Taxus

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Taxus
Temporal range: Early Cretaceous – Recent
Taxus baccata MHNT.jpg
Taxus baccata (European yew) shoot with mature and immature cones
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Pinophyta
Class: Pinopsida
Order: Cupressales
Family: Taxaceae
Genus: Taxus
L.
Type species
Taxus baccata
L.
Species

See text

Taxus is a genus of coniferous trees or shrubs known as yews in the family Taxaceae. [1] Yews occur around the globe in temperate zones of the northern hemisphere, northernmost in Norway and southernmost in the South Celebes. Some populations exist in tropical highlands. [2]

Contents

The oldest known fossil species are from the Early Cretaceous. [3]

Morphology

Seeds of Taxus baccata Taxus baccata MHNT seed.jpg
Seeds of Taxus baccata

They are relatively slow-growing and can be very long-lived, and reach heights of 2.5–20 m (8.2–65.6 ft), with trunk girth averaging 5 m (16 ft). [4] They have reddish bark, lanceolate, flat, dark-green leaves 10–40 mm (1⁄2–1+1⁄2 in) long and 2–3 mm (3⁄32–1⁄8 in) broad, arranged spirally on the stem, but with the leaf bases twisted to align the leaves in two flat rows either side of the stem. [5]

The male cones are globose, 3–6 mm (1⁄8–1⁄4 in) across, and shed their pollen in early spring. Yews are mostly dioecious, but occasional individuals can be variably monoecious, or change sex with time. [5]

The seed cones are highly modified, each cone containing a single seed 4–7 mm (5⁄32–9⁄32 in) long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, 8–15 mm (5⁄16–19⁄32 in) long and wide and open at the end. The arils are mature 6–9 months after pollination, and with the seed contained are eaten by thrushes, waxwings and other birds, which disperse the hard seeds undamaged in their droppings; maturation of the arils is spread over 2–3 months, increasing the chances of successful seed dispersal. [5]

Taxonomy and systematics

Taxus is the Latin word for this tree and its wood that is used to make javelins. [6] The Latin word is probably borrowed, via Greek τόξονtóxon, from taxša, the Scythian word used for "yew" and "bow" [7] (cognate of Persian تخشTaxš meaning bow) [8] [9] because the Scythians used its wood to make their bows. [8]

All of the yews are very closely related to each other, and some botanists treat them all as subspecies or varieties of just one widespread species; under this treatment, the species name used is Taxus baccata , the first yew described scientifically. [10]

Taxus species appear similar. Attempts at taxonomy vary from describing all yews as subspecies of T. baccata, as did RKF Pilger in 1903, to splitting species by even very small morphological differences, as did R. W. Spjut in 2007 with 25 species and over 50 varieties. Some species have traditionally been recognized by geographic distribution, but Asian species have been more difficult to classify. Taxus contorta in the Western Himalaya and Taxus sumatrana in Malesia are now generally agreed upon, but overlapping ranges in the Eastern Himalaya, China, and subtropical southeast Asia have led to greater confusion, with the species Taxus chinensis, Taxus mairei, and Taxus wallichiana being elucidated only in the 21st century with the aid of molecular phylogenetics. [2]

Foliage of Mexican yew Taxus globosa foliage.jpg
Foliage of Mexican yew

The most distinct is the Sumatran yew (T. sumatrana, native to Sumatra and Celebes north to southernmost China), distinguished by its sparse, sickle-shaped yellow-green leaves. The Mexican yew (Taxus globosa, native to eastern Mexico south to Honduras) is also relatively distinct with foliage intermediate between Sumatran yew and the other species. The Florida yew, Mexican yew and Pacific yew are all rare species listed as threatened or endangered.[ citation needed ]

Distribution

Yews typically occur in the understory or canopy of moist temperate or tropical mountain forests. Elevation varies by latitude from 3,000 m (9,800 ft) in tropical forests to near sea level in its northernmost populations. [2] Yews are common in landscape architecture, giving rise to widespread naturalized populations in the United States. There, both T. baccata and Taxus cuspidata are common ornamental shrubs. [11]

T. baccata appears throughout Europe and into western Asia. [2] T. cuspidata occurs over much of East Asia, in China, Japan, Korea, and Sakhalin. [12] Taxus brevifolia ranges in the United States from California to Montana and Alaska, [11] while Taxus canadensis appears in the northeastern United States and southeast Canada. [2]

Species and hybrids

4112 year old Taxus in Anatolia 4112 year Yew 3.jpg
4112 year old Taxus in Anatolia

Plants of the World Online recognizes 12 confirmed species: [1]

Fossil (extinct) species

Commonly reported hybrids

Phylogeny

Below are cladograms showing the evolutionary relationships between yew species and their global distribution.

