Is the Mesopotamian region a main source of Western European segetal plants?

The Mesopotamian Region is often recognised as the origin of the Western European (W European) segetal plants that have been coevolving with winter cereals since the emergence of agriculture. This eastern origin assumption is based on the close association between cereal domestication and arable weed occurrence. However, it has never been properly tested and the debate of their biogeographical origin continues. Here, we conducted a comparative floristic analysis of the complete French segetal plant list to provide a global comprehension vision on their hypothetic Mesopotamian origin. We found a total of 58 of the 102 segetal French taxa that occur both in the fields and in primary natural habitats in the Upper Mesopotamian Region. In contrast, in France, only 39 species are facultative weeds under the Mediterranean bioclimate while they are obligatory weeds under Temperate bioclimate. A significant part of them is endemic to W Europe occurring in primary natural habitats, and thus contributing to enrich the local segetal assemblage. Contrary to the general belief of their eastern origin, these French segetal taxa are originated from various biogeographical regions (Eurasiatic, European, Eury-Mediterranean, Mediterranean, Mediterranean-Touranian and W-Asiatic) and not only from the Upper Mesopotamian Region. Hence, we propose a hypothetical scheme to illustrate the various segetal assemblages as the result of an accumulative local colonization/extinction process alongside the cereal migration routes. Therefore, primary natural source versus secondary field sink habitats have considerably contributed to the segetal assemblage and thus represent crucial new contributions to our knowledge of their various biogeographical origin.