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National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Sperm morphology in the secondary contact zone of Common Nightingale and Thrush Nightingale
 Opletalová, Kamila ; Reifová, Radka (advisor) ; Piálek, Jaroslav (referee)
The male gametes (sperms) are under strong sexual selection and are therefore very diverse in their morphology and often differ even amongst closely related species. Sperms are thus assumed to play very important role in reproductive isolation between species, due to their fast evolution in morphology. In my master thesis, I have studied the possible role of sperm morphology divergence in reproductive isolation in two sister species of passerine birds, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia). The areas of these species overlap in secondary contact zone running across central and Eastern Europe, where they occasionally hybridize. I have compared sperm morphology of males of both species originating in allopatric and sympatric localities as well as interspecies hybrids. The results showed significant differences in total sperm length which is approximately 20 % longer in the common nightingale. That is caused by great interspecies divergence in midpiece (containing mitochondria) length. Interspecific hybrids showed sperms with intermediate length but despite expectations completely morphologically normal. This outcome corresponds with observed fertility in F1 hybrid males. What I consider to be an essential finding is a significant divergence in head...
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Evolution of intrinsic postzygotic reproductive isolation in birds
 Opletalová, Kamila ; Reifová, Radka (advisor) ; Vošlajerová, Barbora (referee)
Hybrid sterility plays a key role in reproductive isolation during evolution of species. The mechanisms responsible for hybrid sterility are relatively well understood in organisms with heterogametic males, such as drosophila or mouse but are largely unknown in organisms with heterogametic females (e.g. birds). Studies on reproductive isolation in birds takes place in natural hybrid zones, instead of captivity. Hybrid sterility preferentially affects the heterogametic sex, males in mammals (XY) and females in birds (ZW), according to Haldane's rule. This leads to reduced introgression in sex chromosomes and mitochondrial DNA compared to autosomal DNA. The purpose of this thesis is to summarize known information on hybrid sterility and its expression in two models of interspecies hybridization: flycatchers and nightingales. Additionally, this thesis contains also a practical part, which compares morfology of sperms of two species of nightingales. Powered by TCPDF (www.tcpdf.org)
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See also: similar author names
3 Opletalová, Kateřina
1 Opletalová, Klára
7 Opletalová, Kristýna
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