S1a is found primarily in Melanesia (especially in Papua New Guinea), Micronesia, Maritime Southeast Asia and among indigenous Australians.
The "~" symbol is ISOGG's way of indicating that an unverified and as-yet unnamed immediate ancestor may exist.
Haplogroup S1 (B255) includes the following subclades: S1a Z41335 Basal S1a* appears to be extremely rare or extinct in living males.
The primary subclade S-P405* is also relatively rare, but is found at significant levels among various Micronesian populations: 5.6%.
One subclade, Haplogroup S1a1b1d1a (S-M226.1) has been found at low frequencies in the Admiralty Islands and along the coast of mainland PNG.