On the origin of present Neotropical biodiversity: a preliminary meta-analysis about speciation timing using molecular phylogenies

The evolutionary origin of extant species has been largely debated. The controversy is especially vivid in the Neotropics, one of the more biodiverse regions of the world. One hypothesis is that Neotropical species emerged primarily during the Quaternary (the last ~2 million years), favored by the alternating glacial/interglacial climates. An opposite view proposes an older Tertiary origin linked primarily to paleogeographic changes. Here, a thorough review of the available literature on DNA molecular dating shows that the TertiaryQuaternary debate no longer makes sense. Indeed, the >1400 Neotropical species dated so far appeared in a continual fashion since the late Eocene/early Oligocene (~39 million years before present) to the Quaternary. Speciation rates maximized during the Plio-Pleistocene (the last ~5 million years), coinciding with a global climatic cooling. Paleogeographic mechanisms of speciation are relatively well known, but diversification processes linked to climate are still poorly understood. These results are important to understand the origin of present-day biodiversity patterns at both local and global scales, as well as the genetic and environmental mechanisms involved, two crucial aspects for suitable biodiversity conservation strategies.