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Role of microorganisms in the evolution of reproductive strategies in birds
Novotná, Lucie ; Javůrková, Veronika (advisor) ; Ferenc, Michal (referee)
Microorganisms are ubiquitous and can be found on the body of birds, in avian nests or may be carried into the nest along with nest-lining material. Microorganisms may therefore colonize eggshells of eggs in a clutch and subsequently penetrate into the egg contents. This so called trans-shell infection has been observed to affect hatching success, cause embryo mortality or subsequently influence hatchlings phenotype. Nevertheless, the probability of eggshell bacterial load or trans-shell infection depends on many factors, including environmental conditions, nest type, incubation pattern, and nest-lining material. Furthermore, some modifications of avian reproductive strategies may lead to reduction of negative effect of trans-shell infections, and significantly improve reproductive success. These mechanisms include incubation, mechanical and chemical barriers of egg, eggshell pigments or using of feathers and specific plants as nest lining material. Based on these findings, it can be concluded that the different reproductive strategies in birds should be a result of strong selective pressure caused by microorganisms. Although many recent studies have supported this assumption, research on this issue still suffers from many methodological shortcomings that must be eliminated in future studies.
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Investment in reproduction and nest defense in waterfowl
Javůrková, Veronika ; Albrecht, Tomáš (advisor) ; Remeš, Vladimír (referee) ; Weidinger, Karel (referee)
Investment in reproduction is considered to be crucial component of life history traits. Reproductive success is however constrained by generally unpredictable environmental conditions. Based on "bet hedging" theory, individuals are forced to eliminate such unpredictability via the mixed strategy to maximize their long-term fitness. Predation represents underlying factor affecting individual reproductive success, and it undoubtedly lies behind the evolution of alternative reproductive strategies such as extra-pair paternity and conspecific brood parasitism. Behavioral mechanisms related to nest defense are thought to be investment in reproduction in accordance with trade-off between actual and residual reproductive value. Despite the extensive interest in the principles associated with parental investment into the nest defense, studies describing in detail the pattern of particular antipredator strategies are rare. Similarly, mechanisms responsible for maintenance of egg- viability during prolonged egg-laying period in species delayed the onset of incubation are poorly understood. In accordance with mentioned themes, this thesis includes publications aimed at aspects of reproductive biology and antipredator behavior in Mallards (Anas platyrhynchos). Particular publications concretely documented: a)...
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