|
|
Colonisation of Central Europe by benthic frehwater crustacean Asellus aquaticus (Isopoda, Crustacea)
Střížek, Antonín ; Sacherová, Veronika (advisor) ; Špaček, Jan (referee)
Longterm climate changes are an inseparable part of the evolution of Earth. In the last few milions of years the changing of glacials and interglacials was as ordinary and regular phenomenon as changing from day to night or from spring to summer. These cycles also have similar influance on evolution of nature on Earth. Eventhough the state of nature appears to us stable for the few last human generations, the reality from the long term point of view is differnt. During these cycles, the location of climatic zones, size of glaciers, deserts, savannahs, steppes or rainforests have changed. Organisms changed locations of their areas of distribution, many nowadays widespread species were pushed into isolated local populations. This Master's thesis reveals the impact of glacial cycles on a freshwater crustacean aquatic Isopod (Asellus aquaticus). Very variable mitochondrial COI gene was sequenced within 139 individuals of this species from 62 different localities in Europe. This data were included into an extensive scope of an already known phylogeographic structure of the continent. An Aquatic Sowbug shows a quite high rate of a genetic heterogenity (maximum Nucleotide Divergence discovered is 0,132 and average is 0,016) in the area of the Czech Republic. Where there are found representatives of two...
|
|
|
Diet quality impact on growth and survival of freshwater zooplankton species
Sýkorová, Veronika ; Sacherová, Veronika (advisor) ; Nedbalová, Linda (referee)
Food quality has a significant influence on freshwater zooplankon. It influences its growth rate and development generally. By quality we understand a certain stoichiometric ratio of the main biogenic elements (carbon, nitrogen, phosphorus) in the biomass of food. Ecological stechiometry is helping to understand the balance of chemical elements in ecological interactions and processes. Freshwater zooplankton consists mostly of two groups of organisms: rotifers (Rotifera) and crustaceans (Crustacea) - cladocerans (Cladocera) and copepods (Copepoda). Each of this groups requires different quality of food. Most of filtering cladocerans are fast- growing organisms, which need a phosphorus-rich food for their fast development (small C:P ratio in food) and vice versa for most of the copepods. The food offered is not always ideal for all members of zooplankton, that is why various pre- and post- absorptional mechanisms developed to help them to cope with unsuitable food. The ability to survive unvafourable conditions is closely linked to the zoolpankton's reactions to unsuitable C:N:P ratio in its food. The C:N:P ratio in food of zooplankton also influences the species distribution in water bodies. Key words: stoichiometry, food quality, zooplankton
|
|
|
Phylogeny, phylogeography and taxonomy of selected members of the family Bosminidae
Faustová, Markéta ; Sacherová, Veronika (advisor) ; Hudec, Igor (referee) ; Schwenk, Klaus (referee)
Phylogeography, taxonomy, and systematics of chosen members of family Bosminidae Abstract of Ph.D. Thesis MSc Markéta Faustová Supervisors: RNDr. Veronika Sacherová, Ph.D. - Charles University in Prague, Czech Republic Dr. Derek J. Taylor, Ph.D. - New York State University at Buffalo, U.S.A. For their life cycles, phenotypic plasticity, presence of sibling species and worldwide distribution, cladocerans are useful organisms for evolutionary studies with the aim to understand mechanisms of speciation, adaptive radiation, and polymorphism. While members of the genus Daphnia (family Daphniidae) became an iconic model in such studies, members of the family Bosminidae posses comparably interesting set of characteristics that could help to elucidate speciation mechanisms. In particular, members of the genus Eubosmina are known for extreme levels of phenotypic plasticity, especially in the Circumbaltic region, which puzzled the taxonomy and confused relationships of all described morphotypes since the first Eubosmina was described in 1857. The presented thesis explores genetic and morphometrical relationships with the aim to clarify how closely related all the described morphospecies are, to find out if there are some reproductive barriers and how strong these barriers are, how is the present-day structure of...
