''Metrosideros'' is a genus of approximately 60

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

s, and

vine A vine is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas, or runners. The word ''vine'' can also refer to such stems or runners themselves, for instance, when used in wicker work.Jackson; Benjamin; Da ...

s in the family

Myrtaceae Myrtaceae (), the myrtle family, is a family of dicotyledonous plants placed within the order Myrtales. Myrtle, pōhutukawa, bay rum tree, clove, guava, acca (feijoa), allspice, and eucalyptus are some notable members of this group. All ...

, mostly found in the Pacific region. 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 Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

''metra'' or "

heartwood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

" and ''sideron'' or "iron". Perhaps the best-known species are the

pōhutukawa Pōhutukawa (''Metrosideros excelsa''), also known as the New Zealand Christmas tree, or iron tree, is a coastal evergreen tree in the Myrtus, myrtle family, Myrtaceae, that produces a brilliant display of red (or occasionally orange, yellow o ...

(''M. excelsa''),

northern rātā Northern may refer to the following: Geography * North, a point in direction * Northern Europe, the northern part or region of Europe * Northern Highland, a region of Wisconsin, United States * Northern Province, Sri Lanka * Northern Range, a ra ...

(''M. robusta'') and southern rātā (''M. umbellata'') of New Zealand, and '' ōhia lehua'' (''M. polymorpha'') from the

Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

Distribution

''Metrosideros'' is one of the most widely spread flowering plant genera in the Pacific.

New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...

has 21 species,

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

has 12,

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

has seven and

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

has 5. The genus is present on most other high

Pacific Islands The Pacific islands are a group of islands in the Pacific Ocean. They are further categorized into three major island groups: Melanesia, Micronesia, and Polynesia. Depending on the context, the term ''Pacific Islands'' may refer to one of several ...

, including

Solomon Islands Solomon Islands, also known simply as the Solomons,John Prados, ''Islands of Destiny'', Dutton Caliber, 2012, p,20 and passim is an island country consisting of six major islands and over 1000 smaller islands in Melanesia, part of Oceania, t ...

Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (; ), is an island country in Melanesia located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of northern Australia, northeast of New Caledonia, east o ...

Fiji Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about ...

Samoa Samoa, officially the Independent State of Samoa and known until 1997 as Western Samoa, is an island country in Polynesia, part of Oceania, in the South Pacific Ocean. It consists of two main islands (Savai'i and Upolu), two smaller, inhabited ...

Cook Islands The Cook Islands is an island country in Polynesia, part of Oceania in the South Pacific Ocean. It consists of 15 islands whose total land area is approximately . The Cook Islands' Exclusive Economic Zone (EEZ) covers of ocean. Avarua is its ...

French Polynesia French Polynesia ( ; ; ) is an overseas collectivity of France and its sole #Governance, overseas country. It comprises 121 geographically dispersed islands and atolls stretching over more than in the Pacific Ocean, South Pacific Ocean. The t ...

Bonin Islands The Bonin Islands, also known as the , is a list of islands of Japan, Japanese archipelago of over 30 subtropical and Island#Tropical islands, tropical islands located around SSE of Tokyo and northwest of Guam. The group as a whole has a total ...

and

Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland Port ...

, but absent from

Micronesia Micronesia (, ) is a subregion of Oceania, consisting of approximately 2,000 small islands in the Northwestern Pacific Ocean. It has a close shared cultural history with three other island regions: Maritime Southeast Asia to the west, Poly ...

. The genus is also represented by one species in the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

, one in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

(Chile and Argentina), and one outlier in

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

. ''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, 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, the genus does not occur in mainland Australia.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.

Fossil record

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 Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia, Zealandia, Arabia, and the ...

landmasses. The oldest conclusive fossil evidence of ''Metrosideros'' in New Zealand is fossil fruits from the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

aged Manuherikia sediments of

Central Otago Central Otago is an area located in the inland part of the Otago region in the South Island of New Zealand. The motto for the area is "A World of Difference". The area is dominated by mountain ranges and the upper reaches of the Clutha River ...

. 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

and as such, fossil pollen cannot be reliably used as the oldest record of the genus. The oldest conclusive record of ''Metrosideros'' are fossil fruits and flowers of '' Metrosideros leunigii'', an extinct species, from

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

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.

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

of New Zealand has several cultivars grown in Australia, Hawaii and

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. It has been planted successfully in the north of

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

and on the

Scilly Isles The Isles of Scilly ( ; ) are a small archipelago off the southwestern tip of Cornwall, England. One of the islands, St Agnes, is over farther south than the most southerly point of the British mainland at Lizard Point, and has the souther ...

off the south-west coast of

Britain Britain most often refers to: * Great Britain, a large island comprising the countries of England, Scotland and Wales * The United Kingdom of Great Britain and Northern Ireland, a sovereign state in Europe comprising Great Britain and the north-eas ...

