Metrosideros

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Eudicots
Cladus: Core eudicots
Cladus: Rosids
Cladus: Eurosids II
Ordo: Myrtales

Familia: Myrtaceae
Subfamilia: Myrtoideae
Tribus: Metrosidereae
Genus: Metrosideros
Species: M. albiflora – M. angustifolia – M. arfakensis – M. bartlettii – M. boninensis – M. brevistylis – M. cacuminum – M. carminea – M. cherrieri – M. colensoi – M. collina – M. cordata – M. demonstrans – M. diffusa – M. dolichandra – M. elegans – M. engleriana – M. excelsa – M. fulgens – M. gregoryi – M. halconensis – M. humboldtiana – M. kermadecensis – M. laurifolia – M. longipetiolata – M. macropus – M. microphylla – M. nervulosa – M. nitida – M. ochrantha – M. operculata – M. oreomyrtus – M. ovata – M. paniensis – M. parallelinervis – M. parkinsonii – M. patens – M. perforata – M. polymorpha – M. porphyrea – M. punctata – M. ramiflora – M. regelii – M. robusta – M. rotundifolia – M. rugosa – M. salomonensis – M. sclerocarpa – M. stipularis – M. tetragyna – M. tetrasticha – M. tremuloides – M. umbellata – M. waialealae – M. whitakeri – M. whiteana – M. ×subtomentosa
Name

Metrosideros Banks ex Gaertn., Fruct. Sem. Pl. 1: 170. (1788) nom. cons.

Type species: Metrosideros collina (J.R.Forst. & G.Forst.) A.Gray, U.S. Expl. Exped., Phan. 1: 558 (1854) Designated as synonym Metrosideros spectabilis Sol. ex Gaertn., Fruct. Sem. Pl. 1: 172 (1788).

Synonyms

Heterotypic
Agalmanthus (Endl.) Hombr. & Jacquinot in J.S.C.Dumont d'Urville, Voy. Pôle Sud, Atlas: 78 (1845)
Tepualia Griseb., Abh. Königl. Ges. Wiss. Göttingen 6: 119 (1854)
Ballardia Montrouz., Mém. Acad. Imp. Sci. Lyon, Sect. Sci., sér. 2, 10: 204 (1860)
Mearnsia Merr., Philipp. J. Sci., C 2: 283 (1907)
Carpolepis (J.W.Dawson) J.W.Dawson, Bull. Mus. Natl. Hist. Nat., B, Adansonia 1984: 466 (1984 publ. 1985)
Microsideros Baum.-Bod., Syst. Fl. Neu-Caledonien 5: 77 (1989), without replaced synonym ref.

References

Banks, J. 1788. De Fructibus et Seminibus Plantarum: accedunt seminum centuriae quinque priores cum tabulis Aeneis LXXIX. Stutgardiae, Tubingae 1: 170 BHL
Govaerts, R. et al. 2016. Metrosideros in World Checklist of Selected Plant Families. The Board of Trustees of the Royal Botanic Gardens, Kew. Published online. Accessed: 2016 Apr. 2. Reference page.
International Plant Names Index. 2016. Metrosideros. Published online. Accessed: Apr. 2 2016.
Pillon, Y., Lucas, E., Johansen, J.B., Sakishima, T., Hall, B., Geib, S.M. & Stacy, E.A. 2015. An expanded Metrosideros (Myrtaceae) to include Carpolepis and Tepualia based on nuclear genes. Systematic Botany 40(3): 782–790. DOI: 10.1600/036364415X689249 Reference page.
Wright, S.D. et al. 2000: Riding the ice age El Niño? Pacific biogeography and evolution of Metrosideros subg. Metrosideros (Myrtaceae) inferred from nuclear ribosomal DNA. PNAS 97(8): 4118-4123. Full article (PDF) Reference page.
Oliver, W.R.B. 1928: The New Zealand species of Metrosideros with a note on Metrosideros collina (Forst.) Gray. Transactions of the New Zealand Institute 59: 419–423, plate 67. full text and PDF Reference page.
Wilcox, M.D. 2012. Auckland's remarkable urban forest. Auckland Botanical Society. 347 pp. ISBN 978-0-9583447-5-3 Reference page.

Metrosideros /ˌmɛtrəˈsɪdərəs, -troʊ-/[3] is a genus of approximately 60 trees, shrubs, and vines mostly found in the Pacific region in the family Myrtaceae. Most of the tree forms are small, but some are exceptionally large, the New Zealand species in particular. The name derives from the Ancient Greek metra or "heartwood" and sideron or "iron". Perhaps the best-known species are the pōhutukawa (M. excelsa), northern (M. robusta) and southern rātā (M. umbellata) of New Zealand, and ʻōhiʻa lehua (M. polymorpha), from the Hawaiian Islands.

