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{{Short description|Species of tree endemic to New Zealand}}
{{Taxobox
{{italic title}}
| name = Bartlett's rātā
{{good article}}
| image = MBartettii877.jpg
{{Use New Zealand English|date=July 2024}}
| image_width = 220px
{{Use dmy dates|date=December 2024}}
| image_caption = Bartlett's rātā
{{Speciesbox
| status = EN
|name = Bartlett's rātā
| regnum = [[Plant]]ae
|image = Metrosideros bartlettii 1754747.jpg
| divisio = [[Flowering plant|Magnoliophyta]]
|image_caption = ''M. bartlettii'' (centre) observed by botanist [[Peter de Lange (botanist)|Peter de Lange]] in 2011
| classis = [[Magnoliopsida]]
|image_alt = A New Zealand native forest with Bartlett's rātā (Metrosideros bartlettii_ in the centre of an image.
| ordo = [[Myrtales]]
|status = CR
| familia = [[Myrtaceae]]
|status_system = IUCN3.1
| genus = ''[[Metrosideros]]''
|status_ref = {{Sfn|De Lange|2014}}
| species = '''''M. bartlettii'''''
| binomial = '' Metrosideros bartlettii''
|genus = Metrosideros
|species = bartlettii
| binomial_authority = [[J.W.Dawson]]
|authority = [[J.W.Dawson]]
}}
}}

'''Bartlett's rātā''' (''Metrosideros bartlettii''), or the '''Cape Reinga white rātā''', is one of twelve ''[[Metrosideros]]'' species endemic to [[New Zealand]] and is notable for its extreme rarity and its white flowers, somewhat uncommon in that genus of red-flowered trees and plants. Its natural range is in the far north of the [[North Island]] at Te Paki, in three patches of dense native forest near [[Spirits Bay]] that escaped destruction by fire, namely Radar Bush, Kohuronaki Bush, and Unuwhao Bush. Only 34 adult trees are known to exist in the wild. The lack of fossil evidence elsewhere suggests that the tree may always have been restricted to the North Cape area, which was an island until it was connected to the mainland by the sandspit that constitutes [[Ninety Mile Beach, New Zealand|Ninety Mile Beach]].
'''''Metrosideros bartlettii''''', commonly known as the '''Bartlett's rātā''', is a tree [[endemism|endemic]] to only a few parts of the [[Northland Region]] in New Zealand's [[North Island]]. It is one of twelve ''[[Metrosideros]]'' species in the family [[Myrtaceae]]. The Bartlett's rātā was first discovered in 1975 by New Zealand botanist and schoolteacher, [[John Bartlett (botanist)|John Bartlett]]. There are three known patches of dense native forest near [[Piwhane / Spirits Bay]] that contain Bartlett's rātā: Radar Bush, Kohuronaki Bush, and Unuwhao Bush. Bartlett's rātā has a high chance of becoming [[extinct]] unless immediate [[Conservation biology|conservation]] measures are taken, due to its ongoing decline. {{as of|2018}}, only 13 adult trees are known to exist in the wild. Bartlett's rātā is common in cultivation, with it being found in several private and botanic gardens throughout New Zealand. Its current conservation status was assessed by the [[IUCN Red List]] in 2013 as "Critically Endangered" and its population trend was assessed as "Decreasing".


