Pereskia

Pereskia
Pereskia grandifolia
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Caryophyllales
Family:	Cactaceae
Subfamily:	Pereskioideae
Genus:	Pereskia Mill.
Species
See text.

Pereskia is a genus of about 25 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. The genus is named after Nicolas-Claude Fabri de Peiresc, a 16th century French botanist, which also has been given its own subfamily Pereskioideae. 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.

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, Pereskia is the only cactus genus that has persistent non-succulent leaves. It is believed that the ancestor of all cacti resembled Pereskia.

Shrub species usually grow to 1 m (3.3 ft) in height, but climbing or arborescent species can reach 5 to 20 m (16 to 66 ft). Flowers may appear alone or in clusters. They generally resemble roses and reach a diameter of 1 to 5 cm (0.39 to 2.0 in). Colors of the flower depend on each species and vary from white, yellow to magenta or red. Fruits are ordinarily spherical, of 2 to 5 cm (0.79 to 2.0 in) diameter, and are wine red when ripe.

Most of the species are found in dry forests or thorny scrub, in tropical climates with a dry season of two to five months. They are found from southern Mexico to Colombia and Venezuela, and throughout the Caribbean, as well as the eastern part of Brazil south to northern Uruguay and Argentina. Several types are native to the Andes in Peru and Bolivia, though not on the Pacific side. They have been found in the U.S. state of Florida, but are probably introductions rather than natives.^{[citation needed]}

Phylogeny and evolution

A 2005 study suggested that the genus Pereskia was basal within the Cactaceae, but confirmed earlier suggestions that it was not monophyletic, i.e. did not include all the descendants of a common ancestor. The Bayesian consensus cladogram from this study is shown below.

Cactaceae	Pereskia Clade A caulocacti Pereskia Clade B core cacti Opuntioideae Maihuenia Cactoideae

The species studied divide into the two clades as shown below.

Clade A	Clade B
P. aureiflora P. bleo P. guamacho P. lychnidiflora P. marcanoi P. portulacifolia P. quisqueyana P. zinniiflora	P. aculeata P. bahiensis P. diaz-romeroana P. grandifolia P. horrida P. nemorosa P. sacharosa P. stenantha P. weberiana

A more recent 2011 study using fewer genes also found that Pereskia was divided into these two clades.

The two clades of Pereskia differ in their geographical distribution: with one exception, Clade A is found around the Gulf of Mexico and the Caribbean Sea whereas Clade B occurs south of the Amazon Basin. Species of Pereskia within Clade A 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 Clade B typically delay forming bark and have stomata on their stems, thus giving the stem the potential to become a major organ for photosynthesis.

If Pereskia is divided into two genera, based on these two clades, then Rhodocactus is a possible name for Clade A.

Species

Detail of the flower of Pereskia grandifolia

Stem of a tree-shaped Pereskia grandifolia

• Pereskia aculeata - Barbados gooseberry
  • Pereskia aculeata var. rotundifolia
• Pereskia aureiflora
• Pereskia bahiensis
• Pereskia bleo
• Pereskia colombiana
• Pereskia corrugata
• Pereskia cubensis
• Pereskia diaz-romeroana
• Pereskia godseffiana
• Pereskia grandifolia
  • Pereskia grandifolia var. violacea
• Pereskia guamacho
• Pereskia horrida
• Pereskia humboldtii
  • Pereskia humboldtii var. rauhii (syn. P. horrida)
• Pereskia lychnidiflora
• Pereskia marcanoi
• Pereskia nemorosa
• Pereskia philippi
• Pereskia portulacifolia
• Pereskia quisqueyana
• Pereskia sacharosa
• Pereskia stenantha
• Pereskia subulata
• Pereskia vargasii
  • Pereskia vaugasii var. longispina
• Pereskia weberiana
• Pereskia zehntneri
• Pereskia ziniiflora
• Pereskia zinniaefolia

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.).

Uses

The genus is not of great economic importance, the most common usage being as hedges; they are easily transplanted and quickly grow into an impenetrable thicket, as well as flowering prolifically. Being more tolerant of moisture than more succulent cacti, they can be used as rootstock for grafting of Zygocactus to create miniature trees.

Pereskias have been naturalised in the Caribbean and West Africa.

These species contain tyramine, and phenethylamine.

References

• Anderson, Edward F. (2001). The Cactus Family. Timber Press. pp. 566–572. 
• Leuenberger, Beat (1986). "Pereskia (Cactaceae)". Memoirs of the New York Botanical Garden 14. 
• Charles A. Butterworth and Robert S. Wallace, "Molecular Phylogenetics of the Leafy Cactus Genus Pereskia (Cactaceae)", Systematic Botany 30(4):800-808. 2005.
• Beat Ernst Leuenberger, "Pereskia, Maihuenia, and Blossfeldia —Taxonomic History, Updates, and Notes", Haseltonia 14 : 54-93. 2008