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Jeanine L. Olsen - One of the best experts on this subject based on the ideXlab platform.
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evolution and diversification within the intertidal brown macroalgae fucus spiralis f vesiculosus species complex in the north atlantic
Molecular Phylogenetics and Evolution, 2011Co-Authors: James A Coyer, B Hogerdijk, Galice Hoarau, Elisabeth Billard, Emmanuel Adilson S Serrao, Gareth A Pearson, Joana Costa, Myriam Valero, Jeanine L. OlsenAbstract:We examined 733 individuals of Fucus spiralis from 21 locations and 1093 Fucus vesiculosus individuals from 37 locations throughout their northern hemisphere ranges using nuclear and mitochondrial markers. Three genetic entities of F. spiralis were recovered. In northern and sympatric populations, the presence of ‘‘F. spiralis Low’’ in the mid-intertidal and ‘‘F. spiralis High’’ in the high-intertidal was confirmed and both co-occurred with the sister species F. vesiculosus. The third and newly-discovered entity, ‘‘F. spiralis South’’, was present mainly in the southern range, where it did not co-occur with F. vesiculosus. The South entity diverged early in allopatry, then hybridized with F. vesiculosus in sympatry to produce F. spiralis Low. Ongoing parallel evolution of F. spiralis Low and F. spiralis High is most likely due to habitat preference/local selection and maintained by preferentially selfing reproductive strategies. Contemporary populations of F. spiralis throughout the North Atlantic stem from a glacial Refugium around Brittany involving F. spiralis High; F. spiralis South was probably unaffected by glacial episodes. Exponential population expansion for F. vesiculosus began during the Cromer and/Holstein interglacial period (300,000– 200,000 yrs BP). Following the last glacial maximum (30,000–22,000 yrs BP), a single mtDNA haplotype from a glacial Refugium in SW Ireland colonized Scandinavia, the Central Atlantic islands, and the W
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Evolution and diversification within the intertidal brown macroalgae Fucus spiralis/F. vesiculosus species complex in the North Atlantic.
Molecular Phylogenetics and Evolution, 2010Co-Authors: James A Coyer, B Hogerdijk, Galice Hoarau, Elisabeth Billard, Emmanuel Adilson S Serrao, Gareth A Pearson, Joana Costa, Myriam Valero, Jeanine L. OlsenAbstract:We examined 733 individuals of Fucus spiralis from 21 locations and 1093 Fucus vesiculosus individuals from 37 locations throughout their northern hemisphere ranges using nuclear and mitochondrial markers. Three genetic entities of F. spiralis were recovered. In northern and sympatric populations, the presence of ‘‘F. spiralis Low’’ in the mid-intertidal and ‘‘F. spiralis High’’ in the high-intertidal was confirmed and both co-occurred with the sister species F. vesiculosus. The third and newly-discovered entity, ‘‘F. spiralis South’’, was present mainly in the southern range, where it did not co-occur with F. vesiculosus. The South entity diverged early in allopatry, then hybridized with F. vesiculosus in sympatry to produce F. spiralis Low. Ongoing parallel evolution of F. spiralis Low and F. spiralis High is most likely due to habitat preference/local selection and maintained by preferentially selfing reproductive strategies. Contemporary populations of F. spiralis throughout the North Atlantic stem from a glacial Refugium around Brittany involving F. spiralis High; F. spiralis South was probably unaffected by glacial episodes. Exponential population expansion for F. vesiculosus began during the Cromer and/Holstein interglacial period (300,000– 200,000 yrs BP). Following the last glacial maximum (30,000–22,000 yrs BP), a single mtDNA haplotype from a glacial Refugium in SW Ireland colonized Scandinavia, the Central Atlantic islands, and the W
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glacial refugia and recolonization pathways in the brown seaweed fucus serratus
Molecular Ecology, 2007Co-Authors: Galice Hoarau, James A Coyer, Wytze T. Stam, Jan Veldsink, Jeanine L. OlsenAbstract:The last glacial maximum (20,000-18,000 years ago) dramatically affected extant distributions of virtually all northern European biota. Locations of refugia and postglacial recolonization pathways were examined in Fucus serratus (Heterokontophyta; Fucaceae) using a highly variable intergenic spacer developed from the complete mitochondrial genome of Fucus vesiculosus. Over 1,500 samples from the entire range of F. serratus were analysed using fluorescent single strand conformation polymorphism. A total of 28 mtDNA haplotypes was identified and sequenced. Three refugia were recognized based on high haplotype diversities and the presence of endemic haplotypes: southwest Ireland, the northern Brittany-Hurd Deep area of the English Channel, and the northwest Iberian Peninsula. The Irish Refugium was the source for a recolonization sweep involving a single haplotype via northern Scotland and throughout Scandinavia, whereas recolonization from the Brittany-Hurd Deep Refugium was more limited, probably because of unsuitable soft-bottom habitat in the Bay of Biscay and along the Belgian and Dutch coasts. The Iberian populations reflect a remnant Refugium at the present-day southern boundary of the species range. A generalized skyline plot suggested exponential population expansion beginning in the mid-Pleistocene with maximal growth during the Eems interglacial 128,000-67,000 years ago, implying that the last glacial maximum mainly shaped population distributions rather than demography.
