XVI International Botanical Congess

The Macaronesian Crassulaceae flora contains 70 species, 65 of which are endemic. They belong to 6 genera, Crassula (1), Umbilicus (1), Aeonium (39), Aichryson (12), Monanthes (10), and Sedum (6). Molecular phylogenetic analyses indicate that the Macaronesian Crassulaceae flora is the result of six independent introductions. Crassula and Umbilicus were introduced once, the Sempervivoideae (Aeonium, Aichryson, Monanthes), evolved from a common, herbaceous Sedum-like ancestor, and Sedum was introduced three times. In the Sempervivoideae island speciation an adaptive radiation resulted in a great diversity of growth-forms. Adaptation to increasingly dryer habitats and the corresponding lignification is a general trend within this lineage. Adaptive radiation in Sedum series Macaronesia (4 species) followed a similar pattern. Distinctly woody forms adapted to dry cliffs evolved from a herbaceous immigrant. Macaronesian Sedum is sister to the c 250 Crassulaceae of Mexico and South America. The enormous growth-form variation within this large comparium offers a unique challenge for studies of adaptive radiation in a continental setting.