PREMISE OF THE STUDY: Studies of domestication of cacti in the Tehuacán Valley have identified morphophysiological divergences between wild and cultivated populations. To determine whether such divergences are associated with differential survivorship in xeric and mesic environments characterizing wild and cultivated habitats, respectively, we hypothesized that seedlings from cultivated populations are less tolerant of xeric environments and that differences between wild and cultivated populations are greater in species with higher management intensity. METHODS: We compared size, survivorship, and absolute and relative growth rates (AGRs, RGRs) in shade and humidity gradients of seedlings from wild and cultivated populations of Stenocereus pruinosus, S. stellatus, Polaskia chichipe, and Escontria chiotilla. These species represent a range of management intensity, from highest to lowest, respectively. KEY RESULTS: Seedlings of cultivated populations were larger than those of wild populations in all species studied. The AGRs were significantly different in P. chichipe and E. chiotilla associated with management, whereas the RGRs and seedling survival were significantly different in S. pruinosus and P. chichipe throughout the shade gradient tested. We also found significant differences in seedling survival among humidity treatments in E. chiotilla and among shade treatments in P. chichipe. CONCLUSIONS: Artificial selection favoring larger fruits favors larger seeds and seedlings. Seedling survivorship and growth of managed plants are generally higher in mesic environments apparently because of natural selection associated with habitat conditions. Such differences may contribute to morphophysiological divergences between wild and cultivated populations. Interspecific differences might be associated with adaptations to the natural environments where each species occurs.
PREMISE OF THE STUDY: Studies of domestication of cacti in the Tehuacán Valley have identified morphophysiological divergences between wild and cultivated populations. To determine whether such divergences are associated with differential survivorship in xeric and mesic environments characterizing wild and cultivated habitats, respectively, we hypothesized that seedlings from cultivated populations are less tolerant of xeric environments and that differences between wild and cultivated populations are greater in species with higher management intensity. METHODS: We compared size, survivorship, and absolute and relative growth rates (AGRs, RGRs) in shade and humidity gradients of seedlings from wild and cultivated populations of Stenocereus pruinosus, S. stellatus, Polaskia chichipe, and Escontria chiotilla. These species represent a range of management intensity, from highest to lowest, respectively. KEY RESULTS: Seedlings of cultivated populations were larger than those of wild populations in all species studied. The AGRs were significantly different in P. chichipe and E. chiotilla associated with management, whereas the RGRs and seedling survival were significantly different in S. pruinosus and P. chichipe throughout the shade gradient tested. We also found significant differences in seedling survival among humidity treatments in E. chiotilla and among shade treatments in P. chichipe. CONCLUSIONS: Artificial selection favoring larger fruits favors larger seeds and seedlings. Seedling survivorship and growth of managed plants are generally higher in mesic environments apparently because of natural selection associated with habitat conditions. Such differences may contribute to morphophysiological divergences between wild and cultivated populations. Interspecific differences might be associated with adaptations to the natural environments where each species occurs.