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phylogeography and population structure of thornback rays raja clavata l rajidae
Molecular Ecology, 2006Co-Authors: Malia Chevolot, Galice Hoarau, Wytze T. Stam, Adriaan D. Rijnsdorp, Jeanine L. OlsenAbstract:The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a Refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia - one around the Iberian Peninsula and one possibly in the Azores. Links to a potential Refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580 000 and 362 000 years ago, which suggests that the Last Glacial Maximum (20 000 years ago) had mainly affected the distribution of populations rather than population size.
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Phylogeography and population structure of the thornback ray (Raja clavata L.).
Molecular Ecology, 2006Co-Authors: Malia Chevolot, Galice Hoarau, Wytze T. Stam, Adriaan D. Rijnsdorp, Jeanine L. OlsenAbstract:The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a Refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia - one around the Iberian Peninsula and one possibly in the Azores. Links to a potential Refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580 000 and 362 000 years ago, which suggests that the Last Glacial Maximum (20 000 years ago) had mainly affected the distribution of populations rather than population size.
Galice Hoarau - One of the best experts on this subject based on the ideXlab platform.
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evolution and diversification within the intertidal brown macroalgae fucus spiralis f vesiculosus species complex in the north atlantic
Molecular Phylogenetics and Evolution, 2011Co-Authors: James A Coyer, B Hogerdijk, Galice Hoarau, Elisabeth Billard, Emmanuel Adilson S Serrao, Gareth A Pearson, Joana Costa, Myriam Valero, Jeanine L. OlsenAbstract:We examined 733 individuals of Fucus spiralis from 21 locations and 1093 Fucus vesiculosus individuals from 37 locations throughout their northern hemisphere ranges using nuclear and mitochondrial markers. Three genetic entities of F. spiralis were recovered. In northern and sympatric populations, the presence of ‘‘F. spiralis Low’’ in the mid-intertidal and ‘‘F. spiralis High’’ in the high-intertidal was confirmed and both co-occurred with the sister species F. vesiculosus. The third and newly-discovered entity, ‘‘F. spiralis South’’, was present mainly in the southern range, where it did not co-occur with F. vesiculosus. The South entity diverged early in allopatry, then hybridized with F. vesiculosus in sympatry to produce F. spiralis Low. Ongoing parallel evolution of F. spiralis Low and F. spiralis High is most likely due to habitat preference/local selection and maintained by preferentially selfing reproductive strategies. Contemporary populations of F. spiralis throughout the North Atlantic stem from a glacial Refugium around Brittany involving F. spiralis High; F. spiralis South was probably unaffected by glacial episodes. Exponential population expansion for F. vesiculosus began during the Cromer and/Holstein interglacial period (300,000– 200,000 yrs BP). Following the last glacial maximum (30,000–22,000 yrs BP), a single mtDNA haplotype from a glacial Refugium in SW Ireland colonized Scandinavia, the Central Atlantic islands, and the W
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Evolution and diversification within the intertidal brown macroalgae Fucus spiralis/F. vesiculosus species complex in the North Atlantic.
