Aboriginal Australian mitochondrial genome variation - an increased understanding of population antiquity and diversity

Abstract

Aboriginal Australians represent one of the oldest continuous cultures outside Africa, with evidence indicating that their ancestors arrived in the ancient landmass of Sahul (present-day New Guinea and Australia) ~55 thousand years ago. Genetic studies, though limited, have demonstrated both the uniqueness and antiquity of Aboriginal Australian genomes. We have further resolved known Aboriginal Australian mitochondrial haplogroups and discovered novel indigenous lineages by sequencing the mitogenomes of 127 contemporary Aboriginal Australians. In particular, the more common haplogroups observed in our dataset included M42a, M42c, S, P5 and P12, followed by rarer haplogroups M15, M16, N13, O, P3, P6 and P8. We propose some major phylogenetic rearrangements, such as in haplogroup P where we delinked P4a and P4b and redefined them as P4 (New Guinean) and P11 (Australian), respectively. Haplogroup P2b was identified as a novel clade potentially restricted to Torres Strait Islanders. Nearly all Aboriginal Australian mitochondrial haplogroups detected appear to be ancient, with no evidence of later introgression during the Holocene. Our findings greatly increase knowledge about the geographic distribution and phylogenetic structure of mitochondrial lineages that have survived in contemporary descendants of Australia's first settlers.

Figure 1. Phylogeny and geographical distributions of Aboriginal Australian mtDNA lineages and those of the surrounding regions of past and present studies.

Length of branches indicative of time since divergence. Colored squares on map indicate presence of specific haplogroups depicted in phylogeny.

Figure 2

Schematic tree of (a) macrohaplogroup M and (b) macrohaplogroup N lineages including those specific to Aboriginal Australians. Diagnostic control-region and coding region positions are as indicated.