Abstract
<em>Dionysia involucrata</em> Zaprjag. (Primulaceae) is known as critically endangered endemic species of Hissar Mountains in Tajikistan. It is reported from few localities mainly in Varzob River valley and its tributaries. The species inhabits steep or overhanging faces of granite rocks in narrow river gorges. During the research all known populations of <em>D. involucrata</em> were examined in respect of the habitat conditions and species composition of vegetation plots. We analyzed the population extent of the species in its range in Tajikistan and the main threats in order to assess its conservation status. The detrended correspondence analysis was performed on a matrix of 65 relevés and 49 species (vascular plants and mosses), to classify the phytocoenosis with domination of <em>D. involucrata</em> according to their floristic composition in relation to other petrophytic vegetation units. Using our field data regarding present extent of occurrence and area of occupancy we conclude that the threat category of <em>D. involucrata</em> should be reassessed from critically endangered to endangered. The species shows decline tendency in extent of occurrence, area of occupancy as well as in number of locations. The vegetation plots with domination of <em>D. involucrata</em> have relatively high level of separateness due to different species composition. We define the new association – <em>Dionysietum involucratae</em> – representing chasmophytic vegetation of submontane and montane zone in Middle Asia (ca. 1000–1600 m a.s.l.). The plots of <em>Dionysietum involucratae</em> were found mainly on granite rocks, on very steep or overhanging faces, on southwestern or southern exposition. The association is rather poor in species with inconsiderable contribution of mosses. Despite the diagnostic species, <em>Campanula incanescens</em>, <em>Carex koshewnikowii</em> and <em>Scutellaria hissarica</em> were the most abundant and frequent taxa within the researched patches of vegetation.
Highlights
The loss of biodiversity is of primary concern to the international scientific community, the government agencies responsible for the sustainable use of natural resources at global level and non-governmental organizations alike
Dionysia involucrata is endemic to the central section of the Hissar Range located in Tajikistan, where it is restricted to several localities in the rocky gorges of the Varzob River and its tributaries
Historical range and present distribution Dionysia involucrata was previously known from 10 locations in the Varzob River Valley in the Hissar Mountains, within the following limits: north, Mayhura River Valley (39°01'51.8"N; 68°46'29.7"E); and south, the Horongonk River Valley (38°38'38.5"N; 68°50'52.1"E)
Summary
The loss of biodiversity is of primary concern to the international scientific community, the government agencies responsible for the sustainable use of natural resources at global level and non-governmental organizations alike. The precise evaluation of the conservation status of a particular species is a requirement crucial to the successful prevention its extinction. To this end, the determination of threat degree or, alternatively, the expectation of survival of taxa to which a special significance is attributed is crucial. One way Tajikistan is a typical mountainous country located in the central part of the Pamir Alai mountain system. It is worth mentioning that Pamir Alai, belongs to the central Asian mountain system recognized by Conservation International as one of thirty-four biodiversity hotspots [10] and as one of the eleven most important focal point of future plant diversity studies and conservation [11]. With very nearly the lowest adaptive capacity to climate instability, Tajikistan is regarded as one of the most sensitive country to climate change in the world [12], and
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