Molecular Phylogenetics and Evolution, 2010Co-Authors: James A Coyer, B Hogerdijk, Galice Hoarau, Elisabeth Billard, Emmanuel Adilson S Serrao, Gareth A Pearson, Joana Costa, Myriam Valero, Jeanine L. OlsenAbstract:We examined 733 individuals of Fucus spiralis from 21 locations and 1093 Fucus vesiculosus individuals from 37 locations throughout their northern hemisphere ranges using nuclear and mitochondrial markers. Three genetic entities of F. spiralis were recovered. In northern and sympatric populations, the presence of ‘‘F. spiralis Low’’ in the mid-intertidal and ‘‘F. spiralis High’’ in the high-intertidal was confirmed and both co-occurred with the sister species F. vesiculosus. The third and newly-discovered entity, ‘‘F. spiralis South’’, was present mainly in the southern range, where it did not co-occur with F. vesiculosus. The South entity diverged early in allopatry, then hybridized with F. vesiculosus in sympatry to produce F. spiralis Low. Ongoing parallel evolution of F. spiralis Low and F. spiralis High is most likely due to habitat preference/local selection and maintained by preferentially selfing reproductive strategies. Contemporary populations of F. spiralis throughout the North Atlantic stem from a glacial Refugium around Brittany involving F. spiralis High; F. spiralis South was probably unaffected by glacial episodes. Exponential population expansion for F. vesiculosus began during the Cromer and/Holstein interglacial period (300,000– 200,000 yrs BP). Following the last glacial maximum (30,000–22,000 yrs BP), a single mtDNA haplotype from a glacial Refugium in SW Ireland colonized Scandinavia, the Central Atlantic islands, and the W
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glacial refugia and recolonization pathways in the brown seaweed fucus serratus
Molecular Ecology, 2007Co-Authors: Galice Hoarau, James A Coyer, Wytze T. Stam, Jan Veldsink, Jeanine L. OlsenAbstract:The last glacial maximum (20,000-18,000 years ago) dramatically affected extant distributions of virtually all northern European biota. Locations of refugia and postglacial recolonization pathways were examined in Fucus serratus (Heterokontophyta; Fucaceae) using a highly variable intergenic spacer developed from the complete mitochondrial genome of Fucus vesiculosus. Over 1,500 samples from the entire range of F. serratus were analysed using fluorescent single strand conformation polymorphism. A total of 28 mtDNA haplotypes was identified and sequenced. Three refugia were recognized based on high haplotype diversities and the presence of endemic haplotypes: southwest Ireland, the northern Brittany-Hurd Deep area of the English Channel, and the northwest Iberian Peninsula. The Irish Refugium was the source for a recolonization sweep involving a single haplotype via northern Scotland and throughout Scandinavia, whereas recolonization from the Brittany-Hurd Deep Refugium was more limited, probably because of unsuitable soft-bottom habitat in the Bay of Biscay and along the Belgian and Dutch coasts. The Iberian populations reflect a remnant Refugium at the present-day southern boundary of the species range. A generalized skyline plot suggested exponential population expansion beginning in the mid-Pleistocene with maximal growth during the Eems interglacial 128,000-67,000 years ago, implying that the last glacial maximum mainly shaped population distributions rather than demography.
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phylogeography and population structure of thornback rays raja clavata l rajidae
Molecular Ecology, 2006Co-Authors: Malia Chevolot, Galice Hoarau, Wytze T. Stam, Adriaan D. Rijnsdorp, Jeanine L. OlsenAbstract:The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a Refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia - one around the Iberian Peninsula and one possibly in the Azores. Links to a potential Refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580 000 and 362 000 years ago, which suggests that the Last Glacial Maximum (20 000 years ago) had mainly affected the distribution of populations rather than population size.
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Phylogeography and population structure of the thornback ray (Raja clavata L.).
