A new species of the wild dragon tree, Dracaena (Dracaenaceae) from Gran Canaria and its taxonomic and biogeographic implications

Abstract

The arborescent taxa of Dracaena which form the dragon tree group comprise five species found in Macaronesia, Morocco (D. draco), East Africa (D. ombet, D. schizantha), Arabia (D. serrulata) and the island of Socotra (D. cinnabari). A new species of dragon tree, Dracaena tamaranae A. Marrero, R.S. Almeida & M. Gonzalez-Martin, is described from Gran Canaria, Canary Islands. This new species differs from D. draco, the only other Dracaena species currently known in Macaronesia, in having a growth form and inflorescence type and leaves more similar to the Ease African and Arabian species of Dracaena. In contrast D. draco appears to be related to D. cinnabari. In this paper, we also present a study of the taxonomy; habitat and ecology of all the species of the dragon tree group. These are found in thermo-sclerophyllous plant communities of tropical-subtropical regions which are rather xerophilous and have a rainfall range of 200-500 mm. Our study indicates two independent colonization events for Dracaena in Macaronesia. In addition, we suggest that the dragon tree group provides an example of two major biogeographical disjunctions between East and West Africa. We postulate that this group has a Tethyan origin, a hypothesis supported by fossil and palaeoclimatic data, and thus parallels the distribution and dispersal pattern of other taxonomic groups.