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.

Keywords: Broussonetia papyrifera; DNA of herbarium specimens; Voyaging Corridor Triple I; commensal approach; out of Taiwan hypothesis.

Fig. S1.

ITS haplotype network (n = 17, A–Q) and haplotype distribution and frequency. The haplotype network was reconstructed using TCS (34), with alignment gaps treated as missing data. The sizes of the circles and pie charts are proportional to the frequency of the haplotype (shown in parentheses). Squares denote unique haplotypes (haplotype found only in one individual).

Fig. 1.

Distribution of ndhF-rpl32 haplotypes and haplotype network. The sizes of the circles and pie charts are proportional to the number of individuals sampled (N) for both distribution maps and haplotype network. In the haplotype network, numbered and colored circles represent shared haplotypes and squares denote unique haplotypes. Thicker lined circles and squares (cp-1 to cp-19) are haplotypes found in Taiwan. The distributions of haplotypes in Taiwan (and its offshore islands) and the Hawaii islands are shown in enlarged maps. The map of Taiwan is demarcated by the seven major climatic regions of the island (36), with areas above 2,000 m shown in gray. Detailed distributions of haplotypes in Fujian (FJ) and Guangdong (GD) are shown in Fig. S2. Voucher information for herbarium collections of Oceania is shown as collector number (year; Herbarium). BJ, Beijing; CB, Cambodia; CV, central Vietnam; FJ, Fujian; GD, Guangdong; GI, Green Island; GS, Gansu; GX, Guangxi; HA, Hainan; HN, Henan; JL, Jilin; LY, Lanyu; NV, northern Vietnam; PH, Penghu; RK, Ryukyus; SC, Sichuan; SD, Shandong; SH, Shanghai; SV, southern Vietnam; SX, Shanxi; TH, Thailand; TK, Tokyo; YN, Yunnan; ZJ, Zhejiang.

Fig. S2.

Distribution of ndhF-rpl32 haplotypes in Fujian, Guangdong, and Taiwan.

Fig. S3.

Schematic figure of primer locations and primer sequences designed for amplifying herbarium collections. Primers in bold are adopted from Shaw et al. (33) for amplifying the entire region of ndhF-rpl32 of fresh collected materials.