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Sökning: L773:0028 0836 OR L773:1476 4687 > (2010-2019) > (2014)

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  • Alström, Per (författare)
  • Niche filling slows the diversification of Himalayan songbirds
  • 2014
  • Ingår i: Nature. - Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 509, s. 222-225
  • Annan publikation (refereegranskat)abstract
    • Speciation generally involves a three-step process-range expansion, range fragmentation and the development of reproductive isolation between spatially separated populations(1,2). Speciation relies on cycling through these three steps and each may limit the rate at which new species form(1,3). We estimate phylogenetic relationships among all Himalayan songbirds to ask whether the development of reproductive isolation and ecological competition, both factors that limit range expansions(4), set an ultimate limit on speciation. Based on a phylogeny for all 358 species distributed along the eastern elevational gradient, here we show that body size and shape differences evolved early in the radiation, with the elevational band occupied by a species evolving later. These results are consistent with competition for niche space limiting species accumulation(5). Even the elevation dimension seems to be approaching ecological saturation, because the closest relatives both inside the assemblage and elsewhere in the Himalayas are on average separated by more than five million years, which is longer than it generally takes for reproductive isolation to be completed(2,3,6); also, elevational distributions are well explained by resource availability, notably the abundance of arthropods, and not by differences in diversification rates in different elevational zones. Our results imply that speciation rate is ultimately set by niche filling(that is, ecological competition for resources), rather than by the rate of acquisition of reproductive isolation.
  • Andersson, Claes, 1973-, et al. (författare)
  • Group size and cultural complexity
  • 2014
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 511:7507, s. E1
  • Tidskriftsartikel (refereegranskat)abstract
    • A decade ago, Henrich1 proposed group size as a driver of cultural complexity. Derex et al now present experimental results they say support this ‘group size hypothesis’ by seemingly showing that larger groups perform better than smaller groups under imitation-based cultural evolution. Our reanalysis of their experimental data, however, shows that larger groups actually perform worse than smaller groups. Thus, contrary to their claim, their data are consistent with empirical evidence discounting the group size hypothesis for non-food producing societies.
  • Arnegard, Matthew E., et al. (författare)
  • Genetics of ecological divergence during speciation
  • 2014
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 511:7509, s. 307-311
  • Tidskriftsartikel (refereegranskat)abstract
    • Ecological differences often evolve early in speciation as divergent natural selection drives adaptation to distinct ecological niches, leading ultimately to reproductive isolation. Although this process is a major generator of biodiversity, its genetic basis is still poorly understood. Here we investigate the genetic architecture of niche differentiation in a sympatric species pair of threespine stickleback fish by mapping the environment-dependent effects of phenotypic traits on hybrid feeding and performance under semi-natural conditions. We show that multiple, unlinked loci act largely additively to determine position along the major niche axis separating these recently diverged species. We also find that functional mismatch between phenotypic traits reduces the growth of some stickleback hybrids beyond that expected from an intermediate phenotype, suggesting a role for epistasis between the underlying genes. This functional mismatch might lead to hybrid incompatibilities that are analogous to those underlying intrinsic reproductive isolation but depend on the ecological context.
  • Bonaventure Omondi, Aman, et al. (författare)
  • Evolution of mosquito preference for humans linked to an odorant receptor
  • 2014
  • Ingår i: Nature. - Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 515, s. 222-227
  • Tidskriftsartikel (refereegranskat)abstract
    • Female mosquitoes are major vectors of human disease and the most dangerous are those that preferentially bite humans. A 'domestic' form of the mosquito Aedes aegypti has evolved to specialize in biting humans and is the main worldwide vector of dengue, yellow fever, and chikungunya viruses. The domestic form coexists with an ancestral, 'forest' form that prefers to bite non-human animals and is found along the coast of Kenya. We collected the two forms, established laboratory colonies, and document striking divergence in preference for human versus non-human animal odour. We further show that the evolution of preference for human odour in domestic mosquitoes is tightly linked to increases in the expression and ligand-sensitivity of the odorant receptor AaegOr4, which we found recognizes a compound present at high levels inhuman odour. Our results provide a rare example of a gene contributing to behavioural evolution and provide insight into how disease-vectoring mosquitoes came to specialize on humans.
