Passiflora is the most species-rich genus of both the family Passifloraceae and the tribe Passifloreae. With over 550 species, an extensive hierarchy of infrageneric ranks is required to represent the relationships of the species. The infrageneric classification ofPassiflora not only uses the widely used ranks of subgenus, section and series, but also the rank of supersection.
The New World species ofPassiflora were first divided among 22 subgenera by Killip (1938) in the first monograph of the genus.[8] More recent work has reduced these to 4, which are commonly accepted today (in order from most basal to most recently branching):[9]
Astrophea (Americas, ~60 species), trees and shrubs with simple, unlobed leaves
Passiflora (Americas, ~250 species), woody vines with large flowers and elaboratecorolla
Deidamioides (Americas, 13 species), woody or herbaceous vines
Decaloba (Americas, Asia and Australasia, ~230 species), herbaceous vines with palmately veined leaves
Some studies have shown that the segregateOld World generaHollrungia andTetrapathaea are nested withinPassiflora, and form a fifth subgenus (Tetrapathaea).[10] Other studies support the current four subgenus classification.[11]
Relationships below the subgenus level are not known with certainty and are an active area of research. The Old World species form two clades – supersectionDisemma (part of subgenusDecaloba) and subgenusTetrapathaea. The former is composed of 21 species divided into sectionsDisemma (three Australian species),Holrungiella (one New Guinean species) andOctandranthus (seventeen south and east Asian species).[12]
The remaining (New World) species of subgenusDecaloba are divided into seven supersections. SupersectionPterosperma includes four species fromCentral America and southern Mexico. SupersectionHahniopathanthus includes five species from Central America, Mexico and northernmost South America. SupersectionCicea includes nineteen species, with apetalous flowers. SupersectionBryonioides includes twenty-one species, with a distribution centered on Mexico. SupersectionAuriculata includes eight species from South America, one of which is also found in Central America. SupersectionMultiflora includes nineteen species. SupersectionDecaloba includes 123 species.[13]
Passiflora has a largelyneotropic distribution, unlike other genera in the familyPassifloraceae, which includes more Old World species (such as the genusAdenia). The vast majority ofPassiflora are found in Mexico, Central America, the United States and South America, although there are additional representatives inSoutheast Asia andOceania.[14] New species continue to be identified: for example,P. xishuangbannaensis andP. pardifolia have only been known to the scientific community since 2005 and 2006, respectively.
Some species ofPassiflora have been naturalized beyond their native ranges. For example, theblue passion flower (P. caerulea) now grows wild in Spain.[15] Thepurple passionfruit (P. edulis) and its yellow relativeflavicarpa have been introduced in many tropical regions as commercial crops.
Passion flowers have floral structures adapted forbiotic pollination. Pollinators ofPassiflora includebumblebees, carpenter bees (e.g.,Xylocopa sonorina),wasps,bats, andhummingbirds (especiallyhermits such asPhaethornis); some others are additionally capable ofself-pollination.Passiflora often exhibit high levels of pollinator specificity, which has led to frequent coevolution across the genus. Thesword-billed hummingbird (Ensifera ensifera) is a notable example: it, with its immensely elongated bill, is the sole pollinator of 37 species of highAndeanPassiflora in the supersectionTacsonia.[16]
The leaves are used for feeding by thelarvae of a number of species ofLepidoptera. Famously, they are exclusively targeted by manybutterfly species of the tribeHeliconiini. The many defensive adaptations visible onPassiflora include diverse leaf shapes (which help disguise their identity), colored nubs (which mimic butterfly eggs and can deter heliconians from ovipositing on a seemingly crowded leaf),extrafloral nectaries,trichomes,variegation, and chemical defenses.[17] These, combined with adaptations on the part of the butterflies, were important in the foundation ofcoevolutionary theory.[18][19]
Recent studies have shown that passiflora both grow faster and protect themselves better in high-nitrogen soils. In low-nitrogen environments, passiflora focus on growth rather than defense and are more vulnerable to herbivores.[20]
The following lepidoptera larvae are known to feed onPassiflora:
Cydno longwing (Heliconius cydno), one of few heliconians to feed on multiple species ofPassiflora[21]
Gulf fritillary (Agraulis vanillae), which feeds on several species ofPassiflora, such asPassiflora lutea,Passiflora affinis,[22][23] stinking passion flower (P. foetida),[24] andmaypop (P. incarnata)
The generally high pollinator and parasite specificity inPassiflora may have led to the tremendous morphological variation in the genus. It is thought to have among the highestfoliar diversity among all plant genera,[8] with leaf shapes ranging from unlobed to five-lobed frequently found on the same plant.[26]Coevolution can be a major driver of speciation, and may be responsible for the radiation of certain clades ofPassiflora such asTacsonia.
