The South American Transition Zone

We identify and describe endemic areas within the Andes Range and adjacent areas that make up the South American Transition Zone (STZ), and analyse their relationships using published molecular phylogenies to produce a general areagram. Two clades are well resolved, one linking the Páramo province (northern STZ) to Central America, which in turn is a sister group to the Caribbean forming part of a South American clade, and the other linking the Cuyan High Andes (southern STZ) to the Patagonia terrane. Both the northern STZ and southern STZ are transition zones. The central STZ is not well resolved, and we argue that it may be better interpreted as an ecogeographical endemic area until further evidence is presented. We interpret these three distinct parts of the STZ in terms of biotectonic processes. It is clear from our analysis that the STZ is non-monophyletic and composite.