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- Lehtonen, PK, et al.
(author)
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Candidate genes for colour and vision exhibit signals of selection across the pied flycatcher (Ficedula hypoleuca) breeding range
- 2012
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In: Heredity. - : Springer Science and Business Media LLC. - 1365-2540 .- 0018-067X. ; 108:4, s. 431-440
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Journal article (peer-reviewed)abstract
- The role of natural selection in shaping adaptive trait differentiation in natural populations has long been recognized. Determining its molecular basis, however, remains a challenge. Here, we search for signals of selection in candidate genes for colour and its perception in a passerine bird. Pied flycatcher plumage varies geographically in both its structural and pigment-based properties. Both characteristics appear to be shaped by selection. A single-locus outlier test revealed 2 of 14 loci to show significantly elevated signals of divergence. The first of these, the follistatin gene, is expressed in the developing feather bud and is found in pathways with genes that determine the structure of feathers and may thus be important in generating variation in structural colouration. The second is a gene potentially underlying the ability to detect this variation: SWS1 opsin. These two loci were most differentiated in two Spanish pied flycatcher populations, which are also among the populations that have the highest UV reflectance. The follistatin and SWS1 opsin genes thus provide strong candidates for future investigations on the molecular basis of adaptively significant traits and their co-evolution.
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- Saetre, G. P., et al.
(author)
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Single origin of human commensalism in the house sparrow
- 2012
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In: Journal of Evolutionary Biology. - : Wiley. - 1010-061X. ; 25:4, s. 788-796
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Journal article (peer-reviewed)abstract
- The current, virtually worldwide distribution of the house sparrow (Passer domesticus) is a result of its commensal relationship with humans. It has been suggested that long before the advent of agriculture, an early glacial advance resulted in two disjunct ranges of ancestral house sparrows one in the Middle East and another on the Indian subcontinent. Differentiation during this period of isolation resulted in two major groups of subspecies: the domesticus group and the indicus group. According to this hypothesis, commensalism with humans would have evolved independently in the two regions and at least twice. An alternative hypothesis is that morphological differences between the subspecies represent very recent differentiation, following expansions from a single source. To test between these hypotheses, we analysed genetic variation at the mitochondrial DNA control region and at three nuclear loci from several house sparrow populations in Europe, Asia and North Africa. No differentiation between the indicus and domesticus groups was found, supporting the single origin hypothesis. One of the subspecies in the indicus group, P. d. bactrianus, differs ecologically from other house sparrows in being migratory and in preferentially breeding in natural habitat. We suggest that bactrianus represents a relict population of the ancestral, noncommensal house sparrow. When agricultural societies developed in the Middle East about 10 000 years ago, a local house sparrow population of the bactrianus type adapted to the novel environment and eventually became a sedentary, human commensal. As agriculture and human civilizations expanded, house sparrows experienced a correlated and massive expansion in range and numbers. The pattern of genetic variation analysed here is consistent with this scenario.
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- Eroukhmanoff, F., et al.
(author)
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Effect of Species Interaction on Beak Integration in an Avian Hybrid Species Complex
- 2014
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In: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 41:3, s. 452-458
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Journal article (peer-reviewed)abstract
- Theory predicts that variability in size and the shape of a morphological trait should often be stable both at the intra- and interspecific level. We studied variation in beak integration among several populations of two species of the genus Passer, a hybrid species, the Italian sparrow (Passer italiae) and one of its parents, the Spanish sparrow (Passer hispaniolensis). We show that the general shape of the beak has been conserved in these two species and that hybrid speciation has had no major effects on beak integration. However, in young, sympatric populations, phenotypic integration between beak height and length decreased significantly, to the extent that these two dimensions apparently became independent. This displacement in phenotypic integration seems to be accompanied with changes in the distribution of phenotypic variation at the univariate level. This suggests that while beak shape may have been constrained over evolutionary time-scales and major hybridization events (i.e. the formation of the hybrid Italian sparrow), under specific selection regimes linked to secondary contact, it can evolve rapidly.
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- Saetre, Peter, et al.
(author)
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Methylenetetrahydrofolate Reductase (MTHFR) C677T and A1298C Polymorphisms and Age of Onset in Schizophrenia : A Combined Analysis of Independent Samples
- 2011
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In: American Journal of Medical Genetics, Part B: Neuropsychiatric Genetics. - : Wiley. - 1552-4841. ; 156B156:2, s. 215-224
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Journal article (peer-reviewed)abstract
- Methylenetetrahydrofolate reductase (MTHFR) is involved in the one-carbon cycle, which is of importance for nucleotide synthesis and methylation of DNA, membranes, proteins and lipids. The MTHFR gene includes two common polymorphisms (rs1801133 or C677T; rs1801131 or A1298C) which both alter enzyme activity. The T-allele of the C677T polymorphism has recently been associated with earlier age at onset of schizophrenia. In the present study we examined the association between the MTHFR C677T and A1298C polymorphisms and age at onset of schizophrenia in twelve samples consisting of 3,213 unrelated schizophrenia patients, including the original Scandinavian sample. There was no consistent relationship between MTHFR C677T, A1298C or combined 677T/1298C carriers and age of onset in schizophrenia when the results of each study were combined using meta-analysis. The present results suggest that the investigated MTHFR polymorphisms do not influence age of onset in schizophrenia.
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