| 61. |
- Lira, Jaime, et al.
(författare)
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Ancient DNA reveals traces of Iberian Neolithic and Bronze Age lineages in modern Iberian horses
- 2010
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 19:1, s. 64-78
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Tidskriftsartikel (refereegranskat)abstract
- Multiple geographical regions have been proposed for the domestication of Equus caballus. It has been suggested, based on zooarchaeological and genetic analyses that wild horses from the Iberian Peninsula were involved in the process, and the overrepresentation of mitochondrial D1 cluster in modern Iberian horses supports this suggestion. To test this hypothesis, we analysed mitochondrial DNA from 22 ancient Iberian horse remains belonging to the Neolithic, the Bronze Age and the Middle Ages, against previously published sequences. Only the medieval Iberian sequence appeared in the D1 group. Neolithic and Bronze Age sequences grouped in other clusters, one of which (Lusitano group C) is exclusively represented by modern horses of Iberian origin. Moreover, Bronze Age Iberian sequences displayed the lowest nucleotide diversity values when compared with modern horses, ancient wild horses and other ancient domesticates using nonparametric bootstrapping analyses. We conclude that the excessive clustering of Bronze Age horses in the Lusitano group C, the observed nucleotide diversity and the local continuity from wild Neolithic Iberian to modern Iberian horses, could be explained by the use of local wild mares during an early Iberian domestication or restocking event, whereas the D1 group probably was introduced into Iberia in later historical times.
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| 62. |
- 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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| 63. |
- Meyer-Lucht, Yvonne, et al.
(författare)
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MHC diversity and the association to nematode parasitism in the yellow-necked mouse (Apodemus flavicollis)
- 2005
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 14:7, s. 2233-2243
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Tidskriftsartikel (refereegranskat)abstract
- In vertebrates, the genes of the major histocompatibility complex (MHC) are among the most debated candidates accounting for co-evolutionary processes of host-parasite interaction at the molecular level. The exceptionally high allelic polymorphism found in MHC loci is believed to be maintained by pathogen-driven selection, mediated either through heterozygous advantage or rare allele advantage (= frequency dependent selection). While investigations under natural conditions are still very rare, studies on humans or mice under laboratory conditions revealed support for both hypotheses. We investigated nematode burden and allelic diversity of a functional important MHC class II gene (DRB exon2) in free-ranging yellow-necked mice (Apodemus flavicollis). Twenty-seven distinct Apfl-DRB alleles were detected in 146 individuals with high levels of amino acid sequence divergence, especially at the antigen binding sites (ABS), indicating selection processes acting on this locus. Heterozygosity had no influence on the infection status (being infected or not), the number of different nematode infections (NNI) or the intensity of infection, measured as the individual faecal egg count (FEC). However, significant associations of specific Apfl-DRB alleles to both nematode susceptibility and resistance were found, for all nematodes as well as in separate analyses of the two most common nematodes. Apodemus flavicollis individuals carrying the alleles Apfl-DRB*5 or Apfl-DRB*15 revealed significantly higher FEC than individuals with other alleles. In contrast, the allele Apfl-DRB*23 showed a significant association to low FEC of the most common nematode. Thus, our results provide evidence for pathogen-driven selection acting through rare allele advantage under natural conditions.
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| 64. |
- Mobley, Kenyon B.
(författare)
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Grandfathering in a new era of parentage analysis
- 2011
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 20:6, s. 1080-1082
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Tidskriftsartikel (refereegranskat)abstract
- The advent of DNA fingerprinting and microsatellite techniques has revolutionized the way in which we investigate genetic pedigrees in the wild (Pemberton 2008). With large and often incomplete data sets consisting of hundreds to thousands of individuals over multiple generations becoming commonplace, new methods in parentage analysis are being developed to rise to the next generation of questions and challenges. In this issue, Christie et al. (2011) provide a simple yet elegant solution to the problem of identifying missing parents and assessing hybrid fitness in a mixed population of wild and hatchery steelhead trout (Oncorhynchus mykiss) where not all individuals can be sampled effectively. They develop a new method of grandparent analysis where parental genotypes can be reconstructed using data from candidate grandparent crosses and F2 offspring genotypes, allowing for new explorations of hybridization, migration and gene flow in wild populations.
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| 65. |
- Muñoz-Fuentes, Violeta, et al.
