So, what is so special about ? For a start, it’s fun, a seven-letter word that incorporates all five vowels. Our abstemious (but never facetious) of the Week narratives rarely offer the chance to see all the vowels in perfect alphabetical order so there’s a first!

Seriously, for biologists, Aeonium are of particular interest as their distribution amongst the off the north-west coast of Africa, is a classic model of adaptive radiation. This is the process in which organisms diversify rapidly from an ancestral species into new forms that evolve to fill different environmental niches. The process begins with a common, recent ancestry of species and results in the evolution of new species with differences in morphological (outward appearance) and physiological (functional) characteristics. Charles Darwin’s Galapagos Island finches are the most commonly quoted example of adaptive radiation.

Aeonium arboreum, a common and popular garden plant, produces rosettes of relatively thin succulent at the top of erect succulent stems. in late autumn and winter are magnificent, arranged in golden-yellow cones.

There are 42 species of Aeonium, 36 Lanzarote: 2 La Palma: 9 are endemic to the Canary Islands, two Teneriffe: 14 species are found on Madeira, one on the Cape La Gomera: 11 Verde Islands, one in spp. Fuerteventura: 1 () and two in El Hierro: 5 : 6 East Africa. Botanists believe that Aeonium Aeonium, number of species recorded from each island of the Canary originated in the Canary Archipelago. Modified from: Jorgensen & Olesen. 2001. Adaptive radiation of island : evidence from Aeonium () of Islands, and later the Canary Islands. dispersed via long distance dispersal to the other island groups, to Africa (Morocco and east Africa (, , , Uganda, Tanzania) and to Yemen on the Arabian Peninsula, rather than being a relict of an African Aeonium Tertiary flora. Most species are endemic to just one island, and usually confined to particular habitats.

Vegetative characteristics of Aeonium, such as growth habit (creeping to upright, branched Azores shrubs), morphology Madeira (variation in shape, pubescence, Morocco presence of glands and of ciliate [hairy] margins) and size Canary Islands and number of are some of Yemen the traits considered in studies of adaptive radiation of the . Cape Verde Ethiopia Somalia Kenya Uganda Tanzania

Alison Downing, Brian Atwell, Kevin Downing Department of Biological Sciences

Jorgensen T H, Olesen J M. 2001. Adaptive radiation of island plants: evidence from Aeonium (Crassulaceae) of the Canary Islands. Perspectives in Plant Ecology, Evolution and Systematics. Vol. 4(1): 29-42. Mes T H M, van Brederode J, Hart H. (1996). Origin of the Woody Macaronesian and the Phylogenetic Position of the East African Species of Aeonium. Botanica Acta, 109(6): 477-491. doi:10.1111/j.1438-8677.1996.tb00601.x Wikipedia: https://en.wikipedia.org/wiki/Aeonium Wikipedia: https://en.wikipedia.org/wiki/Aeonium_arboreum