Distribution

Metrosideros is one of the most widely spread flowering plant genera in the Pacific. New Caledonia has 21 species of Metrosideros, New Zealand has 12, New Guinea has seven and Hawaii has 5. The genus is present on most other high Pacific Islands, including Solomon Islands, Vanuatu, Fiji, Samoa, Cook islands, French Polynesia, Bonin Islands and Lord Howe Island, but absent from Micronesia . The genus is also represented by one species in the Philippines, one in South America (Chile and Argentina), and one outlier in South Africa. Metrosideros seeds are very lightweight and easily dispersed by wind. The seeds can also survive freezing temperatures, and up to 30 days submerged in salt water and still germinate.[4] which probably accounts for their wide distribution. They are often found as pioneer trees on lava flows and on mountain ridges.

Despite the clear propensity towards long-distance dispersal, this genus does not occur in mainland Australia.[5]
Fossil record
Further information: Metrosideros leunigii

For some time it had been hypothesised that Metrosideros evolved in New Zealand, and dispersed from there throughout the Pacific. This was due to the long fossil record of Metrosideros in New Zealand coupled with the absence of any Metrosideros fossils on other Gondwanan landmasses. The oldest conclusive fossil evidence of Metrosideros in New Zealand is fossil fruits from the Miocene aged Manuherikia sediments of Central Otago.[6] There is a fossil pollen record going back much further, but it has been shown that Metrosideros pollen is very similar morphologically to many other genera within the family Myrtaceae and as such, fossil pollen cannot be reliably used as an oldest record of the genus.[7]

The oldest conclusive record of Metrosideros are fossil fruits and flowers of Metrosideros leunigii, an extinct species, from Oligocene aged sediments in Tasmania, Australia. This is very curious considering that Metrosideros is one of the most widely spread plants in the Pacific, and is not present in Australia today. These fossils may also point towards an Australian origin for the genus.[8]
Cultivation

Metrosideros are often cultivated for their showy flowers, as street trees or in home gardens. The flowers are generally red, but some cultivars have orange, yellow or white flowers. Some names listed in horticultural catalogues and other publications, such as M. villosa and M. vitiensis, are actually the names of varieties or cultivars (usually of M. collina) rather than valid scientific species. The pōhutukawa of New Zealand has several cultivars grown in Australia, Hawaii and California and it has been planted successfully in the north of Spain[9] and on the Scilly Isles off the south-west coast of Britain,[10] but the species is considered an invasive pest in parts of South Africa and in the Azores.[11] Metrosideros kermadecensis is recently naturalised in Hawaii, and has the potential to become a pest. In turn, various cultivars of M. collina and M. polymorpha are widely grown in New Zealand under various names. Metrosideros umbellata occurs naturally south of mainland New Zealand in the Auckland Islands at 50° South latitude, and is the hardiest member of the genus, and a few cultivated specimens are growing in Scotland.
Metrosideros species

New Caledonia

Metrosideros brevistylis J.W. Dawson
Metrosideros cacuminum J.W. Dawson
Metrosideros cherrieri J.W. Dawson
Metrosideros dolichandra Schltr.
Metrosideros elegans (Montrouz.) Beauvis.
Metrosideros engleriana Schltr.
Metrosideros humboldtiana Guillaumin
Metrosideros laurifolia Brongn. & Gris
Metrosideros longipetiolata J.W.Dawson
Metrosideros microphylla (Schltr.) J.W.Dawson
Metrosideros nitida Brongn. & Gris
Metrosideros operculata Labill.
Metrosideros oreomyrtus Däniker
Metrosideros paniensis J.W.Dawson
Metrosideros patens J.W.Dawson
Metrosideros porphyrea Schltr.
Metrosideros punctata J.W.Dawson
Metrosideros rotundifolia J.W.Dawson
Metrosideros tardiflora (J.W.Dawson) Pillon
Metrosideros tetrasticha Guillaumin
Metrosideros whitakeri J.W.Dawson

South America

Metrosideros stipularis (Hook. & Arn.) Hook.f.

South Africa

Metrosideros angustifolia (L.) Sm.

