Climate and categories: Two key elements for understanding the Mesoamerican hot-cold classification of illnesses and medicinal plants.

ETHNOPHARMACOLOGICAL RELEVANCE: The concepts of health and illness, and their causes, are fundamental for understanding medicinal plant choice and use by traditional people. The hot-cold system is widespread in Mesoamerican traditional medicine and guides many therapeutic decisions. AIM OF THE STUDY: This study explores a hypothesis that climate influences the hot-cold classification of illnesses and medicinal plants, and the perception of hazard of illnesses. In addition, we examine the classification categories within the system used in different regions of Mexico. MATERIALS AND METHODS: Studies from Mexico with quantitative and qualitative data on the hot-cold properties of medicinal plants and ailments were reviewed. The information was organized and then related to the climate type of the study areas. RESULTS: In temperate climates, most diseases were considered cold, and hot medicinal plants were dominant. Conversely, in warm-tropical climates, hot diseases dominated, and the majority of medicinal plants were cold; however, this evidence was weaker. The perception of hazard was congruent with the number of illnesses for temperate climates. There were additional classification categories within the hot-cold system for diseases and medicinal plants, and they were expressed in different terms in Spanish, English, and indigenous languages. Although similar terms and categories were used in the classification of diseases and medicinal plants, they can differ conceptually and vary between places and cultures. Publications are sometimes unclear if the terms used are emic or etic. The basic principle of using plants with the opposite property of the disease does not always apply strictly. CONCLUSIONS: Climate appears to influence the hot-cold classification of diseases and medicinal plants in Mexico, and the system is not strictly dual. Improved knowledge of the hot-cold system is necessary to understand Mesoamerican medicinal plant use and culture.

Pillar of strength: Columnar cactus as a key factor in Yoreme heritage and wildland preservation.

The persistence of traditional cultures and modes of land use within rapidly changing, globalized societies is a central issue in understanding ecological and cultural change in the Anthropocene. Located in the heart of the Green Revolution, the Yoreme (Mayo) people of the Mayo Valley in Mexico still obtain a significant proportion of their sustenance from wild ecosystems in the midst of this intensive technological and agricultural development. They live in and around the thornscrub dominated by pitaya (Stenocereus thurberi (Engelm.) Buxb.). In this study, we hypothesize that pitaya supports Yoreme heritage and sustenance amidst anthropogenic changes to the landscape, and we asked three specific questions: What is the land-use status of the S. thurberi habitat? What are its potential uses? Does S. thurberi provide economic value? To address these questions, we conducted interviews, vegetation surveys, and land-use analysis based on geographic information systems. We found that (a) land conversion of the pitaya-rich thornscrub is occurring at a precipitous rate, (b) local producers preserve and adapt their traditions, and (c) S. thurberi supports Yoreme heritage while providing economic benefit. The resulting land-use projections along with the cultural value of pitaya products shows the importance of conserving land and promoting sustainable projects instead of clearing land for other uses. If habitat shrinking continues at the current rate, it is likely that both Yoreme livelihoods and continued cultural practices will suffer.

Genetic structure of coexisting wild and managed agave populations: implications for the evolution of plants under domestication.

Domestication is a continuous evolutionary process guided by humans. This process leads to divergence in characteristics such as behaviour, morphology or genetics, between wild and managed populations. Agaves have been important resources for Mesoamerican peoples since prehistory. Some species are domesticated and others vary in degree of domestication. Agave inaequidens Koch is used in central Mexico to produce mescal, and a management gradient from gathered wild and silvicultural populations, as well as cultivated plantations, has been documented. Significant morphological differences were reported among wild and managed populations, and a high phenotypic variation in cultivated populations composed of plants from different populations. We evaluated levels of genetic diversity and structure associated with management, hypothesizing that high morphological variation would be accompanied by high genetic diversity in populations with high gene flow and low genetic structure among managed and unmanaged populations. Wild, silvicultural and cultivated populations were studied, collecting tissue of 19-30 plants per population. Through 10 nuclear microsatellite loci, we compared population genetic parameters. We analysed partition of variation associated with management categories to estimate gene flow among populations. Agave inaequidens exhibits high levels of genetic diversity (He = 0.707) and moderate genetic structure (FST = 0.112). No differences were found in levels of genetic diversity among wild (He = 0.704), silviculturally managed (He = 0.733) and cultivated (He = 0.698) populations. Bayesian analysis indicated that five genetic clusters best fit the data, with genetic groups corresponding to habitats where populations grow rather than to management. Migration rates ranged from zero between two populations to markedly high among others (M = 0.73-35.25). Natural mechanisms of gene flow and the dynamic management of agave propagules among populations favour gene flow and the maintenance of high levels of variation within all populations. The slight differentiation associated with management indicates that domestication is in an incipient stage.

