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Taxus brevifolia

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Taxus brevifolia,thePacific yeworwestern yew,is aspeciesof tree in the yewfamilyTaxaceaenative to thePacific NorthwestofNorth America.It is a smallevergreenconifer,thriving in moisture and otherwise tending to take the form of ashrub.

Taxus brevifolia
Taxus brevifolia(Pacific yew) foliage and fruit
Scientific classificationEdit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Pinophyta
Class: Pinopsida
Order: Cupressales
Family: Taxaceae
Genus: Taxus
Species:
T. brevifolia
Binomial name
Taxus brevifolia
Natural range
Synonyms[2][3]
  • Taxus baccatasubsp.brevifolia(Nutt.) Pilg.
  • Taxus baccatavar.brevifolia(Nutt.) Koehne
  • Taxus baccatavar.canadensisBenth.
  • Taxus boursieriCarrière
  • Taxus brevifoliavar.polychaetaSpjut
  • Taxus brevifoliasubsp.polychaeta(Spjut) Silba
  • Taxus brevifoliavar.reptanetaSpjut
  • Taxus brevifoliasubsp.reptaneta(Spjut) Silba
  • Taxus lindleyanaA. Murray bis
  • Taxus occidentalisNutt.

Description

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A smallevergreenconifer(sometimes appearing as ashrub),[4]the Pacific yew grows to 10–15 metres (33–49 feet) tall and with a trunk up to 50 centimetres (20 inches) in diameter, rarely more. In some instances, trees with heights in excess of 20 m (66 ft) occur in parks and other protected areas, quite often in gullies. The tree is extremely slow growing, and has a habit of rotting from the inside, creating hollow forms. This makes it difficult and sometimes impossible to make accuratering countsto determine a specimen's true age. Often damaged bysuccessionof the forest, it usually ends up in a squat, multiple-leader form, able to grow new sprouts from decapitated stumps.[4]In its shrub form, sometimes called "yew brush", it can reproduce vegetatively vialayering.[4]

It has thin, scalybark,red then purplish-brown,[4]covering a thin layer of off-white sap wood with a darkerheartwoodthat varies in color from brown to a purplish hue to deep red, or even bright orange when freshly cut.[4]Theleavesare lanceolate, flat, dark green,1–3 cm (3⁄8–1+3⁄16in) long[4]and2–3 millimetres (3⁄32–1⁄8in) 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 except on erect leading shoots where the spiral arrangement is more obvious.

Theseed conesare highly modified, each cone containing a singleseed4–7 mm (3⁄16–1⁄4in) long partly surrounded by a modified scale which develops into a soft, bright redberry-like structure called anaril,[4]8–15 mm (5⁄16–9⁄16in) long and wide and open at the end. The arils are mature 6–9 months after pollination. The seeds contained in the arils are eaten bythrushesand otherbirds,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. The male cones are globose,3–6 mm (1⁄8–1⁄4in) diameter, and shed theirpollenin early spring. It is mostlydioecious,but occasional individuals can be variablymonoecious,or change sex with time.[citation needed]

Taxonomy

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Varieties

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Taxus brevifoliavar.reptaneta

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T. brevifoliavar.reptaneta(thicket yew) is a shrub variety that generally occurs in the mid to upper elevation range of the typical variety, 1,000–1,220 m (3,280–4,000 ft) at its southernmost occurrence in theKlamath Mountainsregion, and at lower elevations further north.[5]It is distinguished from young trees of the typical variety (var.brevifolia) by its stems initially creeping along the ground for a short distance before ascending (curving) upwards and by the branches growing off to one side of the stem, usually the upper side.[6]The epithetreptanetais from the Latinreptanswhich means "creeping, prostrate, and rooting",[7]which is exactly what this variety does; in rooting it forms yew thickets; hence, the epithetreptaneta(-etummeans "collective place of growth" ) and hence the common name, thicket yew.

Unlike the typical variety, thicket yew grows in abundance on open sunny avalanche shoots or ravines as well as in the forest understory. It also occurs along forest margins. In northwestern Montana, a variant of the thicket yew does not ascend upwards; rather, it remains along the ground.[5]This is probably the ancestral form; the upright form with branches along the upper side would be the expected growth pattern that might evolve from one with stems that strictly creep along the ground since branches can only arise from the upper surface.