Möller et al., 2020 [19] Stull et al., 2021 [20]

Austrotaxus

Toxicity

All species of yew contain highly poisonous taxine alkaloids, with some variation in the exact formula of the alkaloid between the species. All parts of the tree except the arils contain the alkaloid. The arils are edible and sweet, but the seed is dangerously poisonous; unlike birds, the human stomach can break down the seed coat and release the toxins into the body. This can have fatal results if yew 'berries' are eaten without removing the seeds first. Grazing animals, particularly cattle and horses, are also sometimes found dead near yew trees after eating the leaves, though deer are able to break down the poisons and will eat yew foliage freely. In the wild, deer browsing of yews is often so extensive that wild yew trees are commonly restricted to cliffs and other steep slopes inaccessible to deer. The foliage is also eaten by the larvae of some Lepidopteran insects including the moth willow beauty.[ citation needed ]

Male (pollen-producing) cones of Taxus baccata Taxus baccata MHNT flowers male.jpg
Male (pollen-producing) cones of Taxus baccata

Allergenic potential

All parts of a yew plant are toxic to humans with the exception of the yew berries (which however contain a toxic seed); additionally, male and dioecious yews in this genus release cytotoxic pollen, which can cause headaches, lethargy, aching joints, itching, and skin rashes; it is also a trigger for asthma. These pollen granules are extremely small, and can easily pass through window screens. Male yews bloom and release abundant amounts of pollen in the spring; completely female yews only trap pollen while producing none. [21]

Yews in this genus are primarily separate-sexed, and males are extremely allergenic, with an OPALS allergy scale rating of 10 out of 10. Completely female yews have an OPALS rating of 1, and are considered "allergy-fighting". [21]

Uses and traditions

A replica of Otzi's yew and copper axe ReconstructedOetziAxe.jpg
A replica of Ötzi's yew and copper axe

Bows

Yew wood is reddish brown (with whiter sapwood), and is very springy. It was traditionally used to make bows, especially the longbow. These longbows were used by Scythian people who were part of the police force in ancient Athens. This use was lent into the Ancient Greek word for "bow" [8] and later probably borrowed into the Latin word and now generic name of Taxus.

Ötzi, the Chalcolithic mummy found in 1991 in the Italian Alps, carried an unfinished bow made of yew wood. Consequently, it is not surprising that in Norse mythology, the abode of the god of the bow, Ullr, had the name Ydalir (Yew Dales). Most longbow wood used in northern Europe was imported from Iberia, where climatic conditions are better for growing the knot-free yew wood required. [22] The yew longbow was the critical weapon used by the English in the defeat of the French cavalry at the Battle of Agincourt, 1415. British yews tend to be too gnarly, and thus the wood for English longbows used at the Battle of Agincourt was imported from Spain or northern Italy. [23]

Cultivation

It is suggested that English parishes were required to grow yews and, because of the trees' toxic properties, they were grown in the only commonly enclosed area of a village – the churchyard. [24] The yew tree can often be found in church graveyards and is symbolic of sadness. Such a representation appears in Lord Alfred Tennyson's poem "In Memoriam A.H.H." (2.61–64).

The yew can be very long-lived. The Fortingall Yew has been considered to be the oldest tree in Europe, at something over 2,000 years old. Tradition has it that Pontius Pilate slept under it while on duty before 30 AD. This has been topped by a tree in the churchyard of a small Welsh village called St Cynog. It has been dated to 5,000 years old by dendrologist Janis Fry. [25] Such old trees usually consist of a circular ring of growths of yew, since their heart has long since rotted away.

The Eihwaz rune is named after the yew, and sometimes also associated with the "evergreen" world tree, Yggdrasil.

Horticulture

Foliage of Irish yew; note the leaves spreading all round the erect shoots English Yew close 250.jpg
Foliage of Irish yew; note the leaves spreading all round the erect shoots

Yews are widely used in landscaping and ornamental horticulture. Over 400 cultivars of yews have been named, the vast majority of these being derived from European yew (Taxus baccata) or Japanese yew (Taxus cuspidata). The hybrid between these two species is Taxus × media. A popular fastigiate selection of the European yew (Taxus baccata 'Fastigiata') is often called the Irish yew, illustrating the difficulties with common names. A few cultivars with yellow leaves are collectively known as golden yews.

