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Centers of origin and diversification
Centers of cultivated plants
Mexico as a world center of domestication and origin of cultivated plants
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In contrast to the groups of wild plants and animals, the creation of groups or varieties of cultivated plants and domesticated animals is associated with the intervention, direction and influence of human groups in their phase of transition from hunting-gathering to agriculture. This transition was accelerated during a relatively recent period of around 10,000 years ago on different continents independently.

The great body of knowledge, built by human hunter-gatherer groups regarding their environment, and the ecology, distribution and seasonality of groups of plants or animals that are of interest and use, lead directly to the subsequent exploitation of those species that had contributed to their sustenance and maintenance.

The management, use, guidance, preference and protection of certain groups of plants and animals are collectively known as a process of domestication or selection under domestication.

In this process, the human groups select, favor and maintain populations of species with certain useful characteristics: better-tasting plants, with larger uniformly ripening fruits of suitable size for harvest and with lower content of toxic substances; animals accustomed to human presence, with increased docility and better production of meat, skin, fur, and milk, or that are more capable of work. While many species of interest undergo management, domesticated species are those that have become completely dependent on humans. Through the process of artificial selection, they have lost different attributes or characteristics that allowed them to survive as a wild species (seed dormancy, different means and strategies of dispersal, toxic substance content, etc.). This loss and the effect of management for better utilization of useful species has been called
the domestication syndrome.
 

Mesoamerican centers of origin and domestication: conceptual framework

Recently, five types of centers of origin, diversity and domestication were identified:

  1. Phylogenetic center of origin of the wild progenitor: the area where the wild progenitor species originated, that will eventually be domesticated. The origin of a wild taxon results from evolutionary processes common to all biota (e.g., mutation, natural selection, genetic drift, hybridization) and does not imply human intervention. Thus, the area where this processes occur is of phylogenetic importance on an evolutionary time scale; however, it may or may not harbor, at present, the wild relatives of the crop species.

  2. Center of origin of the wild progenitor: the current geographic and ecological distribution of the immediate wild progenitor species. This area is essential from a conservation point of view and therefore must be separated from area (1) although they may or may not correspond. Both are subjected to the same evolutionary processes; however, this area corresponds to the actual region that can be protected today.

  3. Center of diversity of the wild progenitor: a diversification area where outstanding levels of genetic and phenotypic (e.g., morphologic, physiologic, or ecologic) diversity are displayed by the wild progenitor species prior to domestication.

  4. Center of domestication: is the bio-cultural area where the wild progenitor populations and those under artificial selection differentiate genotypic and phenotypically, that is, where the actual domestication process takes place. A bio-cultural area is an area in which converge cultural diversity with biological diversity, where possible processes such as domestication of species begin. This region may contain those wild progenitor populations most closely related to extant domesticates, but in other cases the domestication process may occur away from the natural area of distribution of the wild progenitor populations, due to human transportation. The process is not necessarily punctual and may continue over a long time, begin several times and vary in intensity, depending on the degree of human intervention. As a consequence, domesticated plants can exhibit a wide range of differentiation from its wild progenitors as well as variable levels of dependency from human beings.

  5. Center of diversity of the domesticate: the area(s) where the domesticated plant acquires genotypic and phenotypic diversity post-domestication under cultivation. The causes for the higher levels of crop variation are related to environmental, social, and cultural conditions that operate jointly, enhancing the process of differentiation in several domesticated forms. The diversification centers of domesticated plants are the areas where different domesticated forms are developed through the artificial selection of plant populations’ variation. This selection is tightly related to the diversity of uses and management practices of human groups.


References

Alavez V. and A. Wegier 2016. Box 1: A Conceptual Framework for Conservation and Biosafety at Mesoamerican Crop Centers of Origin and Domestication in: Acevedo F, E. Huerta and C. Burgeff. Chapter 21 Biosafety and Environmental Releases of GM Crops in Mesoamerica: Context Does Matter. In: R. Lira et al. (eds.), Ethnobotany of Mexico, Interactions of People and Plants in Mesoamerica. Ethnobiology, Springer-Verlag New York. DOI 10.1007/978-1-4614-6669-7.

Wegier A., Alavez V., Jardón L. y S. Petrone. Prueba superada: un marco conceptual para la conservación y bioseguridad en los centros de origen y domesticación mexicanos. Revista Oikos N. 5 Enero 2012, pp. 23–28.

 
 
 
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