Dataset Information

Hitchhiking and the population genetic structure of avian influenza virus.

ABSTRACT: Previous studies have revealed a major difference in the phylogenetic structure, extent of genetic diversity, and selection pressure between the surface glycoproteins and internal gene segments of avian influenza viruses (AIV) sampled from wild birds. However, what evolutionary processes are responsible for these strikingly different evolutionary patterns is unclear. To address this issue, we estimated the rate of evolutionary change and time of origin of each segment of AIV sampled globally. Strikingly, the internal segments of the sampled AIV strains possess common ancestors that existed less than 200 years ago. Similarly recent times of origin were observed for each of the individual subtypes within the HA, NA, and NS gene segments. Such a shallow history of genetic diversity suggests an evolutionary model in which the genetic structure of AIV is shaped by a combination of occasional selective sweeps in the HA and NA (and possibly NS) segments, coupled with transient genetic linkage to the internal gene segments.

SUBMITTER: Chen R

PROVIDER: S-EPMC2826789 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Hitchhiking and the population genetic structure of avian influenza virus.

Chen Rubing R Holmes Edward C EC

Journal of molecular evolution 20091230 1

Previous studies have revealed a major difference in the phylogenetic structure, extent of genetic diversity, and selection pressure between the surface glycoproteins and internal gene segments of avian influenza viruses (AIV) sampled from wild birds. However, what evolutionary processes are responsible for these strikingly different evolutionary patterns is unclear. To address this issue, we estimated the rate of evolutionary change and time of origin of each segment of AIV sampled globally. St ...[more]

PMID: 20041240

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Project description:BACKGROUND: Few models of genetic hitchhiking in subdivided populations have been developed and the rarity of empirical examples is even more striking. We here provide evidences of genetic hitchhiking in a subdivided population of the marine mussel Mytilus edulis. In the Bay of Biscay (France), a patch of M. edulis populations happens to be separated from its North Sea conspecifics by a wide region occupied only by the sister species M. galloprovincialis. Although genetic differentiation between the two M. edulis regions is largely non-significant at ten marker loci (average FST~0.007), a strong genetic differentiation is observed at a single locus (FST = 0.25). We validated the outlier status of this locus, and analysed DNA sequence polymorphism in order to identify the nature of the selection responsible for the unusual differentiation. RESULTS: We first showed that introgression of M. galloprovincialis alleles was very weak in both populations and did not significantly affect their differentiation. Secondly, we observed the genetic signature of a selective sweep within both M. edulis populations in the form of a star-shaped clade of alleles. This clade was nearly fixed in the North Sea and was segregating at a moderate frequency in the Bay of Biscay, explaining their genetic differentiation. Incomplete fixation reveals that selection was not direct on the locus but that the studied sequence recombined with a positively selected allele at a linked locus while it was on its way to fixation. Finally, using a deterministic model we showed that the wave of advance of a favourable allele at a linked locus, when crossing a strong enough barrier to gene flow, generates a step in neutral allele frequencies comparable to the step observed between the two M. edulis populations at the outlier locus. In our case, the position of the barrier is now materialised by a large patch of heterospecific M. galloprovincialis populations. CONCLUSION: High FST outlier loci are usually interpreted as being the consequence of ongoing divergent local adaptation. Combining models and data we show that among-population differentiation can also dramatically increase following a selective sweep in a structured population. Our study illustrates how a striking geographical pattern of neutral diversity can emerge from past indirect hitchhiking selection in a structured population. NOTE: Nucleotide sequences reported in this paper are available in the GenBanktrade mark database under the accession numbers EU684165 - EU684228.

Dataset Information

Hitchhiking and the population genetic structure of avian influenza virus.

Publications

Hitchhiking and the population genetic structure of avian influenza virus.

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