Chemistry

The Pacific yew (Taxus brevifolia), native to the Pacific Northwest of North America, and the Canada yew (Taxus canadensis) of Eastern and Central North America were the initial sources of paclitaxel or Taxol, a chemotherapeutic drug used in breast and lung cancer treatment and, more recently, in the production of the Taxus drug eluting stent by Boston Scientific. Over-harvesting of the Pacific yew for paclitaxel led to fears that it would become an endangered species, since the drug was initially extracted from the bark of the yew, the harvesting of which kills the tree. [26] On January 18, 2008, the Botanic Gardens Conservation International (representing botanic gardens in 120 countries) stated that "400 medicinal plants are at risk of extinction, from over-collection and deforestation, threatening the discovery of future cures for disease." These included yew trees, whose bark is used for the cancer drug paclitaxel. [27] [28]

However, methods were developed to produce the drug semi-synthetically from the leaves of cultivated European yews. Those can be sustainably harvested without the need to further endanger wild populations, and the Pacific yew is no longer at risk. [29] The more common Canada yew is also being successfully harvested in northern Ontario, Quebec and New Brunswick, and has become another major source of paclitaxel. Other yew species contain similar compounds with similar biochemical activity. Docetaxel, an analogue of paclitaxel, is derived from the European yew (Taxus baccata).

Oldest Polish specimen of European yew (1200 years) Taxus baccata henrykow poland 01.jpg
Oldest Polish specimen of European yew (1200 years)

In culture

The yew tree is a frequent symbol in the Christian poetry of T. S. Eliot, especially his Four Quartets .

Related Research Articles

<span class="mw-page-title-main">Paclitaxel</span> Medication used for cancer

Paclitaxel, sold under the brand name Taxol among others, is a chemotherapy medication used to treat ovarian cancer, esophageal cancer, breast cancer, lung cancer, Kaposi's sarcoma, cervical cancer, and pancreatic cancer. It is administered by intravenous injection. There is also an albumin-bound formulation.

<span class="mw-page-title-main">Conifer</span> Group of cone-bearing seed plants

Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta, also known as Coniferophyta or Coniferae. The division contains a single extant class, Pinopsida. All extant conifers are perennial woody plants with secondary growth. The great majority are trees, though a few are shrubs. Examples include cedars, Douglas-firs, cypresses, firs, junipers, kauri, larches, pines, hemlocks, redwoods, spruces, and yews. As of 2002, Pinophyta contained seven families, 60 to 65 genera, and more than 600 living species.

<span class="mw-page-title-main">Taxaceae</span> Family of conifers

Taxaceae, commonly called the yew family, is a coniferous family which includes six extant and two extinct genera, and about 30 species of plants, or in older interpretations three genera and 7 to 12 species.

<span class="mw-page-title-main">Aril</span> Membranous or fleshy appendage that partly or wholly covers a seed

An aril, also called an arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode or false aril is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ovary, an arillode forms from a different point on the seed coat. The term "aril" is sometimes applied to any fleshy appendage of the seed in flowering plants, such as the mace of the nutmeg seed. Arils and arillodes are often edible enticements that encourage animals to transport the seed, thereby assisting in seed dispersal. Pseudarils are aril-like structures commonly found on the pyrenes of Burseraceae species that develop from the mesocarp of the ovary. The fleshy, edible pericarp splits neatly in two halves, then falling away or being eaten to reveal a brightly coloured pseudaril around the black seed.

<i>Tsuga</i> Genus of conifers

Tsuga is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliage to that of the unrelated plant poison hemlock. Unlike the latter, Tsuga species are not poisonous.

<i>Taxus baccata</i> Species of conifer in the family Taxaceae

Taxus baccata is a species of evergreen tree in the family Taxaceae, native to Western Europe, Central Europe and Southern Europe, as well as Great Britain and Ireland, Northwest Africa, northern Iran, and Southwest Asia. It is the tree originally known as yew, though with other related trees becoming known, it may be referred to as the common yew, English yew, or European yew. It is primarily grown as an ornamental. Most parts of the plant are poisonous, with toxins that can be absorbed through inhalation, ingestion and through the skin; consumption of even a small amount of the foliage can result in death.

<i>Torreya</i> Genus of conifers

Torreya is a genus of conifers comprising six or seven species placed in the family Taxaceae, though sometimes formerly placed in Cephalotaxaceae. Four species are native to eastern Asia; the other two are native to North America. They are small to medium-sized evergreen trees reaching 5–20 m, rarely 25 m, tall. Common names include nutmeg yew.

