| 1. |
- Berlin, Sofia, et al.
(författare)
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Low mitochondrial variability in birds may indicate Hill-Robertson effects on the W chromosome
- 2007
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 99:4, s. 389-396
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Tidskriftsartikel (refereegranskat)abstract
- Interference among loci subject to selection ( the Hill Robertson effect) may considerably reduce levels of adaptation and variability in genomic regions that lack recombination. Y- or W chromosomes are particularly vulnerable to such effects, since they represent large, non-recombining blocks of genetic material. In birds, the W chromosome and mitochondrial genomes are both maternally transmitted, and hence fail to recombine with each other, whereas in mammals the Y chromosome is paternally transmitted. We show here that mitochondrial DNA sequence diversity is reduced in non-ratite birds compared with mammals. After considering possible confounding factors, such as differences in generation times, mutation rates and demography, we conclude that Hill-Robertson effects associated with the W chromosome provide the most likely explanation for this difference.
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| 2. |
- Florin, A-B, et al.
(författare)
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Population structure of flounder (Platichthys flesus) in the Baltic Sea : differences among demersal and pelagic spawners
- 2008
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 101:1, s. 27-38
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Tidskriftsartikel (refereegranskat)abstract
- We found significant population structure and isolation by distance among samples of flounder (Platichthys flesus) in the Baltic, Kattegat and Skagerrak seas using microsatellite genetic markers. This pattern was almost entirely due to a difference between flounder that have demersal spawning in the northern Baltic, as compared to pelagic spawners in the southern Baltic and on the west coast of Sweden. Among demersal spawners we found neither genetic differentiation nor any isolation by distance among sampling sites. We speculate that demersal flounder are descendants of a population that colonized the Baltic previous to pelagic spawners. The demersal flounder may thus have had longer time to adapt to the low salinity in the Baltic, and accordingly display egg characteristics that make it possible to reproduce at the low salinity levels in the northern Baltic. Among pelagic spawners significant isolation by distance was detected. Pelagic spawners have previously been shown to display clinal variation in egg size, which allows them to float also at the moderate salinity levels up to the region north of the island Bornholm. Management units for harvesting should ideally be based on true biological populations, and for the commercially important flounder up to 15 different management stocks in the Baltic have been suggested. We could not find a population genetic foundation for such a high number of management units, and our data suggest three management units: the northern Baltic (demersal populations), southern Baltic with the Oresund straits and the most northwestern sampling sites (Skagerrak, Kattegat and North Sea).
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| 3. |
- Garcia Gil, Rosario, et al.
(författare)
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Joint analysis of spatial genetic structure and inbreeding in a managed population of Scots pine
- 2009
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 103, s. 90-96
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the fine-scale spatial genetic structure in a managed Scots pine forest. For this purpose, we perform a Bayesian genetic-cluster analysis of 96 geographically mapped individual seed trees of Swedish Scots pine based on 14 microsatellite loci. The analysis was carried out with the recently developed program GENECLUST (Francois et al., 2006), which provides the facility to jointly incorporate both spatial information from a geographical neighborhood structure through a Potts-Dirichlet model and account for variable degrees of inbreeding within the clusters. To evaluate whether inbreeding and spatial interaction should be included in the best-fitting statistical model for our data, we used the deviance information criterion (DIC), a weighted measure of model fit that accounts for an effective number of free parameters in a model. Analysis shows that a model with a single estimated cluster, with high levels of inbreeding (0.25) and with a moderate amount of spatial dependency within the unique cluster (Psi = 0.2-0.4), best explains the data. We also carried out Bayesian parentage analysis, which enabled us to exclude the possibility that the sample constitutes one single full-sib family. Heredity (2009) 103, 90-96; doi: 10.1038/hdy.2009.33; published online 22 April 2009
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| 4. |
- Jensen, Per
(författare)
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Genomics : The chicken genome sequence
- 2005
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540.
