ABSTRACT
In South America, many seasonally dry tropical forest (SDTF) species are found in different areas all around the Amazon basin and separated by thousands of kilometres. This pattern suggests that there may have been a wider expansion of SDTF in the cool dry climates of the Quaternary. Alternatively, these current distribution patterns of SDTF may have been caused by long-distance dispersal events. In this chapter, we explain how population genetics and coalescence theory can help in inferring SDTF history by means of the study of two representative forest trees: Astronium urundeuva (Fr. Allemão) Engl. (Anacardiaceae) and Geoffroea spinosa Jacq. (Leguminosae). The results reveal a higher differentiation level for G. spinosa than for A. urundeuva using micro-satellite markers (θ = 0.151 versus 0.064; P < 0.01), which may reflect different dispersal abilities and historical events. The preliminary analysis of three chloroplast markers on A. urundeuva does not allow discrimination between the two hypotheses of vicariance and dispersal.
