Beta-diversity and structuring forces of diatom communities in small lakes of the Carpathian Basin

Investigating the dynamics beyond the patterns (structure, diversity) of microbial communities at regional level in different spatial scales has been a developing area in ecology and studies on diatoms with such approach receive increasing scientific interest. In this study, phytobenthos samples were collected from 41 lakes (<7 km2) in the Carpathian Basin in August 2010 and physical and chemical parameters were also determined simultaneously. Our aim was to quantify the regional species pool (γ-diversity), the local species richness (α-diversity), the dissimilarity among diatom communities (β-diversity) and to assess whether β- diversity is supported by species replacement or richness differences (nestedness). Furthermore, we investigated the local contribution to β-diversity (LCBD) of our sampling sites and that which factors play a key role in establishment of β-diversity. In the study region, we experienced high γ- (a total of 302 diatom species) and α-diversity (average species richness of 45±13). The diatom community was characterised by high β-diversity (> 0.93 multiple-site Sorensen dissimilarity) which was explained mainly by species turnover. Although deterministic processes were more decisive based on null model analyses, stochasticity can also take part in community assembly. The degree of β-diversity (and thus assembly of communities, as well) was related significantly to the local environmental variables, especially to TP content and to the geographical distance between samplig sites. Samples from Kun-Feher-to, Pirtoi Nagy-to, Sarkany-to and Vadasa-to showed significant relative contribution to β-diversity. Cl- and HCO3 - content were determining factors for LCBD, whereas local species richness was related to HCO3 - and water temperature. Moreover, we found a decline in LCBD with the increase of species richness. The study was supported by the National Scientific Research Foundation (OTKA K81599), the Szechenyi 2020 under the EFOP-3.6.1-16-2016-00015 and the UNKP-17-3-IV-PE-5 New National Excellence Program of the Ministry of Human Capacities.