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Annan publikation (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Mank, J. E., et al.
(författare)
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All dosage compensation is local : Gene-by-gene regulation of sex-biased expression on the chicken Z chromosome
- 2009
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 102:3, s. 312-320
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Tidskriftsartikel (refereegranskat)abstract
- Recent reports have suggested that birds lack a mechanism of wholesale dosage compensation for the Z sex chromosome. This discovery was rather unexpected, as all other animals investigated with chromosomal mechanisms of sex determination have some method to counteract the effects of gene dosage of the dominant sex chromosome in males and females. Despite the lack of a global mechanism of avian dosage compensation, the pattern of gene expression difference between males and females varies a great deal for individual Z-linked genes. This suggests that some genes may be individually dosage compensated, and that some less-than-global pattern of dosage compensation, such as local or temporal, exists on the avian Z chromosome. We used global gene expression profiling in males and females for both somatic and gonadal tissue at several time points in the life cycle of the chicken to assess the pattern of sex-biased gene expression on the Z chromosome. Average fold-change between males and females varied somewhat among tissue time-point combinations, with embryonic brain samples having the smallest gene dosage effects, and adult gonadal tissue having the largest degree of male bias. Overall, there were no neighborhoods of overall dosage compensation along the Z. Taken together, this suggests that dosage compensation is regulated on the Z chromosome entirely on a gene-by-gene level, and can vary during the life cycle and by tissue type. This regulation may be an indication of how critical a given gene's functionality is, as the expression level for essential genes will be tightly regulated in order to avoid perturbing important pathways and networks with differential expression levels in males and females.
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| 6. |
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| 7. |
- Palm, S, et al.
(författare)
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Panmixia in European eel revisited : no genetic difference between maturing adults from southern and northern Europe
- 2009
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 103:1, s. 82-89
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies of genetic structure in the European eel have resulted in seemingly conflicting results, ranging from no detectable heterogeneity to small but statistically significant differences and isolation by distance patterns among eels sampled across the continental range. Differences with respect to sampling design and choice of molecular markers, combined with a lack of power estimates, complicate comparisons of existing results. In this study we have used six microsatellite markers and, for the first time, compared maturing silver eels of known age from southern and northern Europe (Italy and Baltic Sea). In comparison with previous studies, our data may give a better representation of potential spawning stocks because eels were sampled when having begun their migration toward the presumed spawning area in the Sargasso Sea. Despite large sample sizes (404 and 806 individuals) we could not observe any signs of genetic differentiation (average F-ST = -0.00003, P = 0.61), and a power analysis showed that the true level of heterogeneity (if existing) must be exceedingly small to have remained undetected (say, F-ST <0.0004). A tendency for slightly increased genetic differences between cohorts over time could be seen, but the amount of temporal change was minor and not statistically significant. Our findings reiterate the notion that previous reports of continental genetic differentiation in the European eel may be largely explained by uncontrolled temporal variation between juvenile glass eel samples. Heredity (2009) 103, 82-89; doi: 10.1038/hdy.2009.51; published online 6 May 2009
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| 8. |
- Qvarnström, Anna, et al.
