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Detailed taxonomic and clonal structure of the Daphnia longispina species complex on the longitudinal gradient of the Želivka Reservoir
Stodola, Jakub ; Petrusek, Adam (advisor) ; Vaníčková, Ivana (referee)
Canyon shaped reservoirs are characteristic by specific environmental horizontal gradients, so they enable existence of several species of the Daphnia longispina complex in one water body. Due to preference of distinct environmental conditions Daphnia species occurre in the different localities. The aim of my thesis was to analyze detail taxonomical and clonal structure of Daphnia longispina group by ten microsatellite markers on longitudinal gradient and compare it between two consecutive seasons. Simultaneously I received newly discovered divergent mitochondrial lineage from Želivka reservoir. It was confirmed, that the distribution of species and their hybrids in water reservoir was non-concidental and the taxonomic spatial distribution is in two consecutive seasons relatively constant. On the contrary the spatial and temporal distribution of clones was very heterogeneous. Clonal diversity in the interspecific hybrids was lower than in the coexisting parental species. This finding supports the hypothesis, that there exist reproductive barriers between parental genomes. Most of the clones were substantively variable, but several clones that occurred in both seasons in similar localities were found. It is possible that some clones are able of overwintering in hypolimnion and in the spring...
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Detailed taxonomic and clonal structure of the Daphnia longispina species complex on the longitudinal gradient of the Želivka Reservoir
Stodola, Jakub ; Petrusek, Adam (advisor) ; Vaníčková, Ivana (referee)
Canyon shaped reservoirs are characteristic by specific environmental horizontal gradients, so they enable existence of several species of the Daphnia longispina complex in one water body. Due to preference of distinct environmental conditions Daphnia species occurre in the different localities. The aim of my thesis was to analyze detail taxonomical and clonal structure of Daphnia longispina group by ten microsatellite markers on longitudinal gradient and compare it between two consecutive seasons. Simultaneously I received newly discovered divergent mitochondrial lineage from Želivka reservoir. It was confirmed, that the distribution of species and their hybrids in water reservoir was non-concidental and the taxonomic spatial distribution is in two consecutive seasons relatively constant. On the contrary the spatial and temporal distribution of clones was very heterogeneous. Clonal diversity in the interspecific hybrids was lower than in the coexisting parental species. This finding supports the hypothesis, that there exist reproductive barriers between parental genomes. Most of the clones were substantively variable, but several clones that occurred in both seasons in similar localities were found. It is possible that some clones are able of overwintering in hypolimnion and in the spring...
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Influence of experimental conditions on hatching of diapausing stages of the cladoceran Daphnia obtusa
Sailerová, Martina ; Petrusek, Adam (advisor) ; Vaníčková, Ivana (referee)
Diapause is often an adaptation for survival during periods of harsh environmental conditions. Some diapausing stages do not terminate the dormancy once the favourable conditions are restored. Such prolonged diapause may be enforced by environment if a diapausing stage cannot be reached by the cues inducing termination of dormancy. However, it may also be an advantageous bet-hedging strategy to allow only a fraction of dormant stages produced in any given season to hatch the next time conditions become favourable. I tested whether such strategy can be observed in hatching patterns of dormant eggs of Daphnia obtusa - a cladoceran occurring in small Central European temporary waters. I investigated the influence of intensity of illumination on hatching success, and effect of isolating the eggs encased in ephippia from the sediment. Fraction of eggs terminating diapause, fraction of embryos successfully leaving the egg membranes, and timing of the response were assessed at 15 ˚C under four intensities of illumination (100% = 35µmol.m2 .s-1 , 75%, 50%, 25%; photoperiod 12h light: 12h dark) and in complete darkness for 21 days. My results support previous suggestions that there is no genetically-fixed bet-hedging strategy in D. obtusa. I observed high proportion of eggs which terminated diapause in all...
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The dynamics of sexual reproduction and ephippia production of Daphnia in reservoirs
VANÍČKOVÁ, Ivana
This thesis focused on the dynamics of the sexual reproduction of microcrustacean Daphnia (Cladocera, Anomopoda). Sex in Daphnia is induced environmentally after rounds of asexual parthenogenesis in favorable conditions. The onset of sexual reproduction and the occurrence of sexual individuals was investigated with respect to their distribution in the water column and clonal structure. The produced sexual eggs were genotyped and their density and distribution in sediment were analyzed. The impact of massive floods was investigated. The role of sexual reproduction in stable habitats and its relevance and importance for Daphnia communities is further discussed.
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