Mitochondrial DNA variation in the Fijian Archipelago

Abstract

The purpose of this thesis is to explore the evolutionary history of Fijians with respect to maternal ancestry. Geographically situated between Melanesia and Polynesia, Fiji has been a place of cultural exchange between Pacific Islanders for at least three thousand years. Traditionally, Fijians have been classified as Melanesians based on geography, culture, and skin pigmentation. However, Fijians share much in common linguistically, phenotypically, and genetically with Polynesians. Four questions motivated my research. First, are Fijians more Melanesian or Polynesian genetically? Second, is there a relationship between geography and genetic variation? Third, are Rotumans more similar to Fijians or Polynesians? And lastly, are Lau Islanders more similar to Fijians or Tongans? I used maternally inherited mitochondrial DNA (mtDNA) as my tool of investigation. In addition, I used various lines of anthropological evidence to synthesize my conclusions. I examined a sample of over 100 Fijians from five island populations, namely: Viti Levu, Kadavu, Vanua Levu, the Lau Islands, and Rotuma. In addition, my sample included two Melanesian and two Polynesian island populations. The results of the analyses place Fijian mtDNAs intermediate between Melanesians and Polynesians. However, the Fijians appear slightly more Polynesian than Melanesian based on a Multidimensional Scaling (MDS) plot and a comparison of frequencies of Near-Oceanic versus Asian mtDNA lineages. I did not detect a genetic-geographic association. Other factors besides geographic distance shaped maternal migration patterns. This is the first genetic study of Rotumans. The Rotumans are very similar to Polynesians genetically. The Rotuman sample has little genetic diversity suggesting that a maternal genetic bottleneck occurred at some point in their history. Finally, Lau Islanders are as diverse as the Fijian mainlanders, which supports a hypothesis that the Lau Group historically functioned as a crossroads for Fijians and Tongans. Lau Islanders are more similar to Tongans than they are to other Fijian Islanders (excluding Rotuma) based on a MDS plot and a comparison of frequencies of Near-Oceanic versus Asian mtDNA lineages.