EVIDENCE FOR AN ANCIENT AREA OF ENDEMISM? THE POTENTIAL INFLUENCE OF LAGO AMAZONAS ON MODERN AMAZONIAN BIRD DIVERSITY

In the field of biogeography, areas of endemism (AoEs) are defined as regions where groups of species have overlapping distributions due to historical features of the landscape. In Amazonia, AoEs are centered in primary forest that are largely river-delimited, but in other parts of South America, the borders of AoEs are defined generally by significant ecological breaks. We examine the distributions of western Amazonian birds and ask whether groups of species may exist that could have evolved in an AoE that no longer exists today. This area is the proposed Lago Amazonas, which is the large wetland hypothesized in the paleogeological literature to have formed in the western Amazon after the uplift of the Andes and before the formation of the modern Amazon river drainage. Such a wetland could have formed a significant area of endemism for species and we argue that aspects of modern distributions and ecology of some western Amazonian species support this hypothesis. This research provides a case of reciprocal illumination for the fields of paleogeology and biogeography.