Civáň, P., Ivaničová, Z., Brown, T.A.
PLoS ONE
8 (11):
e81955,
2013
Keywords:
Abstract:
We used supernetworks with datasets of nuclear gene sequences and novel markers detecting retrotransposon
insertions in ribosomal DNA loci to reassess the evolutionary relationships among tetraploid wheats. We show that
domesticated emmer has a reticulated genetic ancestry, sharing phylogenetic signals with wild populations from all
parts of the wild range. The extent of the genetic reticulation cannot be explained by post-domestication gene flow
between cultivated emmer and wild plants, and the phylogenetic relationships among tetraploid wheats are
incompatible with simple linear descent of the domesticates from a single wild population. A more parsimonious
explanation of the data is that domesticated emmer originates from a hybridized population of different wild lineages.
The observed diversity and reticulation patterns indicate that wild emmer evolved in the southern Levant, and that the
wild emmer populations in south-eastern Turkey and the Zagros Mountains are relatively recent reticulate
descendants of a subset of the Levantine wild populations. Based on our results we propose a new model for the
emergence of domesticated emmer. During a pre-domestication period, diverse wild populations were collected from
a large area west of the Euphrates and cultivated in mixed stands. Within these cultivated stands, hybridization gave
rise to lineages displaying reticulated genealogical relationships with their ancestral populations. Gradual movement
of early farmers out of the Levant introduced the pre-domesticated reticulated lineages to the northern and eastern
parts of the Fertile Crescent, giving rise to the local wild populations but also facilitating fixation of domestication
traits. Our model is consistent with the protracted and dispersed transition to agriculture indicated by the
archaeobotanical evidence, and also with previous genetic data affiliating domesticated emmer with the wild
populations in southeast Turkey. Unlike other protracted models, we assume that humans played an intuitive role
throughout the process.
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IEB authors: Zuzana Ivaničová
