San Diego Sarah on 10 Aug 2024  •  Link

The coconut (the fruit of the palm Cocos nucifera) is the Swiss Army knife of the plant kingdom: in one neat package it provides a high-calorie food, potable water, fiber that can be spun into rope, and a hard shell that can be turned into charcoal. It can also serve as flotation device.

No wonder people from ancient Austronesians to Capt. Bligh pitched a few coconuts aboard before setting sail.

So extensively is the history of the coconut interwoven with the history of people traveling that Kenneth M. Olsen, PhD, a plant evolutionary biologist at Washington University in St. Louis, didn’t expect to find much geographical structure to coconut genetics when he examined the DNA of more than 1,300 coconuts from all over the world.

It turned out that there are 2 populations of coconuts, a finding that suggests the coconut was cultivated in 2 locations, one in the Pacific basin and the other in the Indian Ocean basin.
Coconut genetics also preserve a record of prehistoric trade routes and of the colonization of the Americas.

The discoveries ... are described in a 2011 online issue of the journal PLoS One.

Before the DNA era, biologists recognized a domesticated plant by its morphology. But it was hard to translate coconut morphology into a plausible evolutionary history.

A tall coconut with niu kafa fruit. The meat of these coconuts, called copra, is often dried, ground and pressed for oil, and their fiber is spun into rope, or coir.

There are two distinctively different forms of the coconut fruit, known as niu kafa and niu vai, Samoan names for traditional Polynesian varieties. The niu kafa form is triangular and oblong with a large fibrous husk. The niu vai form is rounded and contains abundant sweet coconut “water” when unripe.

“Quite often the niu vai fruit are brightly colored when they’re unripe, either bright green, or bright yellow. Sometimes they’re a beautiful gold with reddish tones,” Olsen says.

Coconuts also have been traditionally classified into tall and dwarf varieties based on the tree “habit,” or shape. Most coconuts are talls, but there are also dwarfs that are only several feet tall when they begin reproducing. Dwarfing suggests domestication, but only 5 percent of the world’s coconuts have the dwarf form.
Dwarfs tend to be used for “eating fresh,” and the tall forms for coconut oil and fiber.
“Almost all the dwarfs are self-fertilizing and those three traits — being dwarf, having the rounded sweet fruit and being self-pollinating — are thought to be the definitive domestication traits,” Olsen says.

“You almost always find coconuts near human habitations,” Olsen says, and “while the niu vai is an obvious domestication form, the niu kafa form is also heavily exploited for copra (the dried meat ground and pressed to make oil) and coir (fiber woven into rope).

San Diego Sarah on 10 Aug 2024  •  Link

PART 2

The coconut in the grocery store is like a cherry pit without the fleshy part. What’s fleshy in the stone fruits like cherries is the fibrous husk of the coconut.

“The lack of universal domestication traits together with the long history of human interaction with coconuts, made it difficult to trace the coconut’s cultivation origins strictly by morphology,” Olsen says.

The DNA project got started when Gunn, who had long been interested in palm evolution, and who was then at the Missouri Botanical Garden, contacted Olsen, who had the laboratory facilities needed to study palm DNA.
Together they won a National Geographic Society grant that allowed Gunn to collect coconut DNA in regions of the western Indian Ocean for which there were no data. She sent home snippets of leaf tissue from the center of the coconut tree’s crown in zip-lock bags to be analyzed.

“We had reason to suspect that coconuts from these regions — especially Madagascar and the Comoros Islands — might show evidence of ancient ‘gene flow’ events brought about by ancient Austronesians setting up migration routes and trade routes across the southern Indian Ocean,” Olsen says.

Olsen’s lab genotyped 10 microsatellite regions in each palm sample. Microsatellites are regions of stuttering DNA where the same few nucleotide units are repeated many times.
Mutations pop up and persist pretty easily in these regions because they usually don’t affect traits that are important to survival and so aren’t selected against, Olsen says. “So we can use these genetic markers to ‘fingerprint’ the coconut,” he says.

The most striking finding of the new DNA analysis is that the Pacific and Indian Ocean coconuts are quite distinct genetically. “About a third of the total genetic diversity can be partitioned between two groups that correspond to the Indian Ocean and the Pacific Ocean,” Olsen says.

In the Pacific, coconuts were probably first cultivated in the Philippines, Malaysia, Indonesia, ... In the Indian Ocean, the likely center of cultivation was the southern periphery of India, including Sri Lanka, the Maldives and the Laccadives.

The definitive domestication traits —the dwarf habit, self-pollination and niu vai fruits — arose only in the Pacific, and then only in a small subset of Pacific coconuts, which is why Olsen speaks of origins of cultivation rather than of domestication.

One exception to the general Pacific/Indian Ocean split is Madagascar and the Comoros Islands, where Gunn had collected the samples. Their coconuts are a genetic mixture of Indian Ocean and Pacific types.

San Diego Sarah on 10 Aug 2024  •  Link

CONCLUSION:

Olsen and his colleagues believe the Pacific coconuts were introduced to the Indian Ocean thousands of years ago by ancient Austronesians establishing trade routes connecting Southeast Asia to Madagascar and coastal east Africa.

Olsen points out that no genetic admixture is found in the more northerly Seychelles, which fall outside the trade route. He adds that a recent study of rice varieties found in Madagascar shows there is a similar mixing of the japonica and indica rice varieties from Southeast Asia and India.

To add to the historical shiver, the present-day inhabitants of the Madagascar highlands are descendants of the ancient Austronesians, Olsen says.

The scientists were astonished by the amount of structure in the coconut DNA, enough structure to allow them to trace some of the coconuts travels with humans.

The Indian Ocean coconut was transported to the New World by Europeans much later.
The Portuguese carried coconuts from the Indian Ocean to the West Coast of Africa, Olsen says, and the plantations established there were a source of material that made it into the Caribbean and also to coastal Brazil.

So the coconuts that you find today in Florida are largely the Indian ocean type, Olsen says, which is why they tend to have the niu kafa form.

On the Pacific side of the New World tropics the coconuts are Pacific Ocean coconuts. Some appear to have been transported there in pre-Columbian times by ancient Austronesians moving east rather than west.

During the colonial period, the Spanish brought coconuts to the Pacific coast of Mexico from the Philippines, which was for a time governed on behalf of the King of Spain from Mexico.
This is why, Olsen says, you find Pacific type coconuts on the Pacific coast of Central America and Indian type coconuts on the Atlantic coast.

Excerpted from
https://source.wustl.edu/2011/06/…
Deep history of coconuts decoded
Written in coconut DNA are two origins of cultivation, several ancient trade routes, and the history of the colonization of the Americas
By Diana Lutz June 24, 2011