Abstract
Escontria chiotilla, Polaskia chichipe, and Stenocereus pruinosus are species of Mexican columnar cacti that are economically important because of their edible fruits. These species are managed by gathering fruits from the wild, silvicultural management in agroforestry systems, and cultivation in home gardens. Previous studies reported that artificial selection favored individuals that produced larger fruits, which indirectly led to the production of larger seeds and seedlings, with possible effects on survival. We hypothesized that seedlings from managed populations would be larger but more susceptible to xeric conditions than those from wild populations. We evaluated the effects of artificial and natural selection on seedling survival of the three species in wild and managed populations, which were managed with low and high intensity, respectively. We tested seedling performance in gradients of shade (0, 40, and 80%) and humidity (low and high). A GLM of seedling survival showed significant differences among species, shade, and humidity treatments, with each species having environmental requirements associated with their particular adaptations. High humidity decreased seedling survival of all species, and high solar radiation decreased survival of S. pruinosus and P. chichipe. The effect of management type was significant only in S. pruinosus. Significant differences in the initial growth of seedlings among species were detected with ANOVA. In optimal conditions, the hypocotyl and the cotyledons decreased in size and the epicotyl grew, whereas under stress, these structures remained unchanged. The optimum conditions of shade and humidity varied among species and management types. The seedlings of S. pruinosus were the largest and the most susceptible, but in all species, seedlings from managed populations were more susceptible to environmental conditions. Thus, artificial selection influenced the susceptibility of these cacti to xeric environments.
Highlights
Domestication is an evolutionary process through which managed plant or animal populations become adapted to environments created by humans, diverging from the wild populations in morphological, physiological, reproductive, and genetic aspects (Hawkes 1983; Harlan 1992)
Ecology and Evolution published by John Wiley & Sons Ltd
We identified some morphophysiological patterns that were associated with artificial selection and identified others associated with natural selection
Summary
Domestication is an evolutionary process through which managed plant or animal populations become adapted to environments created by humans, diverging from the wild populations in morphological, physiological, reproductive, and genetic aspects (Hawkes 1983; Harlan 1992). Domestication occurs primarily as a consequence of artificial selection, which favors the fitness of organisms with features desirable to people. In these domesticated environments, natural selection influences the survival of organisms with specific characteristics that favor survival, reproduction, or both in the particular environmental conditions (Gepts 2004). Artificial and natural selection both contribute to the adaptation of organisms to different human cultural and natural environments, and through time, both types of selection influence the evolutionary divergence between wild and domesticated populations (Gepts 2004; McKey et al 2012).
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