Admixture and natural selection shaped genomes of an Austronesian-speaking population in the Solomon Islands

Mariko Isshiki,Ryosuke Kimura,Nao Nishida,Taro Yamauchi,Minato Nakazawa,Jun Ohashi,Takuro Furusawa,Takafumi Ishida,Izumi Naka,Kazumi Natsuhara,Ricky Eddie,Yusuke Watanabe,Ryutaro Ohtsuka

doi:10.1038/s41598-020-62866-3

Abstract

People in the Solomon Islands today are considered to have derived from Asian- and Papuan-related ancestors. Papuan-related ancestors colonized Near Oceania about 47,000 years ago, and Asian-related ancestors were Austronesian (AN)-speaking population, called Lapita, who migrated from Southeast Asia about 3,500 years ago. These two ancestral populations admixed in Near Oceania before the expansion of Lapita people into Remote Oceania. To understand the impact of the admixture on the adaptation of AN-speaking Melanesians in Near Oceania, we performed the genome-wide single nucleotide polymorphism (SNP) analysis of 21 individuals from Munda, the main town of the New Georgia Islands in the western Solomon Islands. Population samples from Munda were genetically similar to other Solomon Island population samples. The analysis of genetic contribution from the two different ancestries to the Munda genome revealed significantly higher proportions of Asian- and Papuan-related ancestries in the region containing the annexin A1 (ANXA1) gene (Asian component > 82.6%) and in the human leukocyte antigen (HLA) class II region (Papuan component > 85.4%), respectively. These regions were suspected to have undergone natural selection since the time of admixture. Our results suggest that admixture had affected adaptation of AN-speaking Melanesians in the Solomon Islands.

Highlights

The first immigrants into Oceania colonized Near Oceania, which comprises mainland New Guinea and surrounding islands such as the Bismarck Archipelago and the main Solomon Islands, about 47,000 years ago[1]
Genetic studies of Near and Remote Oceanian populations demonstrated that most Oceanian people had both Asian- and Papuan-related ancestry components; it is considered that the Lapita people, Asian-related ancestors, admixed with NAN-speaking indigenous people, Papuan-related ancestors, in Near Oceania, before their expansion into Remote Oceania[5,6,7,8]
We investigated the following genetic characteristics of Munda population using the genome-wide single nucleotide polymorphism (SNP) data: genetic relationship between Munda and other Oceanian populations, a sign of the admixture in Munda genomes, and signals of positive selection based on the excess of either Asian-related or Papuan-related ancestry observed in specific genomic regions of Munda

Summary

Introduction

The first immigrants into Oceania colonized Near Oceania, which comprises mainland New Guinea and surrounding islands such as the Bismarck Archipelago and the main Solomon Islands, about 47,000 years ago[1]. Our results revealed that: (1) the Munda people were genetically related to other populations from the Solomon Islands, (2) the Munda genomes consisted of both Asian- and Papuan-related ancestry components, and (3) the significant amounts of Asian- and Papuan-related ancestries were observed in the region containing the annexin A1 (ANXA1) gene and in the HLA class II region, respectively. These genomic regions are considered to have experienced natural selections since the time of admixture. Considering that HLA class II molecules and annexin A1 protein both play important roles in immunity, infectious diseases may have been a strong selective pressure in Munda

Methods

Results

Conclusion