Editing Welwitschia

{{Short description|Monotypic genus of gnetophytes}}
{{for|the sports team|Welwitschias}}
{{Speciesbox
| image = Welwitschia mirabilis(2).jpg
| image_caption = The largest known ''Welwitschia'', nicknamed "The Big ''Welwitschia''", stands {{convert|1.4|m|ft|abbr=on}} tall and is over {{convert|4|m|ft|abbr=on}} in diameter
| genus = Welwitschia
| parent_authority = [[Hook.f.]]
| species = mirabilis
| authority = [[Joseph Dalton Hooker|Hook.f.]]
| range_map = Welwitschia Mirabilis Area of Circulation.png
| range_map_caption = Range of ''Welwitschia''
| synonyms = *''Tumboa'' <small>Welw. ''nom. rej.''</small>
*''Tumboa bainesii'' <small>Hook. f. ''nom. inval.''</small>
*''Welwitschia bainesii'' <small>(Hook. f.) Carrière</small>
*''Tumboa strobilifera'' <small>Welw. ex Hook. f. ''nom. inval.''</small>
| synonyms_ref = <ref>[http://www.tropicos.org/Name/14300073?tab=synonyms Tropicos, ''Welwitschia mirabilis''] and [http://www.tropicos.org/Name/40020640 Topicos ''Tumboa''  Welw.]</ref>
}}

'''''Welwitschia''''' is a [[monotypic taxon|monotypic]] genus of [[Gnetophyta|gnetophytes]], with the only species being '''''Welwitschia mirabilis'''''. It is named after the Austrian botanist [[Friedrich Welwitsch]], who discovered the plant in the 1850s. It is native to Angola and Namibia, where it grows in the extreme conditions of the Namib desert, tolerating high heat and low precipitation. ''Welwitschia'' is the only extant genus of the family [[Welwitschiaceae]] and order [[Welwitschiales]], and is one of three extant genera of gnetophytes, alongside ''[[Gnetum]]'' and ''[[Ephedra (plant)|Ephedra]]''.

''Welwitschia'' is well known for its unique [[Morphology (biology)|morphology]]. The plant only has two leaves that grow out of a large woody stem, dubbed a crown, and continue to grow over the plant's entire life. ''Welwitschia'' is one of the longest-living plants on Earth, with some individuals being thousands of years old. As such, the leaves can become quite large, often reaching several meters in length.

Like other [[gymnosperm]]s, ''Welwitschia'' uses cones to reproduce. Both male and female plants produce nectar from their cones that attract [[insect]]s who then carry the pollen off to other plants. The species is not in any significant danger of becoming extinct, although it may become vulnerable in the future; It only grows in one environment, and while its age protects it from temporary hardships, it makes it susceptable to sudden environmental changes and disease.

==Naming==
[[File:Welwitschia mirabilis00.jpg|thumb|300px|Female cones, from ''[[Curtis's Botanical Magazine]]'' (1863)]]
''Welwitschia'' is named after Austrian botanist and doctor [[Friedrich Welwitsch]], who documented the plant in Angola in 1859. Welwitsch was fascinated by the plant, writing, "I could do nothing but kneel down [...] and gaze at it, half in fear lest a touch should prove it a figment of the imagination."<ref name=Trimen>{{cite book |last=Trimen |first=Henry |date=1873 |page=7 |title=Friedrich Welwitsch |location=United Kingdom |publisher=Ranken and Company}}</ref><ref name=POWO>{{cite POWO|id=383591-1|title=''Welwitschia mirabilis''|url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:383591-1/general-information|access-date=21 July 2023}}</ref> [[Joseph Dalton Hooker]] of the [[Linnean Society of London]] formally described the species using Welwitsch's description and collected material along with material from artist [[Thomas Baines]] who had independently recorded the plant in Namibia.<ref name="LinnSoc">{{cite journal |url=https://www.biodiversitylibrary.org/item/8355#page/186/mode/1up |title=Extract from a letter, addressed to Sir William J. Hooker, on the botany of Benguiela, Mossameded, &C, in Western Africa |first=Frederick |last=Welwitsche |journal=Journal of the Proceedings of the Linnean Society. Botany |volume=5 |year=1861 |issue=20 |pages=182–186 |doi=10.1111/j.1095-8312.1861.tb01048.x}}</ref><ref name=PlantZAfrica>{{cite web|url=https://pza.sanbi.org/welwitschia-mirabilis|title=''Welwitschia mirabilis''|last=Notten|first=Alice|date=March 2003|website=PlantZAfrica|publisher=[[South African National Biodiversity Institute]]|access-date=21 July 2023}}</ref> Welwitsch proposed calling the genus ''Tumboa'' after what he believed to be the local name, ''tumbo''. Hooker asked Welwitsch for permission to name the genus ''Welwitschia'' instead. Welwitsch concurred and supplied some well-preserved material from which Hooker was able to study.<ref name="HookWel">{{cite journal |last1=Hooker |first1=Joseph Dalton |title=On ''Welwitschia'', a new Genus of Gnetaceae |journal=Transactions of the Linnean Society of London |date=1863 |volume=24 |issue=1 |pages=1–48 |postscript=, Pl. I–XIV. |doi=10.1111/j.1096-3642.1863.tb00151.x |url=https://archive.org/details/mobot31753002433701 |id={{BHL page|27558549}} }}</ref> 

