Use, management and domestication of Agave americana in Mexico.

backgroundDomestication is an evolutionary process guided by humans. It operates continuously in multiple directions, with species undergoing adaption to diverse human-influenced environments and cultural and technological contexts. Mesoamerica is among the world's main regions of domestication and the Agave genus is widely used and managed in this region, 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 by analysing morphological variation and its relation to environmental and management settings.

methodsEthnobotanical studies were conducted to document uses, management practices, and targets of human selection, together with patterns of morphological variation across different ecological and cultural contexts. Semi-structured interviews were carried out with agave managers throughout the species' distribution range in Mexico. Morphometric analyses were performed on populations occurring under contrasting environmental and management conditions. Multivariate and univariate statistical analyses were used to evaluate morphological variation in relation to geographic distribution, environmental conditions, and management regimes.

resultsA. 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 managed, but the subspecies protamericana clearly has wild populations. Morphometric studies confirm the presence of traits indicative of domestication in most varieties of the subspecies americana.

conclusionsPhenotypic variation within the Agave americana complex is associated with taxonomic identity, geographic distribution, and management intensity. The observed patterns are consistent with the effects of human selection, particularly in traits related to plant size and the reduction of defensive structures. However, further studies integrating common-garden experiments, population genetics, and phylogeographic analyses are required to clarify the evolutionary history and genetic basis of the observed variation.