Ofterdingen and Kropotkin

In 1859, on a field trip to the Malay archipelago, the naturalist and geographer Alfred Russel Wallace noticed that wholly different species of fauna inhabited islands only a few miles apart. The observation gave rise to what is now known as the Wallace Line, a meandering path of evolutionary separation that runs in a northeasterly direction through the Java Sea, dividing Bali from its neighbour Lombok, and Borneo from Sulawesi, before skirting the Philipines to the south, To the north-west are the animals, birds and insects of Asia; to the south-east the distinctive zoology of Australia and its adjacent islands. In the middle, where, to a limited extent, species overlap, is an area known to biogeographers as Wallacea. [...]in the case of Wallacea and its adjacent zones [...] after millions of years, distant cousins in the evolutionary tree found themselves reacquainted with each other.

Fiona Gruber, "Adventures in deep time", TLS January 11 2008, p. 9.