Evolution der Gattung Echium auf den Kanarischen Inseln: vom Kraut zum Strauch zum Rosettenbaum

The genus Echium is represented on the seven volcanic Canary islands by 24 closely related endemic species. As in other genera on the archipelago, the diversityin Echium is a result of rapid adaptive radiation during the last few million years. Withmolecular markers, the evolution of Echium on the Canary Islands can be traced backto a single colonisation event. In contrast to Echium species on the continent, most ofthe insular endemics are woody perennials. Some of the more spectacular species aregiant rosette trees that flower only once and then die. The evolutionary diversificationin Echium results from the drastic climatic changes in the past, from the climatic andedaphic diversity of habitats, and from genetic bottleneckevents during the colonisationof newly formed volcanic islands. Today, the predominance of woodiness inendemic island species is explained by selection for longevity due to the scarcity ofpollinators. The red-flowered E. wildpretii occurring in the volcanic Caldera of the highestmountain on Tenerife, Pico el Teide, is the most spectacular giant rosette tree ofthe archipelago and is pollinated by an endemic bird. From molecular studies the phylogeneticrelationship among Echium species are well known. Their ecology, however,needs to be better explored in order to protect them from harmful consequences ofhabitat destruction and climatic change.