==Description==
==Description==
{{Stack|float=right|
[[Image:MetroBartlettiiFoliage.jpg|thumb|left|220px|The leaves of Bartlett's rātā taper to a point at the tip]]''Metrosideros bartlettii'' was discovered by John Bartlett, a schoolteacher from [[Auckland]], in 1975. He found an unusual tree growing in Radar Bush, 9.5 km south-east of Cape Reinga. Almost ten years passed before the flowers were collected, making possible a scientific description of the tree. Bartlett's rātā grows to a height of up to thirty [[metre]]s, usually beginning life as a hemi-epiphyte on taraire (''[[Beilschmiedia tarairi]]''), pūriri (''[[Vitex lucens]]''), rewarewa (''[[Knightia excelsa]]'') or tree ferns (''[[Cyathea]]'' spp.). Occasionally, the tree is found growing on the ground on rock outcrops and rocky cliffs. The tree bears white flowers made up of a mass of [[stamen]]s in November or December. Seed ripens in March or April. The trunk is up to 1.5 m in diameter. Apart from the colour of the flowers, Bartlett's rātā resembles northern rātā (''[[Metrosideros robusta]]'') but can be distinguished by the small white flowers and by the leaves, which taper to a point at the tip, while those of northern rātā are notched at the tip. Also distinctive is the white or whitish-grey bark that peels easily into soft flakes, which it is thought may offer resistance to fire damage. This may have been a key factor in the tree's precarious survival in an area prone to forest fire.
[[File:Bartlett's rata MRD Otari.jpg|thumb|left|210px|Leafage of Bartlett's rātā (''M. bartlettii'') in [[Ōtari-Wilton's Bush]]|alt=Bright green leafage of Bartlett's rātā (Metrosideros bartlettii), in Ōtari-Wilton's Bush]]
}}
''Metrosideros bartlettii'' (Bartlett's rātā) is a rare tree in the family [[Myrtaceae]] and it is [[endemic]] to the [[Northland Region]] of the [[North Island]] of New Zealand. It grows to a height of up to {{convert|25–30|m|abbr=on}} with a trunk up to {{convert|1–1.5|m|abbr=on}} in diameter. Its [[twig]]s are often coloured dark red. Its [[Bark (botany)|bark]] is "papery" and pale grey to whitish in colour. The leaves are [[wikt:chartaceous|chartaceous]] to [[wikt:coriaceous|coriaceous]] in character, glossy, palish-green in colour with [[Lamina (leaf)|lamina]] being 30–50 × 15–26 mm long. There are 3–4 pairs of cymules (very small flowers) on an [[inflorescence]] (flower spike) with densely spreading white hairs.{{Sfn|Dawson|1985|p=1}}{{Sfn|Wassilieff|2007}}

Flowering generally occurs from October to November. It produces white coloured [[Pedicel (botany)|pedicel]]s of up to 3 x 1, 2.5–3 mm high, 2–2.5 mm wide, and spreading 1–1.5 x 1–1.5 mm.{{Sfn|Dawson|1985|p=1}}{{Sfn|Bercusson|Torrence|1998|p=67}}{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|p=3}} Fruiting occurs from March to April, producing a [[hypanthium]] fruit being 2.0–2.5 × 2.5–3.0 mm long, with persistent, deflexed [[sepal]]s and 1.5–2.5 mm-long capsules. The pale orange-yellow seeds are 2.3–3.0 mm long and narrowly elliptic to narrowly oval-shaped.{{Sfn|De Lange|2024}}

Compared to other species in the genus ''[[Metrosideros]]'', flowering of the Barlett's rātā is unpredictable, making it unlikely the small wild population can regenerate without human assistance.{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|p=3}}

==Taxonomy==

It was first [[Discovery (observation)|discovered]] in 1975 by New Zealander [[John Bartlett (botanist)|John Bartlett]], a schoolteacher and botanist from [[Hamilton, New Zealand|Hamilton]].{{Sfn|Galloway|Edgar|1987|p=2}}{{Sfn|Wassilieff|2007}} Bartlett discovered the tree in Radar Bush, {{convert|9.5|km|abbr=on}} south-east from [[Cape Reinga]].{{sfn|Drummond|Keeling|Richardson|Gardner|2000|p=1}}{{Sfn|Bercusson|Torrence|1998|p=67}} It was discovered while Bartlett was searching for [[liverworts]] in the Northland Region of New Zealand, where he found a specimen growing at the base of a large tree. Bartlett realised it was a new species of rātā, but was unable to reach any branches, so he instead took fragments of the bark to the [[Victoria University of Wellington]]. Botanist [[John Dawson (botanist)|John Dawson]] incorrectly thought the find was [[northern rātā]] (''M. robusta''). Bartlett later returned to the area and was able to collect a branch, which he brought back to [[Wellington]].{{Sfn|Judd|2000}} Bartlett's rātā is closely related to northern rātā;{{Sfn|De Lange|2024}} its leaves are of similar size and share characteristics to [[southern rātā]] (''M. umbelata'') and northern rātā. Bartlett's rātā's flowers and flowers are significantly diffrent and smaller than those of northern rātā. ''M. oreomyrtus'', endemic to [[New Caledonia]], is the only other tree in the genus ''Metrosideros'' with white-coloured flowers.{{Sfn|Dawson|1985|p=3}}

===Etymology===
The [[etymology]] of Bartlett's rātā's genus, ''Metrosideros'', translates to English to 'iron heart'. ''Metrosideros'' derives from the [[Greek language]]; the word {{lang|el|metra}} means 'core' or 'heart', and {{lang|el|sideron}} means 'iron'.{{Sfn|De Lange|2024}}{{sfn|Bylsma|Clarkson|Efford|2014|p=4}} The scientific name, ''bartlettii'', is the [[Latinisation of names|Latinisation]] after the tree's discoverer John Bartlett.{{Sfn|Dawson|1985|p=1}} Bartlett's rātā is also commonly known as rātā moehau.{{Sfn|De Lange|2024}}

