What is the general rule for tipping in South America. In particular Ecuador and Peru?

No need for tipping is required in Latin America except for fine dining. Just round up to the nearest bill and you'll be fine!

Well there's never any NEED to tip but it certainly seems to be expected of you in Peru. If in doubt look at the what the locals do - in even moderate cafes they usually tip. Friends in Lima say they add about 10%, but it depends what change you've got.

Don't tip taxi drivers. They don't expect it.

Locals usually do not tip. So, service providers usually love foreigners because they tip better than the locals. I notice that often because of that I get better service, and I am better liked. So, I always leave them something.