Pereskioideae

Pereskia, as traditionally circumscribed, is a genus of 17 tropical species and varieties of cacti that do not look much like other types of cacti, having substantial leaves and thin stems. They originate from the region between Brazil and Mexico. Members of this genus are usually referred to as lemon vines, rose cacti or leaf cacti, though the latter also refers to the genus Epiphyllum. The genus is named after Nicolas-Claude Fabri de Peiresc, a 16th-century French botanist. Molecular phylogenetic studies have shown that species traditionally assigned to Pereskia fall into two clades, so that the genus is paraphyletic (i.e. it does not comprise all the descendants of a common ancestor). In 2013, it was suggested that eight species be moved to the genus Leuenbergeria, with the other nine species remaining in Pereskia. This has been accepted by sources such as Plants of the World Online. Species of Pereskia generally resemble other types of plants, such as roses. Pereskia species have large, bright green, privet-like leaves and long spiny stems. Not always succulent plants, they can be classified as shrubs, climbing plants or slightly succulent trees. However, close examination shows spines developing from areoles, and the distinctive floral cup of the cactus family. Unlike Pereskiopsis, Maihuenia, Quiabentia and Austrocylindropuntia which have persistent succulent leaves, when defined broadly Pereskia is the only cactus genus that has persistent non-succulent leaves. It is believed that the ancestor of all cacti resembled Pereskia. Plants are leafy and spiny, treelike, shrubby, and often scrambling. Many species may be treelike or shrubby, 2–7 m high, but occasionally at 10 m. Pereskia aculeata forms clambering shrubs or climbing vines 3–10 m long. Roots are sometimes thickened and tuberous. Leaves are generally alternate, broad, flattened, deciduous, usually with petioles, 2–20 cm long. Areoles exist on the axils of the leaves, usually with wool, and bear spines and leaves. The young primary areoles on twigs normally have up to eight spines, while areoles on trunks usually have more (15 to 40, up to 120) straight, usually black spines of unequal length. Flowers are solitary, or sometimes in inflorescences of 2–15 flowers (P. aceulata can have 70, while P. grandiflora can have 10–30); the flowers are 2–8 cm in diameter, usually pink, rose, or purple, but sometimes orange, yellow, white, or cream. Fruits, 2–7 (or up to 10 cm) long, are solitary or in clusters. They are variable in shape, but generally oblong and/or pear-shaped. When mature, fruits usually become green or yellow-green but also orange, reddish, or brownish. Three species have very small, glossy black, and globose fruits, at 0.5 to 1.5 cm. Seeds are 2–7 mm large, obovate to kidney shaped, and glossy black. Most likely Charles Plumier collected the first Pereskia specimens from the Caribbean between 1689 and 1695, but none of these have survived. Although Plumier described Pereskia in 1703, Linnaeus placed Plumier's two species in his Cactus, as C. pereskia and C. portacifolius. Philip Miller brought the original name back in 1754, and so by the rules of botanical nomenclature, he is credited as the author. The genus Rhodocactus (A.Berger) F.M.Knuth has been brought into synonymy with this genus, as well as different orthographic variants: Peirescia Zucc. (orth. var.), Peireskia Steud. (orth. var.) and Perescia Lem. (orth. var.). A 2005 study suggested that the genus Pereskia was basal within the Cactaceae, and confirmed earlier suggestions that it was paraphyletic, i.e. did not include all the descendants of a common ancestor. The Bayesian consensus cladogram from this study is shown below.