Opuntia in the food web. Charles Darwin was the first to note that these cacti have thigmotactic anthers: when the anthers are touched, they curl over, depositing their pollen. This movement can be seen by gently poking the anthers of an open "Opuntia" flower. The same trait has evolved convergently in other cacti (e.g. "Lophophora"). The first introduction of prickly pears into Australia is ascribed to Governor Philip and the earliest colonists in 1788. Brought from Brazil to Sydney, prickly pear grew in Sydney, New South Wales, where they were rediscovered in a farmer's garden in 1839. They appear to have
Opuntia ficus-indica the wild origin of "O. ficus-indica" is likely to have been in Mexico due to the fact that its close genetic relatives are found in central Mexico. "Opuntia ficus-indica" is polyploid, hermaphrodite and autogamous. As "Opuntia" species grow in semi-arid environments, the main limiting factor in their environment is water. They have developed a number of adaptations to dry conditions, notably succulence. The perennial shrub "Opuntia ficus-indica" can grow up to 3-5m height, with thick, succulent and oblong to spatulate stems called cladodes. It has a water-repellent and sun-reflecting waxy epidermis. Cladodes that are 1–2 years old produce flowers, the