Speciation in Amazonia
Speciation in Amazonia
Patterns and Predictions of A Network of Hypotheses
Recent work on the phylogeographic patterns of Amazonian organisms and a better understanding of the geologic history of the region have enabled scientists to specify and test the spatial, temporal, and phylogenetic predictions of these biogeographic models. Four main causal factors have been postulated, and their expectations and predictions are reviewed here: Firstly, the role of rivers as barriers to species dispersal is evident, but their role as primary agents of speciation is still unclear. Secondly, geotectonic changes associated with uplift of the central Andes and increase in global sea levels produced gradual submersion of western Amazonia, creating the wetland system known as Lake Pebas. The effects of marine incursions have been associated with diversification of several organisms, but no mammalian phylogenetic pattern has been effectively linked to Lake Pebas. Thirdly, the genetic structure of rodents and frogs in Western Amazonia is correlated with the location and orientation of the Iquitos Paleoarch, an ancient drainage barrier that survived until the Pliocene. Fourthly, several variations of refugia in response to Quaternary climatic fluctuations are not supported by genetic studies of small mammals. The knowledge of the biogeographic processes leading to patterns within Amazonia is still incomplete, as the mammalian fauna of this vast region and the spatial and temporal genetic patterns of most of its species remain poorly known.
Keywords: organisms, biographic, geotectonic, mammals, Pliocene
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