Why do many of todays biogeographers reject some of Wallaces most famous ideas on biogeography?
In part because of important new discoveries in the earth sciences, and in part because of new approaches to systematics and the goals of biogeographic explanation. In Wallace’s time the characteristics of organic distribution were thought to be linked largely to vertical movements in the earth’s crust; that is, to whether elevation or lowering of the land or sea had resulted in connections being made where once they did not exist (or vice versa), and how this might affect the dispersal and evolution of species. The notion that horizontal movements (plate tectonics-based ocean-floor spreading and continental drift) of the crust might also take place was quite beyond the level of discussion; thus, Wallace’s understanding that the ocean basins and continental masses were more or less permanent features, while satisfactorily addressing the issues of his day, has since been superseded by a more complete model of surface evolution. Further, the nineteenth century notion that dispersal into
