Resumen:
Comparison of the populations and their site conditions in the CR and other European countries showed that all Czech native and artificially established sites are exposed to eutrophication and its consequences, which are the most important factors affecting the survival of P. praelongus. The Czech sites for P. praelongus have distinctly lower water depth and transparency, and conversely, higher conductivity, temperature, and shade levels than the Nordic ones. These extreme conditions in most biotopes of this light-demanding and mesotrophic species in the CR result in lower fitness and different morphological parameters in the Czech populations. These changes lead to decreased competitive ability against filamentous algae and more competitive aquatic plant species and increase the impact of animals. In the CR, P. praelongus can currently only survive in rivers and their oxbows, but these are heavily influenced by intensive landscape management and fishing.
