The abstracts of SIAL 4 were published as a special issue of Berliner Paläobiologische Abhandlungen (Kossler et al., 2006 ). Selected full papers can be found in the Hydrobiologia special issue “Patterns and processes of Speciation in Ancient Lakes” (edited by Wilke et al., 2008), which was reprinted as hard cover version in the Springer series Developments in Hydrobiology (Wilke et al., 2009). The contributions in this issue deal with three ancient lakes systems. One system is the famous East African Great Lakes, which have been studied extensively over the past decades, resulting in significant new findings about evolutionary processes in general. On the other hand, we include a set of papers on two other prominent lake systems that have so far received much less attention, the European ancient sister lakes Ohrid and Prespa, which have long been recognized as hotspots of biodiversity but were largely neglected in the international scientific literature until recently, and the two central lake systems on the Indonesian island of Sulawesi, the rich biodiversity and interesting evolutionary patterns of which only very recently have started to draw the attention of evolutionary biologists.