Opuntia is a genus containing over 200 cacti species, all of which have paddle-shaped leaves and are commonly referred to as prickly pear cactus. Of the 200 species of prickly pear that grow across the Americas, only six grow in the Galapagos Islands:
- Opuntia echios
- Opuntia galapageia
- Opuntia helleri
- Opuntia insularis
- Opuntia saxicola
- Opuntia megasperma
After reaching Galapagos, these six species rapidly diversified into 14 different varieties – an example of adaptive radiation. Tall varieties thrive on islands where there are giant tortoises, whereas on islands where tortoises are absent, shorter varieties can be found. The cacti are consumed by land iguanas, giant tortoises, doves, cactus finches and mockingbirds, as well as invasive species such as goats. Prickly pears have thigmotactic anthers; when they are touched they curl over, depositing their pollen. This allows them to self-pollinate, so that they can reproduce even when there are no other cacti in the surrounding area.
Where to see them: All over the Galapagos Islands, mainly in arid inland areas
When to see them: They are visible all year round
Threats: The lack of pollinators has caused the O. echios species to be registered as vulnerable. The introduction of goats to the Islands also pose a threat to prickly pears, as they consume the cacti.
Conservation Actions: The cacti lie inside the Galapagos National Park, which covers 97% of the land area of the islands and provides protection to the species within it. There have also been efforts to eradicate invasive species such as goats.