Analysis of the Eurasian steppe flora – species inventory, species richness and rates of endemism

The Eurasian steppe belt extends from the Danube to the Amur River and represents the largest expanse of steppe vegetation in the world. Despite numerous studies of the flora of individual regions, there is no a reliable estimate of the total number of higher plant species characteristic of this biome as a whole. Filling this gap is the aim of this study. Based on an analysis of modern floristic summaries, a count of species associated with steppe ecosystems was conducted, with an emphasis on the Euro-Siberian and Mongol-Chinese subregions. Special attention is paid to the correct assignment of taxa to the steppe flora, taking into account possible errors in taxonomic status and anthropogenic landscape changes. Estimates of the number of steppe species vary: for northern Kazakhstan – 750–850, for Mongolia – 800–900. Our calculations revealed that the species composition of the Pontic steppe ranges from 200 to 400 species, while for the Kazakh, Mongolian, and Chinese steppe regions, it ranges from 700 to 900 species. The rate of endemism in the ‘lowland’ steppes was extremely low (less than 1 %), which contrasts with the high rates in mountainous provinces such as Anatolia and Altai. This is primarily explained by the history of climate change in the Late Pleistocene, as well as the fact that the cryoarid conditions of glacial periods contributed to the impoverishment of flora and decreased isolation, hindering speciation. The results emphasize the dominant role of paleoclimatic factors in shaping the modern floristic structure of the Eurasian steppes and point to the need for further comprehensive research, particularly in the poorly studied regions of Central Asia.