Regional biogeographic background Biogeographic classificationA recent classification of the world's biomes divides the Puna into three ecoregions (Olson et al., 2001), based mainly on precipitation and moisture trends: the Dry Puna of the Central Andes, the Puna of the Central Andes and the Southern Andean Steppe, also recognised as regional centres of endemism and wealth (Olson & Dinerstein, 2002).