Climate changes and speciation pulses in a nearly flooded continent: tackling the riddle of South America’s high diversity

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Abstract
Understanding the origin of South America’s diversity is of great importance especially considering our current extinction crisis in the face of climate change. While great debate exists about the sources of Amazonian diversity, there is no consensus about an overarching process that explains the Amazon’s uniquely high diversity. In this contribution, I present the following model considering the impact of tectonics on the hydrology of the continent. When the Andes rose, it dammed the paleo-Amazon, which ran west at the time. This produced generalized flooding with a mosaic of forest in the more elevated areas surrounded by flooded habitats. Because of the flat relief of the Amazon basin, small changes in water level produced forest expansion and contraction, resulting in speciation pulses. Using data from the literature on species distribution, as well as the age of new lineages from molecular studies, I show that the space and timing of speciation process in the South America was consistent with the predictions of this model. This model also posits that there were no marine incursions on the continent. Rather, marine conditions developed in situ, might be a better explanation for the marine conditions found in paleo-history of the region. This model provides a theoretical framework for evolutionary processes in South America that explains its uniquely high diversity.

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