ABSTRACT
South American tropical dry forests (TDFs) have a peculiar and well-studied biogeographical history. Because of low temperature and moisture changes at the time of Hemisphere Wisconsin-Würn (between 18,000 and 12,000 years before present (BP), the dry forests (caatinga) expanded across the Amazon, cerrado, and Chaco, resulting in what was dened as the “Pleistocene arc” (Prance 1973; Brown and Ab`Sáber 1979; Oliveira et al. 2005). At that time, tropical rain forests went through a contraction to isolated areas. Although in recent times during the expansion of tropical rain forests and the concurrent retraction of dry forests, some semideciduous and deciduous forests have remained surrounded by Amazonian, cerrado, and Chaco vegetation as witnesses of important preterit environmental changes (Meguro et al. 2007). Many studies have accumulated evidences of those climatic uctuations with dry alternating to wet periods (Pennington et al. 2009). Furthermore, the current distributions of some species co-occurring on different Brazilian domains (Amazon, caatinga, cerrado, Chaco, and the Atlantic rain forest) reinforce the biogeographical history of seasonal formations and reveal biological links among deciduous and semideciduous forests across South America (Prado and Gibbs 1993; Santos et al. 2012).