Molecular Ecology, 2006Co-Authors: Malia Chevolot, Galice Hoarau, Wytze T. Stam, Adriaan D. Rijnsdorp, Jeanine L. OlsenAbstract:The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a Refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia - one around the Iberian Peninsula and one possibly in the Azores. Links to a potential Refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580 000 and 362 000 years ago, which suggests that the Last Glacial Maximum (20 000 years ago) had mainly affected the distribution of populations rather than population size.
Jan M. Wójcik - One of the best experts on this subject based on the ideXlab platform.
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post glacial colonization of eastern europe from the carpathian Refugium evidence from mitochondrial dna of the common vole microtus arvalis
Biological Journal of The Linnean Society, 2015Co-Authors: Joanna Stojak, Allan D. Mcdevitt, Jeremy S. Herman, Jeremy B Searle, Jan M. WójcikAbstract:There is now considerable evidence for the survival of temperate species within glacial refugia that were situated at relatively high latitudes, notably the Carpathian Basin and Dordogne region in Europe. However, the prevalence of fossil remains in such locations is rarely matched by molecular evidence for their contribution to subsequent geographical and demographic expansion of the species in question. One obstacle to this has been insufficient analysis of modern samples from the relevant areas, in particular the parts of eastern Europe that surround the Carpathian Refugium. In the present study, we examine the patterns of variation in mitochondrial DNA of the common vole (Microtus arvalis), obtained from existing museum specimens and from newly-collected samples obtained in this area. We show that common voles from one of six extant mitochondrial DNA lineages have colonized most of the species' range in eastern Europe. We contend that the post-glacial dispersal of this lineage most likely originated from the Carpathian Refugium, adding support to the argument that such northern refugia made an important contribution to existing genetic diversity in Europe.
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Post‐glacial colonization of eastern Europe from the Carpathian Refugium: evidence from mitochondrial DNA of the common vole Microtus arvalis
Biological Journal of the Linnean Society, 2015Co-Authors: Joanna Stojak, Allan D. Mcdevitt, Jeremy S. Herman, Jeremy B Searle, Jan M. WójcikAbstract:There is now considerable evidence for the survival of temperate species within glacial refugia that were situated at relatively high latitudes, notably the Carpathian Basin and Dordogne region in Europe. However, the prevalence of fossil remains in such locations is rarely matched by molecular evidence for their contribution to subsequent geographical and demographic expansion of the species in question. One obstacle to this has been insufficient analysis of modern samples from the relevant areas, in particular the parts of eastern Europe that surround the Carpathian Refugium. In the present study, we examine the patterns of variation in mitochondrial DNA of the common vole (Microtus arvalis), obtained from existing museum specimens and from newly-collected samples obtained in this area. We show that common voles from one of six extant mitochondrial DNA lineages have colonized most of the species' range in eastern Europe. We contend that the post-glacial dispersal of this lineage most likely originated from the Carpathian Refugium, adding support to the argument that such northern refugia made an important contribution to existing genetic diversity in Europe.
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Climate and refugial origin influence the mitochondrial lineage distribution of weasels (Mustela nivalis) in a phylogeographic suture zone
Biological Journal of The Linnean Society, 2012Co-Authors: Allan D. Mcdevitt, Karol Zub, Agata Kawałko, Matthew Oliver, Jeremy S. Herman, Jan M. WójcikAbstract:Overarching trends can be seen in European mammalian phylogeography, yet it is clear that species responded differently depending on adaptations to past environments. We built upon previous work on the phylogeography of weasels (Mustela nivalis) in Europe by using well-preserved museum specimens from a proposed phylogeographic suture zone. The complete cytochrome b gene was amplified from 49 individuals from present-day Poland and analyzed with previously published data on a European scale to identify glacial refugia and infer recolonization processes. Bayesian coalescent analysis revealed the importance of the Last Glacial Maximum and the Younger Dryas in the diversification of, and demographic changes in, identified mitochondrial lineages. Our analysis, in conjunction with the available fossil data, strongly points to a Carpathian origin for one of the lineages, and further highlights the importance of this region as a Refugium for European mammals. Mustela nivalis originating from this Refugium appear to have a selective advantage over M. nivalis from other lineages in certain environments in the suture zone in central Europe, with climate clearly influencing the distribution of mitochondrial DNA lineages. This has important implications not only for our understanding of how past climatic events shaped the genetic architecture of species, but also how they will respond to current and future climatic changes. (c) 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 5769.
