Use, management and domestication of Agave americana in Mexico

Background Domestication is an evolutionary process guided by humans. It operates continuously and dynamically in multiple directions, with species undergoing adaption to diverse human-influenced environments and cultural and technological contexts. Mexico and the neighbouring Mesoamerican area are among the world’s main regions of domestication. The Agave genus is widely used and managed, with at least eleven domesticated and semi-domesticated species. One species, Agave americana , comprises two subspecies and four varieties, the diversification of which is hypothetically related to human management. This study explores this hypothesis. Methods Ethnobotanical studies were conducted on the use, management, and targets of human selection, as well as the patterns of morphological variation, in different ecological and cultural contexts. Semi-structured interviews were conducted with people managing these Agave s across their distribution range, from northern to southern Mexico. Morphometric studies were also conducted on populations distributed in contrasting social and ecological contexts to explore phenotypic variation and trends in relation to selection targets. Multivariate and univariate statistical analyses were performed to analyse patterns of variation in relation to environmental conditions, geographical distribution and forms of use and management. Results A. americana is used to extract sap for preparing the fermented beverage called pulque. Its stems have been used as food since prehistoric times, when they were cooked in underground ovens. This cooked matter forms the basis of current fermentation and the production of distilled mescal. The fibre of some varieties has been used to make cords and textiles. Both subspecies are used and managed, but the subspecies protamericana clearly has wild populations. Morphometric studies confirm the presence of traits indicative of domestication syndrome in most varieties of the subspecies americana . Conclusions Phenotypic variation is clearly related to the taxonomic status and geographic distribution area of the analysed plants, but the influence of human selection favouring gigantism and reduced spines on the leaves is also evident. Further studies of population genetics and phylogeographic patterns would improve our understanding of these patterns.