Opuntia, also known as nopales or paddle cactus (see below), is a genus in the cactus family, Cactaceae. Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. In the Galapagos Islands, there are six different species: O. echios, O. galapageia, O. helleri, O. insularis, O. saxicola, O. megasperma. These species are divided into 14 different varieties; most of these are confined to one or a few islands. For this reason, they have been described as "an excellent example of adaptive radiation". On the whole, on islands where there are tall, trunked varieties there are also giant tortoises, and islands lacking tortoises have low or prostrate forms of Opuntia.