"Ancient lakes have long been recognized as natural evolutionary laboratories and hot spots of endemism; the evolution of their morphologically often highly diverse species flocks has received much attention. Ancient lakes are evolutionary reservoirs assuring the survival of endemic species, but at the same time can act as engines generating novel diversity through intralacustrine speciation. The discovery of cryptic diversity, defined as two or more distinct species that were classified as a single morphological one is believed to be an important factor increasing estimates of current biodiversity and influencing future conservation decisions. Genetic studies have highlighted cryptic diversity in many animal taxa including ostracods (Crustacea), with the general implication that there are many more species than currently recognised. Besides assessing the importance of cryptic ostracod species for biodiversity estimates and conservation of ancient lakes, CRYSTAL will also investigate the underlying evolutionary and ecological processes that may have led to the high diversity in explosive lacustrine radiations, using the Baikalian Cytherissa species flock as a model system. The Cytherissa-radiation (Cytherideidae) from Lake Baikal is one of the most species-rich ostracod flocks and contains 47 (sub-) species. Preliminary genetic results indicate that the Cytherissa morphospecies are not monophyletic and might thus contain cryptic species. CRYSTAL will estimate diversity patterns at three specific levels: ecosystem, taxic and genetic. It will try to identify the processes that may have led to the current diversity pattern investigating trophic specialisation, substrate preferences, sexual selection and hybridisation. Also the speciation of Cytherissa in space and time will be considered revealing whether sym- or allopatric processes were most important and when and how fast the Cytherissa radition took place during the millions of years since Lake Baikal exists."