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| This is a comprehensive bibliography (under construction) of primary and secondary sources on the neutral theory of molecular evolution. It currently covers the period 1973-2001. |
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Author :
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Funk, D. J.;Wernegreen, J. J.;Moran, N. A.
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Year :
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2001
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Title :
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Intraspecific variation in symbiont genomes: Bottlenecks and the aphid-buchnera association
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Journal :
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Genetics
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Volume :
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157
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Issue :
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2
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Pages :
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477-489
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Date :
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Feb
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Short Title :
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Intraspecific variation in symbiont genomes: Bottlenecks and the aphid-buchnera association
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Alternate Journal :
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Genetics
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Custom 2 :
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ISI:000166810200006
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Abstract :
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Buchnera are maternally transmitted bacterial endosymbionts that synthesize amino acids that are limiting in the diet of their aphid hosts. Previous studies demonstrated accelerated sequence evolution in Buchnera compared to free-living bacteria, especially for nonsynonymous substitutions. Two mechanisms may explain this acceleration: relaxed purifying selection and increased fixation of slightly deleterious alleles under drift. Here, we test the divergent predictions of these hypotheses for intraspecific polymorphism using Buchnera associated with natural populations of the ragweed aphid, Uroleucon ambrosiae. Contrary to expectations under relaxed selection, U. ambrosiae from across the United States yielded strikingly low sequence diversity at three Buchnera loci (dnaN, trpBC, trpEG), revealing polymorphism three orders of magnitude lower than in enteric bacteria. An excess of nonsynonymous polymorphism and of rare alleles was also observed. Local sampling of additional dnaN sequences revealed similar patterns of polymorphism and no evidence of food plant-associated genetic structure. Aphid mitochondrial sequences further suggested that host bottlenecks and large-scare dispersal may contribute to genetic homogenization of aphids and symbionts. Together, our results support reduced N-e as a primary cause of accelerated sequence evolution in Buchnera. However, our study cannot rule out the possibility that mechanisms other than bottlenecks also contribute to reduced N-e at aphid and endosymbiont loci.
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Notes :
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Times Cited: 2
399KL
GENETICS
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| | -- contributed by John Beatty, March 29, 2002 |
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