Speciation
The existence of sympatric speciation as a mechanism of speciation was hotly contested. People argued that the evidences of sympatric speciation are in fact examples of micro-geographic speciation. In general, this is not now the preferred explanation. Rather, it is the result of hybridisation between closely related species, followed by natural selection working on the offspring of such crosses. One widely accepted example of sympatric speciation is that of the cichlids of Lake Nabugabo in East Africa, which is thought to be due to sexual selection.