Evolutionary Ethnobotanical Studies of Incipient Domestication of Plants in Mesoamerica

Abstract

Human cultures that occupied the area currently known as Mesoamerica developed a broad repertory of technologies for managing the biotic resources and ecosystems of the surrounding areas they lived. These technologies emerged from early experiences and had long time, enough for leading to the first forms of agriculture of the New World. Mesoamerica is actually recognized as one of the regions where agriculture and domestication of plants originated, with nearly 10,000 years of antiquity. This chapter summarizes ethnobotanical, ecological, and evolutionary information documented in different regions of Mexico, combining different research approaches in order to understand the human motives for managing plant resources, and the ecological and evolutionary consequences of management of plants and ecosystems. We therefore analyse those processes involving domestication as part of general design of nature according to human needs and desires, occurring at the levels of plant population of particular species, but also at the level of ecosystems and landscapes. We pay particular attention in the analysis of plant species that in the Mesoamerican area have wild and domesticated populations and maintain reproductive interactions. These interactions allow exploring practices and natural processes intervening in conforming populations in which divergence populations guided by natural and artificial selection and other evolutionary forces are occurring. Because natural processes continually weaken the human activities, the divergence is relatively slight and we have therefore called these processes incipient domestication. We analyse the cases of traditional greens called ‘quelites’ such as Anoda cristata and Crotalaria pumila in which people distinguish favourable and unfavourable morphs and practice artificial selection resulting in the abundance of the favourable morphs in areas more intensively managed. Similarly, some examples are analysed of trees (Leucaena esculenta, Crescentia spp. Spondias purpurea, S. mombin, and Sideroxylon palmeri), agaves (Agave inaequidens and A. hookeri), and columnar cacti (Escontria chiotilla, Myrtillocactus schenckii, Pachycereus hollianus, Polaskia spp., Stenocereus spp.). In the cases studied we analysed divergence in morphology, reproduction, population genetics, and germination patterns, among other features, between wild, silvicultural managed and cultivated populations. These case studies allow demonstrating that evolutionary divergence influenced by humans occurs not only under agriculture but also under silvicultural management and we hypothesize that domestication under silvicultural systems could have leaded to the origins of agriculture.