Contrasting patterns of plant evolution in the Canarian and Galápagos islands: the origin of dispersal and colonization

Abstract

Evolution on islands is so simplified that Humboldt (1817) and Darwin (1859) developed theories of vegetation and organic evolution on the basis of cursory observations in the Canary and Galápagos archipelagos. Since then, scholars have been providing solid data and results confirming that the oceanic islands are living laboratories for plant evolution. Flora accounts and checklists tell us of major biodiversity differences between oceanic islands (c. 500 native species of angiosperms in Galápagos; c. 1000 spp. in Hawaii; c. 1500 in the Canary Islands). The knowledge of disharmonic floras is not only caused by differential biotic and abiotic characteristics since archipelago origins but also by different scientific interest in the last two centuries. For instance, the Canary Islands are the most profoundly studied in terms of phylogenetic reconstructions. Nevertheless, common features lead us to interpret evolutionary forces responsible for common trends: morphologicalcharacter release, sex separation, woodiness, radiation, adaptive radiation, endemism, among others. Results accumulated in the last decades confer the empirical basis to reformulate the theories of island biogeography and island relictualism. Geological, climatic, ecological and evolutionary characteristics are herein compiled in order to contrast general patterns of insular evolution. In addition, we show plant groups from the Canarian and Galápagos islands that illustrate all these concepts and evolutionary patterns