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Sense of patterns and indices in macroecology
Pacák, Robert ; Šizling, Arnošt Leoš (advisor) ; Storch, David (referee)
Ecological patterns and indices are often used and highly informative tool, which could express otherwise hardly conceivable ecological facts by poor numerical figures. When using simplification of the complex biological reality, however, we take a risk that the mere number-result will not have sufficient predictive value. Therefore, it is imperative to deeply understand to the mathematical ecological basis of all indices and equations that we decide to apply in our research. This paper will deal primarily with indices and equations for expression biodiversity and their potential environmental meanings in macreocology. Abstrakt Ekologické patterns a indexy jsou často užívaným a silně informativním nástrojem, kterým se dají vyjádřit jinak těžko představitelná ekologická fakta. Takovým zjednodušením komplexní biologické skutečnosti se ovšem vystavujeme nebezpečí, že pouhé číslo- výsledek nebude mít dostatečnou výpovědní hodnotu o reálné situaci. Proto je naprosto nezbytné do hloubky rozumět matematicko ekologickému základu všech indexů a vztahů, které se při výzkumu rozhodneme použít. Tato práce se bude zabývat především indexy a vztahy pro vyjádření biodiverzity a jejich možnými ekologickými interpretacemi v makroekologii. Key words: Ecological patterns, similarity indices, mathematical ecology,...
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Bird diversity and diversification: Different processes converging to the same pattern?
Černá, Vladimíra ; Storch, David (advisor) ; Hulva, Pavel (referee)
Latitudinal diversity gradient is one of the oldest known trends in the distribution of life on the Earth. Scientists have been trying to find causes of its formation for more than two hundred years. There are several hypotheses suggested to explain this gradient. Recently, it is one of the main themes of discussion among ecologists and evolutionary biologists. By this Thesis, I will try to contribute to understanding of processes that generate the latitudinal diversity gradient. Particularly, I study if there is a relationship between ambient temperature and diversification rate. Is this relationship different for individual groups of animals? I choose birds as a model group. Specifically, these six families of birds: Accipitridae, Columbidae, Furnariidae, Picidae, Psittacidae and Strigidae. These groups include more than 1500 species. Each of them has the same universal gradient of diversity, with the highest diversity concentrated in the tropics. My objective was to find out, whether the universal gradients of bird's diversity had been shaped by the same historical processes. Or alternatively, whether different evolutionary trajectories had converged to the same gradients. The main outcome of my work is a discovery that some of the selected families diversified faster in warmer climates...
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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.
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Population trends of animals of different taxa and regions on the basis of the Living Planet Database
Váňová, Lenka ; Storch, David (advisor) ; Hulva, Pavel (referee)
The analysis of population trends of animals is increasingly being used not only as an indicator of population changes, but also as an indicator of biodiversity decline. Living Planet Index is one of such indicators, as it shows a proportional decline or increase of all populations by means of mean annual changes in population abundance. Since the first presentation of the index in 1998, its values have been decreasing, which was interpreted as indication of a critical state of global biodiversity. Nevertheless, there are some issues concerning the index. It is unclear to what extent is it robust, if it is not too much influenced by biased data or if it does not comprise a systematic error. This thesis focuses on four vertebrate taxa and its aim is to examine the level of data heterogeneity and their potential influence on the index. For this purpose, two parameters were defined for each population, Growth and Trend. Overall, the trends in abundances were quite balanced, some populations being decreasing, some increasing, and stable populations were also present. Despite of our expectations, the heterogeneity in the data was not large enough to have a substantial effect on the index. Analysis of trends in variously defined groups (e. g. "biomes", taxa or biogeographic realms) revealed only little...
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Methodological problems of the analyses of insect decline
Chlup, Petr ; Storch, David (advisor) ; Sedláček, Ondřej (referee)
In recent years, several studies reporting a severe decline of insect populations across several continents turned the spotlight on the problem of insect decline. However, the reported declining parameters may vary, and it is necessary to differentiate between declines in biomass, abundance, diversity, or geographical range reduction. This thesis aims to summarize how the conclusions about insect decline are shaped by the methods researchers use, especially by the variables they measure, emphasizing the potential methodological issues and limitations of the various facets of insect decline. Furthermore, we offer a brief digest of the most relevant potential biases and interpretative risks threatening population monitoring surveys. The review also provides concise insight into the state of knowledge on the matter of insect population trends. Keywords: insects, insect decline, insect population trends, methodology, methodological issues
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Marine Mammals as Apex Predators
Slavíčková, Tereza ; Černý, Martin (advisor) ; Storch, David (referee)
Amongst marine mammals there are many predators, however only four species can be considered truly apex predators. Polar bears, killer whales, leopard seals and sperm whales all dominate their environments, moreover, killer whales and sperm whales hold their position at the top of trophic relationships globally. Apart from being generally abundant and being large in relation to their closely related species, these four predators share very little. They differ in social structure, foraging ecology, life histories and levels of intraspecific cooperation. Very few studies focus on what characteristics makes each one of them such a dominant predator. Considering how abundant these species and their prey are, there is not enough research exploring predatory and non-predatory interactions with other large mammalian predators of our oceans. Our understanding of trophic relationships, large predators' influence on species hierarchy and ecosystem balance is poor. Considering the influence human population has on the oceans and large marine predators, more future research should be focused on exploring the complex interspecific relationships.
