The llama dung story got me thinking about high-altitude maize. Maize is a tropical plant and it would have taken quite a bit of effort to get it adapted to high elevations. This is what Genesys knows about maize around the world:
And this is (in red) where maize collected above 3,500 masl has been collected:
Those Andean agriculturalists obviously did a pretty good job of breeding maize to fit the new environment, and in fact still are.
LATER: As Jacob helpfully points out in a comment on this post, a 2002 paper confirmed, using microsatellites, that Andean maize is genetically quite distinct.
If you look at the phylogenetic tree in the article below, you see that the “Core Andean” group is fairly separate from the “Other South American” group.
http://teosinte.wisc.edu/pdfs/Matsuoka_et_al_PNAS.pdf
Very Useful information! Greetings from Pakistan