The ‘latitudinal diversity gradient’ is the name given to the upsurge in species richness from the poles to the equator. The evolutionary forces that drive the gradient are still poorly understood. This study examines stony corals (order Scleractinia), as they have one of the clearest and most exemplary gradients of all clades. Based on analyses of historical occurrences accessed through GBIF and other sources, the researchers concluded that the gradient demonstrated in stony corals is rather young, originating only after the end of the Cretaceous mass extinction. As a result, the evolutionary force behind the gradient pattern fails to meet the predictions of the so-called ‘out of the tropics’ (OTT) model, as it doesn’t show an origin in the higher tropics, but instead demonstrates a far greater tendency for migration towards the tropics.
Spano CA, Hernández CE and Rivadeneira MM (2015) Evolutionary dispersal drives the latitudinal diversity gradient of stony corals. Ecography. Wiley-Blackwell, 836–843. Available at doi:10.1111/ecog.01855.