TY - JOUR AU - Nevrova, E. L. PY - 2016/03/09 Y2 - 2024/03/29 TI - The structural basis of regional differences in taxonomic diversity of benthic diatoms (Bacillariophyta) of the Black Sea JF - Marine Biological Journal JA - mbj VL - 1 IS - 1 SE - Scientific communications DO - 10.21072/mbj.2016.01.1.05 UR - https://marine-biology.ru/mbj/article/view/5 SP - 43-63 AB - <p>The important aim for preservation of the Black Sea microalgae is evaluation of diatom flora diversity and revelation of its formation patterns. The focus of this paper is analysis of benthic diatoms diversity in the regions of Northern shelf of the Black Sea and disclosure of the causes for their differences on the different hierarchical levels within each of the three classes of Bacillariophyta. Based on the own sampling surveys results and published sources, the revision of benthic diatom flora of the Black Sea was evaluated and current taxonomic diversity was estimated by using of Taxonomical Distinctness Indices (TaxDI). Updated diatom inventory from 5 regions (Bulgarian, Romanian, North-Western, Crimean and Caucasian shelf) holds 1094 species and intraspecific taxa, pooled in 953 species, 149 genera, 61 families, 32 order and 3 classes Bacillariophyta. Current taxonomic richness of the Black Sea benthic diatoms has 1094 species and intraspecific taxa (953 species, 149 genera, 61 families, 32 orders and 3 classes). At the Crimean coast registered 884 species (81 % of the total species number), at NWBS – 556 (51 %) off the coast of Bulgaria – 271 (25 %), Romania – 358 (33 %), the Caucasus – 310 (28 %). Mean TaxDI values (∆<sup>+</sup> and Λ<sup>+</sup>) for diatom assemblages from these regions were calculated and its deviation from expected average level, corresponding to Black Sea master-list, was assessed. Deviation of the index from expected average level in each of the three classes was found to depend on the structure of the phylogenetic branches. The greatest influence on the hierarchical tree of Bacillariophyta is revealed to bring the mono- and oligospecies branches. Character of deviation of the regional diatom flora structure fromexpected average level is caused of the species, which forming a mono- or oligospecies branches up to the node of order. Suchlike species (33) with high rank of taxonomic exclusiveness are highlighted from the several regions. Disappearance of such species leads to reducing of entire phylogenetic branch from the regional tree of Bacillariophyta. Among mono- and oligospecific taxa the group of 12 species was marked out particularly. These species have the highest rank of taxonomic exclu-siveness and were cited once in the only regions. Elimination of these species from the regional flora entails to dis-appearance of the monospecies branch (including genus, family and order) from the Black Sea flora. It would deter-mine the decrease of taxonomic diversity and significant changes in hierarchical tree of Bacillariophyta as the con-crete region as well the whole Black Sea. Structure of regional tree of Crimean region almost approached the ex-pected mode for the whole Black Sea diatom flora. The value of ∆<sup>+</sup> for Crimean coast was the lowest (81.38). It may evidence about great share of polyspecies branches in the hierarchical tree and the maximum value of species/genus ratio (7) and lead to decreasing the vertical evenness in diatom taxocene structure for Crimea. On the contrary, the value of ∆<sup>+</sup> for Romania coast was highest (85.9). It were caused of great number of oligospecies branches closingup on genus and family taxonomic levels and minimum value of this ratio (4) and determined more flattened pattern of taxonomical tree structure.</p> ER -