Reconstructing patterns of migration and translocation of different animal taxa across the Indian Ocean and Island South-East Asia

Abstract

The Indian Ocean represents one of the oldest exchange networks connecting South-East-Asia with India, the Arabian peninsula, as far as Africa in the West. Since the beginning of the Common Era, extensive trade between geographically distant and culturally diverse people enabled the transmission of not only new technologies, exotic goods and food items, but also diverse plant and animal species. Although archaeological remains, particularly from the 1st millennium AD, reflect an intensification of maritime connectivity across the Indian Ocean, the exact routes of travel and trade across this vast area in early times are still subject to discussion.
This thesis presents different projects that aim to assess the potential of using commensal animals, such as the house mouse Mus musculus, the black rat Rattus rattus, and the Asian house gecko Hemidactylus frenatus, as proxies to infer pathways of human travel and trade. Commensal species are usually small animals, that live in close association with humans and opportunistically exploit their habitat and food sources. Utilisation of these new resources has led to a close relationship between humans and certain species, and thus favoured their global distribution due to translocations through humans.
Therefore, genetic analyses from modern and museum samples of the species in question have been employed, and embedded in a phylogeographic approach. This integrative methodology connects genealogy and geography, with the aim to reconstruct evolutionary, demographic, and biogeographic processes that led to the contemporary distribution of genetic lineages of the commensal species and subsequently mirrors travel routes of the humans who carried them. The incorporation of ancient DNA analysis provides a powerful method, not only enabling the detection of source populations, but direct monitoring of their genetic change through time. Given that people have moved them around for a long time, undirected distribution pattern of populations were expected for each species. However, the results demonstrate that several unique and geographically restricted lineages have been identified, reflecting past human-mediated translocation throughout the Indian and Pacific Ocean from the 1st millennium AD onwards.