| Gunnera | |
|---|---|
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| Gunnera tinctoria at theSan Francisco Botanical Garden at Strybing Arboretum | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Gunnerales |
| Family: | Gunneraceae Meisn.[1] |
| Genus: | Gunnera L. |
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| The range of the genusGunnera[2] | |
| Synonyms[3] | |
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Gunnera is the sole genus ofherbaceousflowering plants in the familyGunneraceae, which contains 63 species. Some species in this genus, namely those in the subgenusPanke, have extremely large leaves. Species in the genus are variously native toLatin America,Australia,New Zealand,Papuasia,Hawaii,insular Southeast Asia, easternAfrica, andMadagascar.[3] The stalks of some species are edible.[4]
Gunnera is the only genus in the family Gunneraceae.[5] TheAPG II system, of 2003, also recognizes this family and assigns it to the order Gunnerales in the cladecore eudicots. The family then consisted of one or two genera,Gunnera and, optionally,Myrothamnus, the latter optionally segregated as a separate family,Myrothamnaceae. This represents a change from theAPG system, of 1998, which firmly recognized two separate families, unplaced as to order. TheAPG III system andAPG IV system recognizes the family Gunneraceae and placesMyrothamnus in Myrothamnaceae; both families are placed in the order Gunnerales in the core eudicots.[6]
The genusGunnera was named after the Norwegian botanistJohann Ernst Gunnerus. At first it was assigned to the familyHaloragaceae, though that presented difficulties that led to the general recognition of the family Gunneraceae, as had been proposed about the beginning of the 20th century. In the meantime, in many publications it had been referred to as being in the Haloragaceae, variously misspelt (as for example "Halorrhagidaceae".[7]) Such references still cause difficulties in consulting earlier works. However, currentlyGunnera is firmly assigned to themonogeneric family Gunneraceae.[8]
Gunnera is thought to be a rather ancient group, with a well-documented fossil history due to the presence of fossilizedpollen spores, known by thepalynotaxonTricolpites reticulatus. It is aGondwanan lineage, having originated inSouth America during theCretaceous. The earliest fossilized pollen is known from theLate Cretaceous (Turonian) of Peru, about 90 million years ago, and within the following 10 million years,Gunnera had achieved a worldwide distribution, with fossil pollen grains being found in areas where it is not found today, such as westernNorth America, mainlandAustralia, andAntarctica.[9][10] Based on fossil pollen recovered from drilling cores,Gunnera is also known to have inhabited the now-submerged islands of theNinetyeast Ridge during thePaleocene, likely having dispersed there from eitherAustralasia or the then-emergentKerguelen Plateau islands.[11]
Due to the widespread distribution ofGunnera during the Cretaceous, it was previously thought that the modern disjunct distribution of the genus was a relic of this period. However, phylogenetic analysis indicates that the majority ofGunnera species, even those found on entirely different continents, diverged from each other during theCenozoic, indicating that the modern distribution ofGunnera is a consequence oflong-distance dispersal from South America to other parts of the world, rather than relics of a former cosmopolitan distribution. The only species that diverged prior to the Cenozoic isGunnera herteri, described from Uruguay[12] and distributed in Uruguay and southeasternBrazil, which is thought to be the most ancient species of the genus, its lineage having diverged during the Late Cretaceous, roughly concurrent with the oldestGunnera fossil pollen from Peru. The persistence of theGunneracrown group since the Cretaceous makes it unique among flowering plants, and may have been facilitated by strongniche conservatism,dispersal ability, and being able to aggressively colonize disturbed land.[10]
The 40–50 species vary enormously inleaf size, with the iconic large-leaved species belonging to the subgenusPanke. Thegiant rhubarb, orCampos des Loges (Gunnera manicata), native to the Serra do Mar mountains of southeasternBrazil, is perhaps the largest species, withreniform or sub-reniform leaves typically 1.5 to 2.0 meters (4 ft 11 in to 6 ft 7 in) long, not including the thick, succulentpetiole which may be up to 2.5 meters (8 feet 2 inches) in length. The width of the leaf blade is typically 2.5 meters (8 feet 2 inches), but on two occasions cultivated specimens (inDorset, England in 2011[13] and at Narrowwater,Ulster,Ireland[14] in 1903) produced leaves fully 3.3 meters (10 feet 10 inches) in width. The seeds germinate best in very moist, but not wet, conditions and temperatures of 22–29 °C.
