National Repository of Grey Literature 27 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Diversity dynamics across scales
Macháč, Antonín ; Storch, David (advisor) ; Remeš, Vladimír (referee) ; Ricklefs, Robert (referee)
Charles University, Prague Diversity dynamics across scales Antonin Machac 2018 Abstract Diversity dynamics remain controversial. It has been suggested that the dynamics are expansionary, such that the number of species across regions and clades increases constantly. However, the opposite has also been suggested, namely that species numbers are relatively stable, following equilibrial dynamics. Both views (expansionary and equilibrial) have been supported by compelling phylogenetic, biogeographic, and fossil evidence and, currently, it remains largely unclear how the two seemingly conflicting views could be reconciled. My dissertation addresses this question, based on the premise that diversity dynamics change systematically with scale. Specifically, I hypothesize that expansionary dynamics typify regionally distributed, small, and young clades whose diversity tends to expand, driven by a variety of regionally relevant factors (e.g. habitat-level adaptation, biotic interactions, or montane shifts leading to ecological divergence and speciation). Conversely, equilibrial dynamics typify large, ancient, and globally distributed clades, whose diversity is environmentally limited (e.g. by the total amount of resources that can sustain only a limited number of populations and species). Consequently, it seems...
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...
Dominance of different groups of animals in terrestrial ecosystems
Matysová, Barbora ; Storch, David (advisor) ; Tropek, Robert (referee)
There are some beliefs about the abundance and biomass of different animal groups, which persist in general awareness. At the same time, the ideas of the general public relate to the influence and importance of the animals for an ecosystem. The aim of this paper is to make sure that these assumed concepts of dominating entities are based on truth or if they are only mistaken rumors, and to answer the following questions: whether the biomass of large herbivores or termites is significant in the tropics, what is their influence on decomposition of vegetation matter; if the biomass of all ants actually exceeds the biomass of all people in the world; whether the abundance of prey and predators is stable across ecosystems; if there are more herbivores in tropical or cold ecosystems; or when predominant abundance of ants or termites is present in tropical ecosystems. Responses are gained through the extensive collection of abundance and animal biomass data from expert articles and publications. In order to be verifiable as well as the stability of the given ratios over the years,there were used data from the oldest traceable materials about 80 years old to the current data from current works. In addition to biomass and abundance values, attention is also paid to the methods used by scientists to collate...
Influence of landscape fragmentation on characteristics of pollination networks in meadows
Filip, Jan ; Tropek, Robert (advisor) ; Storch, David (referee)
Traditionally managed semi-natural grasslands are unique for their high plant species richness. Pollinators are crucial for maintaining this plant biodiversity. Plant-pollinator interactions of these grasslands are influenced by habitat fragmentation since the 20th century. Main drivers of this landspace disturbance are abandonment and agricultural usage. Network analysis of structural characteristics changes in plant-pollinator interactions can facilitate understanding of habitat fragmentation and its impacts on pollination interactions.
Dichromatism in Passerine Males and other aspects of sexual selection
Schwarzová, Lucie ; Fuchs, Roman (advisor) ; Grim, Tomáš (referee) ; Storch, David (referee)
Dichromatism in Passerine Males and Other Aspects of Sexual Selection Lucie Schwarzová 1. Summary of PhD Thesis Themaingoalof thepresentedlhesiswasto testsomeof thepredictionsof lrypotheses conoerningdolayedplumagemefurstion(DPM) in ťreBlack Frodsbrrt(Phoenicurus ochraros),a speoiossuitablefor suoha studydueto itshighbreodingdensityin urban hebitats.I studiedarrival pattorrl size, quality anddishibutional pattemoftemitories and aggressivebehaviourofsubadultandadultmalegandhormonaloorrelatosofplumage colourationin Black Redstart. ThebirdsinhabitingSoulhMoravianvillagesdid notshowdifferentialtimingof anivals betweenyearlings andolder birds in thoresource-richenvironment. On theotheÍ hand,undersuboptimaloonditionsin Praguetheyoarlingsworedelayedofthroedayson averagecomparedtotheadultmales.Thoreis thepossibiliý for theyoungbirdsofthis speciesb samplethesituationona potentialbroedingsite during autumnalsinging periď andflexibly fit its migratingbehaviouraccordingto tro circumstances.In suoha casethorďuction investnenthypothosisis thobestexplanationfor diÍferentarrival timingof yearlingandadultmalosin Black Redstart. To testp,redictionsof statussignallrypothesigwhich olaimsthattheadultsless frequently attrokdull colourď subadultmales,andconsoquerrtlyDPM facilitatessurvivalofsubadults...
