Karaka (tree)

Karaka
illustrated by John Frederick Miller
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Magnoliids
(unranked):	Rosidae
Order:	Cucurbitales
Family:	Corynocarpaceae
Genus:	Corynocarpus
Species:	C. laevigatus
Binomial name
Corynocarpus laevigatus

Karaka (Corynocarpus laevigatus), is an evergreen laurifolia tree, of the family Corynocarpaceae, with large glossy leaves endemic to New Zealand, where it is widespread in mainly coastal situations, often forming a major component of coastal forest, although it is rarely a dominant tree. Sometimes Karaka occurs inland, usually the result of Māori plantings near former village sites.^[1]

Distribution

Karaka is widespread in mainly coastal situations. The tree is endemic to New Zealand, where the original distribution is unclear because of widespread planting by Maori and usually as the result of seed dispersal by birds or Maori plantations near old villages. The tree is common throughout the North and South Islands to Banks Peninsula (43°45′S) and Okarito (43°20′S), on the Three Kings Islands, on Raoul Island in the Kermadecs, and on the Chatham Islands. In the last two localities the presence of the tree is probably the result of Polynesian plantings. The ecological requirements of the species, are those of the laurel forest and like most of their counterparts laurifolia in the world, is a vigorous species with a great ability to populate the habitat that is conducive. Most botanists accept it as native only in the northern half of the North Island.^[2]

Description

The orange fruit, produced in summer, contain highly poisonous kernels.

Mature tree showing trunk and foliage.

Karaka is a leafy canopy tree with erect or spreading branches. It grows to heights of up to 15 metres and has a stout trunk up to 1 metre in diameter. The thick, leathery leaves are dark green above and paler beneath, 50 to 200mm wide and 30 to 70 mm wide. The leaves are glossy. In winter and spring (August to November) it produces stout, erect panicles of tiny flowers with petioles 10-15 mm long. The individual flowers are 4 to 5 mm in diameter, greenish-cream to off-white or pale yellow. The fruit is an ellipsoid to ovoid drupe 25 to 46 mm long, with pale yellow to orange flesh, and the seed is a single kernel. The fruit ripens in summer and autumn January to April and the seed dispersion is the result of scattering by columbiform birds mostly.

Ecology

Many botanical species are having similar foliage to the Lauraceae due to convergent evolution. Those plants are adapted to high rainfall and humidity. The patterns of speciation indicate that since the onset of aridification on the continents 15 million years ago, rainforest species diversified.^[3] One of the products of aridification is the isolation of populations and this likely caused the increase in the rate of speciation. This genus has species adapted to the laurel forest habitat, so common in the Corynocarpaceae. The morphology of sclerophyllous species is divergent from humid tropical climate species. The greatest diversity of species and a greater presence of the genus is given in Cloud forest and tropical rainforest in Asia and Southeast Asia.^[4][5]

Corynocarpaceae grows well in moist, well drained ground, and tolerate a variety of soil types, attained a maximun in tropical and wetter areas of distribution, but its pattern of speciation is resulting in some cases from the product of aridification of the habitat. Some endangered relict species are living in temperate areas and are distributed in tropical and subtropical lowland forests and montane rainforest. Corynocarpus laevigatus responded to favourable climatic periods and expanded across the available habitat adapting also to more extreme conditions but depending on favorable soil edaphic conditions. Corynocarpus laevigatus need an annual oscillation of the temperature moderated by the proximity of the ocean and resist bad frost.

A related vegetal community evolved millions of years ago on the supercontinent of Gondwana, and species of this community are now found on several separate areas of the Southern Hemisphere, including South America, Africa, New Zealand, Australia and New Caledonia. These lauroide leaves plant communities are twofold to tropical climate and temperate climate, having the more temperate climate their origin in the named Antarctic flora.^[6]

The toxicity of the fruit necessitates care when handling. This evergreen tree is a popular place for smaller birds to sleep in during the winter. It is of great value to birds and other fauna, including invertebrates that feed on their fruits and disperse their seeds. The fact to bear fruit in winter gives this plant a very important ecological value, being a good food source for many species, especially birds, at the station hard by the shortage of resources. These same fruits are considered toxic to mammalia. The seeds of Karaka also exhibit anitimicrobial activity against S. aureus and E.coli.

It has great ecological value because it is a rugged pioneer species that preserve and enriches the soil facilitating colonization by others. It is a ecological indicator of a well-preserved area, slightly degraded or recovering.

The pulp of the fruit is edible, although bitter, but the fresh kernels contain the lethal alkaloid poison karakin. Accounts from the 19th century record that extensive processing was used by Māori to convert the kernels to an edible form, and mention that if the processing was not done with the greatest care, poisoning would result with symptoms including violent convulsions and severe muscle spasms which could leave the limbs permanently fixed in contorted positions. Death resulted in a few cases.^[7]

Karaka may be easily grown from fresh seed, but cuttings are very difficult to strike. Young plants are frost-tender and sensitive to cold. The tree will often naturalise in suitable habitats. It is common in cultivation and widely available for sale both in New Zealand and in suitable climates elsewhere. It is regarded as a serious pest species in Hawaii for native ecosystems.

On Chatham Islands this tree (local name - kopi) has played distinguished role in the history of Moriori people: the soft bark of these trees has been used for making dendroglyphs. In late 1998 there were remaining 147 known kopi trees with dendroglyphs^[8].

References

• "Corynocarpus laevigatus". New Zealand Plant Conservation Network. http://www.nzpcn.org.nz/flora_details.asp?ID=1762. Retrieved 2010-10-02. 
• W. Skey (1871). "Preliminary Notes on the Isolation of the Bitter Substance of the Nut of the Karaka Tree (Corynocarpus lævigata)". Transactions and Proceedings of the Royal Society of New Zealand. Volume 4, 1871, pp. 316-321. http://rsnz.natlib.govt.nz/volume/rsnz_04/rsnz_04_00_002360.html. Retrieved 2007-09-10. 

Notes

1. ^ The common name Karaka comes from the Māori language, and has become the Māori term for the colour orange, from the colour of the fruit. An alternative name, which is little used is New Zealand Laurel. In the Chatham Islands, it is called ‘Kopi’, its name in the Moriori language.
2. ^ New Zealand Plant Conservation Network
3. ^ http://www.saber.ula.ve/bitstream/123456789/24186/1/articulo44_1_5.pdf
4. ^ http://www.mnhn.fr/publication/adanson/a03n1a8.pdf
5. ^ http://www.mobot.org/mobot/research/APweb/orders/studentone.html
6. ^ http://www.chileflora.com/Florachilena/FloraEnglish/HighResPages/EH0980.htm
7. ^ Skey 1871:318
8. ^ "Hapupu dendroglyphs". Wondermondo. http://www.wondermondo.com/Countries/Au/NZ/Chatham/Hapupu.htm.