<gallery mode="packed" widths="210" heights="200">
File:Metrosideros bartlettii kz2.jpg|Close up of Bartlett's rātā's white-coloured flowers|alt=An image of Bartlett's rātā's blooming white-coloured flowers
File:Metrosideros bartlettii bark.jpg|"Papery" bark of Bartlett's rātā|alt=The "Papery" grey to whitish coloured bark of Bartlett's rātā
File:Metrosideros bartlettii.jpg|Recently formed [[bud]]s of the tree|alt=Recently formed buds of Bartlett's rātā
</gallery>

==Ecology==
Bartlett's ratā is often observed to be utilised by birds and insects (such as [[bee]]s and [[flies]]), which may help spread pollen from other ''Metrosideros'' species.{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|p=8}}{{Sfn|Lehnebach|Van der Walt|2018|p=3}} New Zealand species of ''Metrosideros'' are pollinated by nectar-feeding birds, such as the [[tūī]] (''Prosthemadera novaeseelandiae'') which are known to forage over distances of {{convert|15|km|abbr=on}}.{{sfn|Drummond|Keeling|Richardson|Gardner|2000|p=8}} Wind and rain may cause self-pollination but the likelihood of producing viable seeds is low or non-existent. A 2022 study by the ''[[Pacific Conservation Biology]]'' revealed [[cross-pollination]] is the only method that produces viable Barlett's rātā seeds that can be utilised in other augmented wild populations.{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|p=8}}{{sfn|Van der Walt|Alderton-Moss|Lehnebach|2022|p=2}}

A 2021 study by the ''[[New Zealand Journal of Botany]]'' conducted scientific analyses of Bartlett's rātā at [[Ōtari-Wilton's Bush]] (in Wellington). The study confirmed the [[self-incompatibility]] of Bartlett's rātā; individuals depend on pollen from unrelated individuals to fruit. Recent and historical genetic research has confirmed [[Hybrid (biology)|hybridisation]] and [[introgression]] are possible between closely related species in the genus ''Metrosideros''. The average [[germination]] of the seeds from hand pollination in this study was low, which is consistent with other species in the family [[Myrtaceae]], such as [[pōhutukawa]] (''Metrosideros excelsa'') and [[mānuka]] (''Leptospermum scoparium'').{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|p=14}}

The liveworts; ''[[Frullania wairua]]'' and ''Siphonolejeunea raharaha-nehemiae'', are two endemic liverwort species (both at risk of extinction) are supported by the Bartlett's rātā.{{Sfn|De Lange|2024}}

==Distribution==

Bartlett's rātā is endemic to New Zealand's North Island to the Northland Region. It is only known to be located in Te Paki, in three patches of forest remnants near [[Piwhane / Spirits Bay]]; these being Kohuronaki Bush, Radar Bush, and Unuwhao Bush.{{Sfn|De Lange|2024}}{{sfn|Drummond|Keeling|Richardson|Gardner|2000|p=8}} It is usually found growing near bodies of water (such as streams) and in swamplands.{{Sfn|Dawson|1985|p=2}} An article from ''[[Molecular Ecology (journal)|Molecular Ecology]]'', published in 2000, documented 31 adult trees.{{sfn|Drummond|Keeling|Richardson|Gardner|2000|p=1}} A 2018 study by the ''New Zealand Journal of Botany'' has since documented only 13 adult trees,{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|pp=2–3}}{{Sfn|Lehnebach|Van der Walt|2018|pp=2–3}} and most of these trees are located on private land.{{Sfn|Stowell|2017}} Bartlett's rātā was likely never a common tree. A number of surveys conducted in the 1990s revealed individuals were only present in three populations.{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|p=1}}


