Centro de Investigaciones en Ecosistemas (CIECO), Universidad Nacional Autónoma de México (campus Morelia), Antigua Carretera a Pátzcuaro 8711 Col, Ex Hacienda de San José de la Huerta, Morelia, Michoacán, 58190, Mexico.
J Ethnobiol Ethnomed. 2012 Aug 14;8:32. doi: 10.1186/1746-4269-8-32.
Use 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.
Semi-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.
People 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.
Artificial 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.
中美洲的土著人民使用植物资源和生态系统，通常涉及对植物种群和景观的驯化。我们的研究分析了共生的野生和管理种群之间的相互作用，这些种群是柱状仙人掌仙人球 stenocereus pruinosus，其可食用的果实存在于天然森林中，在 milpa 农林复合系统中进行林分管理，在墨西哥特瓦坎山谷的家庭菜园中进行农业管理。我们的目的是分析人工选择的标准及其对表型多样性和分化的影响，并记录景观水平上繁殖体的管理及其对种群间基因流动的可能贡献。
对该地区的 83 户家庭进行半结构访谈，以记录对变异的认识、人工选择的标准以及在野生和管理种群之间移动繁殖体的模式。通过单变量和多变量统计方法分析了来自九个野生、林分和农业管理种群的 37 个特征的树木形态变异。此外，使用特征状态和频率计算了每个种群的形态多样性（MD）指数和种群间的表型分化（PD）。
人们根据果肉颜色、果实大小、形状、味道和刺的数量识别出 15 种火龙果品种。平均而言，在野生种群中，每个种群有一种品种，在林分管理种群中，每个地块有 1.58 ± 0.77 个品种，在农业管理种群中，每个家庭菜园有 2.19 ± 1.12 个品种。农民选择有利于甜味（71%的被访家庭）和果肉颜色（46%）主要是红色、橙色和黄色。人工选择在家庭菜园和 65%的被访农民中进行，也在农林复合系统中进行。人们从不同的种群类型中获取果实和枝条，并相互传播繁殖体。多变量分析表明，野生和农业管理种群存在形态分化，主要是由于繁殖特征的差异；然而，所有研究种群的表型分化指数相对较低。仙人球 pruinosus 的形态多样性（平均 MD=0.600）高于之前分析的其他柱状仙人掌物种。
为了获得高质量的果实，人工选择促进了形态的变化和分化，因为不断更换繁殖材料，并从其他村庄和地区引入繁殖体。然而，自然因素（传粉者和种子传播者）以及人类管理（种群间繁殖体的移动）所产生的高基因流，会抵消这种变化，这决定了种群间的表型分化相对较低。仙人球 pruinosus 的遗传资源保护应基于当地人传统的种质管理形式。
