José Blancas

Plant Management in the Tehuacán-Cuicatlán Valley, Mexico1

Plant Management in the Tehuacán-Cuicatlán Valley, Mexico. Plant management types currently practiced in the Tehuacán-Cuicatlán Valley, México, were documented and analyzed based on ethnobotanical studies conducted in 13 villages with six indigenous groups and Mestizo people. The information was organized in a data base, and then detailed and guided to a consensus through six workshops carried out by ethnobotanists working in the area. From a total of 1,608 useful plant species, we identified 610 with at least one management type other than simple gathering. Managed species are mainly used as food, fodder, medicinal, and ornamental, and they belong to 101 plant families. The higher species numbers were recorded in Cactaceae, Asteraceae, Fabaceae, Crassulaceae, and Agavaceae. Nearly 60% of the managed species are native to the region and the rest are introduced from other regions of Mexico and the world. In total, 400 species are ex situ managed out of their natural environments through seed sowing and/or planting their vegetative propagules or entire young plants; 373 species are in situ managed in their natural habitats as follows: all these species are deliberately left standing during vegetation clearance, 76 species are also enhanced intentionally favoring their abundance through modifications of their habitat, or directly by planting their propagules, and 51 receive protection through regulations, particular strategies of extraction, and actions against herbivores, competitors, freezing, radiation, and drought. Most management forms involve artificial selection at different intensity levels. The information allows visualizing co-occurrence of incipient and advanced forms of management at different intensity levels within and among species, which helps to postulate testable hypotheses on factors influencing plant management and domestication in an important area for studying the origins of agriculture.Manejo de plantas en el Valle de Tehuacán-Cuicatlán, México. Se documentaron los diferentes tipos de manejo de plantas que practican actualmente los pobladores del Valle de Tehuacán-Cuicatlán, México. El análisis se basa en estudios etnobotánicos llevados a cabo en 13 comunidades campesinas con seis grupos indígenas y poblados mestizos. La información se organizó en una base de datos, la cual posteriormente se detalló y se consensó a través de seis talleres en los que participaron los etnobotánicos trabajando en la región y cuyos trabajos son la base de esta investigación. De un total de 1,608 especies de plantas útiles, identificamos 610 con al menos un tipo de manejo distinto a la recolección simple. Las especies manejadas pertenecen a 101 familias botánicas y se utilizan principalmente como alimento, forraje, medicina y ornamentales. Los mayores números de especies manejadas se registraron entre las Cactaceae, Asteraceae, Fabaceae, Crassulaceae y Agavaceae. Aproximadamente 60% de las especies manejadas son nativas de la región y el resto son introducidas de otras regiones de México y del mundo. En total, 400 especies se manejan ex situ, fuera de sus ambientes naturales, mediante la siembra de sus semillas y la plantación de sus propágulos vegetativos o plantas juveniles; 373 especies se manejan in situ en sus hábitats naturales como sigue: todas estas especies se dejan en pie deliberadamente durante el aclareo de la vegetación; 76 especies son además promovidas intencionalmente, favoreciendo sus abundancias mediante modificaciones a sus hábitats o directamente plantando sus propágulos; y 51 especies reciben protección a través de reglas comunitarias, estrategias particulares de extracción y acciones contra herbívoros, competidores, heladas, radiación solar y sequías. La mayor parte de las formas de manejo involucran selección artificial a diferentes niveles de intensidad. La información permite visualizar la ocurrencia de formas de manejo incipientes y avanzadas a diferentes niveles de intensidad, simultáneamente dentro de una misma especie y entre especies. Esto permite postular hipótesis probables sobre los factores que influyen el manejo de plantas y su domesticación en una región importante para el estudio sobre el origen de la agricultura.

