EVOLUTION OF GRASSES AND GRASSLANDS IN SOUTH AMERICA

Summary This is a discussion of the South American grasslands from the standpoint of their evolution and composition. The tribes are considered in relation to climate, and grasses are classified as mega‐, meso‐, or microthermic with respect to their temperature requirements. The principal grassland regions are three: (A) Tropical and Subtropical, which include the Llanos of the Orinoco River system and the Campos Cerrados of Central Brazil; (B) Temperate, including the Pampa of Argentina and the Campos of Uruguay; and (C) Cold Country Grasslands, which are the Steppes of the high Andes and Patagonia, and also the Páramos of Colombia and Ecuador. Some attention is given to the floristic composition of each of these regions. The subject of endemism is dealt with, as well as the problem of disjunct distribution. Included is a discussion of changes brought about by agriculture and ranching in historic times, and what may be expected in the future.