Pseudotaxus chienii, the whiteberry yew, is a species of plant in the yew family, Taxaceae. It is the sole species in the genus Pseudotaxus, but closely related to the other yews in the genus Taxus. It is endemic to southern China, occurring in northern Guangdong, northern Guangxi, Hunan, Southwest Jiangxi and southern Zhejiang.

<i>Austrotaxus</i> Genus of conifers

Austrotaxus spicata, the New Caledonia yew or southern yew, is a species of yew, the sole species in the genus Austrotaxus. It is related to the other yews in the genera Taxus and Pseudotaxus.

<i>Taxus cuspidata</i> Species of plant

Taxus cuspidata, the Japanese yew or spreading yew, is a member of the genus Taxus, native to Japan, Korea, northeast China and the extreme southeast of Russia.

<i>Taxus brevifolia</i> Species of conifer

Taxus brevifolia, the Pacific yew or western yew, is a species of tree in the yew family Taxaceae native to the Pacific Northwest of North America. It is a small evergreen conifer, thriving in moisture and otherwise tending to take the form of a shrub.

<i>Taxus canadensis</i> Species of plant

Taxus canadensis, the Canada yew or Canadian yew, is a conifer native to central and eastern North America, thriving in swampy woods, ravines, riverbanks and on lake shores. Locally called simply "yew", this species is also referred to as American yew or ground-hemlock.

<i>Taxus wallichiana</i> Species of conifer

Taxus wallichiana, the Himalayan yew, is a species of yew, native to the Himalaya and parts of south-east Asia. The species has a variety of uses in traditional medicine. It is currently classified as endangered by the IUCN.

<i>Taxus chinensis</i> Species of conifer

Taxus chinensis is a species of yew. It is commonly called the Chinese yew, though this term also refers to Taxus celebica or Taxus sumatrana.

<i>Taxus floridana</i> Species of conifer

Taxus floridana, the Florida yew, is a species of yew, endemic to a small area of under 10 km² on the eastern side of the Apalachicola River in mesophytic forests of northern Florida at altitudes of 15–40 m. It is listed as critically endangered. It is protected in reserves at the Torreya State Park and at the Nature Conservancy's Apalachicola Bluffs and Ravines Preserve, and has legal protection under the United States and Florida Endangered Species laws.

<i>Taxus sumatrana</i> Species of conifer

Taxus sumatrana, or the Sumatran yew, is a large evergreen shrub and one of the eight species of yew. Its taxonomic namesake is indicative of the species being found in Indonesia ; however, T. sumatrana is also found in a number of South and Southeast Asian countries, including parts of Afghanistan, Bangladesh, Bhutan, China, India, Indochina, Nepal, Pakistan, the Philippines, Taiwan, and Tibet. Given this broad geographical range, it is also known as the Taiwan yew, the Chinese yew, as well as the East Himalayan yew. Plants of the World Online recognizes T. sumatrana as a synonym of Taxus wallichiana.

<i>Torreya grandis</i> Species of conifer

Torreya grandis (Chinese: 香榧 is a species of conifer in either the family Taxaceae, or Cephalotaxaceae. Originated in the Jurassic period, about 170 million years ago, it is known as a "living fossil". 榧/fěi in 香榧/xiāngfěi is the genus name, and 香/xiāng" means fragrant. T. grandis is a large tree that can attain height of 25 metres, and possibly as high as 39 metres. T. grandis is endemic to eastern and south-eastern China; it is found in the coastal provinces Fujian, Zhejiang, and Jiangsu, as well as in Anhui, Guizhou, Hunan, and Jiangxi inland. Its natural habitat are mountains and open valleys, often by streams, between 200–1,400 metres ASL. One common name is Chinese nutmeg yew, which refers to its edible seeds that superficially resemble nutmeg and its yew-like foliage.T. grandis is a precious tree species with multiple values. According to the survey data, its economic life is more than a thousand years.

<span class="mw-page-title-main">Yew</span> Index of plants with the same common name

Yew is a common name given to various species of trees.

<span class="mw-page-title-main">Taxine alkaloids</span> Chemical compound

Taxine alkaloids, which are often named under the collective title of taxines, are the toxic chemicals that can be isolated from the yew tree. The amount of taxine alkaloids depends on the species of yew, with Taxus baccata and Taxus cuspidata containing the most. The major taxine alkaloids are taxine A and taxine B although there are at least 10 different alkaloids. Until 1956, it was believed that all the taxine alkaloids were one single compound named taxine.

<i>Taxus mairei</i> Species of plant in the family Taxaceae

Taxus mairei, Maire's yew, is a species of conifer in the yew family Taxaceae, native to Nepal, Assam, central and southern China, Hainan, Taiwan and Vietnam. It is extensively harvested for its paclitaxel (taxol) content in China.

