Plants, Their Pollinating Bees, and the Great American Interchange

Abstract

The “Great American Interchange” refers to the mixing of North and South American faunas following the emergence of the Panamanian land bridge (Marshall et al., 1982) about 3–3.5 million years ago. The unequivocal paleontological documentation of the exchange of mammals in the post-land bridge period has led to the tacit assumption that the closing of the Panama gap was as important for other groups of organisms as it was for mammals. In the case of plants, such an assumption may not be warranted. However, paleobotanical evidence across the Pliocene-Pleistocene boundary is poor compared to that of vertebrates in general, and there is practically no fossil plant material from Central America or from lowland regions of tropical South America. In our assessment of the effects of the closing of the Panama portal on New World plant distributions, we therefore take an ecological approach to show that the formation of a land corridor per se had mixed effects on exchanges of North and South American elements.