National Repository of Grey Literature 9 records found  Search took 0.00 seconds. 
Whole-genome analysis of the house mouse hybrid zone
Janoušek, Václav ; Munclinger, Pavel (advisor) ; Choleva, Lukáš (referee) ; Chan, Yingguang Frank (referee)
Hybrid zones provide a valuable opportunity to study the process of speciation in real time. Untested combinations of genes from diverging populations come to the contact here causing a breakdown of genetic interactions and giving rise to reproductive isolation. Two house mouse subspecies (Mus musculus musculus/Mus musculus domesticus) form a narrow zone of secondary contact across Central Europe which is thought to be maintained by a balance between selection against unfit hybrids and dispersion of individuals. During my PhD study my collaborators and I used an array of ~ 1400 SNP markers to study patterns of introgression on a genome-wide scale across two/three house mouse hybrid zone transects. Our aim was to identify the genomic regions putatively harboring genes which are involved in the reproductive isolation between the two subspecies, characterize their distribution in mouse genome and assess genomic features associated with them. We were able to confirm on a genome-wide scale the importance of the X chromosome in the evolution of reproductive isolation. This chromosome exhibited introgression corresponding to strong negative epistasis and the patterns were consistent between transects pointing out to a common basis of reproductive isolation playing a role in two transects. Contrary to the...
Implemenation of the RAD sequencing methods to the population genetic studies of hedgehogs from the genus Erinaceus
Loudová, Miroslava ; Černá Bolfíková, Barbora (advisor) ; Choleva, Lukáš (referee)
Hedgehogs from the genus Erinaceus are an important model organism for studying the postglacial recolonisation of Europe and the processes that take place in the secondary contact zones of their areas of distribution. In this study, five individuals of white-breasted hedgehog (Erinaceus roumanicus), four individuals of western hedgehog (Erinaceus europaeus) and one estimated hybrid were analysed. Geographical distribution of individuals used in the study covers the region of the Central Europe, however in the further research expansion of analsysed individuals will be needed and the whole Palearct should be sampled. The main goal was to implement novel methods in research of hedgehogs, which will enable to map the population-genomic structure of the genus Erinaceus in western Palearct. The method RADSeq (Restriction site associated DNA sequencing) enables to obtain polymorphic markers, e.g., SNPs which we used (Single Nucleotide Polymorphisms) across the genome. In this work it was analyzed 16382 SNPs. Using the binary data which indicates the presence and absence of SNPs for each species, hypotheses raised under classical analyzes of genetic markers from previous studies have not been fully confirmed. In further research it will be necessary to verify possible occurrence of biases connected with...
Origin of species by interspecific hybridization in animals
Štiková, Jana ; Reifová, Radka (advisor) ; Choleva, Lukáš (referee)
Speciation mostly occur by splitting an ancestral species into two daughter species. Alternatively, new species may arise by hybridization, a phenomenon known as hybrid speciation. This type of speciation is frequent especially in plants, but recently, a growing number of example has been described also in animals. The aim of this thesis is to summarize the current knowledge about hybrid speciation and describe known examples of hybrid speciation in animals. Hybrid speciation in animals is mostly homoploid, e.g. without the change of number of chromosomes. I found 23 homoploid hybrid species in animals. Most of them belong to insects and fishes, but know examples are also among birds and mammals. Origin of species in animals by hybrid speciation seems to be more commons than was previously thought. Powered by TCPDF (www.tcpdf.org)
Evolution of sex chromosomes and karyotypes in geckos (Squamata: Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Choleva, Lukáš (referee)
Gekkota is species-rich and diverse group of squamate reptiles (Reptilia: Squamata) with almost global distribution. There were many hypothesis defined about the phylogeny of this group, traditionally based on morphological data. The essential reversal in phylogenetic relationships occurred with the entry of molecular analysis, whose differ in their conclusions from traditional approach fundamentally, even in positions of mayor lineages. This fact has an essential importance for the karyotype evolution study of this group. The ancestral state is considered as 2n=38 karyotype with all chromosomes acrocentric. In some species is this karyotype kept, in another there is apparent an influence of chromosome changes, mostly Robertsonian fusions and pericentric inversions. Diploid chromosome number is from 16 to 46, but the most common is 2n=38 karyotype of mostly acrocentric chromosomes, gradually decreasing in size. The interesting character of this group is extraordinary variability in sex determining mechanisms. We can find there species with temperature sex determination and also species with genotypic sex determination (both types XX/XY and ZZ/ZW). Sex chromosomes data are documented in only 17 species. Sex chromosomes differ rapidly in their morphology and their homology between sister taxa was not proved...
