Reptiles of the Southwestern Tajikistan desert plains: Spatial distribution, population density and communities structure

Population density of reptiles in four desert areas of southwestern Tajikistan was estimated in spring 2018–2019. The structure of reptile communities in seven typical landscapes was described. The highest species diversity and population density were observed in sandy landscapes. Seven species of psammobionts formed the basis of these reptile communities. Among them Phrynocephalus interscapularis (56.4), Crossobamon eversmanni (27.8), Eremias lineolata (15.6), Eremias scripta (13.0) had the highest distribution and high population density (individuals/hectare). The relationship of cohabitating species was considered. The highest total population density of reptiles (89.0 ind./ha) was discovered on sandy ridges along the Amu Darya. On the loamy plain the population density of four species was 8.4 ind./ha, and on the foothill plain 2.4 ind./ha. Eremias nigrocellata (2.0 ind./ha) dominated in reptile communities on solid ground. In total, 25 species of reptiles inhabit the desert plains of Southwestern Tajikistan. 17 out of 25 (68%) species are included in the national Red Data Book. The level of endemism and similarity of reptile fauna in desert areas were high. Fauna similarity indices calculated according to Sørensen were 0.9–0.8. These values indicate close contact and connection between desert communities. The formation of the reptile fauna in southwestern Tajikistan occurred as a result of dispersal of Turanian species across the left bank of the Amu Darya River from Turkmenistan. They moved to the right bank due to the changes in the riverbed at the Pleistocene Epoch. The absence of some reptile species (Teratoscincus scincus, C. eversmanni, Phrynocephalus mystaceus, E. lineolata, Eremias grammica, E. scripta, etc.) in Northern Afghanistan along the border with Tajikistan is explained by the lack of herpetological study of this territory. Their habitat in the area is highly probable. Isolation and autonomy of desert areas in the Amu Darya valley create the opportunity for formation of new taxonomic forms. Examples are lizards E. scripta ladzinni and P. interscapularis sogdianus. The desert plains of Southwest Tajikistan have a small area and are subjected to significant anthropogenic pressure. Protection of small species, including lizards (Phrynocephalus raddei, P. mystaceus, Varanus griseus) and snakes (Eryx tataricus, Spalerosophis diadema, Boiga trigonatum, Naja oxiana, Echis carinatus) is needed. For widespread and numerous psammobiont species (P. interscapularis, E. lineolata, E. grammica, E. scripta, C. eversmanni) there is no threat of extermination at the moment.