, but the species is considered an invasive pest in parts of South Africa and in the

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

.Governo dos Açores: "Government invests in fight against invasive exotic species"
/ref> ''

Metrosideros kermadecensis ''Metrosideros kermadecensis'', with common names ''Kermadec pōhutukawa'' and New Zealand Christmas bush is an evergreen tree of the myrtle family which is endemic to the volcanic Kermadec Islands about north-east of New Zealand. The tree p ...

'' 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 ''Metrosideros umbellata'', the southern rātā, is a tree endemic to New Zealand. It grows up to or more tall with a trunk up to or more in diameter. It produces masses of red flowers in summer. Unlike its relative, northern rātā, this sp ...

'' occurs naturally south of mainland New Zealand in the

Auckland Islands The Auckland Islands ( Māori: ''Motu Maha'' "Many islands" or ''Maungahuka'' "Snowy mountains") are an archipelago of New Zealand, lying south of the South Island. The main Auckland Island, occupying , is surrounded by smaller Adams Island ...

at 50° South latitude, and is the hardiest member of the genus, and a few cultivated specimens are growing in

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

''Metrosideros'' species

Metrosideros stipularis ''Metrosideros stipularis'' is a species of the myrtle family commonly known as tepú, trepú, or tepual. It is an evergreen tree or shrub that can attain a height of about seven metres. The plant is native to southern South America in the sou ...

'' South Africa * '' Metrosideros angustifolia'' ;New Zealand * '' Metrosideros albiflora'' - Large white rātā * '' Metrosideros bartlettii'' - Bartlett's rātā * '' Metrosideros carminea'' - Carmine rātā * '' Metrosideros colensoi'' - Colenso's rātā * '' Metrosideros diffusa'' - White rātā * ''

Metrosideros excelsa ''Metrosideros'' is a genus of approximately 60 trees, shrubs, and vines in the family Myrtaceae, mostly found in the Pacific region. Most of the tree forms are small, but some are exceptionally large, the New Zealand species in particular. The ...

'' - Pōhutukawa * '' Metrosideros fulgens'' - Scarlet rātā * ''

'' - Kermadec pōhutukawa (Kermadec Islands) * '' Metrosideros parkinsonii'' - Parkinson's rātā * '' Metrosideros perforata'' - Small white rātā * ''

Metrosideros robusta ''Metrosideros robusta'', commonly known as the northern rātā, is a forest tree endemic to New Zealand. It grows up to or taller, and usually begins its life as a hemiepiphyte high in the branches of a mature forest tree; over centuries th ...

'' - Northern rātā * ''

'' - Southern rātā New Guinea * '' Metrosideros arfakensis'' * '' Metrosideros cordata'' * '' Metrosideros ovata'' * '' Metrosideros parallelinervis'' * '' Metrosideros ramiflora'' * '' Metrosideros regelii'' * '' Metrosideros whiteana'' Philippines * '' Metrosideros halconensis'' ;Hawaii * ''

Metrosideros macropus ''Metrosideros macropus'',commonly known as the ''lehua mamo'' or ohi'a'', is a species of tree in the eucalyptus family, Myrtaceae. It is endemic to the island of Oahu in the Hawaiian Islands. It is closely related to the widespread and highly ...

'' - ''Lehua mamo'' (Oahu) * ''

Metrosideros polymorpha ''Metrosideros polymorpha'', the ''ōhia lehua'',; is a species of flowering evergreen tree in the Myrtus, myrtle family, Myrtaceae, that is Endemism, endemic to the six largest Hawaiian Islands, islands of Hawaii, Hawaii. It is a member of the ...

'' - ''Ōhia lehua'' * ''

Metrosideros rugosa ''Metrosideros rugosa'', commonly known as the ''lehua papa'', is a tree of the myrtle family which is endemic to the island of Oahu in the Hawaiian Islands. It is closely related to the widespread and highly variable ōhia lehua (''Metrosider ...

'' - ''Lehua papa'' (Oahu) * ''

Metrosideros tremuloides ''Metrosideros'' is a genus of approximately 60 trees, shrubs, and vines in the family Myrtaceae, mostly found in the Pacific region. Most of the tree forms are small, but some are exceptionally large, the New Zealand species in particular. The ...

'' - ''Lehua āhihi'' (Oahu) * '' Metrosideros waialealae'' (Kauai, Molokai, and Maui) French Polynesia, Pitcairn and the Cook Islands * ''

Metrosideros collina ''Metrosideros collina'' is a species of flowering plant in the family Myrtaceae. It is a tree or shrub native to French Polynesia, the Cook Islands, and the Pitcairn Islands. Taxonomy The species was first formally described by botanist Johann ...

'' Fiji, Samoa and Vanuatu * '' Metrosideros gregoryi'' (Samoa) * '' Metrosideros ochrantha'' (Fiji) * '' Metrosideros tabwemasanaensis'' (Vanuatu) * '' Metrosideros vitiensis'' Solomon Islands * '' Metrosideros salomonensis'' * '' Metrosideros tetragyna'' Lord Howe Island * '' Metrosideros nervulosa'' - Mountain rose * '' Metrosideros sclerocarpa'' Ogasawara Islands * '' Metrosideros boninensis''

References

External links