==Conservation==
==Conservation==
[[File:Common Brushtail Possum - Flickr - GregTheBusker (1).jpg|210px|thumb|right|Bartlett's rātā historical decline is largely due to land use changes following settlement, and the introduction of [[common brushtail possums|brushtail possums]].|alt=An image of a common bush tail possum. Bartlett's rātā's decline is largely due to their introduction into New Zealand.]]
[[Image:MetroBarlettiiInsect.jpg|thumb|left|220px|The cast-off shell of a Cicada rests on the papery bark of a Bartlett's rātā]]Although in the plant is in cultivation, the majority of cultivated plants come from one tree. Only 34 adult Bartlett's rātā are known to exist in the wild, and most of these are growing on privately-owned land. Many of the specimens are isolated from other trees with the result that there is minimal transfer of pollen and few seeds are set. Analyses of the DNA have shown that there is very little genetic variation. The species is also vulnerable to browsing animals, and at risk of destruction by fire or by changes in the land management practices of the landowners.
Its current conservation status was assessed by the [[IUCN Red List]] in 2013 as "Critically Endangered" and its population trend was assessed as "Decreasing".{{Sfn|De Lange|2014}} The historical decline of Bartlett's rātā is largely due to land use changes following settlement, and the introduction of [[Common brushtail possum in New Zealand|brushtail possums]] (an invasive species in New Zealand).{{sfn|Van der Walt|Alderton-Moss|Lehnebach|2022|p=2}}{{sfn|Pattabiraman|Morgan-Richards|Powlesland|Trewick|2022|p=3}} Although Bartlett's rātā is uncommon in the wild, it is common in cultivation, with it being found in several private and botanic gardens throughout the country (such as Ōtari-Wilton's Bush).{{sfn|Nadarajan|van der Walt|Lehnebach|Saeiahagh|2021|pp=2–3}}{{Sfn|Lehnebach|Van der Walt|2018}}


Bartlett's rātā [[Habitat destruction|habitat disturbance]] began with the arrival of the [[Polynesians|Polynesian]] settlers. Many forests were later cleared when the European ([[Pākehā]]) settlers arrived later, starting in the early 1800s. Its habitat retreated into the steeper valleys, especially those under intense fire shadows. It was not until the late 1960s that the far north's native forest area began to decline. Although the forests in Northland are gradually recovering, the population of Bartlett's rātā remains low and widely scattered.{{sfn|Drummond|Keeling|Richardson|Gardner|2000|p=8}}
==Cultivation==

Bartlett's rātā grows readily from fresh seed, and prefers sunny sites with fertile, well drained soil. It can also be propagated from hardwood cuttings, although these may be very slow to take root. Plants in cultivation in New Zealand are relatively hardy in a range of conditions, and have shown tolerance of mild frosts, which are unknown in the natural habitat.
Bartlett's rātā has a high chance of becoming [[extinct]] unless immediate [[Conservation biology|conservation]] measures are taken, due to its ongoing decline, small population size, and reproductive failure. Bartlett's rātā breeding strategy favours cross-pollination, and has little [[inbreeding]]. Bartlett's rātā under cultivation has low levels of genetic variety, which might restrict its ability to contribute to its overall conservation.{{sfn|Van der Walt|Alderton-Moss|Lehnebach|2022|p=9}}


==See also==
==See also==
{{Portal|New Zealand}}
*[[Metrosideros robusta|Northern rātā]]
*[[List of trees native to New Zealand]]
*[[Metrosideros umbellata|Southern rātā]]

*[[Metrosideros fulgens|Scarlet rātā vine]]
==References==
===Citations===
{{Reflist}}