The taxonomy of ''Welwitschia'' subsequently changed intermittently with the development of new classification systems. Its current taxonomic status is essentially the same as Hooker's placement. Most botanists have treated ''Welwitschia'' as a distinct [[monotypic taxon|monotypic]] [[genus]] in a monotypic family or even [[order (biology)|order]]. Most recent systems place ''Welwitschia mirabilis'' in the family [[Welwitschiaceae]], which also includes several extinct species.<ref>{{cite web|last=Stevens|first= P. F. |title=Angiosperm Phylogeny (2001 onwards) - Version 9, June 2008 |url=http://www.mobot.org/MOBOT/research/APWeb/|website=www.mobot.org}}</ref> The plant is commonly known simply as welwitschia in English, but the name '''tree tumbo''' is also used. It is called {{Lang|naq|kharos}} or {{Lang|naq|khurub}} in [[Nama language|Nama]], {{Lang|af|tweeblaarkanniedood}} ('two leaves; can't die') in [[Afrikaans]], {{Lang|naq|nyanka}} in [[Khoekhoe language|Damara]], and {{Lang|hz|onyanga}} in [[Herero language|Herero]].<ref name=":0">{{Cite web |title=Welwitschia mirabilis |url=https://www.conifers.org/we/Welwitschiaceae.php |access-date=2025-05-13 |website=The Gymnosperm Database}}</ref>