T. brevifoliavar.reptanetahas been described as synonymous with typical yew (var.brevifolia). Though the two varieties may be genetically distinct, some botanists only use this taxon to describe different geographical ranges. For example,T. maireivar.speciosa,which occurs with the typical variety in southern China in 10 of 13 provinces, was rejected for the lack of a "geographic reason" for recognition[8]though it appears genetically distinct.[9]T. brevifoliavar.reptanetahas also been proposed to be elevated to asubspecies,despite that rank being used to define geographically separated groups ofT. baccata.[10][a]

Taxus brevifoliavar.polychaeta

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TypicalT. brevifolia,like most species in the genus, usually produces a single ovule on a complex scaly shoot, composed of a primary shoot and a secondary short shoot. To the casual observer they appear as one funnelform shoot with an ovule at the apex.[12]T. brevifoliavar.polychaetadiffers from var.brevifoliain producing a relatively longer primary shoot[5]with as many five secondary shoots.[13]The epithet,polychaeta,is in reference to the primary shoot resembling apolychaeteworm; hence, its common name 'worm cone yew'. Varietypolychaetaappears to be relatively rare. It may have beenextirpatedfrom the type locality—aroundMud BaynearOlympia, Washington—as a result of urban expansion. It is also known from Northern Idaho andSonoma County, California.[5][14]

As in the case with thicket yew, worm yew has been indicated to be the same as the typical variety, but again there are no specific studies to support this conclusion. The authority of thicket yew and worm cone yew has been involved in the study ofTaxusfor 25 years at the time the varieties were described.[5][15]

Similar species

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Yew foliage is very similar to that ofSequoia sempervirens,the coastal redwood.[4]

Distribution and habitat

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Pacific yew isnativeto thePacific Northwest.It ranges from southernmostAlaskasouth toNorthern California,mostly in thePacific Coast Ranges,but with isolateddisjunctpopulations in southeastBritish Columbiaand inNorthern Idaho.[16][17][18][19][20][21]It grows in varying types of environments; however, in drier environments it is mostly limited to stream-side habitats, whereas in moist environments it will grow up onto slopes and ridgetops,[16]at least as high in altitude as 1,400 metres (4,600 ft) above sea level.[4]Pacific yew isshade tolerant,but can also grow in sun.[22]The tree's shade tolerance allows it to form anunderstory,which means that it can grow along streams providing shade to maintain water temperature.[23]

Ecology

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Birds eat the fruit cups and spread the seeds.[24]Moose feed on the tree in winter in forests of theRocky Mountains.[4]

Toxicity

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Many parts of yews are poisonous and can be fatal if eaten, including the seed which should not even be chewed.[24]

Uses

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Traditionally, the resilient and rot-resistant wood was used byNative Americansto make tools, bows (backed with sinew), arrows, and canoe paddles.[4]Other purposes for yew included making harpoons, fishhooks, wedges,clubs,spoons, drums, snowshoes, and arrowheads.[4]The foliage and bark was used for medicinal purposes.[4]Members of thePit River Tribewould sell this plant to theUkiah.[25]TheConcow tribecalls the treeyōl’-kō(Konkow language).[26]

Modern-daylongbowmakers report that a very small percentage of yew trees are of a grain suitable for their craft.[4]TheJapanesehave used the wood for decorative purposes,[16]and the Taiwanese have valued it as well.[4]

The juicy red cup around the seed seems to be edible (but not the toxic seed within),[24]with a cherry jello-like taste.[4]

Thechemotherapydrugpaclitaxel(taxol), used inbreast,ovarian,andlung cancertreatment, can be derived fromTaxus brevifoliaand other species of yew. As it was already becoming scarce when its chemotherapeutic potential was realized around the 1990s, the Pacific yew was never commercially harvested from its habitat at a large scale; the widespread use of the paclitaxel was enabled circa 2003 when a semi-synthetic pathway was developed from extracts of cultivated yews of other species.[4]

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  • Pacific yew foliage underside
  • Pacific yew form
  • Pacific yew foliage
  • Pacific yew mat form
  • Pacific yew bark
  • Color variations of bark on Pacific yew

Notes

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  1. ^Further, one recommendation strongly discourages taxonomists from "elevating a 'variety' to a 'subspecies' unless there is sufficient scientific evidence to warrant such an elevation," and that "it is crucial to provide continuity."[11]

