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Abundance and habitat use of reintroduced populations of the Hermit (Chazara briseis) in the Czech Republic
Pešová, Lucie ; Sedláček, Ondřej (advisor) ; Vrba, Pavel (referee)
The Hermit (Chazara briseis) belongs to the critically endangered species in the Czech Republic. Its last population survived until recently in the NPR Raná in the České středohoří Protected Landscape Area, but it has gradually declined. The specie's habitat is short-stemmed grasslands, which are maintained mainly by extensive grazing and management. Currently, these sites are declining, traditional management has changed and the sites are gradually becoming overgrown. Therefore, the reconstruction of the butterfly's habitats has been undertaken in selected localities that the butterfly used to inhabit in the past, in the České středohoří Protected Landscape Area (PR Číčov, Dlouhá hora, PP Radobýl) and in the Český kras Protected Landscape Area (Třesina, Radotín). Reintroduction of eggs and caterpillars took place in these sites in 2020-2021. The aim of the thesis was to evaluate the population abundance and habitat use of the Chazara briseis at these sites immediately after reintroduction. I estimated the size of the populations using the mark-capture-recapture method in 2020 and 2021. The size of the populations in the Lonské středohoří (Dlouhá hora and Číčov) was around 400-500 individuals with a fairly balanced sex ratio. Overflights were also recorded between these sites, which may indicate...
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Extinction risk and population size
Váňová, Lenka ; Storch, David (advisor) ; Reif, Jiří (referee)
There is generally accepted assumption that the probability of extinction risk increases with decreasing population size. But it's not sure at all, to what extent does this relation really work in real populations. The amount of studies dealing with this topic is on the increase, but still it's necessary to carry on researching. Previous results indicate that inspected connection is indeed true in many populations, in other words, preferential extinction of less abundant populations functions properly. Yet the dependence isn't as unambiguous and strong as expected. Many exceptions are known as well, which demonstrate that low number of individuals doesn't always have to be a disadvantage in terms of survival chance. Such deviations can be found both in paleontological papers and among current populations. For example, mass extinctions represent that kind of a special exception because each of them was probably driven by a different mechanism, so in one case the abundance could be an advantageous trait, whereas in another it was rather disadvantage. In my work, I briefly mention themes referring to extinction in general and subsequently I try to summarize findings about the phenomenon of population size and its connection to extinction risk. On the basis of explorers' ideas and by means of...
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