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Why are geographic ranges of species mostly small? Causes of range size variation
Kalendová, Pavlína ; Storch, David (advisor) ; Hořák, David (referee)
Species range size is collection of all regions which the specie occupies. Every specie has different range size, the most widespread are marine species. Range size distribution is log-normal, which means that the most of species have narrow ranges, some are widespread, and a few have extremely small ranges. This distribution can be a result of speciation and extinction. Speciation adds new species, which inhabits a part of original range. It causes a reduction of original range. Old species, which are getting closer to their extinction, are also declining their range together with abundance. One of the interesting theories is the stochastic theory, it is based on stochastic differential equation. This equation describes a changes of range size towards its equilibrium, which is the value when the range size is in steady state. The next factor is abundance. It is known that species with more individuals occupy larger ranges. Abundance distribution is also log-normal. In this thesis, I would try to summarize theories which explains why the most of species have small range sizes and how range vary among similar species.
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Bird diversity and life-history patterns along gradients of productivity and its variation
Tószögyová, Anna ; Storch, David (advisor) ; Remeš, Vladimír (referee) ; Field, Richard (referee)
Geographical variability in species richness and life-history strategies shows remarkable and well-documented patterns generated by various processes that have not yet been fully revealed. However, the pronounced correlation between spatial patterns in species and trait diversity and spatial gradients in environmental conditions indicates that the environment may modulate these processes. The mechanisms related to environmental productivity (energy availability), as a strong predictor of biodiversity, have been hypothesized to explain the cause of these broad- scale biodiversity patterns. Still, there is no consensus in the explanation, as many of the environmental and biotic factors are strongly interrelated. We have derived testable predictions that allowed disentangling the mechanisms responsible for spatial distributions of life-histories and species richness. The patterns in spatial distribution of many avian traits across the striking productivity gradient in South Africa show a slow-fast continuum in life-history strategies. High environmental productivity in tropics may result in stable populations that favour slow life-history strategies; birds can utilize stable food resources - low food seasonality selects for small clutch sizes, long parental care and high juvenile survival. The...
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Determinants of abundances in terrestrial vertebrates
Kundelová, Tereza ; Storch, David (advisor) ; Sedláček, Ondřej (referee)
The abundance of animals differs between species, however, they also vary in area and time. These differences relate to biotic and abiotic factors as well as to ecological characteristics of particular species. Studies focusing on these factors are aiming to answer the question; how and what influences the abundance of these species. Besides clarifying the dependence of abundance on particular factors, studies also try to ascertain which key factors are necessary for the determination of abundance. The most frequently studied factor is body size, but trophic level, specialization, net primary productivity, and competition also play a significant role in determination. However, all these factors explain only a small proportion of interspecific variability in abundances. This thesis focuses on terrestrial vertebrates; however, mainly on birds and mammals; since, these two taxa are the most studied. Key words: abundance, population density, terrestrial vertebrates, body size, competition, energy flux
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Population trends of African mammals
Homová, Viktória ; Storch, David (advisor) ; Hulva, Pavel (referee)
The African continent is known for its rich species diversity (biodiversity). We can read about the decline in African mammal populations in various sources. The main reasons of decline include loss of habitats and animal hunting. In spite of the general idea of decline mammals, in some cases the population trend is stable or growing. The aim of my thesis is to explore and summarize what is really known about the changes in the populations of all known mammalian species over the past decades. The attention of public is mainly oriented towards large flagship species, which are very well studied and various measures are put in place to protect them, especially in protected areas. The most marked decline in the number of individuals occurs in the western part of Africa, which is probably caused by a combination of lack of financial and human resources in animal protection, a large range of biotope damage and growing bushmeat trade. Species with increasing population trends are predominantly in South Africa, where there is an improvement in the management and the protection of wildlife receives more attention. Considering small mammals, there is, in most cases, no relevant data available to help determine their population trend. The population trends of species residing in the tropical rainforests are...
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