Morphological variation, management and domestication of 'maguey alto' (Agave inaequidens) and 'maguey manso' (A. hookeri) in Michoacán, México.

BACKGROUND: Agave inaequidens and A. hookeri are anciently used species for producing the fermented beverage 'pulque', food and fiber in central Mexico. A. inaequidens is wild and cultivated and A. hookeri only cultivated, A. inaequidens being its putative wild relative. We analysed purposes and mechanisms of artificial selection and phenotypic divergences between wild and managed populations of A. inaequidens and between them and A. hookeri, hypothesizing phenotypic divergence between wild and domesticated populations of A. inaequidens in characters associated to domestication, and that A. hookeri would be phenotypically similar to cultivated A. inaequidens. METHODS: We studied five wild and five cultivated populations of A. inaequidens, and three cultivated populations of A. hookeri. We interviewed agave managers documenting mechanisms of artificial selection, and measured 25 morphological characters. Morphological similarity and differentiation among plants and populations were analysed through multivariate methods and ANOVAs. RESULTS: People recognized 2-8 variants of A. inaequidens; for cultivation they select young plants collected in wild areas recognized as producing the best quality mescal agaves. Also, they collect seeds of the largest and most vigorous plants, sowing seeds in plant beds and then transplanting the most vigorous plantlets into plantations. Multivariate methods classified separately the wild and cultivated populations of A. inaequidens and these from A. hookeri, mainly because of characters related with plant and teeth size. The cultivated plants of A. inaequidens are significantly bigger with larger teeth than wild plants. A. hookeri are also significatly bigger plants with larger leaves but lower teeth density and size than A. inaequidens. Some cultivated plants of A. inaequidens were classified as A. hookeri, and nearly 10% of A. hookeri as cultivated A. inaequidens. Wild and cultivated populations of A. inaequidens differed in 13 characters, whereas A. hookeri differed in 23 characters with wild populations and only in 6 characters with cultivated populations of A. inaequidens. CONCLUSIONS: Divergence between wild and cultivated populations of A. inaequidens reflect artificial selection. A. hookeri is similar to the cultivated A. inaequidens, which supports the hypothesis that A. hookeri could be the extreme of a domestication gradient of a species complex.

Diversity and structure of landraces of Agave grown for spirits under traditional agriculture: A comparison with wild populations of A. angustifolia (Agavaceae) and commercial plantations of A. tequilana.

Traditional farming communities frequently maintain high levels of agrobiodiversity, so understanding their agricultural practices is a priority for biodiversity conservation. The cultural origin of agave spirits (mezcals) from west-central Mexico is in the southern part of the state of Jalisco where traditional farmers cultivate more than 20 landraces of Agave angustifolia Haw. in agroecosystems that include in situ management of wild populations. These systems, rooted in a 9000-year-old tradition of using agaves as food in Mesoamerica, are endangered by the expansion of commercial monoculture plantations of the blue agave variety (A. tequilana Weber var. Azul), the only agave certified for sale as tequila, the best-known mezcal. Using intersimple sequence repeats and Bayesian estimators of diversity and structure, we found that A. angustifolia traditional landraces had a genetic diversity (H(BT) = 0.442) similar to its wild populations (H(BT) = 0.428) and a higher genetic structure ((B) = 0.405; (B) =0. 212). In contrast, the genetic diversity in the blue agave commercial system (H(B) = 0.118) was 73% lower. Changes to agave spirits certification laws to allow the conservation of current genetic, ecological and cultural diversity can play a key role in the preservation of the traditional agroecosystems.