Chemical water quality gradients in the Mongolian sub-catchments of the Selenga River basin

Even though the Selenga is the main tributary to Lake Baikal in Russia, the largest part of the Selenga River basin is located in Mongolia. It covers a region that is highly diverse, ranging from almost virgin mountain zones to densely urbanized areas and mining zones. These contrasts have a strong impact on rivers and their ecosystems. Based on two sampling campaigns (summer 2014, spring 2015), we investigated the longitudinal water quality pattern along the Selenga and its tributaries in Mongolia. While headwater regions typically had a very good water quality status, wastewater from urban areas and impacts from mining were found to be main pollution sources in the tributaries. The highest nutrient concentrations in the catchment were found in Tuul River, and severely elevated concentrations of trace elements (As, Cd, Cu, Cr, Fe, Mn, Ni, Pb, Zn), nutrients (NH₄ ⁺, NO₂ ^?, NO₃ ^?, PO₄ ^3?), and selected major ions (SO₄ ^2?) were found in main tributaries of Selenga River. Moreover, trace element concentrations during spring 2015 (a time when many mines had not yet started operation) were markedly lower than in summer 2014, indicating that the additional metal loads measured in summer 2014 were related to mining activities. Nevertheless, all taken water samples in 2014 and 2015 from the main channel of the Mongolian Selenga River complied with the Mongolian standard (MNS 1998) for the investigated parameters.     

Phylogeography and genetic structure of the Mediterranean killifish <Emphasis Type="Italic">Aphanius fasciatus</Emphasis> (Cyprinodontidae)

The purpose of this study was to determine the phylogeographic structure of the brackish-hypersaline cyprinodont fish Aphanius fasciatus (Valenciennes, 1821), using sequencing and RFLP analysis of a 1,330 bp mitochondrial DNA segment containing part of the 16S rRNA gene as well as the genes for tRNA-Leu, NADH subunit 1 and tRNA-Ile. Individuals were collected from 13 different sites in Greece and Turkey, while seven published A. fasciatus sequences were also included to cover the area of distribution of the species. Pairwise sequence divergence values ranged from 0 to 4.51%. Congruent phylogenies were recovered with maximum likelihood, maximum parsimony and neighbour-joining methods. All analyses revealed two main groups. The first group consists of populations from almost all localities that drain into the Aegean Sea. The second group comprises the remaining population samples, which in some cases seem to consist of population-specific subgroups. Our results show that vicariant events have predominantly affected the evolution of A. fasciatus, with the Messinian salinity crisis having shaped the present genetic structure of its populations. Additionally, the life-history traits of the species, which determine a low potential for dispersal, coupled with the typical fragmentation of brackish-hypersaline water habitats have led to a high degree of isolation of A. fasciatus populations, even at restricted spatial scales. Analysis of the partitioning of the total amount of polymorphism with analyses of molecular variance (AMOVA) gave a value of F _ST = 84.6%. Potential conservation policies concerning A. fasciatus should also consider the low-genetic variability in the majority of its populations and the presence of fixed haplotypes in some of them.     

The utility of the 16S gene in investigating cryptic speciation within the Brachionus plicatilis species complex

Recent reports indicate an extensive amount of molecular evolution separating cryptic taxa as well as significant population structure at a microgeographical scale. Appropriate molecular markers are particularly suitable for distinguishing cryptic biological species. In this study, we examine the phylogenetic utility of 16S rRNA in elucidating the evolutionary relationships within the recently described euryhaline Brachionus plicatilis species complex. In addition, we assess the applicability of this marker in the genetic identification and monitoring of rotifer populations. We have sequenced a 378-bp fragment of the mitochondrial 16S rRNA gene in laboratory reference strains, hatchery clones as well as collections from a wild population of the subsaline Lake Koroneia (Northern Greece). Also, restriction fragment length polymorphism (RFLP) analysis was performed with eight restriction endonucleases. Rotifer samples are distinguished into six genetically divergent lineages. Average sequence divergence between lineages is 0.1038. The evolutionary relationships and divergence time-scales revealed with the 16S sequence data are in agreement with previous analyses using different mitochondrial and nuclear markers. The 16S region appears to have several advantages over other regions of the genome regarding use of species-specific primers, ease of amplification from single specimens and undiluted informational content over both recent and more ancient separations. It has also exhibited maximum discriminatory power (100% success) between lineages during RFLP analysis. The 16S assayed region has proven especially informative and consistent in detecting, supporting and establishing the lineage status within the B. plicatilis species complex both from a phylogenetic perspective and as an identification tool.