Only slightly smaller isGunnera masafuerae of theJuan Fernandez Islands off theChilean coast. They can have leaves up to 2.9 m (9 ft 6 in) in width on stout leaf stalks 1.5 m (4 ft 11 in) long and 11 cm (4+1⁄2 in) thick according to Skottsberg.[15] These leaf stalks orpetioles are the thickest of anydicot, and probably also the most massive. On nearbyIsla Más Afuera,Gunnera peltata frequently has an upright trunk to 5.5 m (18 ft 1 in) in height by 25–30 cm (10–12 in) thick, bearing leaves up to 2 m (6 ft 7 in) wide. The Hoja de Pantano (Gunnera magnifica) of theColombianAndes bears the largest leaf buds of any plant; up to 60 cm (2 ft) long and 40 cm (16 in) thick.[16] Thesucculent leaf stalks are up to 2.7 m (8 ft 10 in) long. The massiveinflorescence of small, reddishflowers is up to 2.3 m (7 ft 7 in) long and weighs about 13 kg. The flowers of Gunnera species are dimerous ( two sepals, two petals (or none), two stamens (or one), and two carpels.[17] Other giantGunnera species within the subgenusPanke are found throughout theNeotropics andHawaii.Gunnera insignis is also known by the name "poor man's umbrella" inCosta Rica.
Outside of the subgenusPanke, most of the more basalGunnera species have small-to-medium-sized leaves. There are some species with moderately large leaves inAfrica (G. perpensa, in the subgenusGunnera (which is redundant withPerpensum)) andSoutheast Asia (G. macrophylla, in the subgenusPseudogunnera), but the majority of more basal species are low-lying, mat-forming plants with small leaves. There are several small species are found inNew Zealand, notablyG. albocarpa, with leaves only 1–2 cm long, and also in South America, withG. magellanica having leaves 5–9 cm wide on stalks 8–15 cm long. The most basal species in the genus,G. herteri of Uruguay and Brazil, also has small leaves.[18][19]
Some fossil leaf impressions ofGunnera from theCretaceous ofNorth America have large leaves akin to those ofPanke, and the most basal extant species withinPanke (G. mexicana) is the most northern member. For this reason, it has been suggested thatPanke originates from South AmericanGunnera that colonized North America during the Cretaceous and grew into giant forms, with the remaining South AmericanGunnera evolving into the subgenusMisandra, with a low-lying, matlike growth. During the Cenozoic, the North AmericanPanke would have colonizedHawaii and retreated southwards on the mainland before recolonizing South America. However, more recent phylogenetic evidence suggests thatMisandra andPanke diverged only 15 million years ago, much too recent to assign the CretaceousGunnera toPanke. Due to this, the large-leaved CretaceousGunnera from North America may represent a distinct lineage thatconvergently evolved giant leaves similar to those ofPanke, but did not leave any descendants.[10][18][20]
As of April 2023[update],Plants of the World Online accepts the following species[21] separated by subgenus:[22]
| Subgenus | Image | Scientific name | Distribution |
|---|---|---|---|
| OstenigunneraMattfeld, 1933 | Gunnera herteriOsten | Uruguay, S Brazil | |
| PseudogunneraSchindler, 1905 |  | Gunnera macrophyllaBlume | Papuasia, Indonesia, Philippines |
| MilliganiaSchindler, 1905 | Gunnera albocarpa(Kirk) Cockayne | New Zealand | |
| Gunnera arenariaCheeseman ex Kirk | New Zealand | ||
| Gunnera cordifolia(Hook.f.) Hook.f. | Tasmania | ||
| Gunnera densifloraHook.f. | New Zealand | ||
 | Gunnera dentataKirk | New Zealand | |
| Gunnera flavidaColenso | New Zealand | ||
 | Gunnera hamiltoniiKirk ex W.S.Ham. | New Zealand | |
| Gunnera mixtaKirk | New Zealand | ||
 | Gunnera monoicaRaoul | New Zealand incl Chatham Islands | |
.jpg) | Gunnera prorepensHook.f. | New Zealand | |
| Gunnera reniformisRidl. | New Guinea | ||
| Gunnera strigosa(Kirk) Colenso | New Zealand | ||
| PankeSchindler, 1905 | Gunnera aequatoriensisL.E.Mora | Ecuador | |
| Gunnera annaeSchindl. | Peru, Bolivia | ||
| Gunnera antioquensisL.E.Mora | Colombia | ||
| Gunnera apiculataSchindl. | Bolivia, Argentina | ||
| Gunnera atropurpureaL.E.Mora | Colombia, Ecuador | ||
| Gunnera berteroiPhil. | Bolivia, Argentina, Chile | ||
| Gunnera bogotanaL.E.Mora | Colombia | ||
| Gunnera bolivariJ.F.Macbr. | Peru, Ecuador | ||
| Gunnera bolivianaMorong | Bolivia | ||
