Thu, Oct 15, 2015 page5

• Tree distribution supports ‘out of Taiwan’ hypothesis

  DNA EVIDENCE: A research team has discovered that the genetic structure of paper mulberry trees found across the Pacific is concurrent with those found in southern Taiwan

  • By Chen Wei-han / Staff reporter
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  Researchers have found ethnobotanical support for the “out of Taiwan” theory of Austronesian expansion by identifying that the DNA sequences of paper mulberry trees found on Pacific islands originated from Taiwan.

  An international team led by National Taiwan University forestry professor Chung Kuo-fang (鍾國芳) analyzed the chloroplast DNA sequences of 604 paper mulberry samples collected from East Asia, Southeast Asia, and Pacific islands, and found that a specific haplotype, cp-17, which originated in Taiwan, is predominant across the region.

  It is assumed that paper mulberry, a common East Asian tree used for making paper, was transported across the Pacific by Austronesian people, who used the tree to make bark cloth, Chung said.

  The team’s analysis found that the genetic structure and evolutionary development of Oceanic paper mulberries are concurrent with the paper mulberries in southern Taiwan, which offers circumstantial support for the “out of Taiwan” theory of Austronesian expansion, Chung said.

  Paper mulberry is a dioecious species, meaning that the male and female reproductive organs are found on separate plants.

  Most Pacific paper mulberries are of a single sex, so they cannot reproduce naturally, but rely on humans for propagation, Chung said, adding that those conditions are critical to preserving the genetic structure of the tree.

  The study was the first to use the migration of “commensal species” — non-native animals or plants that are instrumental to human survival and are introduced into a region — to support the “out of Taiwan” hypothesis, he said, adding that linguistic, archeological and genetic studies have produced important evidence that points to Taiwan as an Austronesian ancestral homeland.

  The “out of Taiwan” hypothesis is a mainstream model of Austronesian expansion, which assumes that a large-scale expansion began between 5000 BC and 2500 BC, when Austronesian-speaking peoples migrated from Taiwan to Southeast Asia and the Pacific.

  The research also provides insight into the dispersal of paper mulberry from southern China into northern Taiwan, as a large amount of mulberry pollen was discovered in sediments in Taipei that could be dated back to 5000 BC, about the same time pre-Austronesian-speaking peoples from southern China are believed to have migrated to Taiwan, Chung said.

  Stone beaters — that were used by Austronesian migrants to make bark cloth — found at archeological sites in northern Taiwan could also be dated back to about 5000 BC, suggesting that ancestral Austronesians migrated from southern China to northern Taiwan and planted the trees along the migration route, he said.

  The team spent seven years collecting and analyzing paper mulberry samples from Pacific islands and Southeast Asia, and the results were published in the academic journal Proceedings of the National Academy of Sciences earlier this month.
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