Potential Contributions of Ancient Oceanic Islands to Evolutionary Theory

Before much was known about the geology of continental margins and the occurrence of oceanic islands in suspect terranes, tests of theories related to island biogeography were undertaken mostly by ecologists and in paleontological investigations of non-insular biota. A significant new source of paleontological data with which to test models for species equilibrium over evolutionary versus ecological time scales and other important problems in evolutionary theory exists within circum-oceanic belts where ancient oceanic islands are preserved as allochthonous terranes. Research on faunas from these areas simplifies attempts to apply the theory of island biogeography to the fossil record and to trace the history of island populations over evolutionary time scales. Paleontologic data from a Paleozoic island arc (Alexander terrane) show significant fluctuations in the taxonomic diversity of brachiopods and thus question one of the main assertions of the dynamic equilibrium model. These data also support the concept of survival of relict taxa in ancient island refugia.