|
|
|
Dispersal ability of anostracans and its impact on genetic structure of populations
Rychtrmocová, Hana ; Rulík, Martin (referee) ; Sacherová, Veronika (advisor)
1 ABSTRACT The coldstenothermal species Eubranchipus grubii (Dybowski, 1860) is restricted only to vernal temporary pools in floodplain and does not occur in any other type of water habitat. Organisms living in these habitats have to be well adapted to low temperatures, desiccation, low nutrient levels, and have the ability to migrate among habitats and colonize newly established ones. E. grubii survives periods of desiccation in the form of cyst. These cysts serve as a mean of dispersion. In the Czech Republic E. grubii occurs in watersheds of rivers Labe, Morava, Odra and Dyje. We collected 95 populations in these different regions. The extent of genetic divergence among populations was assessed by analyzing sequence variation in mitochondrial gene (COI). Comparing levels of mtDNA sequence divergence divided studied populations into three main groups according to watersheds. Genetic relationships among populations inhabiting different watersheds showed 1,7 - 5,7 % sequence divergence. Sequence divergence within populations is very small. It seems that E. grubii colonized the area of today's Czech Republic from different refugia.
|
|
| |
|
|
Reintroduction of a copepod species Cyclops abyssorum (Crustacea) and its impact on zooplankton in Plešné Lake
Křenová, Radka ; Vrba, Jaroslav (referee) ; Sacherová, Veronika (advisor)
Abstract Plešné Lake is a small glacial lake in the Bohemian Forest. In the 1980th, it was heavily influenced by an acification event caused by severe atmospheric pollution. Due to some extreme parameters in the water chemistry (mainly low pH and high concentration of toxic aluminum compounds) several zooplankton species got extinct. Among these, two species important in lakes food web: Daphnia spp. and Cyclops abyssorum. They, however, survived the acidification period in one of the Bohemian Forest Lake: Prášilské. Although recovery of lakes from acidification is usually followed by return of some species or colonization by others, recolonization of Plešné Lake is assumed to be very slow or impossible from external sources thanks to the remote position of the lake. Therefore in the fall of 2004 two zooplankton species (Daphnia longispina and Cyclops abyssorum) were artificially reintroduced into Plešné Lake. In the course of 4 years that followed only Cyclops abyssorum appeared in the lake, Daphnia longispina was not recorded. My thesis focuses on several aims. First, I evaluate the development of C. abyssorum population. Second, I studied the competition between C. abyssorum and another copepod species - Heterocope saliens, acidotolerant species which never disappeared from the lake. Third, I...
|
|
| |
|
| |
|
| |
|
|
Morphological and genetical variability of Chydorus sphaericus (Crustacea, Cladocera) depending on the environment
Matušková, Ludmila ; Kořínek, Vladimír (referee) ; Sacherová, Veronika (advisor)
Úvod 5 ABSTRACT Genus Chydorus or more specifically the species of Chydorus sphaericus represents an extremely tolerant freshwater organism, which occurs in littoral zone of almost all kinds of aquatic habitats all over the world. It is usually associated with submerged macrophytes or substrate and also plays a key role in food webs of both vertebrate (fish) and invertebrate predators. Not only is this species in most localities the most common chydorid, but it is quite often the most common filtering cladoceran. Moreover, due to its little morphological variation most small globular representatives of the genus Chydorus were in the past all incorrectly ascribed to Chydorus sphaericus. However, thanks to more detailed studies it was suggested that so called species Chydorus sphaericus was not in fact a single taxonomic entity, but a group of several closely related species. It is clear today that for correct taxonomic desision it is necessary to combine all ecological, morphological, and genetic methods. The aim of this study was to explore genetical and morphological variation in populations of Chyrodis sphaericus from localities representing different sets of environmental factors. Four model localities were chosen: eutrophic ponds, temporary pools, mountain lakes and waterbodies affected by mining...
|
guest ::
