Recent demography drives changes in linked selection across the maize genome.
Genetic diversity is shaped by the interaction of drift and selection, but the details of this interaction are not well understood. The impact of genetic drift in a population is largely determined by its demographic history, typically summarized by its long-term effective population size (Ne). Rapidly changing population demographics complicate this relationship, however. To better understand how changing demography impacts selection, we used whole-genome sequencing data to investigate patterns of linked selection in domesticated and wild maize (teosinte). We produce the first whole-genome estimate of the demography of maize domestication, showing that maize was reduced to approximately 5% the population size of teosinte before it experienced rapid expansion post-domestication to population sizes much larger than its ancestor. Evaluation of patterns of nucleotide diversity in and near genes shows little evidence of selection on beneficial amino acid substitutions, and that the domestication bottleneck led to a decline in the efficiency of purifying selection in maize. Young alleles, however, show evidence of much stronger purifying selection in maize, reflecting the much larger effective size of present day populations. Our results demonstrate that recent demographic change-a hall-mark of many species including both humans and crops-can have immediate and wide-ranging impacts on diversity that conflict with expectations based on long-term Ne alone.
Department of Plant Sciences, University of California, Davis, California 95616, USA.|US Department of Agriculture, Agricultural Research Service, Columbia, Missouri 65211, USA.|Division of Plant Sciences, University of Missouri, Columbia, Missouri 65211, USA.
Timothy M
TM
Beissinger
Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa 50011, USA.
Li
L
Wang
Department of Plant Sciences, University of California, Davis, California 95616, USA.
Kate
K
Crosby
Department of Plant Sciences, University of California, Davis, California 95616, USA.
Arun
A
Durvasula
Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa 50011, USA.
Matthew B
MB
Hufford
Department of Plant Sciences, University of California, Davis, California 95616, USA.|Genome Center and Center for Population Biology, University of California, Davis, California 95616, USA.
Jeffrey
J
Ross-Ibarra
D018556:Crops, Agricultural / Q000235:genetics; D000071278:Domestication; D019143:Evolution, Molecular; D018745:Genome, Plant; D012641:Selection, Genetic; D000073336:Whole Genome Sequencing; D003313:Zea mays / Q000235:genetics*