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.
The species studied divide into the two clades as shown below.
|Clade A||Clade B|
A more recent 2011 study using fewer genes also found that Pereskia was divided into these two clades. In 2013, it was suggested that the two clades be recognized as distinct genera, Pereskia Clade A becoming Leuenbergeria and Pereskia Clade B becoming a more tightly circumscribed Pereskia sensu stricto.
The two clades of Pereskia sensu lato differ in their geographical distribution: with one exception, Leuenbergeria (Clade A) is found around the Gulf of Mexico and the Caribbean Sea whereas Pereskia s.s. (Clade B) occurs south of the Amazon Basin. Species of Leuenbergeria always lack two key features of the stem present in most of the remaining "caulocacti": like most non-cacti, their stems begin to form bark early in the plant's life and also lack stomata - structures which control the admission of air into a plant and hence control photosynthesis. By contrast, species of Pereskia s.s. typically delay forming bark and have stomata on their stems, thus giving the stem the potential to become a major organ for photosynthesis.
The two genera have been placed in separate subfamilies of the Cactaceae: Leuenbergeria being the sole genus in the subfamily Leuenbergerioideae, and Pereskia s.s. the sole genus in the subfamily Pereskioideae.
Species recognized by International Cactaceae Systematics Group. (Anderson E. F., 2001)
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Most of the species are found in dry forests or thorny scrub, in tropical climates with a dry season of two to five months. The two clades of Pereskia s.l. differ in their geographical distribution, with one exception.
Species placed in Leuenbergeria (Clade A) are found on Pacific coastal area, around the Gulf of Mexico and the Caribbean Sea.
Pereskia lychnidiflora Pacific coastal area from southern Mexico to Costa Rica in lowland dry forest from sea level to 1000 m (3300 ft).
Pereskia bleo Panama and Colombia along rivers and in secondary forests, from sea level to 500 m (1600 ft).
Pereskia guamacho Drier regions of Colombia and Venezuela, from sea level to 800 m (2600 ft); possibly also the Dutch Antilles.
Caribbean islands species. These plants are functionally dioecious, flowers imperfectly unisexual.
Pereskia aureiflora One exception, occurs in clade B species area. Caatinga formation, Brazil, northeastern Minas Gerais and southern Bahia, at elevations of 300-700 m (980-2300 ft).
Species remaining in Pereskia s.s. (Clade B) occur south of the Amazon Basin, in eastern part of Brazil, south to northern Uruguay and Argentina, Gran Chaco region, and lowlands and dry walleys on the Andes in Peru and Bolivia, though not on the Pacific side.
Brazil lowlands, caatinga formation:
Pereskia nemorosa Drier forests and woodlands in lowlands in southern Brazil, Paraguay, northeastern Argentina, and northwestern Uruguay region.
Pereskia diaz-romeroana Dry mountain valleys of central Bolivia at elevations of 1300-2000 m (4300-6600 ft).
Pereskia weberiana Dry forests in the Bolivian Andean valleys of the Rio Beni, at elevations of 1100-1900 m (3600-6200 ft)
Pereskia horrida Dry forest and brushland in the Peruan mountain valleys of the Maranon at elevations of 500-2100 (1600-6900 ft).
Pereskia aculeata Northern, eastern, and southeastern South America, and Caribbean. From sea level to 1000 m (3300 ft). Introduced in United States, Mexico, South Africa and Australia.
According to Anderson, Edward F. (2001) and Edwards, Erika J.; Nyffeler, Reto & Donoghue, Michael J. (2005).
The genus is not of great economic importance.
Pereskia aculeata The fruit are edible, widely cultivated. Fruits containing numerous small seeds. It somewhat resembles the gooseberry in appearance and is of excellent flavor. This plant is a declared weed in South Africa.
Pereskia guamacho The fruit are edible, collected from wild plants.
Pereskia bleo The crushed leaves have been used to clarify drinking water.
Pereskia lychnidiflora The spines are 12 cm long and have been used as needles in Guatemala.
Pereskia grandifolia Cultivated for flowers.
According to Anderson, Edward F. (2001).