When domestication bottleneck meets weed

Crop domestication is a unique pattern of plant evolution, commonly referred to as the process of generation of cultivated crops from wild species due to morphological and genetic transformation as a result of human intervention and selection. Studies on the relationship between weeds and crops in archaeology, evolutionary biology, and genetics have revolutionized our understanding of the role of weeds in the agroecosystem and of the intricacy of crop domestication. Weeds, generally being effective competitors of crops, are not the targets of human cultivation; however, like crops, they can adapt to human-made habitats and thereby are under unintentional human selection. The peculiar environment of the agricultural system allows some arable weeds to develop domestication syndrome, i.e., to mimic crop characteristics, such as plant architecture and seed size, to escape being detected and eradicated. This domestication scenario was summarized as Vavilovian mimicry, named after the well-known former Soviet geneticist, Nikolai Vavilov, who also proposed another tangled and intimate relationship between weeds and crops. He hypothesized that several crops, such as rye and oat, are secondary domesticates, derived from agricultural weeds, rather than directly domesticated from wild progenitors ( Vavilov et al., 1992 Vavilov N.I. Vavylov M.I. Vavilov N.Í. Dorofeev V.F. Love D. Origin and Geography of Cultivated Plants. Cambridge University Press, 1992 Google Scholar ). In this little-known domestication scenario, the boundary between weeds and crops becomes blurry. Furthermore, the spatial, temporal, and cultural context of crop domestication are currently undergoing heated debates, of which some highlight that domestication is a coevolution process without conscious control ( Allaby et al., 2022 Allaby R.G. Stevens C.J. Kistler L. Fuller D.Q. Emerging evidence of plant domestication as a landscape-level process. Trends Ecol. Evol. 2022; 37: 268-279 Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar ). In a sense, such a view implies the process of mimicry, i.e., the wild-weedy stage is also a part of domestication process. However, in our view, for the secondary domesticates, domestication should only be referred to the latter stage, i.e., the weedy-cultivated stage, an asymmetrical form of mutualism process with emphasis on the dominant and central role of conscious artificial selection.