Luiz and many colleagues from Eawag, WSL, NMBE and the IEE discuss the relative contribution of immigration, speciation and extinction to the assembly of biodiversity in island-like habitats. They detect biogeographic and genetic signatures associated with two mechanisms, namely (i) a glacial species pump where isolation in glacial refugia accelerates allopatric speciation and (ii) adaptive radiation in underused adaptive zones during ice-free periods.