The speckled teal group are similar to the Northern Hemisphere green-winged teal (common, Aleutian, and American), There are 4 recognized subspecies.
altipetens (Conover, 1941) - E Andes of Colombia to NW Venezuela.
andium (P. L. Sclater & Salvin, 1873) - Andes of Colombia and N Ecuador.
oxyptera Meyen, 1834 - Andes from C Peru to NW Argentina.
flavirostris Vieillot, 1816 - N Argentina S to Tierra del Fuego; Falkland Is, South Georgia
oxyptera are generally referred to as sharp-wings. They tend to be the smallest, and have more distinct markings.
As with several other waterfowl groups, the taxonomy here is changing. Some references say there are only 2 subspecies. the story's not done.
I would compare this with the difference between Gulf Coast and Florida mottled ducks. There are small differecnes, but only if you've seen alot of both.
Clint