Ecological and socio-cultural factors influencing plant management in Náhuatl communities of the Tehuacán Valley, Mexico

BackgroundManagement types and their intensity may vary according to indicators such as: (1) practices complexity, (2) degree of techniques specialization, (3) occurrence and types of social regulations, (4) artificial selection intensity, (5) energy invested, (6) tools types, and (7) amounts of resources obtained. Management types of edible plants were characterized and analyzed in Náhuatl communities of the Tehuacán Valley. We expected that both natural and human pressures generate risk on plant resources availability, influencing human responses of management directed to decrease risk. We particularly hypothesized that magnitude of risk would be a direct function of human pressures favored by cultural and economic value and ecological factors such as scarcity (restricted distribution and abundance). Management practices may decrease risk of plant resources, more effectively when they are more intense; however, absence or insufficiency of management practices on endangered plants may favor loss of their populations. Understanding current management motives and their consequences on the purpose of ensuring availability of plant resources might allow us to understand similar processes occurring in the past. This issue is particularly important to be studied in the Tehuacán Valley, where archaeologists documented possible scenarios motivating origins of plant management by agriculture during prehistory.MethodsThrough ethnobotanical collecting, 55 semi-structured and free listing interviews we inventoried edible plant species used in five villages of Coyomeapan, Mexico. We identified: (1) native plant species whose products are obtained exclusively through simple gathering, (2) native species involving simple gathering and other management types, and (3) non-native species managed by agricultural management. We conducted in depth studies on the 33 native species managed through gathering and other types of practices. We carried out a total of 660 sessions of detailed interviews to 20 households randomly selected. We showed to people voucher specimens and photos of the sample of species chosen and documented their cultural and economic values. Spatial availability of these plant species was evaluated through vegetation sampling. Values for each cultural, economic, and ecological indicator were codified and averaged or summed and weighed according to frequency of interviewees’ responses or ecological conditions per plant species. With the standardized values of these indicators we performed a PCA and scores of the first principal component were considered as a risk index, which summarizes information of thirteen indicators of human use, demand and scarcity of each plant species. Similarly, eleven indicators of energy invested, complexity, tools and management strategies were used for performing PCA and scores of the first principal component were considered as management intensity index for each plant species. A linear regression analysis was performed to analyze the relation between risk and management intensity indexes. Amounts of variation of management data explained by ecological, cultural and economic information, as well as their risk level were analyzed through canonical correspondence analyses (CCA).ResultsA total of 122 edible plant species were recorded, nearly 30% of them were introduced domesticated plants, 51 were wild species obtained exclusively by simple gathering and 33 were native species obtained by simple gathering and other management practices, these latter were the ones more deeply studied. People recognized variants in 21 of these latter 33 species, the variants receiving differential use, management, artificial selection and incipient domestication. The lowest values of management intensity corresponded to species under simple gathering and tolerance, mostly annual abundant plants, occasionally consumed by few people. The highest management intensity values were recorded in species with economic importance, mostly perennial with recognized variants whose management requires using tools, and which are protected by collective regulations. The regression analysis indicated significant value R2 = 0.433 (P < 0.001) between risk and management indexes. CCA explained 65.5% of variation of management intensity, mainly by socio-cultural factors (32.6%), whereas ecological data explained 21.3% and the intersection of all factors 11.6%. Variation of management intensity is 67.6% explained by risk variables. Length-span of life cycle, reproductive system type, distribution, number of parts used, number of management and use forms and type of regulations were statistically significant.ConclusionPeople manage plant resources according to the role these play in households’ subsistence, the quantity available and the quality of their useful products; particularly important is the balance between resources availability and demand. Management responses to risk are also influenced by the ease to propagate or manipulate individual plants and time requiring the construction of manipulation strategies and techniques.

Landscape management and domestication of Stenocereus pruinosus (Cactaceae) in the Tehuacán Valley: human guided selection and gene flow