| Gunnera bracteataSteud. ex Benn. | Robinson Crusoe Island in Chile | ||
.jpg) | Gunnera brephogeaLinden & André | Colombia, Ecuador, Peru | |
| Gunnera caucanaL.E.Mora | Colombia | ||
| Gunnera colombianaL.E.Mora | Colombia, Ecuador | ||
| Gunnera ×crypticaJ.M.H.Shaw (G. manicata ×G. tinctoria) | Cultivated | ||
| Gunnera cuatrecasasiiL.E.Mora | Colombia | ||
| Gunnera diaziiL.E.Mora | Colombia | ||
| Gunnera garciae-barrigaeL.E.Mora | Colombia | ||
| Gunnera hernandeziiL.E.Mora | Colombia | ||
| Gunnera insignis(Oerst.) Oerst. | Panama, Nicaragua, Costa Rica | |
| Gunnera ×katherine-wilsoniaeL.D.Gómez (G. insignis ×G. talamancana) | Costa Rica | ||
| Gunnera kauaiensisRock | Kauai in Hawaii | ||
.jpg) | Gunnera killipianaLundell | Chiapas, Guatemala, Honduras | |
| Gunnera lozanoiL.E.Mora | Colombia | ||
| Gunnera magnificaH.St.John | Colombia | ||
-1.JPG) | Gunnera manicataLinden ex André | S Brazil | |
| Gunnera margaretaeSchindl. | Peru, Bolivia | ||
| Gunnera masafueraeSkottsb. | Alejandro Selkirk Island (Isla Mas Afuera) in Chile | ||
 | Gunnera mexicanaBrandegee | Veracruz, Chiapas | |
| Gunnera moraeWanntorp & Klack. | Colombia | ||
| Gunnera peltataPhil. | Robinson Crusoe Island in Chile | ||
| Gunnera peruvianaJ.F.Macbr. | Ecuador, Peru | ||
.jpg) | Gunnera petaloideaGaudich. | Hawaii | |
| Gunnera pilosaKunth | Peru, Bolivia, Ecuador | ||
| Gunnera pittierianaV.M.Badillo & Steyerm. | Venezuela | ||
| Gunnera quitoensisL.E.Mora | Ecuador | ||
| Gunnera saint-johnii(L.E.Mora) L.E.Mora | Colombia | ||
| Gunnera sanctae-marthaeL.E.Mora | Colombia | ||
| Gunnera schindleriL.E.Mora | Bolivia, Argentina | ||
 | Gunnera schultesiiL.E.Mora | Colombia | |
| Gunnera silvioanaL.E.Mora | Ecuador, Colombia | ||
| Gunnera steyermarkiiL.E.Mora | Venezuela | ||
| Gunnera tacueyanaL.E.Mora | Colombia | ||
| Gunnera tajumbinaL.E.Mora | Ecuador, Colombia | ||
 | Gunnera talamancanaH.Weber & L.E.Mora | Costa Rica, Panama | |
| Gunnera tamanensisL.E.Mora | Colombia | ||
.jpg) | Gunnera tayronaL.E.Mora | Colombia | |
 | Gunnera tinctoria(Molina) Mirb. | Chile, Argentina | |
| Gunnera venezolanaL.E.Mora | Venezuela | ||
| MisandraSchindler, 1905 |  | Gunnera magellanicaLam. | W + S South America, Falkland Is. |
| Gunnera lobataHook.f. | Tierra del Fuego | ||
| Gunnera |  | Gunnera perpensaL. | Africa, Madagascar |
In 2022, it was shown that plants in cultivation under the nameGunnera manicata were actually a hybrid,Gunnera ×cryptica.[23]
At least some species ofGunnera hostendosymbioticcyanobacteria such asNostoc punctiforme. The cyanobacteria providefixed nitrogen to the plant, while the plant provides fixed carbon to the microbe.[24] The bacteria enter the plant via glands found at the base of each leaf stalk[2] and initiate an intracellular symbiosis which is thought to provide the plant with fixed nitrogen in return for fixed carbon for the bacterium. The Nostoc-filled symbiotic tissue makes up just a small portion of the plant's total biomass.Gunnera is the only known genus of angiosperms that hosts cyanobacteria, and the only known land plant with intracellularcyanobionts. Although the endosymbionts enters thecell wall, they do not penetrate thecell membrane.[25][26] This relationship may provide insights to allow the creation of novel symbioses between crop plants and cyanobacteria, allowing growth in areas lacking fixed nitrogen in the soil.
The stalks ofG. tinctoria (nalca), from southernChile andArgentina, are edible.[4] Their principal use is fresh consumption, after peeling, but also they are prepared in salads, liquor or marmalade. Leaves of this species are used in coveringcuranto (a traditional Chilean food).
Gunnera perpensa is a source of traditional medicine in southern Africa, both in veterinary and human ailments, largely in obstetric and digestive complaints, but also as a wound dressing.[7] It also is eaten in various ways, largely the petioles, flower stalks and leaves, fresh and raw, preferably with skins and fibre removed, which is said to remove bitterness, but also cooked. The plant also is said to be used in making a beer.[27]
Media related toGunnera at Wikimedia Commons
Data related toGunnera at Wikispecies| National | |
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| Other | |
