| Royal palm | |
|---|---|
 | |
| Native habitat inCollier–Seminole State Park, Florida | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Clade: | Commelinids |
| Order: | Arecales |
| Family: | Arecaceae |
| Genus: | Roystonea |
| Species: | R. regia |
| Binomial name | |
| Roystonea regia | |
 | |
| Natural range ofRoystonea regia | |
| Synonyms[3] | |
Oreodoxa regiaKunth | |
Roystonea regia, commonly known as theroyal palm,Cuban royal palm, orFlorida royal palm,[4] is a species ofpalm native toMexico, theCaribbean,Florida, and parts ofCentral America. A large and attractive palm, it has been planted throughout the tropics and subtropics as an ornamental tree. Although it is sometimes calledR. elata, theconserved nameR. regia is now the correct name for the species. The royal palm reaches heights from 15–24 m (50–80 ft) tall.[5] Populations inCuba and Florida were long seen as separate species, but are now considered a single species.
Widely planted as an ornamental,R. regia is also used for thatch, construction timber, and in some forms oftraditional medicine, although there is currently no valid scientific evidence to support the efficacy or use of any palm species for medicinal purposes. The fruit is eaten by birds and bats (which disperse the seeds) and fed to livestock. Its flowers are visited by birds and bats, and it serves as a roosting site and food source for a variety of animals.Roystonea regia is thenational tree of Cuba,[6] and has a religious role both inSantería and Christianity, where it is used inPalm Sunday observances.
Roystonea regia is a large palm which reaches a height of 20–30 metres (66–98 ft) tall,[7] (with heights up to 34.5 m (113 ft) reported)[8] and a stem diameter of about 47 centimetres (19 in).[7] (K. F. Connor reports a maximum stem diameter of 61 cm (24 in).)[8] The trunk is stout, very smooth and grey-white in colour with a characteristic bulge below a distinctive green crownshaft.[9] Trees have about 15 leaves which can be up to 4 m (13 ft) long.[7] The flowers are white with pinkish anthers.[9] The fruit arespheroid toellipsoid in shape, 8.9–15 millimetres (0.35–0.59 in) long and 7–10.9 mm (0.28–0.43 in) wide.[7] They are green when immature, turning red and eventually purplish-black as they mature.[9]
Root nodules containingRhizobium bacteria have been found onR. regia trees in India. The presence ofrhizobia-containing root nodules is usually associated withnitrogen fixation inlegumes; this was the first record of root nodules in amonocotyledonous tree.[10] Further evidence of nitrogen fixation was provided by the presence ofnitrogenase (an enzyme used in nitrogen fixation) andleghaemoglobin, a compound which allows nitrogenase to function by reducing the oxygen concentration in the root nodule.[10] In addition to evidence of nitrogen fixation, the nodules were also found to be producingindole acetic acid, an importantplant hormone.[11][12]
Roystonea is placed in thesubfamily Arecoideae and thetribe Roystoneae.[13] The placementRoystonea within the Arecoideae is uncertain; aphylogeny based onplastid DNA failed to resolve the position of the genus within the Arecoideae.[14] As of 2008, there appear to be no molecular phylogenetic studies ofRoystonea[13] and the relationship betweenR. regia and the rest of the genus is uncertain.
The species was first described by American naturalistWilliam Bartram in 1791 asPalma elata based on trees growing incentral Florida.[9] In 1816German botanistCarl Sigismund Kunth described the speciesOreodoxa regia[3] based on collections made byAlexander von Humboldt andAimé Bonpland in Cuba.[15] In 1825 German botanistCurt Polycarp Joachim Sprengel moved it to the genusOenocarpus and renamed itO. regius.[3]
The genusOreodoxa was proposed by German botanistCarl Ludwig Willdenow in 1807[16] and applied by him to two species,O. acuminata (now known asPrestoea acuminata) andO. praemorsa (nowWettinia praemorsa). Although these species were transferred to other genera, the genusOreodoxa continued to be applied to a variety of superficially similar species which were not, in fact, closely related.[17] To address this problem, American botanistOrator F. Cook created the genusRoystonea,[18] which he named in honour of American generalRoy Stone,[17] and renamed Kunth's speciesRoystonea regia.[18]
Cook considered Floridian populations to be distinct from both the CubaR. regia and thePuerto RicanR. borinquena, and he placed them in a new species,R. floridana,[17] which is now considered a synonym ofR. regia.[3] In 1906Charles Henry Wright described two new species based on collections fromGeorgetown, British Guiana (nowGuyana) which he placed in the genusEuterpe—E. jenmanii andE. ventricosa.[19] Both species are now considered synonyms ofR. regia.[3] The nameR. regia var.hondurensis was applied byPaul H. Allen to Central American populations of the species. However,Scott Zona determined that they did not differ enough from Cuban populations to be considered a separatevariety.[7]
Based on the rules ofbotanical nomenclature, the oldest properly published name for a species has priority over newer names. Bartram applied theLinnaean binomialPalma elata to a "large, solitary palm with an ashen white trunk topped by a green leaf sheath [the crownshaft] and pinnate leaves"[20] growing in central Florida. While notype collection is known, there are no other native palms that would fit Bartram's description.[20] In 1946Francis Harper pointed out that Bartram's name was valid and proposed a new combination,Roystonea elata.Liberty Hyde Bailey's use of the name in his 1949 revision of the genus, established its usage.[20]