BackgroundUse of plant resources and ecosystems practiced by indigenous peoples of Mesoamerica commonly involves domestication of plant populations and landscapes. Our study analyzed interactions of coexisting wild and managed populations of the pitaya Stenocereus pruinosus, a columnar cactus used for its edible fruit occurring in natural forests, silviculturally managed in milpa agroforestry systems, and agriculturally managed in homegardens of the Tehuacán Valley, Mexico. We aimed at analyzing criteria of artificial selection and their consequences on phenotypic diversity and differentiation, as well as documenting management of propagules at landscape level and their possible contribution to gene flow among populations.MethodsSemi-structured interviews were conducted to 83 households of the region to document perception of variation, criteria of artificial selection, and patterns of moving propagules among wild and managed populations. Morphological variation of trees from nine wild, silviculturally and agriculturally managed populations was analyzed for 37 characters through univariate and multivariate statistical methods. In addition, indexes of morphological diversity (MD) per population and phenotypic differentiation (PD) among populations were calculated using character states and frequencies.ResultsPeople recognized 15 pitaya varieties based on their pulp color, fruit size, form, flavor, and thorniness. On average, in wild populations we recorded one variety per population, in silviculturally managed populations 1.58 ± 0.77 varieties per parcel, and in agriculturally managed populations 2.19 ± 1.12 varieties per homegarden. Farmers select in favor of sweet flavor (71% of households interviewed) and pulp color (46%) mainly red, orange and yellow. Artificial selection is practiced in homegardens and 65% of people interviewed also do it in agroforestry systems. People obtain fruit and branches from different population types and move propagules from one another. Multivariate analyses showed morphological differentiation of wild and agriculturally managed populations, mainly due to differences in reproductive characters; however, the phenotypic differentiation indexes were relatively low among all populations studied. Morphological diversity of S. pruinosus (average MD = 0.600) is higher than in other columnar cacti species previously analyzed.ConclusionsArtificial selection in favor of high quality fruit promotes morphological variation and divergence because of the continual replacement of plant material propagated and introduction of propagules from other villages and regions. This process is counteracted by high gene flow influenced by natural factors (pollinators and seed dispersers) but also by human management (movement of propagules among populations), all of which determines relatively low phenotypic differentiation among populations. Conservation of genetic resources of S. pruinosus should be based on the traditional forms of germplasm management by local people.

Agroforestry systems and biodiversity conservation in arid zones: the case of the Tehuacan Valley, Central Mexico

The role of agroforestry systems in biodiversity conservation was investigated in the semiarid Tehuacán Valley, Central México. Richness and diversity of native plant species were compared between agroforestry systems (6 sampling sites) and the following forests (6 sampling sites) dominated by columnar cacti: (i) “chichipera” dominated by Polaskia chichipe; (ii) “jiotillal” dominated by Escontria chiotilla; and (iii) “garambullal” dominated by Myrtillocactus schenckii. Our information on genetic variation of dominant arboreal species in the study sites was reviewed and included in the analysis. Factors influencing household’s decisions to maintain vegetation cover were compiled through a survey and interviews and analyzed. All the samples of the agroforestry systems studied maintained on average nearly 59% plant species and 94% genetic variation of dominant cacti occurring in the forests, although their ability to preserve endemic rare species is limited. Social factors favoring maintenance of perennial species in agricultural plots include collective rules, households traditions, use of the plants maintained in the systems, and the environmental information gathered from NGOs, the local Biosphere Reserve, and researchers. However, agroforestry systems are losing their capability to maintain vegetation cover, mainly because of (i) decreasing amount of land managed by households, determined by a progressive fragmentation of the land area given to new families, (ii) adoption of technologies to intensify agriculture, and (iii) governmental programs penalizing the presence of vegetation patches within agricultural lands since they are considered “useless” areas. Necessary policies to stop degradation of the agroforestry systems and to improve their conservation capacity are discussed.

Plant management and biodiversity conservation in Náhuatl homegardens of the Tehuacán Valley, Mexico.