References

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  1. ^Thomas, P. (2013)."Taxus brevifolia".IUCN Red List of Threatened Species.2013:e.T34041A2841142.doi:10.2305/IUCN.UK.2013-1.RLTS.T34041A2841142.en.Retrieved13 November2021.
  2. ^Tropicos
  3. ^The Plant List
  4. ^abcdefghijklmnopqArno, Stephen F.; Hammerly, Ramona P. (2020) [1977].Northwest Trees: Identifying & Understanding the Region's Native Trees(field guide ed.). Seattle:Mountaineers Books.pp. 181–186.ISBN978-1-68051-329-5.OCLC1141235469.
  5. ^abcdeSpjut, R. W. 2007. Taxonomy and nomenclature ofTaxus.J. Bot. Res. Inst. Texas 1(1): 203–289.
  6. ^Web page, World Botanical Associates,Taxus brevifoliavar.reptaneta;http://www.worldbotanical.com/taxus_brevifolia_var_reptaneta.htm.Retrieved 9 Dec 2014
  7. ^Stearn, W. T. 1983. Botanical Latin. 3rd ed. David & Charles, London
  8. ^Möller M, Gao L-M, Mill RR, Liu J, Zhang D-Q, Poudel RC, Li D-Z, 2013. A multidisciplinary approach reveals hidden taxonomic diversity in the morphologically challengingTaxus wallichianacomplex. Taxon 62: 1161–1177.
  9. ^Gao L-M, Möller M, Zhang X-M, Hollingsworth ML, Liu J, Mill RR, Gibby M, Li D-Z, 2007. High variation and strong phylogeographic pattern among cpDNA haplotypes inTaxus wallichiana(Taxaceae) in China and North Vietnam. Molec. Ecol. 16: 4684–4698.
  10. ^Pilger R, 1903. Taxaceae-Taxoideae—Taxeae.Taxus.In: Das Pflanzenreich IV (Engler A. ed.): 110–116.
  11. ^Ellison AM, Davis CC, Calie PJ, Naczi RFC, 2014. Pitcher plants (Sarracenia) provide a 21st-century perspective on infraspecific ranks and interspecific hybrids: A modest proposal for appropriate recognition and usage. Syst. Bot. 39: 939–949.
  12. ^Florin R, 1951. Evolution in cordaites and conifers. Acta Horti Berg. 16: 285–388, plate
  13. ^Web page, World Botanical Associates, Overview of the genusTaxus,http://www.worldbotanical.com/TAXNA.HTM,retrieved 9 Dec 2014
  14. ^Web page, World Botanical Associates,Taxus brevifoliavar.polychaeta;http://www.worldbotanical.com/taxus_brevifolia_var_polychaeta.htm;retrieved 9 Dec 2014
  15. ^Spjut, R. W. 1977. USDA, ARS Memorandum, July 14].Taxus brevifolia(Taxaceae) reviewed by GMC (Gudrun M. Christensen). A review of literature on taxonomy, ecology, and geographical distribution of the species, including its description, summary of geographical distribution by state or province, and literature reviewed. Distributed periodically during 1981-1992 by the National Cancer Institute to prospective suppliers, without reference to the author, for solicitations of contract bids on up to 30 tons of bark.
  16. ^abc Bolsinger, Charles; Jaramillo, Annabelle (1990). Russell M Burns; Barbara H. Honkala (eds.)."Taxus brevifolia Nutt. - Pacific Yew".Silvics of North America(Agriculture Handbook #654). 1 - Conifers.USDA,USFS:573–579.RetrievedApril 26,2018.
  17. ^Hitchcock, C. H., A.J. Cronquist, F. M. Ownbey & J. W. Thompson. 1969. Vascular Cryptogams, Gymnosperms, and Monocotyledons. 1: 1–914. In C. L. Hitchcock Vascular Plants of the Pacific Northwest. University of Washington Press, Seattle.
  18. ^Hultén, E. 1968. Flora Alaska i–xxi, 1–1008. Stanford University Press, Stanford.
  19. ^Moss, E. H. 1983. Flora of Alberta (ed. 2) i–xii, 1–687. University of Toronto Press, Toronto.
  20. ^Munz, P. A. & D. D. Keck. 1959. California Flora 1–1681. University of California Press, Berkeley.
  21. ^Welsh, S. L. 1974. Anderson's Flora of Alaska and Adjacent Parts of Canada i–xvi, 1–724. Brigham Young University Press, Provo.
  22. ^Mitchell, A. (1998)."Acclimation of Pacific yew (Taxus brevifolia) foliage to sun and shade".Tree Physiology.18(11): 749–757.doi:10.1093/treephys/18.11.749.PMID12651409.
  23. ^Scher, Stanley; Schwarzschild, Bert (1989)."Pacific Yew: a Faculative Riparian Conifer with an Uncertain Future"(PDF).
  24. ^abcWhitney, Stephen (1985).Western Forests (The Audubon Society Nature Guides).New York: Knopf. p.364.ISBN0-394-73127-1.
  25. ^Chestnut, V. K. 1902 Plants Used by the Indians of Mendocino County, California. Contributions from the U.S. National Herbarium 7:295-408. (p. 305)
  26. ^Chesnut, Victor King(1902).Plants used by the Indians of Mendocino County, California.Government Printing Office.p. 408.Retrieved24 August2012.

Further reading

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