Habitat as a determinant of abundance and distribution of birds in space and time
Reif, Jiří ; Storch, David (advisor) ; Fuchs, Roman (referee) ; Konvička, Martin (referee)
of the thesis The thesis focuses on various aspects of bird-habitat relationships. We found that the positive correlation between local abundance and regional distribution of birds is not a universal pattern. Its strength and direction depends on the similarity of habitat cover at the locality where the species abundances are measured and habitat cover of the wider region where the species distribution is assessed. In the case of the Cameroon Mountains, many locally abundant species had relatively small ranges in subsaharan Africa. They were probably well-adapted to specific conditions of montane environment, and such tight habitat association precluded their occurrence in regions covered by savannah or humid lowland forest. At the same time, isolation and unusual environmental conditions of the montane forest in the Cameroon Mountains reduced possibilities of their colonization by species widespread within Africa. Such species were confined to deforested areas in the Cameroon Mountains. The strongest gradient in bird community structure was between birds of montane forest and birds of non-forest habitats, and this gradient is probably one of the most important bird-habitat gradients worldwide. Endemic species and species confined to afrotropical mountains had the highest association with montane...
Universality in biodiversity trends
Bohdalková, Eliška ; Storch, David (advisor) ; Keil, Petr (referee)
Biodiversity trends (such as the relationship between species richness and temperature or productivity) are always defined for a particular taxon at a specific area (the entire range of the taxon or often just a region arbitrarily chosen by researchers). The form of these trends varies between taxa and regions. The weak relationship between richness and temperature or productivity is sometimes interpreted as a counterevidence for the hypothesis explaining diversity patterns by these variables. However, the delimitation of taxa or region may play a crucial role for the form of the trends. The aim of this thesis is to determine whether some taxon properties (its size) or region properties (its area, range of explanatory variables, the temperature-productivity relationship or average temperature) affect the strength and slope of the richness-temperature and richness-productivity relationships. 46 data sets of species richness for a wide range of plants, invertebrates and ectothermic vertebrates within different regions of the world were used for the analysis. While the taxon size is likely to affect the strength and slope of the relationship when comparing individual (nested) subclades within larger clade, the comparison of different taxa in different regions of the world shows only the effect of the region...
Variability of home ranges and territory sizes in birds
Holubová, Kateřina ; Storch, David (advisor) ; Sedláček, Ondřej (referee)
Territories and home-ranges are the smallest spatial units of species' presence in a landscape and they determine in what ways and on what scales animals perceive and use their environments. Their sufficient sizes encompassing enough resources are critical for survival and reproduction of individuals. Processes and factors affecting territory and home-range sizes therefore belong to fundamental ecological issues. Despite its importance, the knowledge of variation in avian territory and home-range size at large spatial scales is poor. So far it has comprised mainly the findings that the used area is determined by individual's energetic demands, dependent on body size and diet type, and by environmental productivity. Therefore, the aim of this thesis was to use data gathered from available literature to describe the variation in territory and home-range size of birds. I was curious what was the nature of territory and home-range size frequency distribution; whether the sizes were species-specific and whether and how these sizes were affected (beside the body mass and diet type) by various environmental characteristics, such as latitude, temperature, precipitation, seasonality, altitude and habitat type. I have found that the territory and home-range size frequency distribution is approximately...
Mountains as islands
Kačabová, Petra ; Storch, David (advisor) ; Ferenc, Michal (referee)
In this paper I deal with island biogeography and its applicability to isolated mountaintops, as an ecological equivalent of true islands. I discuss both true and mountain islands regarding their origin and the influence of long-term climate evolution on Earth. I underline some features of mountain islands, resulting from their topography and the dissimilarities of both types of island barriers. I find that mountain and true island communities might or might not have a number of species in a state of equilibrium, caused by balance between species immigration on island and their extinction. If the number of species on island is not in equilibrium, species extinction is not balanced by species immigration. I consider patterns of island communities, mainly nestedness, which has been frequently studied on mountain, as well as true islands. I discuss distribution patterns concerning invertebrates. And finally, I concentrate on recent methods of moutain island research and discuss mountain island isolation issues in terms of global warming.
Macroecological analysis of economy
Krupička, Jan ; Storch, David (advisor) ; Petrusek, Adam (referee) ; Kratochvíl, Lukáš (referee)
Abstract​: Brown et al. (2011) proposed a fundamental similarity between organisms and the economies of nation­states based on the distribution networks necessary for the functioning of the metabolism / economics and limitations arising from them according to the Metabolic theory of ecology. This work is primarily intended to investigate whether these limitations figure even within individual sectors of the economy and their relation to some other macroeconomic and demographic indicators. Key words​: ecology, macroecology, metabolic theory of ecology, economy, energy

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