Darwin's biogeography

The year 2009 marks the 150th anniversary of the publication of Charles Darwin’s Origin of Species. This book was so influential that it is often considered to be the most important scientific work ever written. Many volumes have been published about the Origin and its lasting effects on religion and society, but few have examined its influence on biogeography. However, it was Darwin’s initial interest in comparing the natural history of different regions during the voyage of the Beagle that led him to propose natural selection as an evolutionary force. He had visited the Cape Verde Islands and saw the similarity of their biota to that of Africa, and then noted the South American relationships of the Galapagos fauna and flora. But the island plants and animals were different from their mainland relatives, and, in the Galapagos, each island appeared to have its own endemic forms. It was these biogeographical observations that were critical to Darwin’s formulation of a theory to account for them. His subsequent conclusions on the evolutionary importance of centres of origin and dispersal were generally well accepted for the next 100 years, until the advent of vicarianism, which began in the early 1970s. That vicarianist movement received an impetus from two sources: (1) the works of Leon Croizat, who did not believe that living organisms could disperse overseas by themselves; and (2) the development of plate tectonics and its causation of continental drift. Vicarianists believed that primitive species were originally widespread over the Earth’s surface but were rafted to different parts of the world by continental fractionation and movement. However, continental drift in the Mesozoic could not have involved contemporary species or genera as many vicarianists claimed. The development of phylogeography, beginning in the 1980s, and improved knowledge of the fossil record soon demonstrated that multitudes of living species, and even many genera and families, underwent long‐distance dispersal during the Cenozoic. This resulted in a decline of vicarianism and a vindication of Darwin’s conclusions on centres of origin and dispersal.