A holistic picture of Austronesian migrations revealed by phylogeography of Pacific paper mulberry

Abstract

The peopling of Remote Oceanic islands by Austronesian speakers is a fascinating and yet contentious part of human prehistory. Linguistic, archaeological, and genetic studies have shown the complex nature of the process in which different components that helped to shape Lapita culture in Near Oceania each have their own unique history. Important evidence points to Taiwan as an Austronesian ancestral homeland with a more distant origin in South China, whereas alternative models favor South China to North Vietnam or a Southeast Asian origin. We test these propositions by studying phylogeography of paper mulberry, a common East Asian tree species introduced and clonally propagated since prehistoric times across the Pacific for making barkcloth, a practical and symbolic component of Austronesian cultures. Using the hypervariable chloroplast ndhF-rpl32 sequences of 604 samples collected from East Asia, Southeast Asia, and Oceanic islands (including 19 historical herbarium specimens from Near and Remote Oceania), 48 haplotypes are detected and haplotype cp-17 is predominant in both Near and Remote Oceania. Because cp-17 has an unambiguous Taiwanese origin and cp-17–carrying Oceanic paper mulberries are clonally propagated, our data concur with expectations of Taiwan as the Austronesian homeland, providing circumstantial support for the “out of Taiwan” hypothesis. Our data also provide insights into the dispersal of paper mulberry from South China “into North Taiwan,” the “out of South China–Indochina” expansion to New Guinea, and the geographic origins of post-European introductions of paper mulberry into Oceania.

Tracking Austronesian expansion into the Pacific via the paper mulberry plant

“…Most of the economically important plant species introduced to Remote Oceanic islands during prehistory, such as banana, taro, breadfruit, and sugarcane, have Near Oceanic origins, whereas the sweet potato and the bottle gourd are of South American origin. Thus, the results presented by Chang et al (6), indicating that the most common variant of paper mulberry found in the Pacific, and the one most likely introduced by the early colonists, has a clear Taiwanese origin, are significant, providing (to my knowledge) the first direct genetic link between Taiwan and one of the Pacific commensal species.…”

“…The haplotypes found in the north of the island, particularly cp-1, were shared with samples from the east coast region of the mainland of China, and were believed to have been introduced from there during the early phase of Austronesian expansions to the island dating between 8000 and 6000 BP (6). These northern varieties were not introduced further south, where the endemic Taiwanese lineages are found.…”

“…This "commensal approach" to tracking the movement of prehistoric Pacific peoples has to date focused primarily on the animals transported by Pacific colonists, including the Pacific rat (2, 3), pigs (4), and chickens (5). In PNAS, Chang et al (6) now present genetic analyses of one of the important plant species carried into and across the Pacific in colonizing canoes, with their study of the paper mulberry (Broussonetia papyrifera).…”

“…To identify the geographic origins of paper mulberry and reconstruct its spread through Island Southeast Asia and into the Pacific, Chang et al (6) studied genetic variation in a 1,233-bp region of the chloroplast DNA (cpDNA), which, like mtDNA in humans, is maternally inherited. A total of 604 samples of paper mulberry were collected from south China, Cambodia, Vietnam, Thailand, Japan, Taiwan, the Philippines, Sulawesi, the Solomon Islands, Fiji, and several islands in Polynesia.…”

Ecological consequences of human niche construction: Examining long-term anthropogenic shaping of global species distributions

“…(Note that maps use different temporal scales, appropriate to individual species and their temporality of spread; hatching indicates natural distribution.) papyrifera), for example, is a fiber crop introduced across the Pacific in prehistory for making barkcloth (89).…”