Résumé
Date palm (Phoenix dactylifera L.) is a major fruit crop of arid regions
that were domesticated 7,000 y ago in the Near or Middle East. This
species is cultivated widely in the Middle East and North Africa, and
previous population genetic studies have shown genetic differentiation
between these regions. We investigated the evolutionary history of P.
dactylifera and its wild relatives by resequencing the genomes of date
palm varieties and five of its closest relatives. Our results indicate
that the North African population has mixed ancestry with components from
Middle Eastern P. dactylifera and Phoenix theophrasti, a wild relative
endemic to the Eastern Mediterranean. Introgressive hybridization is
supported by tests of admixture, reduced subdivision between North African
date palm and P. theophrasti, sharing of haplotypes in introgressed
regions, and a population model that incorporates gene flow between these
populations. Analysis of ancestry proportions indicates that as much as
18% of the genome of North African varieties can be traced to P.
theophrasti and a large percentage of loci in this population are
segregating for single-nucleotide polymorphisms (SNPs) that are fixed in
P. theophrasti and absent from date palm in the Middle East. We present a
survey of Phoenix remains in the archaeobotanical record which supports a
late arrival of date palm to North Africa. Our results suggest that
hybridization with P. theophrasti was of central importance in the
diversification history of the cultivated date palm.