===Works cited===
'''Journals'''
{{Refbegin}}
* {{cite journal |doi=10.1080/0028825X.1985.10434231 |title=''Metrosideros bartlettii'' (Myrtaceae) a new species from North Cape, New Zealand |url=https://www.tandfonline.com/doi/abs/10.1080/0028825X.1985.10434231 |doi-access=free |year=1985 |last1=Dawson |first1=J. W. |journal=[[New Zealand Journal of Botany]] |volume=23 |issue=4 |pages=607–610 }}
* {{cite journal |doi=10.1046/j.1365-294x.2000.00989.x|title=Genetic analysis and conservation of 31 surviving individuals of a rare New Zealand tree, ''Metrosideros bartlettii'' (Myrtaceae)|year=2000|last1=Drummond|first1=R. S. M.|last2=Keeling|first2=D. J.|last3=Richardson|first3=T. E.|last4=Gardner|first4=R. C.|last5=Wright|first5=S. D.|journal=[[Molecular Ecology (journal)|Molecular Ecology]]|volume=9|issue=8|pages=1149–1157|pmid=10964234|s2cid=20499423|doi-access=free}}
* {{cite journal |last=Van der Walt |first=Karin |last2=Alderton-Moss |first2=Jennifer |last3=Lehnebach |first3=Carlos A. |title=Cross-pollination and pollen storage to assist conservation of ''Metrosideros bartlettii'' (Myrtaceae), a critically endangered tree from Aotearoa New Zealand |journal=[[Pacific Conservation Biology]] |volume=29 |issue=2 |date=1 March 2022 |issn=1038-2097 |doi=10.1071/PC21054 |doi-access=free |pages=141–152 |url=https://www.publish.csiro.au/pc/pdf/PC21054 |access-date=17 December 2024}}
* {{cite journal |last1=Galloway |first1=D. J. |last2=Edgar |first2=Elizabeth |title=Obituaries |journal=[[New Zealand Journal of Botany]] |volume=25 |issue=1 |year=1987 |pages=173–178 |url=https://www.tandfonline.com/doi/pdf/10.1080/0028825X.1987.10409963| access-date=25 December 2024|doi=10.1080/0028825X.1987.10409963 |doi-access=free}}
* {{cite journal |last=Nadarajan |first=Jayanthi |last2=van der Walt |first2=Karin |last3=Lehnebach |first3=Carlos A. |last4=Saeiahagh |first4=Hassan |last5=Pathirana |first5=Ranjith |title=Integrated ''ex situ'' conservation strategies for endangered New Zealand Myrtaceae species |journal=[[New Zealand Journal of Botany]] |volume=59 |issue=1 |date=2 January 2021 |issn=0028-825X |doi=10.1080/0028825X.2020.1754245 |url=https://www.tandfonline.com/doi/full/10.1080/0028825X.2020.1754245 |url-access=subscription |pages=72–89}}
* {{cite journal |last=Pattabiraman |first=Nimeshika |last2=Morgan-Richards |first2=Mary |last3=Powlesland |first3=Ralph |last4=Trewick |first4=Steven A. |title=Unrestricted gene flow between two subspecies of translocated brushtail possums (''Trichosurus vulpecula'') in Aotearoa New Zealand |journal=[[Biological Invasions (journal)|Biological Invasions]] |volume=24 |issue=1 |date=2022 |issn=1387-3547 |doi=10.1007/s10530-021-02635-z |doi-access=free |pages=247–260 |url=https://link.springer.com/content/pdf/10.1007/s10530-021-02635-z.pdf |access-date=17 December 2024}}
* {{cite journal |last=Bylsma |first=Rj |last2=Clarkson |first2=Bd |last3=Efford |first3=Jt |title=Biological flora of New Zealand 14: ''Metrosideros excelsa'', pōhutukawa, New Zealand Christmas tree |url=https://www.tandfonline.com/doi/full/10.1080/0028825X.2014.926278 |journal=[[New Zealand Journal of Botany]] |volume=52 |issue=3 |date=3 July 2014 |issn=0028-825X |doi=10.1080/0028825X.2014.926278 |doi-access=free |pages=365–385}}
* {{Cite journal |title=About the birds and the bees and the flowers of Bartlett's rātā; pollination studies to assist conservation of a threatened—nationally critical species. |journal=Trilpedia |url=https://www.nzpcn.org.nz/site/assets/files/0/51/296/trilepidea-172-180331.pdf |archive-url=https://web.archive.org/web/20220618180236/https://www.nzpcn.org.nz/site/assets/files/0/51/296/trilepidea-172-180331.pdf |archive-date=18 June 2022 |url-status=live |last=Lehnebach |first=C. A. |volume=172 |pages=2–3 |last2=Van der Walt |first2=K. |year=2018 |via=[[New Zealand Plant Conservation Network]]}}
{{Refend}}
'''Miscellaneous'''
{{Refbegin|30em}}
* {{cite web|url= https://dx.doi.org/10.2305/IUCN.UK.2014-2.RLTS.T34295A62743272.en |doi=10.2305/IUCN.UK.2014-2.RLTS.T34295A62743272.en |archive-url=https://web.archive.org/web/20240120102557/https://www.iucnredlist.org/species/34295/62743272 |doi-access=free |archive-date=20 January 2024 |url-status=live |last=De Lange|first=Peter|date=2014|website=[[IUCN Red List]] |title=Bartlett's Rata, ''Metrosideros bartlettii'' |access-date=17 December 2024}}
* {{Cite web |title=''Metrosideros bartlettii'' |url=https://www.nzpcn.org.nz/flora/species/metrosideros-bartlettii/ |archive-url=https://web.archive.org/web/20241203002702/https://www.nzpcn.org.nz/flora/species/metrosideros-bartlettii/ |archive-date=3 December 2024 |url-status=live |last=De Lange |first=Peter |access-date=2024-12-17 |website=[[New Zealand Plant Conservation Network]] |year=2024}}
* {{Cite news |title=Rata: an export success |last=Judd |first=Warren |url=https://www.nzgeo.com/stories/rata-an-export-success/ |archive-url=https://web.archive.org/web/20240303070426/https://www.nzgeo.com/stories/rata-an-export-success/ |url-access=limited |archive-date=3 March 2024 |url-status=live|access-date=2024-12-17 |work=[[New Zealand Geographic]] |year=2000 |issue=47}}
* {{Cite book |title=Pohutukawa: tree of Aotearoa |last=Bercusson |first=Linda |publisher=[[Tandem Press]] |year=1998 |isbn=9781877178351 |location=Auckland, New Zealand |url=https://archive.org/details/pohutukawatreeof0000berc |last2=Torrence |first2=Jacinda |via=the [[Internet Archive]]}}
* {{Cite encyclopedia |title=Tall broadleaf trees — Tree rātā |encyclopedia=[[Te Ara: The Encyclopedia of New Zealand]] |last=Wassilieff |first=Maggy |url=http://www.TeAra.govt.nz/en/tall-broadleaf-trees/page-2 |archive-url=https://teara.govt.nz/en/tall-broadleaf-trees/page-2 |archive-date=22 June 2024 |url-status=live |access-date=18 December 2024 |date=24 September 2007}}
* {{Cite news |title=Rare tree flowers at Virginia Lake |last=Stowell |first=Laurel |date=2017-11-25 |url=https://www.nzherald.co.nz/whanganui-chronicle/news/rare-tree-flowers-at-virginia-lake/SPJYXCTX6W46KT2YVYXP2LNTZU/ |archive-url=https://web.archive.org/web/20241218021400/https://www.nzherald.co.nz/whanganui-chronicle/news/rare-tree-flowers-at-virginia-lake/SPJYXCTX6W46KT2YVYXP2LNTZU/#expand |archive-date=18 December 2024 |url-status=live|access-date=2024-12-18 |work=[[New Zealand Herald]]}}
{{Refend}}


