ANALYSIS OF THE FLORA OF MEDITERRANEAN AND SAHARAN AFRICA1 P. QU�ZEL2 ABSTRACT After defining the state of knowledge and reviewing national inventories, the author looksat the reasons which led him to study Mediterranean and Saharan Africa and to detail theirbiogeographical significance. For Mediterranean and Saharan Africa, the generic and specific richness, the richness ofendemies, and the entire biogeographical range are first analyzed at the family level. In thesecond part, the various biogeographical elements which play a part in the formation of thefloras at the generic and specific levels are defined; several examples are provided respectivelyfor 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 biogeo-graphical significance of the endemic taxa. It appears that the flora of Mediterranean Africais about three times richer than that of Saharan Africa and that endemism there is two timesgreater. Whereas the flora of Mediterranean Africa is for the most part made up of Mediter-ranean 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 con-ditions which govern the Sahara now, but also reflect the climatic disturbances which tookplace during the Pleistocene. A special chapter is devoted to a discussion of the historicalinterpretation of the flora of Mediterranean and Saharan Africa, taking into account the newdata provided by paleoclimatology and paleobotany. It is concluded that the Mediterraneanflora is relatively old and goes back at least as far as the middle Miocene, whereas the presentSaharan flora is a reflection of intense climatic changes which have severely affected thisregion since the Pliocene. In each of these cases emphasis has been placed on the role elementsof African origin played in the development of the present flora. I-INTRODUCTION A little more than the northern quarter of the African continent escapes trop-ical floristic influences. This rather heterogeneous unit poses many problems ofbiogeographical and historical interpretation, but is nevertheless rather wellknown from the point of view of floristic composition. The territory covered by this study includes the whole of MediterraneanAfrica, but also the Sahara down to its southern limits, some close approximationsof which will be defined below. It seemed more meaningful and realistic to abandon the artificial frameworkof political boundaries for the infinitely more realistic one of biogeographicalunits. I. 1-THE LEVEL OF KNOWLEDGE In the Maghreb the present state of floristic knowledgc of vascular plants,which alone are discussed in this work, can be considered satisfactory such aswas stated in the recent symposium of the Centre National de la RechercheScientifique devoted to the flora of the Mediterranean basin held in Montpellier, 1I thank Carol A. Crosby, Marie R. Dwyer, and John D. Dwyer for the translation of thispaper. 2 Facult� des Sciences et Techniques de Saint-J�r�me, Botanique et Ecologie M�diterran�-enne, Universit� de Droit, d'Economie et des Sciences D'Aix-Marseille, Rue Henri-Poincar�,13397 Marseille, France.ANN. MissouRI BOT. GARD. 65: 479-534. 1978. 0026-6493/78/0479-0534/$05.75/0
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