Effective population size is positively correlated with levels of adaptive divergence among annual sunflowers

The role of adaptation in the divergence of lineages has long been a central question in evolutionary biology, and as multilocus sequence data sets have become available for a wide range of taxa, empirical estimates of levels of adaptive molecular evolution are increasingly common. Estimates vary wi...

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Bibliographic Details
Published in:Molecular biology and evolution 2011-05, Vol.28 (5), p.1569-1580
Main Authors: Strasburg, Jared L, Kane, Nolan C, Raduski, Andrew R, Bonin, Aurélie, Michelmore, Richard, Rieseberg, Loren H
Format: Article
Language:English
Subjects:
Adaptation, Biological - genetics
Amino acids
Correlation analysis
Evolution
Evolutionary biology
Expressed Sequence Tags
Flowers & plants
Genetic Fitness
Genetic Loci
Genetic Speciation
Genetic Variation
Helianthus - genetics
Insects
Models, Genetic
Nonnative species
Phylogeny
Plant populations
Polymorphism, Genetic
Population Density
Population number
Sequence Analysis, DNA
Taxa
Taxonomy
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Summary:The role of adaptation in the divergence of lineages has long been a central question in evolutionary biology, and as multilocus sequence data sets have become available for a wide range of taxa, empirical estimates of levels of adaptive molecular evolution are increasingly common. Estimates vary widely among taxa, with high levels of adaptive evolution in Drosophila, bacteria, and viruses but very little evidence of widespread adaptive evolution in hominids. Although estimates in plants are more limited, some recent work has suggested that rates of adaptive evolution in a range of plant taxa are surprisingly low and that there is little association between adaptive evolution and effective population size in contrast to patterns seen in other taxa. Here, we analyze data from 35 loci for six sunflower species that vary dramatically in effective population size. We find that rates of adaptive evolution are positively correlated with effective population size in these species, with a significant fraction of amino acid substitutions driven by positive selection in the species with the largest effective population sizes but little or no evidence of adaptive evolution in species with smaller effective population sizes. Although other factors likely contribute as well, in sunflowers effective population size appears to be an important determinant of rates of adaptive evolution.
ISSN:0737-4038
1537-1719
DOI:10.1093/molbev/msq270