Dataset Information

Molecular demographic history of the annual sunflowers Helianthus annuus and H. petiolaris--large effective population sizes and rates of long-term gene flow.

ABSTRACT: Hybridization between distinct species may lead to introgression of genes across species boundaries, and this pattern can potentially persist for extended periods as long as selection at some loci or genomic regions prevents thorough mixing of gene pools. However, very few reliable estimates of long-term levels of effective migration are available between hybridizing species throughout their history. Accurate estimates of divergence dates and levels of gene flow require data from multiple unlinked loci as well as an analytical framework that can distinguish between lineage sorting and gene flow and incorporate the effects of demographic changes within each species. Here we use sequence data from 18 anonymous nuclear loci in two broadly sympatric sunflower species, Helianthus annuus and H. petiolaris, analyzed within an "isolation with migration" framework to make genome-wide estimates of the ages of these two species, long-term rates of gene flow between them, and effective population sizes and historical patterns of population growth. Our results indicate that H. annuus and H. petiolaris are approximately one million years old and have exchanged genes at a surprisingly high rate (long-term N(ef)m estimates of approximately 0.5 in each direction), with somewhat higher rates of introgression from H. annuus into H. petiolaris than vice versa. In addition, each species has undergone dramatic population expansion since divergence, and both species have among the highest levels of genetic diversity reported for flowering plants. Our results provide the most comprehensive estimate to date of long-term patterns of gene flow and historical demography in a nonmodel plant system, and they indicate that species integrity can be maintained even in the face of extensive gene flow over a prolonged period.

SUBMITTER: Strasburg JL

PROVIDER: S-EPMC2601659 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Publications

Molecular demographic history of the annual sunflowers Helianthus annuus and H. petiolaris--large effective population sizes and rates of long-term gene flow.

Strasburg Jared L JL Rieseberg Loren H LH

Evolution; international journal of organic evolution 20080505 8

Hybridization between distinct species may lead to introgression of genes across species boundaries, and this pattern can potentially persist for extended periods as long as selection at some loci or genomic regions prevents thorough mixing of gene pools. However, very few reliable estimates of long-term levels of effective migration are available between hybridizing species throughout their history. Accurate estimates of divergence dates and levels of gene flow require data from multiple unlink ...[more]

PMID: 18462213

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Project description:Parallels exist between the domestication of new species and the improvement of various crops through selection on traits which favor the sowing, harvest and retention of yield potential and the directed efforts to improve their agronomics, disease resistance and quality characteristics. Common selection pressures may result in the parallel selection of orthologs underlying these traits and homologies between crop species can be exploited by plant breeders to improve germplasm. Perennial grains and oilseeds are a class of proposed crops for improving the diversity and sustainability of agricultural systems. Maximilian sunflower (Helianthus maximiliani Schrad.) is a perennial crop wild relative of sunflower (Helianthus annuus L.) and a candidate perennial oilseed species. Understanding parallels between cultivated H. annuus and H. maximiliani may provide new tools for the development of Maximilian sunflower and other wild relatives of sunflower as crops to enhance functional diversity in cropping systems. F2 populations of Maximilian sunflower segregating for traits associated with the domestication ideotype of cultivated sunflower including branching architecture, capitulum morphology and flowering time were developed to investigate parallels between H. maximiliani and H. annuus. Genotype-by-sequencing (GBS) was employed to genotype novel Maximilian sunflower populations and perform quantitative-trait-loci (QTL) analysis. A total of 11 QTL in five regions were identified across 21 linkage groups using 4142 GBS derived single nucleotide polymorphism markers called using the sunflower reference genome as a guide. A major QTL on linkage group 17b, associated with aspects of floral development and apical dominance, was discovered and corresponds with a known domestication QTL hotspot in H. annuus and candidate genes were identified. This suggests the potential to exploit orthologs for neo-domestication of H. maximiliani for traits such as branching architecture, timing of anthesis, and capitulum size and morphology for the development of a perennial oilseed crop from wild relatives of cultivated sunflower.

Dataset Information

Molecular demographic history of the annual sunflowers Helianthus annuus and H. petiolaris--large effective population sizes and rates of long-term gene flow.

Publications

Molecular demographic history of the annual sunflowers Helianthus annuus and H. petiolaris--large effective population sizes and rates of long-term gene flow.

Similar Datasets

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