Moodley "et al." (2009) identified two distinct populations of the gut bacteria "Helicobacter pylori" that accompanied human migrations into Island Southeast Asia and Oceania, called hpSahul and hspMāori. The study sampled Native Australians, Native Taiwanese, highlanders in New Guinea, and Melanesians and Polynesians in New Caledonia, which were then compared with other "H. pylori" haplotypes from Europeans, Asians, Pacific Islanders, and others. They found that hpSahul diverged from mainland Asian "H. pylori" populations approximately 31,000 to 37,000 years ago and have remained isolated for 23,000 to 32,000 years confirming the Australo-Melanesian substratum in Island Southeast Asia and New Guinea. hspMāori, on the other hand, is a subpopulation of hpEastAsia, previously isolated from Polynesians (Māori, Tongans, and Samoans) in New Zealand, and three individuals from the Philippines and Japan. The study found hspMāori from Native Taiwanese, Melanesians, Polynesians, and two inhabitants from the Torres Strait Islands, all of which are Austronesian sources. As expected, hspMāori showed greatest genetic diversity in Taiwan, while all non-Taiwanese hspMāori populations belonged to a single lineage they called the "Pacific clade." They also calculated the isolation-with-migration model (IMa), which showed that the divergence of the Pacific clade of hspMāori were unidirectional from Taiwan to the Pacific. This is consistent with the Out-of-Taiwan model of the Austronesian expansion.