DIVERSITY & ENDEMISM
The Caucasus hotspot is home to about 6,400 plant species, more than 1,600 of which (25 percent) are restricted to the region. There are 17 endemic genera of plants here, nine of which are associated with high mountain ecosystems. Endemism is particularly high in rocky-scree environments in this range; 80 percent of the plants growing on the Colchic limestone scree are found nowhere else in the world.
The flora of the Caucasus region includes many ancient species, and many forms are still dominant or co-dominant in the hotspot's plant communities. Notable relict species include the endemic rhododendrons (Rhododendron caucasicum, R. ungernii, R. smirnowii) and Persian ironwood (Parrotia persica).
The region also harbors a remarkable concentration of economically important plants, particularly wild crop relatives such as wheat, rye and barley, as well as nuts and fruits like walnuts, apricots and apples.
There are more approximately 380 bird species in the hotspot, though only one is endemic according to the definition of the region adopted here, namely the Caucasian snowcock (Tetraogallus caucasicus). The hotspot hosts several globally threatened waterbird species, including the marbled duck (Marmaronetta angustirostris, VU), lesser white-fronted goose (Anser erythropus, VU) and the white-headed duck (Oxyura leucocephala, EN).
The hotspot contains significant numbers of breeding raptor populations and is an important corridor for migratory birds. Each summer and autumn, millions of birds pass through along two major migration routes on the east coast of the Black Sea and the west coast of the Caspian Sea.
There are about 130 mammal species in the Caucasus hotspot, nearly twenty of which are endemic and several of which are threatened. Like other young mountain ranges, the Caucasus region has both newly evolved species as well as ancient relict species. Here, ancient and primitive mammals are represented by the unusual long-clawed mole-vole (Prometheomys schaposchnikowi), and representatives of the genera Mesocricetus, Sicista, and Apodemus.
Several large threatened mammal species are found in this hotspot, including the Caucasian tur (Capra caucasica, EN), a member of the goat family. The Caspian monk seal (Phoca caspica, VU) also breeds along the shores of the Caspian Sea. Threatened small mammal species occurring in the Caucasus include the Mediterranean horseshoe bat (Rhinolophus euryale, VU), Mehely's horseshoe bat (R. mehelyi, VU), and the Armenian birch mouse (Sicista armenica, CR), which is known only from the type locality.
Reptiles are represented by nearly 90 species, about 20 of which are endemic. The hotspot is a center of endemism for the lizard genera Lacerta and Darevskia; nearly half of the world’s 60 species are present in the Caucasus, and half of those are endemic. Interestingly, several of these species (Darevskia dahli and D. armenica) are parthenogenic, meaning that there are no males, and females reproduce entirely on their own.
Other notable reptiles include the endemic Caucasian viper (Vipera kaznokovi, EN). The venom of this species is useful for stopping excessive bleeding in surgery patients, and the snake is exploited for the black market trade.
Amphibian diversity is relatively low, with 17 species, only a few of which are endemic. The colorful Caucasian salamander (Mertensiella caucasica, VU) is the region's best-known amphibian species, endemic to the West Caucasus of Georgia and Turkey. One of the most remarkable amphibians in the hotspot is the Gorgan salamander (Batrachuperus gorganensis, CR), which numbers only about 100 breeding adults and is restricted to Shir-Abad Cave and the stream flowing from it in northwestern Iran.
The region has more than 125 fish species, though only about a dozen are endemic. Among the most interesting species are three lampreys, Caspiomyzon wagneri, Eudontomyzon mariae and Lampetra lanceolata. Lampreys are ancient jawless, scaleless fish that date back 280 million years, and have the highest number of chromosomes of all vertebrates (164-174). Another ancient group of fish in the hotspot are seven species of sturgeon, including the famous Beluga sturgeon (Huso huso, EN), the largest freshwater fish and the source of high-value caviar. Populations of all sturgeon species have been reduced through overharvesting, primarily for caviar, while other threats include water pollution and damming, which restricts anadromous migrations.
Invertebrates, especially insects, are quite diverse, and, in the uplands of the Caucasus, one can observe many examples of the varied insect life, including an endemic butterfly (Parnassius nordmanni) and the Rosalia longicorn beetle (Rosalia alpine, VU).