(författare)
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Hybridization between white-headed ducks and introduced ruddy ducks in Spain
- 2007
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 16:3, s. 629-638
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Tidskriftsartikel (refereegranskat)abstract
- The ruddy duck, Oxyura jamaicensis, was introduced to Great Britain in the mid-20th century and has recently spread to other Western European countries. In Spain, ruddy ducks hybridize with the globally endangered white-headed duck, Oxyura leucocephala. We assessed the effects of hybridization on the Spanish white-headed ducks, which constitute 25% of the global population of this species, using a panel of eight nuclear intron markers, 10 microsatellite loci, and mtDNA control region sequences. These data allowed parental individuals, F(1) hybrids, and the progeny of backcrossing to be reliably distinguished. We show that hybrids between the two species are fertile and produce viable offspring in backcrosses with both parental species. To date, however, we found no extensive introgression of ruddy duck genes into the Spanish white-headed duck population, probably due to the early implementation of an effective ruddy duck and hybrid control programme. We also show that genetic diversity in the expanding European ruddy duck population, which was founded by just seven individuals, exceeds that of the native Spanish white-headed duck population, which recently recovered from a severe bottleneck. Unless effective control of ruddy ducks is continued, genetic introgression will compromise the unique behavioural and ecological adaptations of white-headed ducks and consequently their survival as a genetically and evolutionary distinct species.
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| 66. |
- Musiani, Marco, et al.
(författare)
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Differentiation of tundra/taiga and boreal coniferous forest wolves : genetics, coat colour and association with migratory caribou.
- 2007
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 16:19, s. 4149-4170
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Forskningsöversikt (refereegranskat)abstract
- The grey wolf has one of the largest historic distributions of any terrestrial mammal and can disperse over great distances across imposing topographic barriers. As a result, geographical distance and physical obstacles to dispersal may not be consequential factors in the evolutionary divergence of wolf populations. However, recent studies suggest ecological features can constrain gene flow. We tested whether wolf-prey associations in uninterrupted tundra and forested regions of Canada explained differences in migratory behaviour, genetics, and coat colour of wolves. Satellite-telemetry data demonstrated that tundra wolves (n = 19) migrate annually with caribou (n = 19) from denning areas in the tundra to wintering areas south of the treeline. In contrast, nearby boreal coniferous forest wolves are territorial and associated year round with resident prey. Spatially explicit analysis of 14 autosomal microsatellite loci (n = 404 individuals) found two genetic clusters corresponding to tundra vs. boreal coniferous forest wolves. A sex bias in gene flow was inferred based on higher levels of mtDNA divergence (F(ST) = 0.282, 0.028 and 0.033; P < 0.0001 for mitochondrial, nuclear autosomal and Y-chromosome markers, respectively). Phenotypic differentiation was substantial as 93% of wolves from tundra populations exhibited light colouration whereas only 38% of boreal coniferous forest wolves did (chi(2) = 64.52, P < 0.0001). The sharp boundary representing this discontinuity was the southern limit of the caribou migration. These findings show that substantial genetic and phenotypic differentiation in highly mobile mammals can be caused by prey-habitat specialization rather than distance or topographic barriers. The presence of a distinct wolf ecotype in the tundra of North America highlights the need to preserve migratory populations.
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| 67. |
- Nadachowska-Brzyska, Krystyna, et al.
(författare)
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Interspecific hybridization increases MHC class II diversity in two sister species of newts
- 2012
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 21:4, s. 887-906
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding of the evolutionary mechanisms generating variation within the highly polymorphic major histocompatibility complex (MHC) genes remains incomplete. Assessing MHC variation across multiple populations, of recent and ancient divergence, may facilitate understanding of geographical and temporal aspects of variation. Here, we applied 454 sequencing to perform a large-scale, comprehensive analysis of MHC class II in the closely related, hybridizing newts, Lissotriton vulgaris (Lv) and Lissotriton montandoni (Lm). Our study revealed an extensive (299 alleles) geographically structured polymorphism. Populations at the southern margin of the Lvdistribution, inhabited by old and distinct lineages (southern Lv), exhibited moderate MHC variation and strong population structure, indicating little gene flow or extensive local adaptation. Lissotriton vulgaris in central Europe and the northern Balkans (northern Lv) and almost all Lm populations had a high MHC variation. A much higher proportion of MHC alleles was shared between Lm and northern Lvthan between Lm and southern Lv. Strikingly, the average pairwise FST between northern Lv and Lm was significantly lower than between northern and southern Lv for MHC, but not for microsatellites. Thus, high MHC variation in Lm and northern Lv may result from gene flow between species. We hypothesize that the interspecific exchange of MHC genes may be facilitated by frequency-dependent selection. A marginally significant correlation between the MHC and microsatellite allelic richness indicates that demographic factors may have contributed to the present-day pattern of MHC variation, but unequivocal signatures of adaptive evolution in MHC class II sequences emphasize the role of selection on a longer timescale.
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| 68. |
- Nyström, Veronica, et al.