New Zealand

Metrosideros albiflora Sol. ex Gartn. - Large white rātā
Metrosideros bartlettii J.W.Dawson - Bartlett's rātā
Metrosideros carminea W.R.B.Oliv. - Carmine rātā
Metrosideros colensoi Hook.f. - Colenso's rātā
Metrosideros diffusa (G.Forst.)Sm. - White rātā
Metrosideros excelsa Sol. ex Gaertn. - Pōhutukawa
Metrosideros fulgens Sol. ex Gaertn. - Scarlet rātā
Metrosideros kermadecensis W.R.B.Oliver - Kermadec pōhutukawa (Kermadec Islands)
Metrosideros parkinsonii Buchanan - Parkinson's rātā
Metrosideros perforata (J.R.Forst. & G.Forst.) Druce - Small white rātā
Metrosideros robusta A.Cunn. - Northern rātā
Metrosideros umbellata Cav. - Southern rātā

New Guinea

Metrosideros arfakensis Gibbs
Metrosideros cordata (C.T.White & W.D.Francis) J.W.Dawson
Metrosideros ovata (C.T.White) J.W.Dawson
Metrosideros parallelinervis C.T.White
Metrosideros ramiflora Lauterb.
Metrosideros regelii F.Muell.
Metrosideros whiteana J.W.Dawson

Philippines

Metrosideros halconensis (Merr.) J.W. Dawson

Hawaii

Metrosideros macropus Hook. & Arn. - Lehua mamo (Oʻahu)
Metrosideros polymorpha Gaudich. - ʻŌhiʻa lehua
Metrosideros rugosa A.Gray - Lehua papa (Oʻahu)
Metrosideros tremuloides (A.Heller) Rock- Lehua ʻāhihi (Oʻahu)
Metrosideros waialealae (Rock) Rock (Kauaʻi, Molokaʻi, and Maui)

French Polynesia, Pitcairn and the Cook Islands

Metrosideros collina (J.R.Forst. & G.Forst.) A.Gray

Fiji, Samoa and Vanuatu

Metrosideros gregoryi Christoph. (Samoa)
Metrosideros ochrantha A.C.Sm. (Fiji)
Metrosideros tabwemasanaensis Pillon (Vanuatu)
Metrosideros vitiensis (A.Gray) Pillon

Solomon Islands

Metrosideros salomonensis C.T.White
Metrosideros tetragyna J.W.Dawson

Lord Howe Island

Metrosideros nervulosa C.Moore & F. Muell. - Mountain rose
Metrosideros sclerocarpa J.W.Dawson

Ogasawara Islands

Metrosideros boninensis (Hayata ex Koidz.) Tuyama

References

"Metrosideros Banks ex Gaertn". Germplasm Resources Information Network. United States Department of Agriculture. 2009-01-27. Archived from the original on 2011-06-05. Retrieved 2009-03-27.
"World Checklist of Selected Plant Families".
Sunset Western Garden Book, 1995:606–607
Wright, S. D.; Yong, C. G.; Wichman, S. R.; Dawson, J. W.; Gardner, R. C. (2001). "Stepping stones to Hawaii: a trans-equatorial dispersal pathway for Metrosideros (Myrtaceae) inferred from nrDNA (ITS+ETS)". Journal of Biogeography 28 (6)
Tarran, Myall, Peter G. Wilson, and Robert S. Hill. "Oldest record of Metrosideros (Myrtaceae): Fossil flowers, fruits, and leaves from Australia." American Journal of Botany 103.4 (2016): 754-768.
Pole, Mike. "Early Miocene flora of the Manuherikia Group, New Zealand. 7. Myrtaceae, including Eucalyptus." Journal of the Royal Society of New Zealand 23.4 (1993): 313-328.
Tarran et al. 2016 Ibid.
Tarran et al. 2016 Ibid.
"New Zealand Plants Overseas". Archived from the original on 2009-02-19.
BBC: Christmas tree, Pohutukawa

Governo dos Açores: "Government invests in fight against invasive exotic species"

Simpson, P., 2005. Pōhutukawa & Rātā: New Zealand's Iron-Hearted Trees. Te Papa Press. 346 pp.
Wagner, W.L., D. R. Herbst, and S.H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. Revised edition. University of Hawaiʻi Press and Bishop Museum Press, Honolulu. 1919 pp.
Wright, S. D.; Yong, C. G.; Wichman, S. R.; Dawson, J. W.; Gardner, R. C. (2001). "Stepping stones to Hawaii: a trans-equatorial dispersal pathway for Metrosideros (Myrtaceae) inferred from nrDNA (ITS+ETS)". Journal of Biogeography. 28 (6): 769–774. doi:10.1046/j.1365-2699.2001.00605.x.
Wright, S. D.; Gray, R. D.; Gardner, R. C. (2003). "Energy and the rate of evolution: inferences from plant rDNA substitution rates in the Western Pacific". Evolution. 57 (12): 2893–2898. doi:10.1111/j.0014-3820.2003.tb01529.x. PMID 14761066. S2CID 29596868.
Wright, S.D.; C. G. Yong; J. W. Dawson; D. J. Whittaker; R. C. Gardner (2000-03-21). "Riding the ice age El Niño? Pacific biogeography and evolution of Metrosideros subg. Metrosideros (Myrtaceae) inferred from nuclear ribosomal DNA" (PDF). PNAS. Retrieved 2007-06-13.