How gathering wild rice under human-mediated drought stress could have inadvertently paved the way to Asian rice incipient domestication and cultivation

In eastern China, on the southern end of the Yangtze Valley, early Holocene hunter-gatherers were foraging various plants, including wild rice – Oryza rufipogon Griff. – an aquatic and perennial plant which is the wild progenitor of domesticated rice. According to optimal foraging theory, these foragers should have tried to enhance the efficiency of harvesting wild rice seeds by draining water around the plants before seeds ripened and shattered. This proto-cultivation practice led to unintended consequences given that wild rice responds to drought stress owing to its phenotypic plasticity. Plant and panicle architectures were modified with transitions to more compact and erect tillers and to a closed panicle shape. They provide incentives to early foragers for intensifying their proto-cultivation practices and so could have also triggered initial cultivation of rice. They also triggered incipient domestication of rice, starting by the transition to selfing. According to this narrative, it is even possible that rice incipient domestication preceded cultivation.

Disentangling Domestication from Food Production Systems in the Neotropics

The Neolithic Revolution narrative associates early-mid Holocene domestications with the development of agriculture that fueled the rise of late Holocene civilizations. This narrative continues to be influential, even though it has been deconstructed by archaeologists and geneticists in its homeland. To further disentangle domestication from reliance on food production systems, such as agriculture, we revisit definitions of domestication and food production systems, review the late Pleistocene–early Holocene archaeobotanical record, and quantify the use, management and domestication of Neotropical plants to provide insights about the past. Neotropical plant domestication relies on common human behaviors (selection, accumulation and caring) within agroecological systems that focus on individual plants, rather than populations—as is typical of agriculture. The early archaeobotanical record includes numerous perennial and annual species, many of which later became domesticated. Some of this evidence identifies dispersal with probable cultivation, suggesting incipient domestication by 10,000 years ago. Since the Pleistocene, more than 6500, 1206 and 6261 native plant species have been used in Mesoamerica, the Central Andes and lowland South America, respectively. At least 1555, 428 and 742 are managed outside and inside food production systems, and at least 1148, 428 and 600 are cultivated, respectively, suggesting at least incipient domestication. Full native domesticates are more numerous in Mesoamerica (251) than the Andes (124) and the lowlands (45). This synthesis reveals that domestication is more common in the Neotropics than previously recognized and started much earlier than reliance on food production systems. Hundreds of ethnic groups had, and some still have, alternative strategies that do involve domestication, although they do not rely principally on food production systems, such as agriculture.

Consequences of Traditional Management in the Production and Quality of Copal Resin (Bursera bipinnata (Moc. & Sessé ex DC.) Engl.) in Mexico

Copal is a resin of ritual uses in Mexico that is extracted from several species of trees of the genus Bursera. The effect of traditional management on phenotypical traits of copal trees has not been sufficiently studied. This research analyzed the traditional management and human selection on populations of Bursera bipinnata, and it also examined their influence on the quantity and quality of the resin produced by wild and managed trees. The management of copal was documented through semi-structured interviews and workshops. Samples of 60 trees from six wild and managed populations were selected to quantify the production of resin during two consecutive years. Fresh resin was collected to identify organic volatile compounds through gas chromatography and Principal Components Analysis (PCA); individuals were classified according to the amount and type of organic compounds produced. We identified management strategies from simple harvesting to seeds planting. The criteria of local people for selecting managed trees and seeds are based on the quantity and quality of the resin produced per tree, which were significantly higher in managed than in wild trees: 190.17 ± 329.04 g vs. 29.55 ± 25.50 g (p = 0.003), and 175.88 ± 179.29 g vs. 63.05 ± 53.25 g (p = 0.008) for the production seasons of 2017 and 2018, respectively. Twenty organic volatile compounds were identified, and the PCA showed that managed trees produce higher percentages of compounds associated with scent. The traditional management of Bursera bipinnata involves selective pressures, which generate the differentiation of wild and managed trees that may represent incipient domestication through silvicultural management.

Consequences of traditional management in the production and quality of copal resin (Bursera bipinnata (Moc. & Sessé ex DC.) Engl.) in Mexico

Background Copal is a resin of ritual uses in Mexico, extracted from several species of trees of the genus Bursera. The effect of traditional management on phenotypical traits of copal trees has not been sufficiently studied. This research analyzed the traditional management and human selection on populations of Bursera bipinnata, and their influence on the quantity and quality of the resin produced by wild and managed trees.Method Management of copal were documented through semi-structured interviews and workshops. Samples of 60 trees from six wild and managed populations were selected to quantify the production of resin during two consecutive years. Fresh resin was collected to identify organic volatile compounds through gas chromatography and Principal Components Analysis (PCA); individuals were classified according to the amount and type of organic compounds produced.Results We identified management strategies from simple harvesting to seeds planting. The criteria for selecting managed trees and seeds are based on the quantity and quality of the resin produced and on higher quantity of resin yield per tree, which were much higher in managed than in wild trees: 190.17 ± 329.04 g vs 29.55 ± 25.50 g, and 175.88 ± 179.29 g vs 63.05 ± 53.25 g for the production seasons of 2017 and 2018, respectively. Twenty organic volatile compounds were identified and the PCA showed that managed trees produce higher percentages of compounds associated with scent.Conclusion Traditional management of Bursera bipinnata involves selective pressures, which generate differentiation of wild and managed trees that may represent incipient domestication through of silvicultural management.

Genética evolutiva del proceso de domesticación en plantas

Studies about the incipient domestication in plants often have based their analysis on morphological characteristics and have attributed those changes to the actions of artificial human selection. This paper remarks the importance of the analysis of incipient domestication in plants using the theoretical and methodological framework of both quantitative and population genetics. The premise of this work is that, considering domestication as an evolutionary process, much knowledge can be gained regarding the phenotypic change, its constraints, and the evolutionary mechanisms that have molded the genetic constitution of plant populations under domestication.

Manejo de la vegetación, domesticación de plantas y origen de la agricultura en Mesoamérica

A model of domestication of plants in Mesoamerica based on selective management of plant populations and communities by silvicultural practices is analyzed. Archaeological and ethnobotanical information suggests that intentional manipulation of vegetation by Mesoamerican peoples has occurred in past and present times in order to control availability of useful plants. Forms of management of plant communities or populations have included tolerance, protection and enhancement of individual plants of particular species during clearance of vegetation and other ways of perturbation. Processes of artificial selection (selection in situ) may be carried out through these forms of plant management. These processes may cause significant morphological differences between wild and managed populations as illustrated by the cases discussed here of Anoda cristata, Crotalaria pumila, Leucaena esculenta and Stenocereus stellatus. Processes of artificial selection in situ are mechanisms of incipient domestication of plants which appear to have been carried out in Mesoamerica, perhaps since pre-agricultural times, and that could contribute to explain the processes that led to the origins of agriculture in this region.