Deep phylogeographic splits but no taxonomic structure in the disjointly distributed Draba pacheri (Brassicaceae), a subendemic of the Eastern Alps

Draba (Brassicaeae), a model group for diversification and evolution in Arctic and mountain habitats, is taxonomically challenging and many of its species are insufficiently investigated. One such species is D. pacheri, an endemic of the eastern European Alps and the western Carpathians (here presumably extinct). Several hypotheses exist with respect to the phylogenetic position and the taxonomy of this species, but none of these has ever been tested using molecular data. In this article we examine (i) DNA sequence data to assess the phylogenetic position of D. pacheri within the genus and (ii) AFLP fingerprint data as well as morphometric data to address whether this species can be divided taxonomically into species or subspecies. DNA sequence data firmly place D. pacheri within the Core Draba Group III, whose internal relationships are, however, insufficiently resolved to precisely identify the closest relative of D. pacheri. AFLP data identify several genetically divergent lineages corresponding to geographically distinct regions. Although these lineages are congruent with hypotheses distinguishing either two species (D. pacheri s. str., D. norica) or one species with several subspecies, the lack of clear morphological separation, both with respect to the entire set of traits and single presumably diagnostic characters such as trichome morphology, renders recognition of a single species D. pacheri, as suggested previously, the best taxonomic solution. The deep and geographically strongly structured splits of D. pacheri likely are the result of isolation in several Pleistocene refugia and warrant that conservation efforts should involve populations from each of the main geographic subgroups.

Vegetation Diversity of Screes and Taluses of The Pamir and South-Western Tian Shan in Middle Asia

This paper presents the results of phytosociological research on scree vegetation of the Pamir and south-western Tian Shan. We collected 222 phytosociological relevés during field studies conducted in 2015–2019, applying the Braun-Blanquet approach. We identified 21 plant communities on mobile and stabilized screes of colluvial cones, aprons and fans, inhabiting mainly the montane and alpine belts in several ranges (e.g. Peter the First, Alichur, Shugnan, Shachdarian, Darvaz, Rushan, Vanch, Fergana, Kyrgyz and Terskey ranges). As a result we provide the first comprehensive hierarchical syntaxonomic synopsis of scree communities at montane and alpine elevations in the eastern Middle Asia. The collected vegetation relevés represent the majority of the variation among the phytocoenoses of gravel, pebble, cobble and rock block slides and screes in the montane and alpine belts. As a result of field studies and Twinspan analyses, nine associations were identified on screes of the Pamir and western Tian Shan. All these communities were assigned to the Sileno brahuicae-Lactucetalia orientalis Nowak et al. 2021. Additionally, within the nitrophilous compact gravel screes one subassociation of Corydalidetum kashgaricae trigonelletosum gontscharovii was distinguished. In the most arid zone two additional plant associations and one subassociation were identified in gravelly semi-deserts zone. The main factors determining the species composition of the studied associations are scree mobility, rock particle size, elevation above sea level and slope inclination. Our research revealed considerable diversity of scree habitats of montane and alpine belts what might be astonishing regarding harsh environment of this mountainous territory. However, a great number of lineages that evolved here and particularly rich species pool of this habitat in Middle Asia facilitate remarkable diversity among vegetation of taluses and screes. The distinctiveness of species composition is additionally enhanced by high degree of endemism of chasmophytic habitats in the eastern part of Middle Asia. Despite recent developments, the prominent chasmophytic vegetation of Middle Asia still needs thorough studies focused on its relationship to semi-desert, tall-forb and petrophytic communities of high mountains of the Pamir, Hindu-Kush, Kunlun and Central Tian Shan.