BackgroundThe Tehuacán Valley is one of the areas of Mesoamerica with the oldest history of plant management. Homegardens are among the most ancient management systems that currently provide economic benefits to people and are reservoirs of native biodiversity. Previous studies estimated that 30% of the plant richness of homegardens of the region are native plant species from wild populations. We studied in Náhuatl communities the proportion of native plant species maintained in homegardens, hypothesizing to find a proportion similar to that estimated at regional level, mainly plant resources maintained for edible, medicinal and ornamental purposes.MethodsWe analysed the composition of plant species of homegardens and their similarity with surrounding Cloud Forest (CF), Tropical Rainforest (TRF), Tropical Dry forest (TDF), and Thorn-Scrub Forest (TSF). We determined density, frequency and biomass of plant species composing homegardens and forests through vegetation sampling of a total of 30 homegardens and nine plots of forests, and documented ethnobotanical information on use, management, and economic benefits from plants maintained in homegardens.ResultsA total of 281 plant species was recorded with 12 use categories, 115 ornamental, 92 edible, and 50 medicinal plant species. We recorded 49.8 ± 23.2 (average ± S.D.) woody plant species (shrubs and trees) per homegarden. In total, 34% species are native to the Tehuacán Valley and nearly 16% are components of the surrounding forests. A total of 176 species were cultivated through seeds, vegetative propagules or transplanted entire individual plants, 71 tolerated, and 23 enhanced. The highest species richness and diversity were recorded in homegardens from the CF zone (199 species), followed by those from the TRF (157) and those from the TDF (141) zones.ConclusionHomegardens provide a high diversity of resources for subsistence of local households and significantly contribute to conservation of native biodiversity. The highest diversity was recorded in homegardens where the neighbouring forests had the least diversity, suggesting that management of homegardens aims at compensating scarcity of naturally available plant resources. Cultivated species were markedly more abundant than plants under other management forms. Diversity harboured and management techniques make homegardens keystones in strategies for regional biodiversity conservation.

Vulnerability and risk management of Agave species in the Tehuacán Valley, México

BackgroundOur study analysed the vulnerability of the useful Agave species of the Tehuacán Valley, Mexico, considering ecological, cultural and economic aspects, and management types. We hypothesized that management intensity is proportional to the degree of risk of a species in order to decrease its vulnerability.MethodsDistribution of Agave species was monitored in 36 types of plant associations. Ethnobotanical studies were conducted in 13 villages and six markets. The vulnerability of each species was calculated by assigning risk values to the variables analysed. The vulnerability and management intensity indexes were estimated through the scores of the first principal component of PCA. Variation of management data explained by ecological, cultural and economic information were analysed through canonical correspondence analyses (CCA). A linear regression analysis identified the relation between vulnerability and management intensity.ResultsWe recorded presence of agave species in 20 of 36 vegetation types. Out of 34 Agave species, 28 were recorded to have one to 16 use types; 16 species are used as food, 13 for live fences, 13 for producing ‘pulque’, 11 for fibre and ornamental, 9 for construction. Seven species are used for preparing mescal, activity representing the highest risk. Seven Agave species are exclusively extracted from the wild and the others receive some management type. Incipient cultivation was identified in A. potatorum whose seedlings are grown in nurseries. Intensive cultivation through vegetative propagation occurs with domesticated species of wide distribution in Mexico. The highest management intensity values were recorded in widely distributed, cultivated and domesticated species, but the regionally native species more intensively managed were those with higher demand and economic value, protected by collective regulations because of their scarcity. The regression analysis indicated significant relation (R2=0.677, P<0.001) between vulnerability and management indexes. CCA explained 61.0% of variation of management intensity, mainly by socio-cultural factors (30.32%), whereas ecological data explained 7.6% and the intersection of all factors 21.36%.ConclusionsThe highest vulnerability was identified in wild species restrictedly distributed and/or highly extracted. Social pressures may increase the natural vulnerability of some species and these species are particularly those native species receiving some management form.

Influence of traditional markets on plant management in the Tehuacan Valley.

