National Repository of Grey Literature 110 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Reproductive Strategies of Geckos: The Role of Macroevolutionary Novelties and Phenotypic Plasticity
Kubička, Lukáš ; Kratochvíl, Lukáš (advisor) ; Rehák, Ivan (referee) ; Boukal, David (referee)
Presented Ph.D. thesis contains an introduction and four chapters concerning reproductive strategies in geckos. The chapters include four peer-reviewed papers and a submitted manuscript. All geckos share rather exceptional reproductive trait known as invariant clutch size, which is characterised by low and invariable clutch size. The first chapter demonstrates that invariant clutch size probably evolved in geckos under selection for enlargement of investment per offspring. On the other hand, in anoles (a group not related to geckos possessing the same mode of reproduction) invariant clutch size allowed considerable decrease of female reproductive burden. Moreover, the interspecific allometries of egg mass and clutch mass in anoles and geckos are informative for understanding of reproductive allometries in a broader context of squamate reptiles. The second chapter is focused on a trade-off in energy investment among reproduction, growth and fat storage in a gecko Paroedura picta. Surprisingly, there seems to exist a clear hierarchical rule for allocation among particular life-history traits. Effect of temperature on reproductive rate in the same species of gecko is the subject of the third chapter. Observed thermal dependence is in contrast to the general relationship suggested under the so-called...
The sex determination in the gecko genus Phelsuma
Peš, Tomáš ; Kratochvíl, Lukáš (advisor) ; Kverková, Kristina (referee)
Geckos (Gekkota) are a diverse group of squamate reptiles. The species richness of geckos is associated with a wide variety of sex determination systems. We can encounter male and female heterogamety, environmental sex determination, or asexuality in this group of reptiles. The diversity of geckos makes this group very interesting for studying of the evolution of sex determination. Due to the large number of species, we know the type of sex determination in just a fraction of taxa. The genus Phelsuma has been little studied in this respect and, with one exception, published data are not very reliable. In this thesis, sex determination in Phelsuma laticauda and Phelsuma nigristriata was investigated using an incubation experiment. I proved that both species have environmental sex determination. The effect of incubation temperature on morphological characteristics was also investigated in hatchlings. The possible persistence of this effect into adulthood was re-tested in one year old geckos.
Evolution of brain complexity and processing capacity in birds: Cracking the problem using isotropic fractionator technique
Kocourek, Martin ; Němec, Pavel (advisor) ; Sedláček, František (referee) ; Kratochvíl, Lukáš (referee)
The most fundamental principle of comparative sciences has always been and still is the search for similarities and differences. Maybe that is why people are fascinated by the cognitive abilities of birds like corvids and parrots and their similarities to those of humans. For a long time, the prevailing explanation for the unique abilities of these species was their high relative brain size. However, the brain's processing capacity is not based on its size but on its internal architecture and the number of neurons and synapses. Today, we already have data on the numbers of neurons for hundreds of mammalian, avian, and reptilian species, obtained with the isotropic fractionator. In this thesis, I analyse cellular scaling rules for brains of birds and compare them between avian clades. Bird brains are characterized by large numbers of neurons and high neuron densities, which are comparable to those of mammals in gallinaceous birds (Galliformes) and in passerine birds (Passeriformes) and parrots (Psittaciformes) even exceed those observed in primates. The distribution of neurons is also different. In songbirds and parrots, the majority of neurons are typically located in the telencephalon, specifically in the pallium. The latest data suggest that this is a common feature of core land birds...
