The roles of time and ecology in the continental radiation of the Old World leaf warblers (PhylloscopusandSeicercus)

Many continental sister species are allopatric or parapatric, ecologically similar and long separated, of the order of millions of years. Sympatric, ecologically differentiated, species, are often even older. This raises the question of whether build-up of sympatric diversity generally follows a slow process of divergence in allopatry, initially without much ecological change. I review patterns of speciation among birds belonging to the...