GEODISPERSAL AS A BIOGEOGRAPHIC MECHANISM FOR CENOZOIC EXCHANGES BETWEEN MADAGASCAR AND AFRICA

The origins of Madagascar’s unique biota have traditionally been explained by Gondwanan vicariance and long-distance overseas dispersal. This chapter examines geodispersal—the expansion of geographic ranges following the removal of biogeographic barriers—as an additional mechanism for Cenozoic exchanges between Madagascar and Africa. Integrating geological, sedimentological, tectonic, and biological evidence, it evaluates the possible role of transient land connections across the Mozambique Channel. Paleogeographic reconstructions suggest three intervals of enhanced connectivity associated with regional uplift: the Early Paleocene (66–60 Ma), Late Eocene–Early Oligocene (36–30 Ma), and Late Miocene (12–5 Ma). These connections differed in continuity and environmental conditions, potentially facilitating exchanges among different groups of plants and vertebrates. Habitat filtering and extinction are considered essential to interpreting the selective composition of Madagascar’s biota, while the discontinuous Late Miocene connection may have particularly favored semiaquatic vertebrates. The chapter argues that episodic geodispersal provides a complementary framework for understanding Madagascar’s colonization history and subsequent biological diversification.