Historical Biogeography of Southern South America

Abstract

Historical biogeographic patterns of relationships among southern and northern South America, North America, and southern temperate areas were investigated by a cladistic biogeographic analysis of 17 taxon cladograms. Three techniques were applied: Wiley's biogeographic parsimony analysis, Nelson and Platnick's component analysis, and Humphries, Ladiges, Roos, and Zandee's quantification of component analysis. Biogeographic parsimony analysis yielded two general area cladograms (CI = 0.74). Under component analysis, six general area cladograms (two under Nelson and Platnick's assumption 1 and four under their assumption 2) were obtained through the intersection of a maximum of 10 sets of area cladograms. Quantification of component analysis produced nine cladograms (CI = 0.50) under assumption 1 and one (CI = 0.45) under assumption 2. The results support a hybrid origin of the South American biota. The northern South American biota is most closely related to that of North America, and southern South America constitutes a monophyletic group together with Australia, Tasmania, New Guinea, New Caledonia, and New Zealand, reflecting the existence of an ancient austral biota. Four conflicting hypotheses of area relationships concerning southern South America and the other austral areas are proposed, suggesting that southern South America may be a composite area in itself. [South America; cladistics; biogeography; parsimony analysis; component analysis.]