Banana passion flower or "banana poka" (P. tarminiana), originally from CentralBrazil, is aninvasiveweed, especially on the islands ofHawaii. It is commonly spread byferalpigs eating the fruits. It overgrows and smothers stands ofendemic vegetation, mainly on roadsides.Blue passion flower (P. caerulea) is an invasive species in Spain and considered likely to threaten ecosystems there.[15]
On the other hand, some species areendangered due to unsustainablelogging and other forms ofhabitat destruction. For example, the Chilean passion flower (P. pinnatistipula) is a rare vine growing in the TropicalAndes southwards fromVenezuela between 2,500 and 3,800 metres (8,200 and 12,500 ft) in altitude, and in Coastal Central Chile, where it only occurs in a few tens of square kilometres of fog forest by the sea, near Zapallar.P. pinnatistipula has a round fruit, unusual inTacsonia group species like banana passion flower andP. mixta, with their elongated tubes and brightly red to rose-colored petals.[citation needed]
Passion flower is not recommended during pregnancy because it may induce contractions.[28][4] Consuming passion flower products may cause drowsiness,nausea, dizziness, abnormalheart rhythms,asthma, orrhinitis.[28][4]
A number of species ofPassiflora are cultivated outside their natural range for both their flowers and fruit. Hundreds of hybrids have been named; hybridizing is currently being done extensively for flowers, foliage and fruit. The following hybrids and cultivars have gained theRoyal Horticultural Society'sAward of Garden Merit:
During theVictorian era the flower (which in all but a few species lasts only one day) was very popular, and many hybrids were created using thewinged-stem passion flower (P. alata), theblue passion flower (P. caerulea) and other tropical species.
Many cool-growingPassiflora from the Andes Mountains can be grown successfully for their beautiful flowers and fruit in cooler Mediterranean climates, such as theMonterey Bay andSan Francisco inCalifornia and along the western coast of the U.S. intoCanada. One blue passion flower or hybrid even grew to large size atMalmö Central Station inSweden.[32]
Most species have round or elongated edible fruit.
Thepassion fruit ormaracujá (P. edulis) is cultivated extensively in theCaribbean,South America, southFlorida andSouth Africa for its fruit, which is used as a source of juice. A small pink fruit that wrinkles easily and a larger shiny yellow to orange fruit are traded under this name. The latter is usually considered just avariety offlavicarpa, but seems to be more distinct.[citation needed]
Sweet granadilla (P. ligularis) is another widely grown species. In large parts ofAfrica it is the plant called "passionfruit": confusingly, inSouth African English the latter species is more often calledgranadilla (without an adjective). Its fruit is somewhat intermediate between the two sold asP. edulis.
Maypop (P. incarnata), a common species in the southeastern US. This is a subtropical representative of this mostly tropical family. However, unlike the more tropical cousins, this particular species is hardy enough to withstand the cold down to −20 °C (−4 °F) before its roots die (it is native as far north asPennsylvania and has been cultivated as far north asBoston andChicago.) The fruit is sweet, yellowish, and roughly the size of a chicken's egg; it enjoys some popularity as a native plant with edible fruit and fewpests.
Theblue passionflower (Passiflora caerulea) produces bright orange fruit with numerous seeds. While the fruit is edible, it is often described as being bland in comparison to other edible passionfruit, or with a flavour vaguely similar toblackberries.[35]
A native source ofbeta-carbolines (e.g., passion flower in North America) is mixed withDesmanthus illinoensis (Illinois bundleflower) root bark to produce a hallucinogenic drink called prairiehuasca, which is an analog of the shamanic brewayahuasca.[38]
Thepassion inpassion flower purportedly refers tothe passion of Jesus inChristian theology;[40] the wordpassion comes from theLatinpassio, meaning 'suffering'. In the 15th and 16th centuries, Spanish Christian missionaries adopted the unique physical structures of this plant, particularly the numbers of its various flower parts, as symbols of the last days ofJesus and especially hiscrucifixion:[41]
The pointed tips of the leaves were taken to represent theHoly Lance.