(författare)
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Microsatellite genotyping reveals end-Pleistocene decline in mammoth autosomal genetic variation
- 2012
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 21:14, s. 3391-3402
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Tidskriftsartikel (refereegranskat)abstract
- The last glaciation was a dynamic period with strong impact on the demography of many species and populations. In recent years, mitochondrial DNA sequences retrieved from radiocarbon-dated remains have provided novel insights into the history of Late Pleistocene populations. However, genotyping of loci from the nuclear genome may provide enhanced resolution of population-level changes. Here, we use four autosomal microsatellite DNA markers to investigate the demographic history of woolly mammoths (Mammuthus primigenius) in north-eastern Siberia from before 60 000 years ago up until the species final disappearance c. 4000 years ago. We identified two genetic groups, implying a marked temporal genetic differentiation between samples with radiocarbon ages older than 12 thousand radiocarbon years before present (ka) and those younger than 9 ka. Simulation-based analysis indicates that this dramatic change in genetic composition, which included a decrease in individual heterozygosity of approximately 30%, was due to a multifold reduction in effective population size. A corresponding reduction in genetic variation was also detected in the mitochondrial DNA, where about 65% of the diversity was lost. We observed no further loss in genetic variation during the Holocene, which suggests a rapid final extinction event.
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| 69. |
- Palo, Jukka, et al.
(författare)
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Latitudinal divergence of common frog (Rana temporaria) life-history traits by natural selection : evidence for a comparison of molecular and quantitative genetic data
- 2003
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 12:7, s. 1963-1978
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Tidskriftsartikel (refereegranskat)abstract
- The relative roles of natural selection and direct environmental induction, as well as of natural selection and genetic drift, in creating clinal latitudinal variation in quantitative traits have seldom been assessed in vertebrates. To address these issues, we compared molecular and quantitative genetic differentiation between six common frog (Rana temporaria) populations along an approximately 1600 km long latitudinal gradient across Scandinavia. The degree of population differentiation (QST approximately 0.81) in three heritable quantitative traits (age and size at metamorphosis, growth rate) exceeded that in eight (neutral) microsatellite loci (FST = 0.24). Isolation by distance was clear for both neutral markers and quantitative traits, but considerably stronger for one of the three quantitative traits than for neutral markers. QST estimates obtained using animals subjected to different rearing conditions (temperature and food treatments) revealed some environmental dependency in patterns of population divergence in quantitative traits, but in general, these effects were weak in comparison to overall patterns. Pairwise comparisons of FST and QST estimates across populations and treatments revealed that the degree of quantitative trait differentiation was not generally predictable from knowledge of that in molecular markers. In fact, both positive and negative correlations were observed depending on conditions where the quantitative genetic variability had been measured. All in all, the results suggest a very high degree of genetic subdivision both in neutral marker genes and genes coding quantitative traits across a relatively recently (< 9000 years) colonized environmental gradient. In particular, they give evidence for natural selection being the primary agent behind the observed latitudinal differentiation in quantitative traits.
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| 70. |
- Pastene, Luis A., et al.
(författare)
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Radiation and speciation of pelagic organisms during periods of global warming : the case of the common minke whale, Balaenoptera acutorostrata
- 2007
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 16:7, s. 1481-1495
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Tidskriftsartikel (refereegranskat)abstract
- How do populations of highly mobile species inhabiting open environments become reproductively isolated and evolve into new species? We test the hypothesis that elevated ocean-surface temperatures can facilitate allopatry among pelagic populations and thus promote speciation. Oceanographic modelling has shown that increasing surface temperatures cause localization and reduction of upwelling, leading to fragmentation of feeding areas critical to pelagic species. We test our hypothesis by genetic analyses of populations of two closely related baleen whales, the Antarctic minke whale (Balaenoptera bonaerensis) and common minke whale (Balaenoptera acutorostrata) whose current distributions and migration patterns extent are largely determined by areas of consistent upwelling with high primary production. Phylogeographic and population genetic analyses of mitochondrial DNA control-region nucleotide sequences collected from 467 whales sampled in four different ocean basins were employed to infer the evolutionary relationship among populations of B. acutorostrata by rooting an intraspecific phylogeny with a population of B. bonaerensis. Our findings suggest that the two species diverged in the Southern Hemisphere less than 5 million years ago (Ma). This estimate places the speciation event during a period of extended global warming in the Pliocene. We propose that elevated ocean temperatures in the period facilitated allopatric speciation by disrupting the continuous belt of upwelling maintained by the Antarctic Circumpolar Current. Our analyses revealed that the current populations of B. acutorostrata likely diverged after the Pliocene some 1.5 Ma when global temperatures had decreased and presumably coinciding with the re-establishment of the polar-equatorial temperature gradient that ultimately drives upwelling. In most population samples, we detected genetic signatures of exponential population expansions, consistent with the notion of increasing carrying capacity after the Pliocene. Our hypothesis that prolonged periods of global warming facilitate speciation in pelagic marine species that depend on upwelling should be tested by comparative analyses in other pelagic species.
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