==Description==
After [[germination]], the seedling produces two [[cotyledon]]s which grow to {{Convert|25–35|mm||abbr=on}} in length.<ref name=Singh>{{cite book|last1=Singh|first1=V.P.|title=Gymnosperm (naked seeds plant) : structure and development|date=2006|publisher=Sarup & Sons|isbn=978-8176256711|page=576|url=https://books.google.com/books?id=F6B_xHO-IpoC&q=Welwitschia+cotyledons&pg=PA576|access-date=24 January 2016}}</ref> They start off as pink, but turn green shortly after germination. Subsequently, two permanent [[Leaf|leaves]] emerge from the crown (large, woody [[Plant stem|stem]]) and are produced opposite (at right angles) to the cotyledons. The permanent leaves grow rapidly and last for the plant's entire life. They are long and ribbon-shaped, with their [[Vascular plant|veins]] running down their length parallel to each other.<ref name="PlantZAfrica" /><ref name="Bornman" /> Shortly after the appearance of the permanent leaves, the [[meristem#Apical meristems|apical meristem]] dies and meristematic activity is transferred to the periphery of the crown.<ref name=Bornman>{{cite book|last=Bornman|first=Chris&nbsp;H|date=1 January 1978|title=Welwitschia: Paradox of a parched paradise|location=Cape Town|publisher=C&nbsp;Struik|isbn=9780869770979}}</ref> The two (rarely three) leaves grow continuously from the crown across its entire circumference, reaching lengths up to {{Convert|4|m||abbr=on}}. The crown is disc-shaped and widens with age, reaching up to a meter in diameter.<ref name=":0" /> The largest specimens may be no more than {{Convert|1.5|m|ft|abbr=on}} tall above ground, but the circumference of the leaves in contact with the sand may exceed {{Convert|8|m|ft|abbr=on}}.<ref name="Bornman et al 72">{{cite journal |last1=Bornman |first1=Chris&nbsp;H |last2=Elsworthy |first2=Janet&nbsp;A |last3=Butler |first3=Valerie |last4=Botha |first4=C&nbsp;E&nbsp;J |date=1 January 1972 |title=''Welwitschia mirabilis'': observations on general habit, seed, seedling, and leaf characteristics |url=https://journals.co.za/doi/10.10520/AJA10115498_46 |journal=Madoqua Series II |volume=1 |issue=1 |pages=53–66 |access-date=21 July 2023}}</ref> The largest known individual is {{Convert|2.77|m|ft}} in diameter and {{Convert|8.7|m||abbr=on}} in circumference.<ref name="Bornman" /> As the plant ages, the leaves often split into ribbons and become frayed from years of weathering.<ref name="PlantZAfrica" /><ref name=":0" /> The age of individual plants is difficult to assess, with [[radiocarbon dating]] is the most common method in determining plant age.<ref>{{Gymnosperm Database|family=Welwitschiaceae|title=''Welwitschia mirabilis''|access-date=21 July 2023|quote=Although ''Welwitschia'' produces no growth rings, radiocarbon dating is feasible and results have indicated maximum ages in excess of 1,500 years.}}</ref> The plant is exceptionaly long-lived, with many being hundreds of years old,<ref>{{Cite journal |last=Henschel |first=Joh R. |last2=Seely |first2=Mary K. |date=2000-10-01 |title=Long-term growth patterns of Welwitschia mirabilis, a long-lived plant of the Namib Desert (including a bibliography) |url=https://link.springer.com/article/10.1023/A:1026512608982 |journal=Plant Ecology |language=en |volume=150 |issue=1 |pages=7–26 |doi=10.1023/A:1026512608982 |issn=1573-5052}}</ref> and the oldest being potentially up to 2,000.<ref name="Bornman" /><ref name=":1" />

''Welwitschia'' is [[dioecious]], with separate male and female plants. Both sexes produce cones that grow out of the crown of the plant, which often number in the hundreds.<ref name="Wetschnig and Depisch" /> Cones can range from green to [[Salmon (color)|salmon]] to various shades of brown in color.<ref name=":0" /><ref>{{Cite web |title=The two subspecies of Welwitschia mirabilis |url=https://www.bgbm.org/en/two-subspecies-welwitschia-mirabilis |website=Freie Universität Berlin}}</ref> The cones produce nectar that atracts various insects, most commonly [[Fly|flies]], that then carry the oval-shaped pollen on them. The Welwitschia bug, [[Probergrothius angolensis|''Probergrothius angolensis'']], is commonly observed on the plant, but likely does not have a role in pollination; they are not particularly atracted to the nectar and are usually found on the leaves of the plant. Infrequently, wasps and bees also play a role as [[pollinator]]s of ''Welwitschia.''<ref name="Wetschnig and Depisch">{{cite journal|author=Wetschnig W, Depisch B|year= 1999|title=[Chrysomya albiceps Pollination biology of ''Welwitschia mirabilis'' HOOK. f. (Welwitschiaceae, Gnetopsida)]|journal=Phyton: Annales Rei Botanicae|volume=39|pages=167|url=http://www.zobodat.at/pdf/PHY_39_1_0167-0183.pdf}}</ref>

[[File:Stem of a Welwitschia which according to a C14 test was far more then 1000 years old on display at the Swakopmund Museum, Namibia.jpg|thumb|Stem of a ''Welwitschia'', which according to a C14 test was more than 1,000 years old, on display at the Swakopmund Museum, Namibia.]]

