Wallace Line by the Sahul Shelf to New Guinea. The biogeographic boundary known as Lydekker's Line, which separates the eastern edge of Wallacea from the Australian region, has a similar origin to the Wallace line. During ice age glacial advances, when the , both Asia and Australia were united with what are now islands on their respective continental shelves as continuous land masses, but the deep water between those two large continental shelf areas was, for over 50 million years, a barrier that kept the flora and fauna of Australia separated from those of Asia. Wallacea consists of islands that were not
Blakiston's Line and spiders, Hatta’s line (Soya line): for reptiles, amphibians and freshwater invertebrates, Hachisuka’s line for birds and Miyake’s line for insects. There has been speculation about why Blakiston was the person who discovered this faunal boundary line and no one before him had done so. Andrew Davis, who has been a professor at Hokkaido University for four years, argued that this may have been because of his unusual position in Japanese society as a European"." Blakiston spent much time researching bird species in Japan. At that time, Japanese ornithology was at its infancy. In 1886 Leonhard Stejneger remarked: "Our knowledge