BackgroundThe Tehuacán Valley, Mexico is a region with exceptionally high biocultural richness. Traditional knowledge in this region comprises information on nearly 1,600 plant species used by local peoples to satisfy their subsistence needs. Plant resources with higher cultural value are interchanged in traditional markets. We inventoried the edible plant species interchanged in regional markets documenting economic, cultural and ecological data and about their extraction and management in order to: (1) assess how commercialization and ecological aspects influence plant management, (2) identify which species are more vulnerable, and (3) analyze how local management contributes to decrease their risk. We hypothesized that scarcer plant species with higher economic value would be under higher pressure motivating more management actions than on more abundant plants with lower economic value. However, construction of management techniques is also influenced by the time-span the management responses have taken as well as biological and ecological aspects of the plant species that limit the implementation of management practices. Plant management mitigates risk, but its absence on plant species under high risk may favor local extinction.MethodsSix traditional markets were studied through 332 semi-structured interviews to local vendors about barter, commercialization, and management types of local edible plant species. We retrieved ethnobotanical information on plant management from ten communities in a workshop and sampled regional vegetation in a total of 98 sites to estimate distribution and abundance of plant species commercialized. Through Canonical Correspondence Analysis (CCA) we analyzed the amount of variation of management types that can be explained from socioeconomic and ecological information. A risk index was calculated relating distribution, abundance, economic value and management of plant resources to identify the most vulnerable species.ResultsWe recorded 122 edible plant species interchanged in the main regional markets. CCA explained significantly 24% of management variation, spatial distribution and plant parts used being particularly important in management decisions. The indeterminate 76% of variation suggests that management decisions depend on particular variables that are not explained by the ecological and socioeconomic factors studied and/or their high variation in the context at the regional scale. The risk index indicated that management was the factor that mostly influences decreasing of risk of interchanged plant species. We identified Clinopodium mexicanum, Pachycereus weberi, Dasylirion serratifolium, Disocorea sp., Ceiba aesculifolia, Neobuxbamia tetetzo, Lippia graveolens, Litsea glaucescens, L. neesiana, Jatropha neopauciflora, Agave potatorum and other agave species used for producing mescal among the more endangered plant species due to human pressure, their relative scarcity and limited or inexistent management.ConclusionSpatial distribution and plant parts used are particularly meaningful factors determining risk and influencing management actions on edible plant species interchanged in the region. Limited or inexistent management may favor extinction of local populations under risk. Local management techniques synthesize knowledge and experiences crucial for designing sustainable management programs. Traditional management techniques supported by ecological information and environmental management approaches could make valuable contributions for sustainable use of plant species, particularly those becoming economically important more recently.

Ethnobotany of Mexico

Ethnobotany is a research aimed at understanding what people know about plants, how plants form part of their systems of beliefs and conceptions of the world, and how humans make use and manage plants for reproducing their social and cultural life. This chapter shows a general panorama of the historical use of ethnobotany in Mexico from pre-Columbian times to the modern arising of ethnobotany as a research fi eld, as well as the main contemporary methodological approaches and challenges of researchers working on Mexican ethnobotany. Such panorama conforms an introductory context for discussing the importance and limits of this book and a general description of the contributions of the each chapter that forms part of the text. We then discuss a general perspective of the Mexican ethnobotany in order to make stronger an “after description step” of this research fi eld, recognizing the importance of descriptive methods but the need of emphasizing the analytical contribution of ethnobotany on research questions connected with research fi elds like anthropology, archaeology, ecology, and evolutionary biology. All these are research areas requiring support from both quantitative and qualitative ethnobotanical approaches in order to analyse social and anthropological problems such as the role of natural resources in human cultures, peoples’ cosmovision, and their social organization and technology for interacting with ecosystems. Also, ethnobotany is necessary to ecology for studying important problems like the human A. Casas , Ph.D. (*) Instituto de Investigaciones en Ecosistemas y Sustentabilidad (IIES), Universidad Nacional Autónoma de México, Campus Morelia, Michoacán , Antigua Carretera a Pátzcuaro 8711, Col. San José de la Huerta , Morelia , Michoacán C.P. 58190 , Mexico e-mail: acasas@cieco.unam.mx J. Blancas , Ph.D. Centro de Investigación en Biodiversidad y Conservación (CIByC), Universidad Autónoma del Estado de Morelos , Av. Universidad No. 1001, Col. Chamilpa , Cuernavaca , Morelos C.P. 62209 , Mexico R. Lira , Ph.D. Unidad de Biotecnología y Prototipos, FES Iztacala, Universidad Nacional Autónoma de, México , Av. de los Barrios No. 1, Los Reyes Iztacala , Tlalnepantla , Estado de México 54090 , Mexico e-mail: rlira@unam.mx