IntroductionDagestan is located in the Caucasus biodiversity hotspot. Nevertheless, in terms of lichenofloristic surveys, the Republic of Dagestan is one of the least-known parts of Russia and the Caucasus Mountains. Due to its diverse geomorphology and altitudinal range, it harbours a species-rich mosaic of vegetation ranging from xerophilous to alpine (e.g., mountainous dry pine forests, mesophytic deciduous forests, steppes, and semi-deserts). Vascular plants are rather well known and comprise approximately 3000 species, including 73 local endemics (Murtazaliev, 2008). However, only 63 lichen species (Barkhalov, 1983) were known before our investigations. In 2010 and 2011, an additional 81 species were reported from the Dagestan State Reserve and some areas of the Republic of Dagestan (Urbanavichus et al., 2010a, 2010b, 2010c. Due to the great diversity of habitat, a fairly high number of species can be expected to occur in Dagestan. The present paper adds further information to our knowledge of the lichen flora of Dagestan, the Caucasus Mountains, and Russia.
Study areaAccording to the Floristic Division of the World (Takhtajan, 1986), Dagestan is located on the border between the Caucasian (Circumboreal Region) and Turanian (Irano-Turanian Region) floristic provinces, or, more broadly, the Boreal and Ancient Mediterranean floristic subkingdoms. The Caucasian province is more humid and the Turanian is more arid.The study area, the Gunib plateau, lies in the central part of inner-mountain limestone Dagestan, which is located in the north-east of the Greater Caucasus (Figure). It is situated at 42°24′N, 46°55′E at altitudes ranging from 1400 to 2351 m and has an area of approximately 1470 ha. This relief consists of strongly inclined dolomite and limestone layers dating from the Jurassic up to the Cretaceous periods. Siliceous rocks are absent from the plateau. External slopes are very steep from all sides (50°-70°) with numerous cliffs. The Gunibka River, with a canyon in the middle flow, runs through the plateau. Continental climate prevails in inner-mountain limestone Dagestan. The mean rainfall per year is 680 mm, and the highest precipitation occurs in June and July. The mean annual relative humidity is 65%, and the mean annual temperature is 6.7 °C. The mean annual maximum temperature is 16.5 °C (August), while the mean minimum temperature is -5.2 °C (January).Although the Gunib plateau is very small, it supports about 22% (approximately 660 species) of the Dagestani flora. Vegetation cover varies with altitude and exposure. Steep south-facing slopes ranging up to 1500-1600 m have petrophytic steppes with Artemisia spp., Salvia canescens