about 9300 species of vascular plant were known to grow in Turkey. By comparison, Europe as a whole contains only about 24% more species (about 11500), despite having thirteen times the area.
The most important reasons for the high plant biodiversity are believed to be the relatively high proportion of endemics, together with the high variety of soils and climate of Turkey.
Endemism
A third of Turkish plant species are endemic to Turkey: one reason there are so many is because the surface of Anatolia is both mountainous and quite fragmented. In fact, the Anatolian mountains resemble archipelagos like the famous Galapagos Islands. Since Darwin we know that geographic isolation between islands or separated mountains is an important means of speciation, leading to high spatial diversity. For Anatolia this assumption is confirmed by concentrations of endemism on highly isolated and relatively old massifs such as Uludağ and Ilgaz Dağ, whereas very young volcanic cones such as Erciyes Dağ and Hassan Dağ are surprisingly poor in endemics. As local endemics take a long time to evolve, we also have to compare the history of the central and north European mountains with the Anatolian ones. During each of the glacial periods the former were covered by thick shields of permanent ice, which destroyed most pre-glacial endemism and hindered neo-endemics from forming. Only less glaciated, peripheral areas, the so-called “massifs de refuge”, offered suitable conditions for the survival of local endemics during glacial periods. In Anatolia the Pleistocene glaciations only covered the highest peaks, so there are many species with small ranges. In other words: Anatolia as a whole is a big “massif de refuge”, showing all degrees of past and recent speciation.
Ecologic diversity
For a visitor from Central Europe, climatic diversity within Turkey is quite astonishing. All climatic zones present in Europe can be found in Turkey on a somewhat smaller scale. The Black Sea coast is humid all year round, with the highest rainfall between Rize and Hopa. South of the Pontic Range there is much less rain so Central Anatolia is dry; also it is cold in the winter. Approaching the southern and western coasts, the climate turns more and more Mediterranean, with mild but very rainy winters and dry, hot summers. This simple scheme is complicated a lot by the mountainous surface of Anatolia. On the high mountains, harsh climatic conditions persist all the year round and, , there are glaciers in Turkey, for example on Mount Ararat.
Also Anatolia’s diversity of soils is astonishingly high. Saline soils are quite common in the driest parts of central Anatolia: and also the Aras valley between Kağızman and Armenia is full of impressive salt outlets, some pouring directly out of the mountains and thus resembling snow patches from a distance. South of Sivas and around Gürün there are extensive gypsum hills with a very special flora. A further lot of endemics have been described from the extensive serpentine areas in South-West Anatolia, especially Sandras Dağ (Cicekbaba D.) near Köyceğiz.
The Anatolian diagonal is an ecological dividing line that runs slant-wise across central and eastern Turkey from the northeastern corner of the Mediterranean Sea to the southeastern part of the Black Sea. Many species of plants that exist west of the diagonal are not present to the east, while others found to the east are not in the west. Of 550 species analysed, 135 were found to be "eastern" and 228 "western". Besides the Anatolian diagonal forming a barrier to floral biodiversity, about four hundred species of plant are endemic to the diagonal itself.