The vertebrate fauna of the Mediterranean Basin has a wide range of biogeographic origins, as does the region’s vascular plants. Sharp climatic oscillations during the Pleistocene led to periodic turnovers of Eurasian and African faunal elements and a resulting isolation of populations. Combined with human hunting pressures, these factors led to a decline in species richness by the beginning of the Holocene.
At present, there are approximately 224 species of land mammals in the Mediterranean Basin, of which 25 are endemic. Because of the biogeographic barriers of the Mediterranean Sea and the Saharan Desert, the mammal faunas of Mediterranean Europe, the Middle East and North Africa are somewhat distinct. The strongest affinities of the North African mammals are with tropical Africa.
Bird diversity of the Mediterranean Basin includes about 497 regularly occurring species. In contrast to mammals, the affinities of bird faunas are more strongly linked to the Asiatic steppes than to tropical Africa. The evolution of these elements of bird faunas can be linked to Eurasian (153 species) and Eremian semiarid habitats (85 species), where Plio-Pleistocene conditions led to ongoing isolation and speciation. Forest birds of boreal origin are widespread and dominant throughout both middle Europe and the Mediterranean Basin. Shrubland bird species characteristic of the region represents only about 12 percent of the total. There are 32 endemic bird species in the Mediterranean Basin.
Reptiles and amphibians of the Mediterranean Basin include 228 and 77 species, respectively, and show distinct holarctic affinities. Much of the endemism within these groups appears to represent archaic lineages that differentiated during the middle Tertiary.
Reptile diversity is highest in the eastern Mediterranean Basin and drops steadily to the west. Species diversity on Mediterranean islands is relatively low. Important reptile groups include lizards of the Lacertidae with 63 species (23 percent of the world total), snakes of the Viviperidae with 19 species (8 percent of the world total), and tortoises of the Testunididae with four species. Overall, 34 percent of Mediterranean Basin reptiles are endemic to this region.
For amphibian diversity, the pattern is reversed compared with reptiles as the highest levels of diversity are found in the Euro-Mediterranean areas compared with the North African and Middle Eastern portions of the region. Notable groups of amphibians include the Discoglossidae with 10 species (71 percent of the world total) and the Salamandridae with 19 species (36 percent of the world total). Endemism for amphibians in the Mediterranean Basin is 31 percent.
Fish diversity is relatively high in the Mediterranean Basin compared to the other MTEs, with 216 species. This group includes 63 endemic species, six endemic genera, and one endemic family.