Friday, June 21, 2019

Wauke tracks Polynesian voyaging routes: New genetic studies

Fiji kapa making. 
Credit: Andrea Seelenfreund
Genetic studies of one of the key canoe plants, wauke, appear to confirm Polynesian voyaging from west to east across the Pacific, but also identify key regions of voyaging.

Wauke, also known as paper mulberry or Broussonetia papyrifera, is the raw material for some of the best Hawaiian and Polynesian kapa or bark cloth. It also produces edible fruit. And interestingly, most of Polynesia only has female plants, while the Hawaiian Islands have both males and females.

How does that happen? The Hawaiian males apparently were brought to these islands after European contact. That will be reviewed later.  On all other Polynesian islands, all plants found today are female, but the research did find a couple of examples of male plants in samples from the early 20th century from the Marquesas and Rapa. 

This is confusing. The authors of one study on the subject said it could be that wauke males were included in early voyaging, and have since disappeared, leaving the plants to be reproduced only by human involvement. But there is an odd alternative possibility. The Broussonetia clan is known to occasionally undergo sex reversion, in which female plants may rarely produce male flowers, or males may change to females. 

Credit: USDA, J.S. Peterson
Hawai`i is different from the rest of Polynesia because it still has male wauke. But those do not appear to be from early Polynesian introductions. Rather, the males apparently descend from a separate, non-Polynesian introduction to the Islands by 19th century Asian immigrants. The male wauke do not appear to have come through Polynesia, like the females. You can read more about the sexual distribution of the paper mulberry here

"Most paper mulberry plants now present in the Pacific appear to be descended from female clones introduced prehistorically," the authors of that paper write.

The dominant wauke stock in the Pacific appears to have originated in Taiwan, where, as in China and Indochina, it is native. But as a valued canoe plant, it was carried by Polynesian voyagers virtually everywhere they went. The plants are found not only in Hawai`i but at New Caledonia, Fiji, Samoa, Wallis and Tonga, in the Marquesas, the Society Islands, the Austral islands (Rapa), Pitcairn and Rapa Nui or Easter Island.

Wauke is a dioecious plant, meaning that male and female flowers occur on different plants. Because the existing plants are all female, the Polynesian wauke can't reproduce itself, and needs human help being transported and being kept alive.

"In the absence of breeding populations, the spread (i.e. movement) of paper mulberry depends entirely on a continuous human cultural tradition of preserving, propagating and transporting the plant," wrote the authors of the paper cited above.

In a new paper, many of the same authors, add to the story of the wauke. The latest paper, published this year in the journal PLOS One, is entitled "Human mediated translocation of Pacific paper mulberry [Broussonetia papyrifera (L.) L’He ´r. ex Vent. (Moraceae)]: Genetic evidence of dispersal routes in Remote Oceania."

The authors are from Chile, New Zealand and Taiwan. They include Gabriela Olivares, Barbara Peña-Ahumada, Johany Peñailillo, Claudia Payacan, Ximena Moncada, Monica Saldarriaga-Cordoba, Elizabeth Matisoo-Smith, KuoFang Chung, Daniela Seelenfreund and Andrea Seelenfreund. 
A Eurekalert press release on the study, which is simpler reading. 

The researchers conducted genetic studies on samples of wauke from 380 modern and museum samples from 33 islands across the Pacific.

They found that while all those female wauke are presumably clones of an original import, there is still some genetic diversity, and it can help understand migration patterns within the remote islands of Oceania.

"Our data detect a complex structure of three central dispersal hubs linking West Remote Oceania with East Remote Oceania. despite its vegetative propagation and short timespan since its introduction into the region by prehistoric Austronesian speaking colonists," wrote co-author Andrea Seelenfreund.

The three clusters where the wauke are most closely related to each other are: 1. Tonga and Fiji; 2. The islands of Samoa, Wallis and New Caledonia; 3. and then all of eastern Polynesia, including Hawai`i, Tahiti, the Marquesas Islands, Austral Islands and Rapa Nui.
There is evidence that Hawai`i had a more complex wauke heritage than other islands. Not counting the modern importation of male plants, it appears that traditional Polynesian strains of wauke came from both eastern Polynesia and Tonga in separate importation voyages. That adds an odd wrinkle to migration theory.

There seems to be a suggestion in the data that the wauke traveled between Taiwan and New Guinea, and from there into the rest of Polynesia. There are also suggestions that the wauke traveled on all voyaging canoes that were in the process of colonizing new areas, but after that were likely not on subsequent back-and-forth voyages.

"Crops important for survival and cultural reproduction were probably aboard all colonizing canoes, although probably not part of later inter-archipelago commercial networks or part of ritual exchanges of high valued objects, such as textiles, adzes, whale teeth, shells and other items between established settlements," the authors wrote.

© Jan TenBruggencate 2019

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