Out of Asia Minor into Danube Drainage: Phylogeography and colonisation pathways in the loach fish Cobitis strumicae
Majtánová, Zuzana ; Choleva, Lukáš (advisor) ; Reichard, Martin (referee)
The spiny loach Cobitis strumicae is a small bottom-dwelling freshwater fish whose progenitor colonised the Balkan Peninsula from the Near East through the Asia Minor. The current geographic distribution of C. strumicae forms a ring around the Stara Planina (Balkan mountains), inhabitting Danube Basin and coastal rivers of Black Sea and Aegean Sea. Using one marker of mitochondrial DNA (gene for cytochrom b) and one marker of nuclear DNA (S7 gene, first intron), we reconstructed the species distribution and phylogenetic relationship of 44 populations throughout C. strumicae distribution. We also analysed its sister species, C. punctilineata, which lives inside the distribution area of C. strumicae. Aplication of four phylogenetic approaches confirm the monophyly and species statut and endemicity of C. punctilineata, and, moreover, the evidence of secondary hybridization with C. strumicae was found. The network analysis using median-joining method showed deep divergence between the both species. Phylogenetic analyses for cyt b gene confirmed the monophyly of C. strumicae, with internal substructure into at least two well divided lineages, which suggests the process of local speciation. Phylogenetic analyses of S7 gene did not support the monophyly of C. strumicae. Instead, the two separated...
Lost sex: multilocus DNA evolution the hybrid fish complex C.taenia (Teleostei)
Choleva, Lukáš ; Janko, Karel (advisor) ; Mikulíček, Peter (referee) ; Hulva, Pavel (referee)
12 General summary "It is unwise to intrude the suggestion of parthenogenesis, even of a modified sort, into vertebrate literatures. The phenomenon is so at variance with what is known and beleived about vertebrates development that I am sure no vertebrate morphologists would admit for a moment that the natural development from egg to sexual maturity of an individual vertebrate without the direct inclusion of the male element is within the realm of probability", reacted the morphologist Howell (1933. Science 77: 389-390) sarcastically on the discovery of the first recognized asexual vertebrate, a live-bearing fish Poecilia formosa (Hubbs et Hubbs 1932. Science 30: 628-630). "The examples of parthenogenesis has been reported in almost all vertebrate groups," (Lampert 2008. Sexual Development 2: 290-301). The ongoing effort to explain the widespread occurrence of sexual reproduction among animals is often called the "queen of problems in evolutionary biology", and there is still no consensus regarding the explanation. Simultaneously, asexual reproduction exists among some animals. Here, the 'asexuality' refers to any reproductive process that does not involve sex (Mendelian meiosis is mising), except self-fertilization. One individuum produces a progeny genetically identical to its parent, except those sites...
Earlier evolutionary dead-ends, now the creators of a reproductive strategy: the origin and reproduction of the all-male water frog lineage Pelophylax esculentus
Doležálková, Marie ; Choleva, Lukáš (advisor) ; Mikulíček, Peter (referee) ; Kratochvíl, Lukáš (referee)
Asexual modes of reproduction are usually based on the principle of copying (cloning) DNA from the female and passing it on to the offspring. For most asexually reproducing vertebrates the progeny develop from an unreduced and often unfertilised egg. This is driven by the mechanisms of parthenogenetic and gynogenetic reproduction. While in the former the clonal germ cell develops spontaneously and separately, in the latter a sexual partner is needed to activate the cleavage of the ovum, although without the fusion of the sperm and egg. Therefore in both cases there is no fertilization and the clonal progeny consist solely of daughters, hence the majority of previous studies have only focused on asexual female lineages. However, on rare occasions asexual clonal males can arise when the right fertilization occurs. Whilst these offspring are usually infertile, fertile diploid asexual males have been discovered in just three genera of hybrid origin in vertebrates. One of these unique cases is the European water frog complex of the genus Pelophylax, whose distribution includes the Czech Republic. In areas around the upper Odra River populations of hybrid males were recently discovered who form stable all-male lineages, similar to those formed by asexual females. The results of this study show that males produce...

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