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 46 opuntia cactus DHJanzen100708.jpg high resolution
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| Prickly pear cactus (Opuntia spp., Cactaceae) are rich in oxalic acids as one line of defense (and especially against herbivorous insects). But they are also firmly dressed in thorniness, the selective agents for which are now long gone. Farmers have even selected for thornless Opuntia varieties, which have been planted as livestock food in North Africa and in Chile, and it is dramatic to watch the camels, horses and cows seletively choose the spineless varieties from among those with spines - even though if hungry enough, all of these animals will browse thorny vegetation. | ||
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