Comparative study of fluvial lakes in floodplains of the Elbe,Lužnice and Svratka Rivers based on hydrochemical and biological approach

The aim of the thesis was to specify key differences in chemistry and biota (zooplankton communities) among fluvial lakes in three regions of the Czech Republic: the central part of the Elbe River, the upper part of the Lu?nice River and the upper part of the Svratka River. The ten studied lakes of the three regions differ in size, geology, shading, connection with the river and the level of anthropogenic impact. The following hypotheses were tested: (1) The water chemistry of fluvial lakes significantly differs in different floodplains. In the central Elbe River floodplain, there are the highest values of conductivity and concentrations of organic matter and nutrients. Fluvial lakes of the Svratka River floodplain show the lowest level of these parameters, and fluvial lakes of the upper Lu?nice River have levels intermediate between the two previous regions. (2) The chemistry of fluvial lakes that have contact with the river through surface connection is significantly influenced by the river. (3) The structure of zooplankton differs in different lakes due to the geographical distance between locations, their different altitude and water chemistry. The PCA analysis of selected parameters of the water chemistry revealed a close relationship of locations in the central Elbe River floodplain on the one side and close relationship of the locations in the upper Lu?nice River and Svratka River on the other. However, the amount of organic matter, nitrogen (with the exception of nitrates) and phosphorus was independent of the region. The relationship between the extent of the lake-river connection and the water chemistry was not significant. The hypothesis that the zooplankton differ in different lakes was not proved—the species composition was similar in all the lakes.     

Water quality of selected fluvial lakes in the context of the Elbe River pollution and anthropogenic activities in the floodplain

The paper evaluates the status of selected fluvial lakes situated in the central part of the Elbe River and the impact of anthropogenic activities including comparison with the Elbe River water quality on them. To achieve the goals of the project, eight researched lakes differed from each other in the intensity of communication with the river, morphometric parameters and in the possibility of anthropogenic contamination (industrial, agricultural and municipal) were chosen. Besides observing the hydrological regime, the research was focused on physical and chemical parameters of water. To sum up, the lakes communicating above ground with the river showed similarities in several parameters, e.g. organic load or conductivity was nearly at the same level, which was lower than in the separated ones. Although the values of nitrates were higher in the river, their content did not reach such concentrations even in the connected lakes because of their more stagnant character. In general, although the Elbe River has a significant effect on water quality of researched lakes, especially in the case of lakes with a restricted communication with the river, their water quality is a result of local conditions, e.g. possibility of contamination by sewage waters, land use in the vicinity, etc.     

Rapid sperm evolution in the bluethroat (Luscinia svecica) subspecies complex

Spermatozoa are among the most variable animal cell types, and much research is currently directed towards explaining inter- and intraspecific variation in sperm form and function. Recent comparative studies in passerine birds have found associations between the level of sperm competition and both sperm length and sperm velocity. In species with sperm competition, postcopulatory sexual selection may shape the morphology of sperm as adaptations to the female environment. The speed of evolutionary change in sperm morphology at the species level is largely unknown. In this study, we analysed variation in sperm morphology among morphologically distinct and geographically isolated bluethroat subspecies in Europe. Consistent with previous studies, our analyses of mtDNA and nuclear introns suggest recent divergence and lack of lineage sorting among the subspecies. We found significant divergence in total sperm length and in the length of some sperm components (i.e. head and midpiece). There was a significantly positive relationship between pairwise divergences in sperm morphology and mitochondrial DNA, suggesting a role for genetic drift in sperm divergence. The magnitude of sperm length divergence was considerably higher than that in other geographically structured passerines, and even higher than that observed between several pairs of sister species. We hypothesize that the rapid sperm evolution in bluethroats is driven by sperm competition, and that strong postcopulatory sexual selection on sperm traits can lead to rapid speciation through reproductive incompatibilities.