Complex sentence: Cacti are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north--except for "Rhipsalis baccifera", which also appears in Africa and Sri Lanka.
Split into simpler sentences: Cacti are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north. There is only one exception, "Rhipsalis baccifera", which is also found in Africa and Sri Lanka.