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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...
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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...
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