Buckwheat: a crop from outside the major Chinese domestication centres? A review of the archaeobotanical, palynological and genetic evidence

Vegetation History and Archaeobotany https://doi.org/10.1007/s00334-017-0649-4 ORIGINAL ARTICLE Buckwheat: a crop from outside the major Chinese domestication centres? A review of the archaeobotanical, palynological and genetic evidence Harriet V. Hunt1 · Xue Shang2 · Martin K. Jones3 Received: 2 December 2016 / Accepted: 24 October 2017 © The Author(s) 2017. This article is an open access publication Abstract The two cultivated species of buckwheat, Fagopyrum esculentum (common buckwheat) and F. tataricum (Tartary buckwheat) are Chinese domesticates whose origins are usually thought to lie in upland southwestern China, outside the major centres of agricultural origins associated with rice and millet. Synthesis of the macro- and microfossil evidence for buckwheat cultivation in China found just 26 records across all time periods, of which the majority were pollen finds. There are few or no identifying criteria distinguishing F. esculentum and F. tataricum for any sample type. The earliest plausibly agricultural Fagopyrum occurs in northern China from the mid 6th millennium cal bp. The archaeobotanical record requires reconciliation with biogeographic and genetic inferences of a southwestern Chinese origin for buckwheat. Scrutiny of the genetic data indicates limitations related to sampling, molecular markers and analytical approaches. Common buckwheat may have been domesticated at the range margins of its wild progenitor before its cultivation expanded in the north, mediated by changing ranges of wild species during the Holocene and/or by cultural exchange or movement of early agriculturalists between southwest China, the Chengdu Plain and the southern Loess Plateau. Buckwheat probably became a pan-Eurasian crop by the 3rd millennium cal bp, with the pattern of finds suggesting a route of westward expansion via the southern Himalaya to the Caucasus and Europe. Keywords Buckwheat · Fagopyrum · Crop domestication · Agricultural origins · China · Polygonaceae Introduction The transition to agriculture in China occurred independently in at least three recognised centres (Zhao 2011). Dry land agriculture, with millets as the principal crops, began in the Loess Plateau and Yellow river catchment in north Communicated by J. Kitagawa. * Harriet V. Hunt * Xue Shang 1 McDonald Institute for Archaeological Research, University of Cambridge, Downing Street, Cambridge CB2 3ER, UK 2 Department of Archaeology and Anthropology, University of Chinese Academy of Sciences, 19A, Yuquan Road, Beijing 100049, China 3 Division of Archaeology, University of Cambridge, Downing Street, Cambridge CB2 3DZ, UK China. Rice agriculture developed in the middle and lower Yangtze valley and a third centre in tropical southern China, along the Zhujiang river south of the Nanling mountains, underwent an early agricultural transition in which roots and tubers, possibly including Colocasia esculenta (taro), were the main crops. The growth of Chinese archaeobotany in the last 10–15 years has rapidly advanced understanding of plant domestication in these regions and their interrelationships. Buckwheat is an intriguing early Chinese crop whose origins appear not to fit the geography of any of these three recognised agricultural centres. In consequence, systematic evaluation of evidence for the origins of buckwheat has been neglected. Buckwheat is a pseudo-cereal belonging to the family Polygonaceae, with the grain either consumed whole after boiling or steaming, or ground into a gluten-free flour. Cultivated buckwheat comprises two species: Fago pyrum esculentum L. (common buckwheat) and F. tatari cum Gaertn. (Tartary buckwheat). The two species differ in importance and cultivated range. F. esculentum is widespread in the temperate zones of the northern hemisphere 13 Vol.:(0123456789) Vegetation History and Archaeobotany (Ohnishi 1998b), while F. tataricum is principally a crop of high altitude zones, such as the circum-Himalaya region (Ohnishi 2000). Ecophysiologically, F. tataricum has some frost tolerance, which is lacking in F. esculentum (Campbell 1997). The two species also differ in breeding system. Tartary buckwheat is self-fertile and largely inbreeding (Tsuji and Ohnishi 2000), while F. esculentum is an insect-pollinated, obligate outbreeder (Cawoy et al. 2009). The aim of this paper is to elucidate the geographical origins and early chronology of both F. esculentum and tataricum within China, through a synthesis of the archaeobotanical microfossil and macrofossil data, in the context of biogeography and genetic evidence. This project is timely for several reasons. First, although it has been concluded from biogeographic and genetic data that both species originated in southwestern China, specifically eastern Tibet, northern Yunnan and southwestern Sichuan (Konishi et al. 2005; Konishi and Ohnishi 2007; Ohnishi 2009), the agreement between the genetic and palaeobotanical data has never been examined. Second, the publication of palynological and macrofossil data from several new Chinese sites in recent years makes a review of the evidence for Fagopyrum appropriate. Third, the spread of agriculture into southwestern China and the Tibetan Himalaya region is a topic of much current interest (d’Alpoim Guedes 2011; d’Alpoim Guedes et al. 2013, 2014, 2015; Chen et al. 2015), to which an improved understanding of buckwheat origins and the differing ecologies of F. esculentum and tataricum is highly relevant. Finally, F. esculentum subsequently became a widespread crop in the Old World northern hemisphere, but the chronology of this globalization is uncertain (Jones et al. 2011; Boivin et al. 2012). A recent review of the European palynological and macrobotanical data (de Klerk et al. 2015) has highlighted this uncertainty. Here we undertake a comparable review of the data set for China. Understanding the spatial and temporal picture of buckwheat origins in China is an essential step to resolving its global pattern, including the status of buckwheat finds in Europe. These issues in turn relate to the wider topic of east–west crop spread. Methods We aimed to collate all published data on archaeobotanical (comprising both macrofossil and microfossil) identifications of (buckwheat/Fagopyrum/qiaomai/荞麦) within the present boundaries of China. We searched the English and Chinese language literature using Google scholar and the China National Infrastructure Database (http://www.cnki. net) respectively, using various combinations of the search terms ‘Fagopyrum’, ‘buckwheat’, ‘vegetation’, ‘China’ on Google scholar and ‘qiaomai/荞麦’ (buckwheat) and ‘yizhi/遗址’ (archaeological site) on the China National 13 Infrastructure Database. From each resulting record, we extracted site information, the number of finds of Fago pyrum, taxonomic identifications, and chronological information or dating results. We would emphasise that this is a meta-data survey; if a record has been published in a suitable me (...truncated)