This book presents the latest topics in ecological and evolutionary research on aquatic biodiversity from bacteria to fishes, with special reference to Lake Biwa, an ancient lake in western Japan. With a geological history of 4 million years, Lake Biwa is the third oldest lake in the world. It is considered a biodiversity hotspot, where 1,769 aquatic species including 61 endemics are recorded, providing a rare opportunity to study the evolutionary diversification of aquatic biota and its ecological consequences. The first chapter introduces the evolutionary history of biodiversity, especially...