Because ''Welwitschia'' only produces a single pair of leaves, the plant was thought by some to be [[neoteny|neotenic]], consisting essentially of a "giant [[seedling]]." However, research showed that its anatomy is not consistent with a "giant seedling". Instead, the plant is more accurately thought to achieve its unusual morphology as a result of having "lost its head" (apical meristem) at an early stage.<ref>{{cite journal|jstor=2442386|title=Welwitschia mirabilis and Neoteny|first=P.|last=Martens|date=4 September 1977|journal=American Journal of Botany|volume=64|issue=7|pages=916–920|doi=10.2307/2442386}}</ref>

==Genetics==
In July 2021, the genome of ''Welwitschia'' was 98% sequenced, totaling 6.8 Gb on 21 chromosomes. There is evidence of a [[whole genome duplication]] followed by extensive reshuffling, probably caused by extreme stress due to a time of increased aridity and prolonged drought some 86 million years ago. As a result of this duplication, the genome contains more "junk" self-replicating DNA sequences. This increase in [[retrotransposon]] activity was counteracted with a [[Gene silencing|silencing]] [[DNA methylation]] process, allowing the metabolic cost of such a large genetic material to be lowered.<ref name=":1">{{Cite journal|last1=Wan|first1=Tao|last2=Liu|first2=Zhiming|last3=Leitch|first3=Ilia J.|last4=Xin|first4=Haiping|last5=Maggs-Kölling|first5=Gillian|last6=Gong|first6=Yanbing|last7=Li|first7=Zhen|last8=Marais|first8=Eugene|last9=Liao|first9=Yiying|last10=Dai|first10=Can|last11=Liu|first11=Fan|date=2021-07-12|title=The Welwitschia genome reveals a unique biology underpinning extreme longevity in deserts|journal=Nature Communications|language=en|volume=12|issue=1|pages=4247|pmid=34253727 |doi=10.1038/s41467-021-24528-4 |pmc=8275611|bibcode=2021NatCo..12.4247W |issn=2041-1723|hdl=1854/LU-8715697|hdl-access=free}}</ref><ref>{{Cite news|last=Sima|first=Richard|date=2021-07-31|title=A Plant That 'Cannot Die' Reveals Its Genetic Secrets|language=en-US|work=The New York Times|url=https://www.nytimes.com/2021/07/31/science/plant-leaves-welwitschia.html|access-date=2021-08-03|issn=0362-4331}}</ref>

==Distribution and habitat==
''Welwitschia'' is endemic to the [[Namib|Namib desert]]. Its range stretches over {{cvt|1000|km}} along the Angolan and Namibian coast, being found between [[14th parallel south|14th]] and [[24th parallel (south)|24th]] southern parallels.<ref>{{cite journal|last1=Jürgens|first1=Norbert|last2=Oncken|first2=Imke|last3=Oldeland|first3=Jens|last4=Gunter|first4=Felicitas|last5=Rudolph|first5=Barbara|date=27 January 2021|title=''Welwitschia'': Phylogeography of a living fossil, diversified within a desert refuge|journal=Scientific Reports|volume=11|issue=1 |page=2385 |article-number=2385 (2021)|doi=10.1038/s41598-021-81150-6|pmid=33504814 |pmc=7840819 |doi-access=free|bibcode=2021NatSR..11.2385J }}</ref> The area is arid; the coast is recorded as having almost zero rainfall, while less than {{Convert|100|mm||abbr=on}} of rain falls annually below the escarpment in the wet season from February to April.<ref>{{cite book|last1=van&nbsp;Wyk|first1=Abraham&nbsp;E|last2=Smith|first2=Gideon&nbsp;F|title=Regions of Floristic Endemism in Southern Africa: A Review with Emphasis on Succulents|publication-place=Hatfield, South Africa|publisher=Umdaus Press|publication-date=30 September 2001|isbn=9781919766188}}</ref> Populations tend to occur in [[Ephemerality|ephemeral]] water sources, indicating a dependence on groundwater in addition to precipitation from fog.<ref>{{cite journal|last1=Henschel|first1=Joh&nbsp;R|last2=Seeley|first2=Mary&nbsp;K|date=October 2000|title=Long-term growth patterns of ''Welwitschia mirabilis'', a long-lived plant of the Namib Desert (including a bibliography)|url=https://link.springer.com/article/10.1023/A:1026512608982|journal=Plant Ecology|volume=150|issue=1|pages=7–26|doi=10.1023/A:1026512608982|s2cid=7760078 |url-access=registration|access-date=21 July 2023}}</ref>

