Resumo

BLANCO, JUAN FELIPE. Darwin and the Empty Island Paradox. Acta biol.Colomb. [online]. 2009, vol.14, suppl.1, pp.269-282. ISSN 0120-548X.

Although Darwin's fascination and interest on marine nature are well known due to his treatises about coral reefs, oceanic islands, and barnacles, little is commented about the many -freshwater- examples that he provided for supporting -The Migration Theory- in his book -The Origin of the Species-. According to this theory, faunas and floras disperse from continents to oceanic islands. However, those islands located at a great distance from the center of origin are very unlikely to be colonized by immigrants, and therefore only a fraction of the continental biota is represented in these islands, and they could be considered as empty. Streams in these islands could also be empty, however, Darwin stated a mechanism to explain the presence of freshwater fish in these streams, unaware of an emerging paradox. This mechanism is consistent with the current definition of a diadromous life cycle observed in fish, shrimp and snails that rely on migrations between marine and freshwaters to complete their development. This life cycle is an evolutionary convergence among unrelated lineages that evolved from both marine and freshwater ancestors. This essay discusses the evolution of insular freshwater faunas, their implications as ecological and evolutionary forces, and some experimental models. A final discussion is presented on the impacts of dams on diadromous fauna in tropical and subtropical islands.

Palavras-chave : Diadromy; island biogeography; island streams; migration theory.

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