The concept of species flocks in evolutionary biology refers toa monophyletic lineage of species that is geographically constrained and has radiated rapidly, resulting in many closely-relatedspecies.The best-known example is Darwins finches, but many examples are known in ancient lakes as well.Perhaps the best known example in lakes are the cichlid fishes of East African Rift Valley lakes, but species flocks also occur in systems from Europe (LakeOhrid), Russian Far East and Mongolia (Lake Baikal and LakeH(o)vsg(o)l, respectively) and Indonesia, on the island of Sumatra (Lake Toba).Additional species flocks have been described from river drainages and in marine environments.