  • Brawand, David, et al. (författare)
  • The genomic substrate for adaptive radiation in African cichlid fish
  • 2014
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 513:7518, s. 375-381
  • Tidskriftsartikel (refereegranskat)abstract
    • Cichlid fishes are famous for large, diverse and replicated adaptive radiations in the Great Lakes of East Africa. To understand themolecular mechanisms underlying cichlid phenotypic diversity, we sequenced the genomes and transcriptomes of five lineages of African cichlids: the Nile tilapia (Oreochromis niloticus), an ancestral lineage with low diversity; and four members of the East African lineage: Neolamprologus brichardi/pulcher (older radiation, Lake Tanganyika), Metriaclima zebra (recent radiation, Lake Malawi), Pundamilia nyererei (very recent radiation, Lake Victoria), and Astatotilapia burtoni (riverine species around Lake Tanganyika). We found an excess of gene duplications in the East African lineage compared to tilapia and other teleosts, an abundance of non-coding element divergence, accelerated coding sequence evolution, expression divergence associated with transposable element insertions, and regulation by novel microRNAs. In addition, we analysed sequence data from sixty individuals representing six closely related species from Lake Victoria, and show genome-wide diversifying selection on coding and regulatory variants, some of which were recruited from ancient polymorphisms. We conclude that a number of molecular mechanisms shaped East African cichlid genomes, and that amassing of standing variation during periods of relaxed purifying selection may have been important in facilitating subsequent evolutionary diversification.
  • Chomiuk, L., et al. (författare)
  • Binary orbits as the driver of gamma-ray emission and mass ejection in classical novae
  • 2014
  • Ingår i: Advanced Radio Astronomy in Europe (RADIONET3).
  • Tidskriftsartikel (refereegranskat)abstract
    • Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems(1). Novae typically expel about 10(-4) solar masses of material at velocities exceeding 1,000 kilometres per second. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of thermonuclear energy(2), prolonged optically thick winds(3) or binary interaction with the nova envelope(4). Classical novae are now routinely detected at gigaelectronvolt gamma-ray wavelengths(5), suggesting that relativistic particles are accelerated by strong shocks in the ejecta. Here we report high-resolution radio imaging of the gamma-ray-emitting nova V959 Mon. We find that its ejecta were shaped by the motion of the binary system: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion(6,7). At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of gamma-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae(8), explaining why many novae are gamma-ray emitters(5).
  • Dupret, Vincent, et al. (författare)
  • A primitive placoderm sheds light on the origin of the jawed vertebrate face
  • 2014
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 507:7493, s. 500-503
  • Tidskriftsartikel (refereegranskat)abstract
    • Extant vertebrates form two clades, the jawless Cyclostomata (lampreys and hagfishes) and the jawed Gnathostomata (all other vertebrates), with contrasting facial architectures(1,2). These arise during development from just a few key differences in the growth patterns of the cranial primordia: notably, the nasal sacs and hypophysis originate from a single placode in cyclostomes but from separate placodes in gnathostomes, and infraoptic ectomesenchyme migrates forward either side of the single placode in cyclostomes but between the placodes in gnathostomes(3-8). Fossil stem gnathostomes preserve cranial anatomies rich in landmarks that provide proxies for developmental processes and allow the transition from jawless to jawed vertebrates to be broken down into evolutionary steps(7,9-12). Here we use propagation phase contrast synchrotron microtomography to image the cranial anatomy of the primitive placoderm (jawed stem gnathostome) Romundina(13), and show that itcombines jawed vertebrate architecture with cranial and cerebral proportions resembling those of cyclostomes and the galeaspid (jawless stem gnathostome) Shuyu(11). This combination seems to be primitive for jawed vertebrates, and suggests a decoupling between ectomesenchymal growth trajectory, ectomesenchymal proliferation, and cerebral shape change during the origin of gnathostomes.
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