==External links==
==External links==
* {{commons category-inline}}
* [https://www.projectcrimson.org.nz Project Crimson]
{{New Zealand Metrosideros Species}}


{{Taxonbar|from=Q5473535}}
== References ==
* {{cite web |title=Bartlett, J.W., 1985. ''Metrosideros bartlettii'' (Myrtaceae) a new species from North Cape, New Zealand. |work=New Zealand Journal of Botany, 1985, Vol. 23: 607-610|url=http://www.rsnz.org/publish/nzjb/1985/56.pdf|accessdate=2007-06-13 }}
* {{cite web |title=''Metrosideros bartlettii''|work=New Zealand Plant Conservation Network |url= http://www.nzpcn.org.nz/vascular_plants/detail.asp?PlantID=26|accessdate=2007-06-06 }}
* Simpson, P., 2005. ''Pōhutukawa & Rātā: New Zealand's Iron-Hearted Trees''. Wellington: Te Papa Press.


{{Commons|Metrosideros bartlettii}}
[[Category:Metrosideros|bartlettii]]
[[Category:Metrosideros]]
[[Category:Endemic flora of New Zealand]]
[[Category:Myrtaceae]]
[[Category:Myrtales]]
[[Category:Trees of New Zealand]]
[[Category:Trees of New Zealand]]
[[Category:Garden plants of New Zealand]]
{{Tree-stub}}
[[Category:Ornamental trees]]

[[Category:Endangered flora of New Zealand]]
[[es:Metrosideros bartlettii]]
[[Category:Taxa named by John Dawson (botanist)]]

Latest revision as of 13:46, 28 December 2024

Bartlett's rātā
A New Zealand native forest with Bartlett's rātā (Metrosideros bartlettii_ in the centre of an image.
M. bartlettii (centre) observed by botanist Peter de Lange in 2011
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Myrtales
Family: Myrtaceae
Genus: Metrosideros
Species:
M. bartlettii
Binomial name
Metrosideros bartlettii

Metrosideros bartlettii, commonly known as the Bartlett's rātā, is a tree endemic to only a few parts of the Northland Region in New Zealand's North Island. It is one of twelve Metrosideros species in the family Myrtaceae. The Bartlett's rātā was first discovered in 1975 by New Zealand botanist and schoolteacher, John Bartlett. There are three known patches of dense native forest near Piwhane / Spirits Bay that contain Bartlett's rātā: Radar Bush, Kohuronaki Bush, and Unuwhao Bush. Bartlett's rātā has a high chance of becoming extinct unless immediate conservation measures are taken, due to its ongoing decline. As of 2018, only 13 adult trees are known to exist in the wild. Bartlett's rātā is common in cultivation, with it being found in several private and botanic gardens throughout New Zealand. Its current conservation status was assessed by the IUCN Red List in 2013 as "Critically Endangered" and its population trend was assessed as "Decreasing".