(författare)
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Speciation through evolution of sex-linked genes
- 2009
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 102:1, s. 4-15
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Forskningsöversikt (refereegranskat)abstract
- Identification of genes involved in reproductive isolation opens novel ways to investigate links between stages of the speciation process. Are the genes coding for ecological adaptations and sexual isolation the same that eventually lead to hybrid sterility and inviability? We review the role of sex-linked genes at different stages of speciation based on four main differences between sex chromosomes and autosomes; ( 1) relative speed of evolution, ( 2) non-random accumulation of genes, ( 3) exposure of incompatible recessive genes in hybrids and ( 4) recombination rate. At early stages of population divergence ecological differences appear mainly determined by autosomal genes, but fast-evolving sex-linked genes are likely to play an important role for the evolution of sexual isolation by coding for traits with sex-specific fitness effects ( for example, primary and secondary sexual traits). Empirical evidence supports this expectation but mainly in female-heterogametic taxa. By contrast, there is clear evidence for both strong X- and Z-linkage of hybrid sterility and inviability at later stages of speciation. Hence genes coding for sexual isolation traits are more likely to eventually cause hybrid sterility when they are sex-linked. We conclude that the link between sexual isolation and evolution of hybrid sterility is more intuitive in male-heterogametic taxa because recessive sexually antagonistic genes are expected to quickly accumulate on the X-chromosome. However, the broader range of sexual traits that are expected to accumulate on the Z-chromosome may facilitate adaptive speciation in female-heterogametic species by allowing male signals and female preferences to remain in linkage disequilibrium despite periods of gene flow.
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| 9. |
- Sahlsten, Jonas, et al.
(författare)
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Inference of hazel grouse population structure using multilocus data : a landscape genetic approach
- 2008
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 101:6, s. 475-482
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- In conservation and management of species it is important to make inferences about gene flow, dispersal and population structure. In this study, we used 613 georeferenced tissue samples from hazel grouse (Bonasa bonasia) where each individual was genotyped at 12 microsatellite loci to make inference on population genetic structure, gene flow and dispersal in northern Sweden. Observed levels of genetic diversity suggest that Swedish hazel grouse do not suffer loss of genetic diversity compared with other grouse species. We found significant F-IS (deviation from Hardy-Weinberg expectations) over the entire sample using jack-knifed estimators over loci, which is most likely explained by a Wahlund effect. With the use of spatial autocorrelation methods, we detected significant isolation by distance among individuals. Neighbourhood size was estimated in the order of 62-158 individuals corresponding to a dispersal distance of 950-1500 m. Using a spatial statistical model for landscape genetics to infer the number of populations and the spatial location of genetic discontinuities between these populations we found indications that Swedish hazel grouse are divided into a northern and a southern population. We could not find a sharp border between these two populations and none of the observed borders appeared to coincide with any potential geographical barriers. These results imply that gene flow appears somewhat unrestricted in the boreal taiga forests of northern Sweden and that the two populations of hazel grouse in Sweden may be explained by the post-glacial reinvasion history of the Scandinavian Peninsula. Heredity (2008) 101, 475-482; doi: 10.1038/hdy.2008.94; published online 1 October 2008
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| 10. |
- Sjödin, Per, et al.
(författare)
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Recent degeneration of an old duplicated flowering time gene in Brassica nigra
- 2007
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 98:6, s. 375-384
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Tidskriftsartikel (refereegranskat)abstract
- Gene and genome duplications play a major role in the evolution of plant species. The Brassica nigra genome is highly replicated as a result of ancient polyploidization events. Two copies of the flowering time gene CONSTANS (COa and COb) have been identified in B. nigra, and previous studies showed that COa is functional. In the present study, the polymorphism of 92 COb alleles sampled in seven populations was analyzed. Both polymorphism and recombination levels were elevated and varied strongly among populations and 8% of COb alleles exhibit apparently disabling mutations. Sequence data, however, do not provide unambiguous support for the presence of relaxed selective constraint on COb as compared to known functional CO genes. On the one hand, some of the disabling mutations reached high-frequency arguing for a loss of function but, on the other hand, the ratio of nonsynonymous to synonymous nucleotide polymorphism and diversity is low and similar to that observed in other B. nigra CO and CO-like genes, supporting the conservation of some function. We also showed that COb is still transcribed. Finally, the flowering time of Arabidopsis thaliana co mutant plants transformed with COb alleles with and without apparent disabling mutations was similar. We propose that COb was retained for a long period after duplication, but a recent fixation of a detrimental mutation, possibly as an effect of a bottleneck, resulted in its nonfunctionalization. We also speculate as to the presence of subsequent selection for rapid degeneration of the gene.
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