The threestigmas represent threenails and the fiveanthers below them five hammers or fivewounds (four by the nails and one by the lance).
The blue and white colors of many species' flowers representHeaven andPurity.
In addition, the flower is open for three days, symbolising the three years of Jesus' ministry.[42]
The flower has been given names related to this symbolism throughout Europe since the 15th century. InSpain, it is known asespina de Cristo ('thorn of Christ'). OlderGermanic names[43] includeChristus-Krone ('Christ's crown'),Christus-Strauss ('Christ's bouquet'),[44]Dorn-Krone ('crown of thorns'),Jesus-Lijden ('Jesus' passion'),Marter ('passion')[45] orMuttergottes-Stern ('Mother of God's star').[46]
Outside the Roman Catholic heartland, the regularly shaped flowers have reminded people of the face of aclock. InIsrael they are known as "clock-flower" (שעונית) and in Greece as "clock plant" (ρολογιά); inJapan too, they are known astokeisō (時計草, 'clock plant'). In Hawaii, they are calledlilikoʻi;<named after the gulch it was first cultivated and/or discovered on the island of Maui. The plant is found on all major Hawaiian islands and in the wild. It is also cultivated for sale. It is popular among locals and incorporated into many juices, jams, ice shave flavoring, and many more products. >
InIndia, it is known asKrishnakamala because of its relation to the EpicMahabharata. The 100 peripheral petals represent the 100Kauravas, while the 5 yellow petals in between stand for thePandavas. The sensitive, but firm green bulb on top isDraupadi, orKrishna.
^abKillip, E.P. (1938).The American Species of Passifloraceae. Chicago, US: Field Museum of Natural History.
^Feuillet, C.; MacDougal, J. (2004). "A new infrageneric classification of Passiflora L. (Passifloraceae)".Passiflora.13 (2):34–35,37–38.
^Krosnick, S.E.; Ford, A.J.; Freudenstein, J.V. (2009). "Taxonomic Revision of Passiflora Subgenus Tetrapathea Including the Monotypic Genera Hollrungia and Tetrapathea (Passifloraceae), and a New Species of Passiflora".Systematic Botany.34 (2):375–385.Bibcode:2009SysBo..34..375K.doi:10.1600/036364409788606343.S2CID86038282.
^Hansen, K.A.; Gilbert, L.E.; Simpson, B.B.; Downie, S.R.; Cervi, A.C.; Jansen, R.K. (2006). "Phylogenetic Relationships and Chromosome Number Evolution in Passiflora".Systematic Botany.31 (1):138–150.Bibcode:2006SysBo..31..138H.doi:10.1600/036364406775971769.S2CID4820527.
^de Castro, É.C.P.; Zagrobelny, M.; Cardoso, M.Z.; Bak, S. (2017). "The arms race between heliconiine butterflies and Passiflora plants - new insights on an ancient subject".Biological Reviews.93 (1):555–573.doi:10.1111/brv.12357.PMID28901723.S2CID23953807.
^Ehrlich, P.R.; Raven, P.H. (1964). "Butterflies and Plants: A Study in Coevolution".Evolution.18 (4):586–608.doi:10.2307/2406212.JSTOR2406212.
^Benson, W.W; Brown, K.S.; Gilbert, L.E. (1975). "Coevolution of plants and herbivores: passion flower butterflies".Evolution.29 (4):659–680.doi:10.2307/2407076.JSTOR2407076.PMID28563089.
^abcdef"Passionflower". National Center for Complementary and Integrative Health, US National Institutes of Health. 1 September 2016. Retrieved30 October 2019.
^The University of Georgia - Center for Invasive Species and Ecosystem Health and the National Park Service (17 February 2011)."Invasive Plant Atlas of the United States". Retrieved8 March 2011.
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