Description

[edit]
Bright green leafage of Bartlett's rātā (Metrosideros bartlettii), in Ōtari-Wilton's Bush
Leafage of Bartlett's rātā (M. bartlettii) in Ōtari-Wilton's Bush

Metrosideros bartlettii (Bartlett's rātā) is a rare tree in the family Myrtaceae and it is endemic to the Northland Region of the North Island of New Zealand. It grows to a height of up to 25–30 m (82–98 ft) with a trunk up to 1–1.5 m (3 ft 3 in – 4 ft 11 in) in diameter. Its twigs are often coloured dark red. Its bark is "papery" and pale grey to whitish in colour. The leaves are chartaceous to coriaceous in character, glossy, palish-green in colour with lamina being 30–50 × 15–26 mm long. There are 3–4 pairs of cymules (very small flowers) on an inflorescence (flower spike) with densely spreading white hairs.[2][3]

Flowering generally occurs from October to November. It produces white coloured pedicels of up to 3 x 1, 2.5–3 mm high, 2–2.5 mm wide, and spreading 1–1.5 x 1–1.5 mm.[2][4][5] Fruiting occurs from March to April, producing a hypanthium fruit being 2.0–2.5 × 2.5–3.0 mm long, with persistent, deflexed sepals and 1.5–2.5 mm-long capsules. The pale orange-yellow seeds are 2.3–3.0 mm long and narrowly elliptic to narrowly oval-shaped.[6]

Compared to other species in the genus Metrosideros, flowering of the Barlett's rātā is unpredictable, making it unlikely the small wild population can regenerate without human assistance.[5]

Taxonomy

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It was first discovered in 1975 by New Zealander John Bartlett, a schoolteacher and botanist from Hamilton.[7][3] Bartlett discovered the tree in Radar Bush, 9.5 km (5.9 mi) south-east from Cape Reinga.[8][4] It was discovered while Bartlett was searching for liverworts in the Northland Region of New Zealand, where he found a specimen growing at the base of a large tree. Bartlett realised it was a new species of rātā, but was unable to reach any branches, so he instead took fragments of the bark to the Victoria University of Wellington. Botanist John Dawson incorrectly thought the find was northern rātā (M. robusta). Bartlett later returned to the area and was able to collect a branch, which he brought back to Wellington.[9] Bartlett's rātā is closely related to northern rātā;[6] its leaves are of similar size and share characteristics to southern rātā (M. umbelata) and northern rātā. Bartlett's rātā's flowers and flowers are significantly diffrent and smaller than those of northern rātā. M. oreomyrtus, endemic to New Caledonia, is the only other tree in the genus Metrosideros with white-coloured flowers.[10]

Etymology

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The etymology of Bartlett's rātā's genus, Metrosideros, translates to English to 'iron heart'. Metrosideros derives from the Greek language; the word metra means 'core' or 'heart', and sideron means 'iron'.[6][11] The scientific name, bartlettii, is the Latinisation after the tree's discoverer John Bartlett.[2] Bartlett's rātā is also commonly known as rātā moehau.[6]

  • An image of Bartlett's rātā's blooming white-coloured flowers
    Close up of Bartlett's rātā's white-coloured flowers
  • The "Papery" grey to whitish coloured bark of Bartlett's rātā
    "Papery" bark of Bartlett's rātā
  • Recently formed buds of Bartlett's rātā
    Recently formed buds of the tree

Ecology

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Bartlett's ratā is often observed to be utilised by birds and insects (such as bees and flies), which may help spread pollen from other Metrosideros species.[12][13] New Zealand species of Metrosideros are pollinated by nectar-feeding birds, such as the tūī (Prosthemadera novaeseelandiae) which are known to forage over distances of 15 km (9.3 mi).[14] Wind and rain may cause self-pollination but the likelihood of producing viable seeds is low or non-existent. A 2022 study by the Pacific Conservation Biology revealed cross-pollination is the only method that produces viable Barlett's rātā seeds that can be utilised in other augmented wild populations.[12][15]

