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Sperm morphology and motility in estrildid finches of the genus Lonchura
Šárová, Markéta ; Reifová, Radka (advisor) ; Frolíková, Michaela (referee)
Sexual selection plays an important role in the evolution of animals. Today we already know that it takes place not only before copulation (precopulatory sexual selection), but also after copulation. This type of sexual selection is called postcopulatory sexual selection, and occurs mainly in promiscuous species, where females mate with multiple males. In this case, sperm competition occurs in the female reproductive tract. To increase the likelihood of their reproductive success, males began to develop surprisingly diverse sperm adaptations at the morphological, physiological, or behavioural levels. These adaptations often affect sperm velocity (motility), which is a key factor for successful egg fertilization. However, the result of reproductive success can also be influenced by females, who may prefer sperm with a certain phenotype in the process of cryptic female choice, and thus, for example, obtain better genes for offspring. In some species, females even can have the ability to sort and store sperm in specialized organs in which the sperms are nourished for some time, and then used to fertilize the egg. Even in this case, the storage of sperm is often affected by sperm morphology. Due to these mechanisms of postcopulatory sexual selection, sperm are under strong selection pressure, which can...
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The role of hybridization in animal evolution
Šárová, Markéta ; Reifová, Radka (advisor) ; Černá Bolfíková, Barbora (referee)
There is a growing number of studies showing that interspecific hybridization and gene introgression have a creative role in the evolution of animals. These studies emphasize that hybridization and a gene introgression represent an important source of a genetic variability. Within the process of adaptive introgression, adaptive traits may spread among species and help them to colonize new environments. Interspecific hybridization may also contribute to the emergence of new phenotypes and evolutionary novelties and thus contribute to adaptive radiations. Hybridization can be also a cause of parallel evolutions in many organisms. Another way how hybridization affects evolution is related to a speciation. Hybrid speciation could be one of ways how new species arise, and in this way increase the biodiversity. However in many cases the hybridization has an opposite impact on species richness and present a danger of species extinction by hybridization. The aim of this bachelor thesis is to explain and discuss the above described processes, introduces selected examples of animals related to these processes, and finally evaluate the role of interspecies hybridization in animal evolution. Key words: interspecific hybridization, adaptive introgression, adaptive radiation, parallel evolution, hybrid speciation
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