Graham Rowe - One of the best experts on this subject based on the ideXlab platform.
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Regular ArticleMicrosatellite analysis of natterjack toad Bufo calamita Laurenti populations: consequences of dispersal from a Pleistocene Refugium
Biological Journal of the Linnean Society, 2000Co-Authors: Trevor J. C. Beebee, Graham RoweAbstract:Populations of the amphibian Bufo calamita were sampled for genetic analysis in eleven areas distributed across its biogeographical range in Europe. Genetic diversity estimates across eight microsatellite loci showed a decline in polymorphism, numbers of alleles and heterozygosity as a function of distance from the presumed ice-age Refugium in Iberia. Trials with a selection of tree-building algorithms indicated that UPGMA of Cavalli-Sforza chord distances (Dc) generated the tree topology most easily reconciled with other biogeographical information. Genetic distance measures were also calibrated against a postglacial event from which the separation of extant populations could be estimated in real time. Dcagain outperformed two other measures (Nei's standard distance,Ds , and δμ2) in producing realistic correlations with minimal variance. The genetic analysis was consistent with the hypothesis that B. calamita survived in a single Refugium (Iberia) during the Pleistocene glaciation and indicated that it spread north and east from there during the last interstadial which commenced about 14 000 years before present (BP). Microsatellites should provide useful tools for biogeographical investigations of other species, especially with respect to patterns of population dispersal.
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Microsatellite analysis of natterjack toad Bufo calamita Laurenti populations: consequences of dispersal from a Pleistocene Refugium
Biological Journal of the Linnean Society, 2000Co-Authors: Trevor J. C. Beebee, Graham RoweAbstract:Abstract Populations of the amphibian Bufo calamita were sampled for genetic analysis in eleven areas distributed across its biogeographical range in Europe. Genetic diversity estimates across eight microsatellite loci showed a decline in polymorphism, numbers of alleles and heterozygosity as a function of distance from the presumed ice-age Refugium in Iberia. Trials with a selection of tree-building algorithms indicated that UPGMA of Cavalli-Sforza chord distances ( D c ) generated the tree topology most easily reconciled with other biogeographical information. Genetic distance measures were also calibrated against a postglacial event from which the separation of extant populations could be estimated in real time. D c again outperformed two other measures (Nei's standard distance, D s , and δμ 2 ) in producing realistic correlations with minimal variance. The genetic analysis was consistent with the hypothesis that B. calamita survived in a single Refugium (Iberia) during the Pleistocene glaciation and indicated that it spread north and east from there during the last interstadial which commenced about 14 000 years before present (BP). Microsatellites should provide useful tools for biogeographical investigations of other species, especially with respect to patterns of population dispersal.
Malia Chevolot - One of the best experts on this subject based on the ideXlab platform.
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phylogeography and population structure of thornback rays raja clavata l rajidae
Molecular Ecology, 2006Co-Authors: Malia Chevolot, Galice Hoarau, Wytze T. Stam, Adriaan D. Rijnsdorp, Jeanine L. OlsenAbstract:The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a Refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia - one around the Iberian Peninsula and one possibly in the Azores. Links to a potential Refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580 000 and 362 000 years ago, which suggests that the Last Glacial Maximum (20 000 years ago) had mainly affected the distribution of populations rather than population size.
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Phylogeography and population structure of the thornback ray (Raja clavata L.).
Molecular Ecology, 2006Co-Authors: Malia Chevolot, Galice Hoarau, Wytze T. Stam, Adriaan D. Rijnsdorp, Jeanine L. OlsenAbstract:The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a Refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia - one around the Iberian Peninsula and one possibly in the Azores. Links to a potential Refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580 000 and 362 000 years ago, which suggests that the Last Glacial Maximum (20 000 years ago) had mainly affected the distribution of populations rather than population size.
