The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Roger K. Butlin - One of the best experts on this subject based on the ideXlab platform.
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What explains rare and conspicuous colours in a snail? A test of time-series data against models of Drift, Migration or selection
Heredity, 2017Co-Authors: Kerstin Johannesson, Roger K. ButlinAbstract:It is intriguing that conspicuous colour morphs of a prey species may be maintained at low frequencies alongside cryptic morphs. Negative frequency-dependent selection by predators using search images (‘apostatic selection’) is often suggested without rejecting alternative explanations. Using a maximum likelihood approach we fitted predictions from models of genetic Drift, Migration, constant selection, heterozygote advantage or negative frequency-dependent selection to time-series data of colour frequencies in isolated populations of a marine snail ( Littorina saxatilis ), re-established with perturbed colour morph frequencies and followed for >20 generations. Snails of conspicuous colours (white, red, banded) are naturally rare in the study area (usually
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What explains rare and conspicuous colours in a snail? A test of time-series data against models of Drift, Migration or selection.
Heredity, 2016Co-Authors: Kerstin Johannesson, Roger K. ButlinAbstract:What explains rare and conspicuous colours in a snail? A test of time-series data against models of Drift, Migration or selection
Philippe Jarne - One of the best experts on this subject based on the ideXlab platform.
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the influence of self fertilization and population dynamics on the genetic structure of subdivided populations a case study using microsatellite markers in the freshwater snail bulinus truncatus
Evolution, 1997Co-Authors: Frédérique Viard, Fabienne Justy, Philippe JarneAbstract:The distribution of neutral genetic variability within and among sets of populations results from the com- bined actions of genetic Drift, Migration, extinction and recolonization processes, mutation, and the mating system. We here analyzed these factors in 38 populations of the hermaphroditic snail Bulinus truncatus. The sampling area covered a large part of the species range. The variability was analyzed using four polymorphic microsatellite loci. A very large number of alleles (up to 55) was found at the level of the whole study. Observed heterozygote deficiencies within populations are consistent with very high selfing rates, generally above 0.80, in all populations. These should depress the variability within populations, because of low effective size, genetic hitchhiking, and background selection, whatever the model of mutation assumed. However, that some populations exhibit much more variability than others suggests that historical demographic processes (e.g., population size variation, bottlenecks, or founding events) may play a significant role. A hierarchical analysis of the distribution of the variability across populations indicates a strong pattern of isolation by distance, whatever the geographical scale considered. Our analysis also illustrates how the mutation rate may affect population differentiation, as different mutation rates result in different levels of homoplasy at microsatellite loci. The effects of both genetic Drift and gene flow vary with the temporal and spatial scales considered in B. truncatus populations.
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THE INFLUENCE OF SELF‐FERTILIZATION AND POPULATION DYNAMICS ON THE GENETIC STRUCTURE OF SUBDIVIDED POPULATIONS: A CASE STUDY USING MICROSATELLITE MARKERS IN THE FRESHWATER SNAIL BULINUS TRUNCATUS
Evolution; international journal of organic evolution, 1997Co-Authors: Frédérique Viard, Fabienne Justy, Philippe JarneAbstract:The distribution of neutral genetic variability within and among sets of populations results from the com- bined actions of genetic Drift, Migration, extinction and recolonization processes, mutation, and the mating system. We here analyzed these factors in 38 populations of the hermaphroditic snail Bulinus truncatus. The sampling area covered a large part of the species range. The variability was analyzed using four polymorphic microsatellite loci. A very large number of alleles (up to 55) was found at the level of the whole study. Observed heterozygote deficiencies within populations are consistent with very high selfing rates, generally above 0.80, in all populations. These should depress the variability within populations, because of low effective size, genetic hitchhiking, and background selection, whatever the model of mutation assumed. However, that some populations exhibit much more variability than others suggests that historical demographic processes (e.g., population size variation, bottlenecks, or founding events) may play a significant role. A hierarchical analysis of the distribution of the variability across populations indicates a strong pattern of isolation by distance, whatever the geographical scale considered. Our analysis also illustrates how the mutation rate may affect population differentiation, as different mutation rates result in different levels of homoplasy at microsatellite loci. The effects of both genetic Drift and gene flow vary with the temporal and spatial scales considered in B. truncatus populations.
Frédérique Viard - One of the best experts on this subject based on the ideXlab platform.
