Analysis of the Flora of Mediterranean and Saharan Africa

Abstract

After defining the state of knowledge and reviewing national inventories, the author looks at the reasons whieh led him to study Mediterranean and Saharan Africa and to detail their biogeographical significance.For Mediterranean and Saharan Africa, the generic and specific richness, the richness of endemics, and the entire biogeographical range are first analyzed at the family level. In the second part, the various biogeographical elements which play a part in the formation of the floras at the generic and specific levels are defined; several examples are provided respectively for the Mesogean (Mediterranean, Saharo-Arabian and Irano-Turanian) and tropical elements, A third part is devoted to endemism: first generic and specific endemism, then the biogeographical significance of the endemic taxa. It appears that the flora of Mediterranean Africa is about three times richer than that of Saharan Africa and that endemism there is two times greater. Whereas the flora of Mediterranean Africa is for the most part made up of Mediterranean taxa, in Saharan Africa there is a nearly equal distribution of Mediterranean, Saharo-Arabian, and tropical elements. These characteristics are related to the hostile ecological conditions which govern the Saliara now, but also reflect the climatic disturbances which took place during the Pleistocene. A special chapter is devoted to a discussion of the historical interpretation of the flora of Mediterranean and Saharan Africa, taking into account the new data provided by paleoclimatology and paleobotany. It is concluded that the Mediterranean flora is relati\'ely old and goes back at least as far as tlie middle Miocene, whereas the present Saharan flora is a reflection of intense chmatic changes which have severely affected this region since the Pliocene. In each of these cases emphasis has been placed on the role elements of African origin played in the de\'elopment of the present flora.

Spatial genetic structure in the Laperrine's olive (Olea europaea subsp. laperrinei), a long-living tree from the central Saharan mountains

“…The number of species present in this area is particularly limited (Quézel, 1965), but the ratio of endemic species is relatively high in mountains that act as refugia for plants and animals due to higher rainfall in altitude. The Saharan flora has affinities with those from adjacent regions, mainly with the Mediterranean Basin, Arabia, Sahelian and Tropical Africa (Quézel, 1978(Quézel, , 1997. Genetic studies have confirmed that some Saharan species are closely related to Mediterranean taxa (for example, Senecio, Coleman et al, 2003;Atriplex, Ortíz-Dorba et al, 2005;Erica, McGuire and Kron, 2005).…”

“…The populations of O. e. laperrinei have regressed with the desert expansion during the Pleistocene (Wickens, 1976;Quézel, 1978;Maley, 1980). Small populations are present in mountains from central Sahara (Algeria: Hoggar, Tassili n'Ajjer, Mouydir; and Niger: Greboun, Tamgak, Bagzane) to northeast Sudan (Jebel Marra, Gourgueil).…”

The genusOlea: molecular approaches of its structure and relationships to other Oleaceae

“…Thus, we can suppose that the subgenus Olea originated in Africa rather in Asia where it is also present. Quezel ( 1978) and Maley ( 1980) have already suggested an African origin for 0. europaea species in the Rand-Flora (indigenous African flora adapted to Mediterranean climate). Consequently, the section Olea and the section Ligustroides probably originated from the Rand-Flora about I 0 to 20 millions years ago.…”

A bio-indicator for the evaluation of quality forestry and landscape fragmentation

“…La persistenza nei secoli di diverse forme di eccessivo sfruttamento da parte dell'uomo ha causato la notevole riduzione di buona parte dei tipi forestali climax della regione mediterranea (Quézel 1978). Le rimanenti foreste sono boschi alterati in modo più o meno intensivo da parte dell'uomo che spesso corrispondono a diversi stadi di successione regressiva della foresta originaria.…”