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The vascular plant flora of the Mediterranean Basin is estimated to include about 25,000 species (22,500 native species), making this region the richest among MTEs in total plant diversity. By comparison, the remaining portions of Europe without mediterranean-type climate regimes cover four times as much area but have only about 6000 vascular plant species.

 

This large flora in the Mediterranean Basin is a broad mixture of species with disparate evolutionary histories and biogeographic origins.  Endemism is high at the species level in the Mediterranean Basin, with a level of about 50%, but no family of vascular plants is strictly endemic to the Mediterranean Basin.
One group of species evolved under subtropical conditions that existed in this region prior to the Quaternary. These include such woody plant genera as Arbutus and Calluna (Ericaceae), Ceratonia (Fabaceae), Chamaerops (Arecaceae), and Laurus (Lauraceae). Another group of taxa represents neo-Mediterranean elements that migrated into the Mediterranean basin after the establishment of a mediterranean-type climate. Examples of woody genera in this group include Amelanchier (Rosaceae), Clematis (Ranunculaceae), and Cistus, Halimium, and Helianthemum (Cistaceae). Three groups of temperate woody elements that evolved after the onset of mediterranean-type climates have been identified. These groups are a mediterranean element evolved in situ in mountain areas and exhibiting high endemism, a desert and cold steppe group of species entering from Africa and the Middle East, and a Holarctic element of species with Eurasian temperate affinities.
Species richness at the scale of 0.1 ha is often remarkably high in lightly grazed or disturbed Mediterranean
woodlands and shrub grasslands, with as many as 119–179 species reported in such stands.

VERTEBRATE DIVERSITY

Vertebrate faunas of the Mediterranean Basin share the characteristic of multiple biogeographic origins with vascular plants. Dramatic climatic oscillations during the Pleistocene led to periodic turnovers of Eurasian and African faunal elements and a resulting isolation of populations.

 

The present fauna of land mammal species for the Mediterranean Basin number about 224 species of which 25 are endemic. Because of the biogeographic barriers of the Mediterranean Sea and the Saharan Desert, mammal faunas of Mediterranean Europe, the Middle East and North Africa are somewhat distinct. For North Africa, the mammal fauna of the Mediterranean Basin shows its strongest affinities with tropical Africa. A decline in species richness occurred at the end of the Pleistocene and into the Holocene with a combination of sharp climate shifts and human pressures through hunting.

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% 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 moving westward. Species diversity on Mediterranean islands is relatively low. Important reptile groups include lizards of the Lacertidae with 63 species (23% of the world total), snakes of the Viviperidae with 19 species (8% of the world total), and tortoises of the Testunididae with four species. Overall, 34% 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% of the world total) and the Salamandridae with 19 species (36% of the world total). Endemism for amphibians in the Mediterranean Basin is 31%.

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.

The Mediterranean Basin represents the largest area of MTEs in the world, covering a complex landscape with a large amount of topographic and climatic heterogeneity. The total area of the region is about 2.3 x 103 km², nearly 10 times greater in size than any other MTE region. This area includes more than20 nations arrayed on both sides of the Mediterranean Sea. While coastal areas are extensive because of the large archipelagos and islands within the Mediterranean, much of this area consists of mountainous terrain with many areas above 2000 m elevation and peaks reaching as high as 4500 m.
The geographic position of the Mediterranean Basin is also an important factor in understanding the biodiversity of this region. Lying at the juncture of three continental landmasses, it holds a geologic history
with dynamic changes associated with plate tectonics, mountain uplift, and active vulcanism. Strong
climatic shifts that took place during the Plio-Pleistocene period, most notably major glacial episodes,
resulted in a telescoping of many communities into the Mediterranean Basin and provided for opportunities
for geographic isolation and speciation. In contrast to other MTEs, the great majority of the Mediterranean Basin is underlain by limestone. Local areas of volcanic or siliceous parent material are present, however.
The climatic features of the Mediterranean Basin are often used to define this region, but the range of dominant and widespread woody species such as holm oak (Quercus ilex) and olive (Olea europea) also are used as bioindicators of the region. To the north, the mediterranean-climate region grades into more mesic regions with summer or year-round patterns of rainfall. To the south, the Mediterranean region intergrades with the winter rainfall desert of the northern Sahara. Climates of the mediterranean Basin are notable for their high interannual variation in both rainfall and temperature extremes.
The large area of the Mediterranean Basin, coupled with its topographic and climatic heterogeneity, make for complex assemblages of vegetation types. There are extensive woodlands dominated by both evergreen and deciduous species of oak and evergreen sclerophyllous shrublands of many forms. These shrublands are often differentiated into types depending on the height of the vegetation. Tall sclerophyllous shrublands that may include small evergreen trees are termed maquis. Several species of mediterranean pine may be present in this community. A middle height shrubland, generally occurring on calcareous substrates, is termed garrigue. Finally, low semiarid evergreen shrublands in the eastern Mediterranean Basin are commonly termed phrygana in Greece and batha in Israel. A long history of human impacts on the natural landscape has strongly impacted community structure and diversity.