Harper's new combination immediately supplanted Cook'sR. floridana, but there was disagreement as to whether Cuban and Floridian populations represented a single species or two species. Zona's revision of the genus concluded that they both belonged to the same species. According to the rules of botanical nomenclature, the correct name of the species should have beenRoystonea elata. Zona pointed out, however, that the nameR. regia (orOreodoxa regia) has a history of use in horticulture that dated from at least 1838, and that the species had been propagated around the world under that name.Roystonea elata, on the other hand, had only been used since 1949, and was used much less widely. On that basis, Zona proposed that the nameRoystonea regia should be conserved.[20]
In cultivation,Roystonea regia is called the Cuban royal palm or simply the royal palm. In Cuba, the tree is called thepalma real orpalma criolla.[7] In India, where it is widely cultivated, it is calledvakka.[21] In Cambodia, where it is planted as decorative along avenues and in public parks, it is known assla barang' ("Western palm").[22]
Roystonea regia producesunisexual flowers that arepollinated by animals.[7]European honey bees and bats are reported pollinators.[7][23] Seeds are dispersed by birds and bats that feed upon the fruit.[7]
Seedgermination isadjacent ligular—during germination, as thecotyledon expands it only pushes a portion of the embryo out of the seed.[7] As a result, the seedling develops adjacent to the seed. The embryo forms aligule, and theplumule protrudes from this.[24] Seedlings in cultivation are reported to begin producing a stem two years after germination, at the point where they produce their thirteenth leaf.[7] Growth rates of seedlings averaged 4.2 cm (1.7 in) per year in Florida.[25]
Roystonea regia is found inCentral America,Cuba, theCayman Islands,Hispaniola (theDominican Republic andHaiti), theLesser Antilles,The Bahamas, southern Florida, and Mexico (inVeracruz,Campeche,Quintana Roo, andYucatán).[3][26] William Bartram described the species fromLake Dexter, along theSt. Johns River in the area of modernLake andVolusia Counties incentral Florida, an area north of its modern range, suggesting a wider distribution in the past.[7][27]
Roystonea regia is most abundant in Cuba, where is occurs on hillsides and valleys. In southern Florida,Roystonea regia occurs instrand swamps andhardwood hammocks.[7] Royal Palm State Park in theEverglades was established due to the high concentration of the species.[28]
Roystonea is cultivated in tropical and subtropical climates in the United States,Australia,Brazil, and parts of southernAsia as a landscape palm. It appears to naturalise with ease, and extensive naturalised populations are present inPanama,Costa Rica, and Guyana.[7] In the United States it grows mostly in central and southern Florida,Hawaii,Puerto Rico, and in SouthTexas in theRio Grande Valley andsouthern California.[29]
The leaves ofRoystonea regia are used as roosting sites byEumops floridanus, the Florida bonneted bat,[30] and is used as a retreat forCuban tree frogs (Osteopilus septentriolalis), a non-native species in Florida.[31] In Panama (whereR. regia is introduced), its trunks are used as nesting sites by yellow-crowned parrots (Amazona ochrocephala panamensis).[32] The flowers ofR. regia are visited bypollen-collectingbees and are considered a good source ofnectar. Its pollen was also found in the stomachs ofPhyllonycteris poeyi, the Cuban flower bat (a pollen-feeder) andMonophyllus redmani, Leach's single leaf bat (a nectar-feeder).Artibeus jamaicensis, theJamaican fruit bat, andMyiozetetes similis, thesocial flycatcher, feed on the fruit.[7]
Roystonea regia is the host plant for the royal palm bug,Xylastodoris luteolus, in Florida.[33] It also serves as a larval host plant for the butterfliesPyrrhocalles antiqua orientis andAsbolis capucinus in Cuba,[34] andBrassolis astyra andB. sophorae in Brazil.[35] It is susceptible to bud rot caused by theoomycetePhytophthora palmivora[36] and by thefungusThielaviopsis paradoxa.[37]
The species is considered aninvasive species insecondary forest in Panama.[38]
Roystonea regia has been planted throughout the tropics and subtropics as an ornamental.[20] The seed is used as a source of oil and for livestock feed. Leaves are used for thatching and the wood for construction.[8] The roots are used as adiuretic,[39] and for that reason they are added totifey, aHaitian drink, by Cubans of Haitian origin.[40] They are also used as a treatment fordiabetes.[39]
Fibres extracted from the leaf sheath ofR. regia have been found to be comparable withsisal andbanana fibres, but lower in density, making it a potentially useful source for the use in lightweight composite materials.[21] An extract fromR. regia fruit known as D-004 reducesbenign prostate hyperplasia (BPH) in rodents. D-004, is a mixture offatty acids, is being studied as a potential alternative tofinasteride for the treatment of BPH.[41]
Roystonea regia plays an important role in popular religion in Cuba. InSantería it is associated primarily withShango or with his fatherAggayú. It also has symbolic importance in thePalo faiths and theAbakuá fraternity. InRoman Catholicism,R. regia plays an important role inPalm Sunday observances.[42]
