A century of islands: From Darwin to the Hawaiian Drosophilidae

Abstract

Darwin visited c. 50 islands during the voyage of the Beagle, and from this, and his reading, was impressed by the difficulty of dispersal to oceanic islands, and the descent with modification shown by forms on such islands. He did not regard isolation as being a normal requisite for speciation. The general importance of this was not shown until the turn of the century. In recent years studies on the Drosophilidae of Hawaii have allowed intensive genetical work to be started on the process of speciation. A quarter to one-third of the world species of Drosophila are Hawaiian endemics. These have evolved both elaborate courtship patterns, with associated bizarre morphological changes, and an apparently simple courtship pattern. This second line has apparently evolved into Scaptomyza on Hawaii. From there, Scaptomyza appears to have spread round the world, in the first instance largely to other oceanic islands. Genetical studies on species on isolated islands are one of the most promising areas for investigating the importance of founder principle, and the processes of speciation.