identification of nestling collared flycatchers
- 1997
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 6:12, s. 1167-1175
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Tidskriftsartikel (refereegranskat)abstract
- Natural selection may act in different directions during different life-history stages, or in different directions on different classes of individuals. Antagonistic selection of this kind may be an important mechanism by which additive genetic variation for quantitative traits is maintained, and can prevent populations or species reaching local adaptive peaks. This paper reports the results of a study of viability selection on morphological traits of nestling collared flycatchers Ficedula albicollis. Analyses performed without knowledge of the sex of nestlings suggested that no selection was occurring on these traits. However, using molecular sex identification with the avian CHD gene, it is shown that selection acts in different directions on male and female body size from fledging to breeding, apparently favouring relatively small males and large females. The results suggest that differential selection on male and female nestlings may contribute to purely phenotypic sexual size dimorphism in this species. These findings highlight the potential of newly developed molecular sexing techniques to reveal the consequences of an individual's gender for many aspects of its life history in taxa where gender cannot be determined on the basis of external appearance.
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| 2. |
- Merilä, Juha, et al.
(författare)
-
Quantitative genetics of sexual size dimorphism in the collared flycatcher, Ficedula albicollis
- 1998
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Ingår i: Evolution. - : Oxford University Press (OUP). - 0014-3820 .- 1558-5646. ; 52:3, s. 870-876
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative genetic theory predicts that evolution of sexual size dimorphism (SSD) will be a slow process if the genetic correlation in size between the sexes is close to unity, and the heritability of size is similar in both sexes. However, there are very few reliable estimates of genetic correlations and sex-specific heritabilities from natural populations, the reasons for this being that (1) offspring have often been sexed retrospectively, and hence, selection acting differently with respect to body size in the two sexes between measuring and sex identification can bias estimates of SSD; and (2) in many taxa, parents may be incorrectly assigned to offspring either because of assignment errors or because of extrapair paternity. We used molecular sex and paternity identification to overcome these problems and estimated sex-specific heritabilities and the genetic correlation in body size between the two sexes in the collared flycatcher, Ficedula albicollis. After exclusion of the illegitimate offspring, the genetic correlation in body size between the sexes was 1.00 (SE = 0.22), implying a severe constraint on the evolution of SSD in this species. Furthermore, sex-specific heritability estimates were very similar, indicating that neither sex will be able to evolve faster than the other. By using estimated genetic parameters, together with empirically derived estimates of sex-specific selection gradients, we further demonstrated that the predicted selection response in female tarsus length is displaced about 200% in the opposite direction from that to be expected if there were no genetic correlation between the sexes. The correspondence between the biochemically estimated rate of extrapair paternity (about 15 % of the young) and that estimated from the "heritability method" (11%) was good. However, the estimated rate of extrapair paternity with the heritability method after exclusion of the illegitimate young was 22%, adding to increasing evidence that factors other than extrapair paternity (e.g., maternal effects) may be resposible for the commonly observed higher mother- offspring than father-offspring resemblance.
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