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THE EFFECT OF COLLECTIVE DISPERSAL ON THE GENETIC STRUCTURE OF A SUBDIVIDED POPULATION
Evolution, 2013Co-Authors: Jonathan M. Yearsley, Frédérique Viard, Thomas BroquetAbstract:Correlated dispersal paths between two or more individuals are widespread across many taxa. The population genetic implications of this collective dispersal have received relatively little attention. Here we develop two-sample coalescent theory that incorporates collective dispersal in a finite island model to predict expected coalescence times, genetic diversities, and F-statistics. We show that collective dispersal reduces mixing in the system, which decreases expected coalescence times and increases FST. The effects are strongest in systems with high Migration rates. Collective dispersal breaks the invariance of within-deme coalescence times to Migration rate, whatever the deme size. It can also cause FST to increase with Migration rate because the ratio of within- to between-deme coalescence times can decrease as Migration rate approaches unity. This effect is most biologically relevant when deme size is small. We find qualitatively similar results for diploid and gametic dispersal. We also demonstrate with simulations and analytical theory the strong similarity between the effects of collective dispersal and anisotropic dispersal. These findings have implications for our understanding of the balance between Drift-Migration-mutation in models of neutral evolution. This has applied consequences for the interpretation of genetic structure (e.g., chaotic genetic patchiness) and estimation of Migration rates from genetic data.
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the influence of self fertilization and population dynamics on the genetic structure of subdivided populations a case study using microsatellite markers in the freshwater snail bulinus truncatus
Evolution, 1997Co-Authors: Frédérique Viard, Fabienne Justy, Philippe JarneAbstract:The distribution of neutral genetic variability within and among sets of populations results from the com- bined actions of genetic Drift, Migration, extinction and recolonization processes, mutation, and the mating system. We here analyzed these factors in 38 populations of the hermaphroditic snail Bulinus truncatus. The sampling area covered a large part of the species range. The variability was analyzed using four polymorphic microsatellite loci. A very large number of alleles (up to 55) was found at the level of the whole study. Observed heterozygote deficiencies within populations are consistent with very high selfing rates, generally above 0.80, in all populations. These should depress the variability within populations, because of low effective size, genetic hitchhiking, and background selection, whatever the model of mutation assumed. However, that some populations exhibit much more variability than others suggests that historical demographic processes (e.g., population size variation, bottlenecks, or founding events) may play a significant role. A hierarchical analysis of the distribution of the variability across populations indicates a strong pattern of isolation by distance, whatever the geographical scale considered. Our analysis also illustrates how the mutation rate may affect population differentiation, as different mutation rates result in different levels of homoplasy at microsatellite loci. The effects of both genetic Drift and gene flow vary with the temporal and spatial scales considered in B. truncatus populations.
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THE INFLUENCE OF SELF‐FERTILIZATION AND POPULATION DYNAMICS ON THE GENETIC STRUCTURE OF SUBDIVIDED POPULATIONS: A CASE STUDY USING MICROSATELLITE MARKERS IN THE FRESHWATER SNAIL BULINUS TRUNCATUS
Evolution; international journal of organic evolution, 1997Co-Authors: Frédérique Viard, Fabienne Justy, Philippe JarneAbstract:The distribution of neutral genetic variability within and among sets of populations results from the com- bined actions of genetic Drift, Migration, extinction and recolonization processes, mutation, and the mating system. We here analyzed these factors in 38 populations of the hermaphroditic snail Bulinus truncatus. The sampling area covered a large part of the species range. The variability was analyzed using four polymorphic microsatellite loci. A very large number of alleles (up to 55) was found at the level of the whole study. Observed heterozygote deficiencies within populations are consistent with very high selfing rates, generally above 0.80, in all populations. These should depress the variability within populations, because of low effective size, genetic hitchhiking, and background selection, whatever the model of mutation assumed. However, that some populations exhibit much more variability than others suggests that historical demographic processes (e.g., population size variation, bottlenecks, or founding events) may play a significant role. A hierarchical analysis of the distribution of the variability across populations indicates a strong pattern of isolation by distance, whatever the geographical scale considered. Our analysis also illustrates how the mutation rate may affect population differentiation, as different mutation rates result in different levels of homoplasy at microsatellite loci. The effects of both genetic Drift and gene flow vary with the temporal and spatial scales considered in B. truncatus populations.
