Maintenance of Phenotypic and Genotypic Diversity in Managed Populations of Stenocereus Stellatus (Cactaceae) by Indigenous Peoples in Central Mexico

Abstract

The columnar cactus Stenocereus stellatus is used in Central Mexico for its edible fruits which are harvested in wild, managed in situ and cultivated populations. Management in situ of wild populations is conducted by selectively sparing and enhancing the abundance of plants with desirable phenotypes when fields are cleared for agricultural use. Cultivation of desirable phenotypes is carried out by vegetative propagation in homegardens. Effects of human management on morphological and genetic variation of S. stellatus were analyzed by comparing morphological diversity indices (MD, based on Simpson's index) and expected (H e ) heterozygosity indices from allozyme analysis, in wild, managed in situ, and cultivated populations from La Mixteca and the Tehuaca´n Valley regions. Morphological diversity was similar among regions, but populations from the wetter La Mixteca region averaged higher genetic variation (H e = 0.279) than populations from Tehuaca´n (H e = 0.265). On average, populations manipulated by people had higher levels of variation (MD = 0.479 ± 0.012, H e = 0.289 in cultivated populations; MD = 0.461 ± 0.014, H e = 0.270 in managed in situ populations) than wild populations (MD = 0.408 ± 0.017, H e = 0.253), which is apparently due to a continual introduction and replacement of plant materials in the manipulated populations. The results illustrate that human management may not only maintain but also increase both morphological and genetic diversity of manipulated plant populations in relation to that existing in the wild. Managed in situ and cultivated populations of S. stellatus are important reservoirs of variation, and are crucial for the general maintenance of diversity in wild populations. These populations may play a principal role in designing strategies for the conservation of variation of this cactus.

Traditional agroforestry systems of multi-crop “milpa” and “chichipera” cactus forest in the arid Tehuacán Valley, Mexico: their management and role in people’s subsistence

“…Species such as mesquite, columnar cacti, and agaves are more abundant in AFS than in wild systems. It has been documented that individual plants of some species of columnar cacti maintained in AFS produce more fruits and have higher quality since some level of artificial selection has operated on them (Casas et al 2006(Casas et al , 2007Parra et al 2010). As in other arid and semiarid zones of the World, livestock is one of the principal components of people subsistence in the study area.…”

“…In these systems people cultivate maize, beans, squashes, and other crops through the Mesoamerican agricultural system called ''milpa'' (Wilken 1977;Casas et al 2008;Moreno-Calles et al 2010). Our previous studies documented that AFS of columnar cacti forests of the region have the capacity of (1) maintaining on average 59% of species richness of native forests, (2) increasing abundance of some endemic useful species, (3) maintaining high percentages of genetic diversity of dominant species in natural forests, and (4) good capacity of population regeneration of some dominant arboreal species (Casas et al 2006;Farfán-Heredia 2006;Moreno-Calles et al 2010).…”

Genetic diversity of bitter and sweet African bush mango trees (Irvingia spp., Irvingiaceae) in West and Central Africa

“…Consequently, the reduction of their ecological variability has narrowed their morphological and genetic diversity. Nevertheless, the domestication and cultivation of sweet trees in various climatic zones in the Dahomey Gap, has helped to preserve or increase the existing diversity (Casas et al, 2005;Jose, 2012). Although, the provenance of sweet ABMTs in the Dahomey Gap is unknown (Harris, 1996;Asaah et al, 2003;Lesley and Brown, 2004;Ude et al, 2006, Vihotogbe et al, 2014a, their higher diversity in this eco-region may well be due to the fact that the ongoing traditional domestication process in this region includes material from geographically different origins: the Upper and Lower Guinean forest blocks as well as the Congolian forest region.…”

Los sistemas agroforestales tradicionales de México: Una aproximación biocultural

“…y pitaya de mayo (S. pruinosus), cuyas poblaciones manejadas en los SAF mantienen altos porcentajes (en promedio 94%) de la diversidad genética que existen en poblaciones silvestres de estas especies (Blancas et al, 2006(Blancas et al, , 2009Carmona y Casas, 2005;Casas et al, 2006;Otero-Arnaiz et al, 2003;Parra et al, 2008). La utilidad de las especies, su valor y las reglas de uso acordadas por las comunidades favorecen el mantenimiento de los SAF y de su diversidad biocultural.…”