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The great journey of coconut

Cocos nucifera L., the coconut tree, is one of the most emblematic palm trees from tropical countries: photographed by tourists on bucolic beaches; basis element for the gastronomy and culture in many countries and a source of inspiration to many artists, is still a mystery for scientists. Where is coconut from originally? The answer to this question is now a little more clear thanks to a phylogeographic study, discipline that integrates population genetics with biogeography. In this post, we reveal this and other questions about this iconic palm.

COCONUT TREE CHARACTERISTICS

Coconut tree belongs to Arecaceae, the family of monocots with tree aspect, known as palm trees. Yes, you read right! All palm trees are closer to grasses (cereals) than to deciduous trees. In fact, its trunk is not a real one because it has no tissues allowing them to growth in diameter and therefore not branches. If you look closely to any palm tree trunk, you’ll see that it always has the same thickness, it only grows vertically. It’s the stipe and it is formed by the superposition of the leaves base and the scarfs we see on the trunk are the marks left by the falling leaves petioles. If you ever see a cut stipe, you’ll see that it doesn’t have the typical structure in growth rings but fiber mass. In fact, this structure is optimal to survive to tropical winds because it is both tough and flexible, providing flexibility necessary not to break while tropical winds and also stand firm.

Public Domain Pictures_estípit
Palm tree stipe (Source: Public Domain Pictures).

The function of the stipe is to support the weight of the leaves, flowers and fruits; that grow on top. The Arecaceae leaves are pinnate. The flowers grows in racemous inflorescences and fruits usually are drupe type, such as date or coconut.

In the Mediterranean region we only have two species of native palms. Mediterranean dwarf palm (Chamaerops humilis) has its northern limit at the Garraf coast. The Cretan palm (Phoenix theophrastii) is endemic to southern Greece, Turkey and Crete.

Wikimedia_margalló
Mediterranean dwarf palm (Chamaerops humilis) at Catalonian coast (Source: Wikimedia).

COCONUT TREE USES

Arecaceae contains approximately 2600 species classified in about 202 genera. The coconut palm is monotypic because it is the only species in the Cocos genus. It is found in 89 tropical countries and is considered the tree of life because it provides resources such as:

– Food: Coconut is a highly nutritious fruit, rich in fat (is the most caloric fruit consumed by humans), micronutrients (it is very rich in potassium) and fiber. From dried endosperm (the white “meat” or copra, which is actually the seed) we can also extract milk and coconut oil, widely used for cooking, cosmetics and even as biofuel. The sweet sap of the inflorescence is also consumed as wine after its alcoholic fermentation.

Wikipedia cocos
Dried coconut to elaborate copra (Source: Peter Davis / AusAID).

–     Water : green coconut contains drinking water rich in micronutrients. It is consumed in many tropical countries as an isotonic drink.

– Construction Material: mesocarp fiber is widely used to make ropes, mats, planting substrate, etc. Endocarp, the layer that covers the meat is used as a container for food and drink, decoration or as a musical instrument. The leaves are also used to produce handicraft (rugs, toys, baskets, etc.), to cover roofs and as carbon. The wood has traditionally been used for houses construction.

– Religious Element: Coconut is part of different spiritual manifestations in Hinduism and some Philippines communities.

estructura coco eng
Coconut inner parts schema.

OCEANIC DISPERSAL

Coconut is adapted to hydrochory, ie dispersal by water. Coconut is one of the little fruits known to have been adapted to oceanic dispersal. The water contained by the coconut enables its floatation and facilitates its dispersal over long distances. In addition, the fruit is resistant to salinity and does not rot. When it gets the beaches, it can germinate after having sailed 110 days (or 4000 km). However, its pantropical distribution is not only due to its oceanic dispersal but is also linked to its cultivation by humans. Human migration to Southeast Asia would not have been possible without the coconut cultivation and coconut should not have been so widely dispersed if not for its value.

It is therefore quite likely that the wide variety of coconut uses has conditioned its migration history. There are several hypotheses about coconut origin. De Candolle, at 1886, proposed that the coconut was American, based on the distribution of all other members of the Cocoseae tribe (200 species distributed in 20 genera from America), except for the African palm oil (Elaeis guineensis, the source of  palm oil). Other hypotheses (Beccari, 1963) claim of an Asian origin because morphological variation in the region is greater, popular names and uses are more diverse on this continent and in addition there is an Asian endemic hermit crab (Brigues latro) that can only live in symbiosis with coconut. So from Asia and with human help, coconut palm tree would have migrated eastwards to the Pacific ocean and westwards to the Indian Ocean.

Coconut_distribution-1024x636
Coconut tree distribution (Source: Gunn et al., 2011).

COCONUT TREE ORIGIN

Recent studies using DNA as a source of information have made new discoveries about coconut origin. It seems that despite the wide variety of cultivars and human manipulation, coconut palm tree populations have a strong structure into two genetic groups, one in the Indian Ocean (including Indian and African populations), and the other in the Pacific ocean (including Southeast Asian, Caribbean and South American populations). Thus, all current coconut populations come from one of these two groups, demonstrating its Asian origin. For example, Brazilian and Caribbean populations come from the Indian group and the American Pacific coast populations come from Southeast Asia.

Gun et al image
Coconut tree genetic groups discovered by Gunn et al. (2011).

Therefore, it seems that the coconut tree is native to both Pacific and Indian coasts and that coconut cultivation arose independently in these two regions.

REFERENCES

  • Beccari, O. 1963. The origin and dispersal of Cocos nucifera. Principes 7: 57–69.
  • de Candolle, A. 1886. Origin of cultivated plants. New York: Hafner. 468 p.
  • Cook, O.F. 1911. History of the Coconut Palm in America. American Journal of Sciences 31(183): 221-226.
  • Gunn, B.F. 2004. The phylogeny of the Cocoeae (Arecaceae) with emphasis on Cocos nucifera. Annals of the Missouri Botanical Garden 91: 505–522.
  • Gunn, B.F., Baudouin, L. & Olsen, K. M. 2011. Independent Origins of Cultivated Coconut (Cocos nucifera L.) in the Old World Tropics. PLoS ONE 6(6): e21143.
  • Meerow, A.W., Noblick, L., Salas-Leiva, Dayana E., Sanchez, V., Francisco-Ortega, J., Jestrow, B. & Nakamura, K. 2015. Phylogeny and historical biogeography of the cocosoid palms (Arecaceae, Arecoideae, Cocoseae) inferred from sequences of six WRKY gene family loci. Cladistics 31: 1096-0031.
  • Scientific American: Coconuts: not indigenous, but quite at home nevertheless

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