National Repository of Grey Literature 42 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Daphnia hybridization in canyon-shaped reservoirs
Ruthová, Štěpánka ; Petrusek, Adam (advisor) ; Wolinska, Justyna (referee)
3 ABSTRACTS Part 1 Canyon-shaped reservoirs, characteristic by elongated morphology and by ecologically diverse conditions along both horizontal and vertical reservoir axes, are good model systems for ecological studies of zooplankton communities. Presence of ecological gradients improves habitat differentiation and may facilitate coexistence of related species. Here we provide detailed study of genetic structure of the Daphnia longispina complex inhabiting three canyon-shaped reservoirs. Using 12 microsatellite loci, we assessed taxonomic and genetic structure of assemblages composed by populations of D. galeata, D. cucullata, D. longispina and their interspecific hybrids. We focused on detailed taxon determination and on patterns of hybridization and introgression. High number of distinct hybrid genotypes in the samples suggested high frequency of hybridization; despite this, later generation hybrids were rare. In one reservoir inhabited by a single species, D. galeata, we also tested if environmental gradients may cause intra-population genetic diversification similar to spatial differentiation in species composition. Subpopulations along horizontal gradient in the reservoir, as well as those in different layers of the stratified water column, were significantly genetically differentiated. We propose...
Historical changes in species composition and interspecific hybridization of the Daphnia longispina species complex (Crustacea: Cladocera) in Lago Maggiore
Faktorová, Zuzana ; Petrusek, Adam (advisor) ; Wolinska, Justyna (referee)
Hybridizing species of the Daphnia longispina complex are key taxa in plankton communities of many European lakes. In several of these lakes, it has been documented that the taxonomic structure of the complex during the 20th century has substantially changed following human-mediated environmental changes, particularly eutrophication and re-oligotrophication and fish stock changes. We characterize these changes in Lago Maggiore (Italy/Switzerland), a southern pre-alpine lake, which also passed through the human-mediated environmental changes. Lago Maggiore is one of best and longest studied European lakes so a large number of historical Daphnia samples from regular monitoring are available. Because local Daphnia do not form dormant egg banks suitable for genetic analysis (being able to overwinter in the water column), we used a combination of morphology and geometric morphometrics (elliptic Fourier analysis) to evaluate the taxonomic and phenotypic changes in the Daphnia longispina complex in Lago Maggiore since the mid-20th century (1948-2012), and attampted to characterize the impact of environmental changes over the respective period on Daphnia body shape and size. Examination of Daphnia phenotype indicates indeed the prevailing presence of D. longispina (hyalina morph) in the 1940s, dominance of...
Lineage distribution of the Gammarus fossarum species complex (Amphipoda) across Bohemian Massif and Western Carpathians
Rutová, Tereza ; Petrusek, Adam (advisor) ; Hulva, Pavel (referee)
Amphipods are an important component of temperate permanent freshwater macrozoobenthos. They have poor dispersal abilities, lack dormant stages, and their phylogeographies often reflect old historical processes. The genus Gammarus itself includes more than 200 described species spread in the Palearctic region. Many of the taxa previously described are, in fact, diversified species complexes, which is case of our most common Gammarus (G. fossarum). We have studied their diversity on the transect across the Bohemian Massif and the Western Carpathians, which form a significant biogeographical boundary for a number of other organisms. We tested whether the border between these areas is reflected in the phylogeography of G. fossarum as a representative of permanent aquatic fauna. Analysis of two mitochondrial markers revealed the presence of eight divergent G. fossarum lineages, which also differed in the nuclear genome. All eight lineages were found in the Western Carpathians, while the Czech Massif is inhabited only by two. The microendemic areas of some lineages and the occurrence of two apparently basal lineages of this complex, which were not found in southern regions, support the hypothesis that these amphipods survived Pleistocene glacial cycles even in West Carpathian refuges. We assume that...
Ecological interactions and niche differentiation of coexisting freshwater amphipods
Bystřický, Pavel Karel ; Petrusek, Adam (advisor) ; Pařil, Petr (referee)
Freshwater amphipods are ecologically important crustacean group. They act mainly as shredders of detritus in fast-running and cold waters, contributing to the nutrient cycles. Ecological interactions within this group are interesting especially in connection with a considerable degree of cryptic diversity, as well as due to contacts of invasive and native species. This thesis deals with so far studied interactions between syntopic species or lineages, especially those that may affect coexistence or competitive exclusion, such as: different levels of selective predation, ecologically significant differences in morphology or behavior, varying degrees of aggressiveness or intraguild predation, and differences in habitat preferences or resource use ability. Due to the large number of newly discovered cryptic lineages, only little effort has been invested to studies of their ecological interactions. For the time being, research has been limited to sexual interactions (potential reproductive interference or hybridization), differences in habitat preferences, or infestation rates by parasites. It is worth mentioning that only a few lineages have been explored in this way, and the lessons learned from these few works cannot yet be generalized. In my work, I focus on cryptic species complexes in which at...

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