A 2021 study by the New Zealand Journal of Botany conducted scientific analyses of Bartlett's rātā at Ōtari-Wilton's Bush (in Wellington). The study confirmed the self-incompatibility of Bartlett's rātā; individuals depend on pollen from unrelated individuals to fruit. Recent and historical genetic research has confirmed hybridisation and introgression are possible between closely related species in the genus Metrosideros. The average germination of the seeds from hand pollination in this study was low, which is consistent with other species in the family Myrtaceae, such as pōhutukawa (Metrosideros excelsa) and mānuka (Leptospermum scoparium).[16]

The liveworts; Frullania wairua and Siphonolejeunea raharaha-nehemiae, are two endemic liverwort species (both at risk of extinction) are supported by the Bartlett's rātā.[6]

Distribution

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Bartlett's rātā is endemic to New Zealand's North Island to the Northland Region. It is only known to be located in Te Paki, in three patches of forest remnants near Piwhane / Spirits Bay; these being Kohuronaki Bush, Radar Bush, and Unuwhao Bush.[6][14] It is usually found growing near bodies of water (such as streams) and in swamplands.[17] An article from Molecular Ecology, published in 2000, documented 31 adult trees.[8] A 2018 study by the New Zealand Journal of Botany has since documented only 13 adult trees,[18][19] and most of these trees are located on private land.[20] Bartlett's rātā was likely never a common tree. A number of surveys conducted in the 1990s revealed individuals were only present in three populations.[21]

Conservation

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An image of a common bush tail possum. Bartlett's rātā's decline is largely due to their introduction into New Zealand.
Bartlett's rātā historical decline is largely due to land use changes following settlement, and the introduction of brushtail possums.

Its current conservation status was assessed by the IUCN Red List in 2013 as "Critically Endangered" and its population trend was assessed as "Decreasing".[1] The historical decline of Bartlett's rātā is largely due to land use changes following settlement, and the introduction of brushtail possums (an invasive species in New Zealand).[15][22] Although Bartlett's rātā is uncommon in the wild, it is common in cultivation, with it being found in several private and botanic gardens throughout the country (such as Ōtari-Wilton's Bush).[18][23]

Bartlett's rātā habitat disturbance began with the arrival of the Polynesian settlers. Many forests were later cleared when the European (Pākehā) settlers arrived later, starting in the early 1800s. Its habitat retreated into the steeper valleys, especially those under intense fire shadows. It was not until the late 1960s that the far north's native forest area began to decline. Although the forests in Northland are gradually recovering, the population of Bartlett's rātā remains low and widely scattered.[14]

Bartlett's rātā has a high chance of becoming extinct unless immediate conservation measures are taken, due to its ongoing decline, small population size, and reproductive failure. Bartlett's rātā breeding strategy favours cross-pollination, and has little inbreeding. Bartlett's rātā under cultivation has low levels of genetic variety, which might restrict its ability to contribute to its overall conservation.[24]

See also

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References

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Citations

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  1. ^ a b De Lange 2014.
  2. ^ a b c Dawson 1985, p. 1.
  3. ^ a b Wassilieff 2007.
  4. ^ a b Bercusson & Torrence 1998, p. 67.
  5. ^ a b Nadarajan et al. 2021, p. 3.
  6. ^ a b c d e f De Lange 2024.
  7. ^ Galloway & Edgar 1987, p. 2.
  8. ^ a b Drummond et al. 2000, p. 1.
  9. ^ Judd 2000.
  10. ^ Dawson 1985, p. 3.
  11. ^ Bylsma, Clarkson & Efford 2014, p. 4.
  12. ^ a b Nadarajan et al. 2021, p. 8.
  13. ^ Lehnebach & Van der Walt 2018, p. 3.
  14. ^ a b c Drummond et al. 2000, p. 8.
  15. ^ a b Van der Walt, Alderton-Moss & Lehnebach 2022, p. 2.
  16. ^ Nadarajan et al. 2021, p. 14.
  17. ^ Dawson 1985, p. 2.
  18. ^ a b Nadarajan et al. 2021, pp. 2–3.
  19. ^ Lehnebach & Van der Walt 2018, pp. 2–3.
  20. ^ Stowell 2017.
  21. ^ Nadarajan et al. 2021, p. 1.
  22. ^ Pattabiraman et al. 2022, p. 3.
  23. ^ Lehnebach & Van der Walt 2018.
  24. ^ Van der Walt, Alderton-Moss & Lehnebach 2022, p. 9.

Works cited

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Journals

Miscellaneous

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