Population structure and reproductive biology of the ti plant (Cordyline fruticosa) with implications for Polynesian prehistory

The Pacific Ocean occupies some 165 million square kilometers, larger than the sum of all terrestrial area on earth. Settlers to the central Pacific region were seafarers and agriculturalists, and their artifacts in the archaeological record constitute the Lapita cultural complex that represents the legacy of the now-extinct Lapita culture. This dissertation is concerned with the emergence of Polynesian culture from its Lapita roots, the patterns of Polynesian colonization in the Pacific, and how the limited resources of insular environments helped to shape cultural phenomena.; Various types of data are used to reconstruct events in Polynesian prehistory, including human genetics, radioisotope dating, palynology, artifacts and linguistics. Another source of important evidence for understanding human colonization patterns in the Pacific comes from phylogeographic studies of the plants and animals that the Polynesians introduced upon colonization. The focus of the present study is the ethnobotany, reproductive biology, and patterns of genetic variation using AFLP markers of a quintessential Polynesian introduction, the "ti" plant (Cordyline fruticosa).; Cordyline fruticosa is ubiquitous in its distribution and ethnobotanic use throughout Oceania, where it has been important for making costumes, wrapping food, and religious uses. The use of its rhizomes for food appears to be uniquely Polynesian; this use may correlate with the emergence of a pollen-sterile and seedless form with green leaves that became dominant in Eastern Polynesia and was the only form introduced to Hawai'i and New Zealand. This sterile form is highly identical in terms of its genetic diversity when compared with sexually reproducing populations, suggesting that the sterile form represents one extremely widespread clonal population. The patterns created by differences in reproductive capacity and genetic diversity of Cordyline fruticosa reflect a split between Western and Eastern Polynesia, which is corroborated by other lines of evidence. The development of the sterile form as a cultural entity likely occurred in Western Polynesia and was later introduced to the east, but possibly further to the west as well. Its ultimate origins remain obscure, however population structure as shown in the molecular analysis calls into question the idea that C. fruticosa is solely a human domesticate.