References

  1. 1 2 "Taxus L." Plants of the World Online. Royal Botanic Gardens, Kew. 2023. Retrieved 29 August 2023.
  2. 1 2 3 4 5 Earle, Christopher J. (19 May 2020). "Taxus (yew) description". The Gymnosperm Database. Retrieved 16 October 2021.
  3. ↑ Xu, Xiao-Hui; Sun, Bai-Nian; Yan, De-Fei; Wang, Jin; Dong, Chong (May 2015). "A Taxus leafy branch with attached ovules from the Lower Cretaceous of Inner Mongolia, North China". Cretaceous Research. 54: 266–282. doi:10.1016/j.cretres.2014.12.014. ISSN   0195-6671.
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  7. ↑ "Taxine". Online Etymology Dictionary. Etymonline.com. 2019. Retrieved January 18, 2019..
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  9. ↑ Dehk̲h̲udā: Lughat-Nāma. Entry تخش.
  10. ↑ "Caroli Linnaei ... Species plantarum". Botanicus.org. Retrieved 2016-11-17.
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  13. ↑ Kvaček, Z. 1984. Tertiary taxads of NW Bohemia. 1982 Acta Univ. Carol., Geol., Pokorny 4: 471–491.
  14. 1 2 Spjut, R. W. (2007). "Taxonomy and nomenclature of Taxus (Taxaceae). A phytogeographical analysis of Taxus (Taxaceae) based on leaf anatomical characters". J. Bot. Res. Inst. Texas. 1 (1): 291–332. 203–289. T. brevifolia and T. globosa var. floridana thought to evolve from ancestral T. globosa by loss of stomata and papillae; T. canadensis recognized in Europe based on leaf fossils from late Tertiary deposits
  15. ↑ Corneanu, G. C. , M. Corneanu and R. Bercu. 2004. Comparison between some morpho-anatomical features at fossil vegetal species and at their actual correspondent species. Studia Universitatis Babeş-Bolyai, Geologia, XLIX: 77–84.
  16. ↑ Manchester, S.R. (1994). "Fruits and Seeds of the Middle Eocene Nut Beds Flora, Clarno Formation, Oregon". Palaeontographica Americana. 58: 30–31.
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  18. ↑ "Overview of the genus Taxus, Taxonomy, Nomenclature, and Ovulate Shoots". Worldbotanical.com. Retrieved 2016-11-17.
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  20. ↑ Stull, Gregory W.; Qu, Xiao-Jian; Parins-Fukuchi, Caroline; Yang, Ying-Ying; Yang, Jun-Bo; Yang, Zhi-Yun; Hu, Yi; Ma, Hong; Soltis, Pamela S.; Soltis, Douglas E.; Li, De-Zhu; Smith, Stephen A.; Yi, Ting-Shuang (2021). "Gene duplications and phylogenomic conflict underlie major pulses of phenotypic evolution in gymnosperms". Nature Plants. 7 (8): 1015–1025. bioRxiv   10.1101/2021.03.13.435279 . doi:10.1038/s41477-021-00964-4. PMID   34282286. S2CID   232282918.
  21. 1 2 Ogren, Thomas (2015). The Allergy-Fighting Garden. Berkeley, CA: Ten Speed Press. p. 205. ISBN   978-1-60774-491-7.
  22. ↑ "Yews in Spain". www.iberianature.com. Retrieved 2 April 2018.
  23. ↑ Eichhorn, Markus (September 2010). "Yew – The Sacred Tree". Test Tube. Brady Haran for the University of Nottingham.
  24. ↑ "YEW TREES IN CHURCHYARDS". Sacred-texts.com. Retrieved 8 August 2011.
  25. ↑ David Sanderson (2014-07-08). "Bronze Age tree survives wars (and the builders) to be claimed as Britain's oldest". The Times . Retrieved 2016-11-17.
  26. ↑ Gersmann, Hanna; Aldred, Jessica (10 November 2011). "Medicinal tree used in chemotherapy drug faces extinction". The Guardian. Retrieved 2017-02-15.
  27. ↑ "Medical plants 'face extinction'". BBC News. 19 January 2008.
  28. ↑ "'Miracle' Cures Face Extinction". Botanic Gardens Conservation International. 16 January 2008.
  29. ↑ "Rare, Threatened and Endangered Species of Oregon. Institute for Natural Resources" (PDF). Portland State University, Portland, Oregon: Oregon Biodiversity Information Center. 2010. Archived from the original (PDF) on 2011-01-28.
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