==Cultivation==
''Welwitschia'' grows from a [[seed]], which may be bought from specialty seed dealers. The seeds have been shown to display [[orthodox seed]] behavior, meaning they may be stored for long periods of time at extreme humidities and temperatures. ''Welwitschia'' seeds are able to survive temperatures as high as {{Convert|80|C|F}} and as low as {{Convert|-20|C|F}} without major side effects.<ref name="Whitaker et al 2004">{{cite journal |last1=Whitaker |first1=C |last2=Berjak |first2=P |last3=Kolberg |first3=H |last4=Pammenter |first4=N&nbsp;W |last5=Bornman |first5=C&nbsp;H |date=October 2004 |title=Responses to various manipulations, and storage potential, of seeds of the unique desert gymnosperm, ''Welwitschia mirabilis'' Hook. fil. |journal=[[South African Journal of Botany]] |volume=70 |issue=4 |pages=622–630 |doi=10.1016/S0254-6299(15)30201-5 |doi-access=free}}</ref>

Seeds collected from the wild often are heavily contaminated with spores of the fungus ''[[Aspergillus niger]]'' which causes them to rot shortly after they germinate.<ref>{{cite journal|last1=Cooper-Driver|first1=Gillian&nbsp;A|last2=Wagner|first2=Christopher|last3=Kolberg|first3=Herta|date=October 2000|title=Patterns of ''Aspergillus niger'' var. ''phoenicis'' (Corda) Al-Musallam infection in Namibian populations of ''Welwitschia mirabilis'' Hook.f.|url=https://www.sciencedirect.com/science/article/abs/pii/S0140196300906608|journal=Journal of Arid Environments|volume=46|issue=2|pages=181–198|doi=10.1006/jare.2000.0660|bibcode=2000JArEn..46..181C |url-access=registration|access-date=21 July 2023}}</ref> The fungus infects the growing cones of ''Welwitschia'' early in their development with a sharp increase in infection occuring when the pollination drop (a sugary substance produced by the [[ovule]]) appears. Because of this, seeds in the wild may be rendered unviable before they fully develop. The fungicide [[tebuconazole]] may be useful in controlling limited ''A. niger'' seed infection.<ref name="Whitaker et al 2008">{{cite journal |last1=Whitaker |first1=C |last2=Pammenter |first2=N&nbsp;W |last3=Berjak |first3=P |date=January 2008 |title=Infection of the cones and seeds of ''Welwitschia mirabilis'' by ''Aspergillus niger'' var. ''phoenicis'' in the Namib-Naukluft Park |journal=[[South African Journal of Botany]] |volume=74 |issue=1 |pages=41–50 |doi=10.1016/j.sajb.2007.08.008 |doi-access=free}}</ref>

Indigenous people sometimes eat the cone of the plant by eating it raw or baking it in hot ashes. The [[Herero language|Herero]] name of the plant, ''onyanga'',<ref name=":0" /> translates to 'onion of the desert'.<ref>{{cite web|url=https://www.usbg.gov/rare-and-endangered-plant-spotlights|title=Rare and Endangered Plant Spotlights|website=[[United States Botanic Garden]]|access-date=21 July 2023|quote=The plant's common name is onyanga, which means "onion of the desert."}}</ref><ref>{{Cite web |title=Welwitschia Facts |url=https://www.softschools.com/facts/plants/welwitschia_facts/556/ |access-date=2022-03-12 |website=www.softschools.com}}</ref> ''Welwitschia'' is also featured on the coat of arms of Namibia growing from a sand dune.<ref>{{cite act|title=National Coat of Arms of the Republic of Namibia Act, 1990|number=1|language=English|date=28 March 1990|url=http://www.parliament.gov.na/acts_documents/155_act_1_of_1990.pdf|accessdate=27 May 2013|url-status=dead|archiveurl=https://web.archive.org/web/20131030061903/http://www.parliament.gov.na/acts_documents/155_act_1_of_1990.pdf|archivedate=30 October 2013|df=dmy-all}}</ref>

