The archaeological record indicates that guanacos inhabited the Patagonia of
Chile and Argentina about 13,600 years ago, but were unable to migrate
further south owing to the presence of glacial and water barriers that
covered much of southern South America including the island of Tierra del
Fuego. As environmental and ecological conditions improved, guanacos, along
with other large mammals including horses, colonized the area. As a result
of continued world-wide glacial melting, ocean levels rose and Tierra del
Fuego became isolated from the mainland approximately 8000 years
ago. Although island populations generally exhibit lower levels of genetic
variation than their counterpart mainland populations, it is difficult to
predict how much less variation island populations will exhibit. An analysis
of mitochondrial cytochrome b and ATPase-8 sequences and 15 nuclear
microsatellite loci revealed that both populations retained appreciable
genetic diversity. The island population, however, exhibited much less
variation than the mainland population. Measures of genetic variation
revealed modest, but significant genetic differentiation, consistent with
separation of the two populations approximately 8000 years ago. The
assessment of levels of genetic diversity and population differentiation
among populations of the wild South American camelids is becoming
increasingly important as interest mounts in their utilization as a
renewable resource.