Kerstin Johannesson - One of the best experts on this subject based on the ideXlab platform.
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What explains rare and conspicuous colours in a snail? A test of time-series data against models of Drift, Migration or selection
Heredity, 2017Co-Authors: Kerstin Johannesson, Roger K. ButlinAbstract:It is intriguing that conspicuous colour morphs of a prey species may be maintained at low frequencies alongside cryptic morphs. Negative frequency-dependent selection by predators using search images (‘apostatic selection’) is often suggested without rejecting alternative explanations. Using a maximum likelihood approach we fitted predictions from models of genetic Drift, Migration, constant selection, heterozygote advantage or negative frequency-dependent selection to time-series data of colour frequencies in isolated populations of a marine snail ( Littorina saxatilis ), re-established with perturbed colour morph frequencies and followed for >20 generations. Snails of conspicuous colours (white, red, banded) are naturally rare in the study area (usually
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What explains rare and conspicuous colours in a snail? A test of time-series data against models of Drift, Migration or selection.
Heredity, 2016Co-Authors: Kerstin Johannesson, Roger K. ButlinAbstract:What explains rare and conspicuous colours in a snail? A test of time-series data against models of Drift, Migration or selection
Hafid Achtak - One of the best experts on this subject based on the ideXlab platform.
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traditional agroecosystems as conservatories and incubators of cultivated plant varietal diversity the case of fig ficus carica l in morocco
BMC Plant Biology, 2010Co-Authors: Hafid Achtak, Ahmed Oukabli, Sylvain Santoni, Finn Kjellberg, Mohamed Ater, Bouchaib KhadariAbstract:Traditional agroecosystems are known to host both large crop species diversity and high within crop genetic diversity. In a context of global change, this diversity may be needed to feed the world. Are these agroecosystems museums (i.e. large core collections) or cradles of diversity? We investigated this question for a clonally propagated plant, fig (Ficus carica), within its native range, in Morocco, but as far away as possible from supposed centers of domestication. Fig varieties were locally numerous. They were found to be mainly highly local and corresponded to clones propagated vegetatively. Nevertheless these clones were often sufficiently old to have accumulated somatic mutations for selected traits (fig skin color) and at neutral loci (microsatellite markers). Further the pattern of spatial genetic structure was similar to the pattern expected in natural population for a mutation/Drift/Migration model at equilibrium, with homogeneous levels of local genetic diversity throughout Moroccan traditional agroecosystems. We conclude that traditional agroecosystems constitue active incubators of varietal diversity even for clonally propagated crop species, and even when varieties correspond to clones that are often old. As only female fig is cultivated, wild fig and cultivated fig probably constitute a single evolutionary unit within these traditional agroecosystems. Core collections, however useful, are museums and hence cannot serve the same functions as traditional agroecosystems.
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Traditional agroecosystems as conservatories and incubators of cultivated plant varietal diversity: the case of fig (Ficus carica L.) in Morocco
BMC Plant Biology, 2010Co-Authors: Hafid Achtak, Ahmed Oukabli, Sylvain Santoni, Finn Kjellberg, Mohamed Ater, Bouchaib KhadariAbstract:Background: Traditional agroecosystems are known to host both large crop species diversity and high within crop genetic diversity. In a context of global change, this diversity may be needed to feed the world. Are these agroecosystems museums (i.e. large core collections) or cradles of diversity? We investigated this question for a clonally propagated plant, fig (Ficus carica), within its native range, in Morocco, but as far away as possible from supposed centers of domestication. Results: Fig varieties were locally numerous. They were found to be mainly highly local and corresponded to clones propagated vegetatively. Nevertheless these clones were often sufficiently old to have accumulated somatic mutations for selected traits (fig skin color) and at neutral loci (microsatellite markers). Further the pattern of spatial genetic structure was similar to the pattern expected in natural population for a mutation/Drift/Migration model at equilibrium, with homogeneous levels of local genetic diversity throughout Moroccan traditional agroecosystems. Conclusions: We conclude that traditional agroecosystems constitue active incubators of varietal diversity even for clonally propagated crop species, and even when varieties correspond to clones that are often old. As only female fig is cultivated, wild fig and cultivated fig probably constitute a single evolutionary unit within these traditional agroecosystems. Core collections, however useful, are museums and hence cannot serve the same functions as traditional agroecosystems
