The Austral Islands occupy a distinctive position in East Polynesia, forming its southern boundary while remaining both geographically central and markedly isolated. This duality has shaped a unique cultural and biological landscape. Although the Australs share strong linguistic and cultural ties with the Society Islands and the southern Cook Islands, their relative remoteness has fostered a distinct identity. The archipelago includes Rimatara, Rurutu, Tubuai, Raivavae, and Rapa, along with Maria atoll and the Marotiri Rocks. Among these, Tubuai stands out for its lower levels of external admixture, reflecting its long-term isolation. This study examines Y-chromosome markers in the population of the island of Tubuai. The most prominent lineage identified was C-M130, accounting for 54.55% of the sample. This haplogroup is widely associated with Polynesian populations and is also found at high frequencies among Aboriginal Australians. Additional significant contributions include haplogroups O-M175 and K-M9, which are linked to Southeast Asian and Melanesian ancestries, respectively. In contrast, haplogroups typically associated with European and Central Asian populations, R1b-M269 (9.09%) and Q-M242 (4.55%), respectively, are present at lower frequencies. Together, these findings highlight the complex interplay between isolation and connectivity shaping the genetic landscape of Tubuai. By focusing on an understudied island within a key region of Polynesia, this research contributes to a more nuanced understanding of human migration patterns across the Pacific. It underscores the Austral Islands as both a boundary and a bridge in East Polynesian history, preserving ancient lineages while bearing subtle traces of more recent global interactions.

Authors

• Belén Navarro-López (BIOMICs Research Group, Department of Zoology and Animal Cellular Biology, Lascaray Research Center, Faculty of Pharmacy, University of the Basque Country, Spain)
• Miriam Baeta (BIOMICs Research Group, Department of Zoology and Animal Cellular Biology, Lascaray Research Center, Faculty of Pharmacy, University of the Basque Country, Spain)
• Leire Palencia-Madrid (Forensic Genetics Section, Forensic Science Unit,  Basque Country Police - Ertzaintza, Spain)
• Olatz Moreno-López (Department of Physical Anthropology, Society of Sciences Aranzadi, Spain)
• Caterina Raffone (BIOMICs Research Group, Department of Zoology and Animal Cellular Biology, Lascaray Research Center, Faculty of Pharmacy, University of the Basque Country, Spain)
• Iñigo Olalde (BIOMICs Research Group, Department of Zoology and Animal Cellular Biology, Lascaray Research Center, Faculty of Pharmacy, University of the Basque Country, Spain)
• Rene J Herrera (Department of Molecular Biology, Colorado College, United States of America)