==Conservation==
The wild population of ''Welwitschia'' is reasonably stable. The international trade in the plant is controlled under the [[Convention on International Trade in Endangered Species of Wild Fauna and Flora]] (CITES).<ref name=CITES>{{Cite web |title=Appendices |url=https://cites.org/eng/app/appendices.php |publisher=Convention on International Trade in Endangered Species of Wild Fauna and Flora ([[CITES]]) |access-date=14 October 2022}}</ref> Plants in Angola are generally better protected than those in Namibia because the relatively high concentration of [[land mine]]s from the [[Angolan Civil War]] that remain in the region.<ref name=POWO/>

Although ''Welwitschia'' is not at present immediately threatened, with there being abundant populations over a large area, its status is far from secure; its recruitment and growth rates are low, and its range, though wide, covers only a single compact, ecologically limited and vulnerable area. The remarkable longevity of Welwitschia favors its survival of temporary periods adverse to reproduction, but it offers no protection against direct threats, such as [[overgrazing]] and disease. Fungal infection of female cones severely reduces seed viability, reducing already inherently low recruitment. Other threats include injury from off-road vehicles, collection of wild plants and overgrazing by zebras, rhinos, and domestic animals.<ref name=POWO/>

==Gallery==
<gallery mode="packed" heights="150">
File:Welwitschia-mirabilis-female.jpg|A female plant
File:Welwitschia mirabilis (female).jpg|A female ''Welwitschia'' beginning to shed seeds
File:N-welwitschia-2.jpg|Detail photograph of ripe female cones after seed dispersal
File:N-welwitschia-3.jpg|Detail photograph of male plant and cones
File:Namib, Welwitschia mirabilis.jpg|Person standing beside ''Welwitschia'' plant for scale
File:Welwitschia at Huntington Library, Art Collections and Botanical Gardens.jpg|Cultivated at [[Huntington Library|Huntington Library and botanical garden]]
File:Welwitschia mirabilis0425.jpg|A ''Welwitschia'' in the petrified forest of [[Khorixas]] (Namibia)
File:Probergrothius angolensis adult and nymphs 1.jpg|Immature nymphs and adult ''Welwitschia'' bugs (''[[Probergrothius angolensis]]'')
File:Welwitschia mirabilis MHNT.BOT.2015.2.2.jpg|''Welwitschia mirabilis'' – [[MHNT|Toulouse Museum of Natural History]]
File:Coat of arms of Namibia.svg|Coat of Arms of Namibia, with a ''Welwitschia'' in the bottom
</gallery>

==See also==
* [[List of Southern African indigenous trees and woody lianes]]

==References==
{{Reflist|40em}}

==External links==
* {{Wikispecies-inline|Welwitschia}}
* {{Commons-inline|Welwitschia mirabilis|Welwitschia}}
* {{Gymnosperm Database|family=Welwitschiaceae|title=''Welwitschia mirabilis''|access-date=21 July 2023}}
* [https://web.archive.org/web/20040607013633/http://florawww.eeb.uconn.edu/acc_num/199700061.html Ecology & Evolutionary Biology Conservatory] (archived)
*[https://mobot.org/gradstudents/olson/welwitschia.html The ''Welwitschia'' page]
* {{cite web|url=https://pza.sanbi.org/welwitschia-mirabilis|title=''Welwitschia mirabilis''|last=Notten|first=Alice|date=March 2003|website=PlantZAfrica|publisher=[[South African National Biodiversity Institute]]|access-date=21 July 2023}}
* [http://www.bihrmann.com/caudiciforms/subs/wel-mir-sub.asp Bihrmann's Welwitschia growing project]
* [https://www.npr.org/sections/krulwich/2014/05/21/314225165/so-what-if-its-ugly-it-just-keeps-on-going "So What If It's Ugly? It Just Keeps On Going ..."]
* {{cite news |last1=Sima |first1=Richard |title=A Plant That 'Cannot Die' Reveals Its Genetic Secrets |url=https://www.nytimes.com/2021/07/31/science/plant-leaves-welwitschia.html |access-date=31 July 2021 |work=New York Times |date=31 July 2021}}

{{Taxonbar|from1=Q156926|from2=Q15044266}}

[[Category:Welwitschiaceae]]
[[Category:Endangered plants]]
[[Category:Flora of Angola]]
[[Category:Flora of Namibia]]
[[Category:Monotypic gymnosperm genera]]
[[Category:Dioecious plants]]