Berezkina A. Population structure and resources of the gastropod mollusk Nacella concinna (Strebel, 1908) in the coastal waters of the Ukrainian Antarctic Station "Academik Vernadsky", Argentine Islands archipelago, West Antarctica

The thesis is dedicated to new data on the population structure of the gastropod mollusk N. concinna for the entire island system of the Argentine Islands, West Antarctica. Patterns of limpet distribution in this water area taking into account the morphological and genetic population structure. The phylogeny of the genus Nacella and possible regions of origin and distribution are reconstructed. The division of the mollusk population into littoral and sublittoral morphotypes has not been confirmed for the water area of the studied island system. The distribution of the N. concinna population in underwater landscapes does not have clear patterns between the morphometric parameters of the shell, the weight of the mollusk and the depth. In some cases, Foster's rule regarding the dependence of size on energy resources may not be followed. N. concinna inhabits all available landscapes, forms a population with high phenotypic plasticity, which includes three morphotypes of shell sculpture, and is a rich resource in the study area. Molecular phylogenetic analysis of mitochondrial 12S, 16S, CO1 genes and nuclear 28S gene showed that three morphotypes (selected by the shell morphology) belong to the same species N. concinna in the Wilhelm archipelago water area, West Antarctica. Phylogenetic reconstructions have shown close relationships between N. concinna and the nacellids of Tierra del Fuego and sub-Antarctic islands. Phylogenetic relationships of nacellids with Patellogastropoda of tropical and temperate Atlantic Ocean waters are shown. It is established that the nacellids are indigenous to Antarctica. The Kerguelen Plateau and the boundary of the Antarctic Peninsula and Tierra del Fuego, which are associated with the ancient Triassic fauna of southern Gondwana, are likely sites of primary speciation by molecular clock. Molecular genetic barcoding of the 16S gene fragment showed that the N. concinna-associated microbiota belonged to Proteobacteria (Pseudoalteromonas, Psychrobacter, Shewanella, Cobetia, Psychromonas), Bacteroidetes (Bizionia) and Firmicutes (Oceanobacillus). Reconstruction of the phylogenetic relationships of mollusk-associated microflora showed their affinity to bacteria in the Arctic region and the possible bipolar nature of their spread. It has been shown that the microbiota associated with N. concinna cannot serve as a phylogenetic marker of evolutionary processes, but can be used as an ecological marker of underwater landscapes and mollusk subpopulations.