Mechanisms of reproductive isolation between two hybridizing passerine species, the common nightingale and the thrush nightingale
Poignet, Manon ; Reifová, Radka (advisor) ; Choleva, Lukáš (referee) ; Kratochvíl, Lukáš (referee)
iv - ABSTRACT (in English) - A key step in the origin of new species is the evolution of the reproductive isolation mechanisms separating the gene pools of newly emerging species. Despite a growing number of studies, we still know very little about the molecular, physiological and genetic mechanisms underlying reproductive isolation. Hybrid zones represent useful examples of ongoing species differentiation and can provide information about the nature of reproductive isolation separating the species and mechanisms facilitating or limiting the hybridization. Using two naturally hybridizing passerine species, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia), we evaluated several mechanisms of reproductive isolation at the chromosomal, phenotypic, and genetic levels, with a focus on postmating prezygotic (PMPZ) and postzygotic isolation mechanisms. These nightingale species diverged ~1.8 Mya and currently hybridize in a secondary contact zone running across Central and Eastern Europe. First, we analysed the genetic composition of the secondary contact zone, demonstrating that parental forms are predominant in the hybrid zone, with few F1 hybrids (3.4%), early backcross hybrids (3.1%) and the absence of F2 hybrids. This suggests strong but incomplete reproductive isolation....
Molecular mechanisms of environmental sex determination in reptiles
Maslova, Mariia ; Kratochvíl, Lukáš (advisor) ; Krylov, Vladimír (referee)
Molecular mechanisms underlying environmental sex determination remained elusive for half a century, until just recently, when new insights into the topic were gained. The thesis summarizes current progress on this issue and focuses, among other things, on the role of oxidative stress and regulation of gene expression in the process of sex determination and sex reversal.
Sex ratios in reptiles according to the type of sex determination
Palata, Tomáš ; Kratochvíl, Lukáš (advisor) ; Rehák, Ivan (referee)
There are many factors influencing sex ratios in reptile populations and these factors can differ among sex ratios in different developmental stages. The observed ratio is the result of many complex processes. One of the key factors is the mechanism of sex determination. In reptiles we distinguish two mechanisms of sex determination. The first is genotypic sex determination (GSD), where sex is determined during the fusion of gametes. Species with GSD show just little variation in sex ratios after birth or hatching and during adulthood there is a higher mortality rate of the heterogametic sex. Secondarily, there are reptiles possesing environmental sex determination (ESD). The sex of the developing individual of this species is influenced by incubation temperature during the thermosensitive phase of development. Reptiles with ESD show much greater variability in sex ratios after hatching and this variability may persist to adulthood. This thesis focuses mainly on the differences in sex ratios between GSD and ESD species. One of its interests is also the question of vulnerability of reptiles with ESD in terms of skewed sex ratios during contemporary climate change. Key words: sex ratio, reptiles, sex determination, GSD, ESD, climate change
Sex chromosome evolution in selected taxa of teleost fishes (Teleostei)
Pavlica, Tomáš ; Sember, Alexandr (advisor) ; Kratochvíl, Lukáš (referee)
Teleosts represent more than half of the extant vertebrate species. They show a wide range of mechanisms driving both sex determination and sex differentiation, including nine sex chromosome systems described to date. Teleost sex chromosomes are generally considered as evolutionarily young, therefore they are suitable for an analysis of the early stages of evolution of these unique genomic regions. The aim of the current thesis was to analyze the presence and degree of differentiation of sex chromosomes in two Nothobranchius killifish species and one Bunocephalus banjo catfish representative using conventional and molecular cytogenetic methods. Different populations of N. kadleci and N. furzeri analysed in this thesis shared anXY sex chromosome system. Despite the obvious heteromorphy of their sex chromosomes, comparative genome hybridization (CGH) did not show any region of differentiation. Analysis of synaptonemal complexes by immunostaining coupled with the mapping of 18S rDNA and telomeric repeats using fluorescent in situ hybridization (FISH) showed mainly standard pairing with the contribution of synaptic adjustment. Pachytene spreads of females from one N. furzeri population contained a small supernumerary chromosome which was not present in metaphases of studied somatic cells. Distribution...
Constraints and the evolution of egg size and juvenile size in amniotes
Kubát, Jan ; Kratochvíl, Lukáš (advisor) ; Hořák, David (referee)
Amniotes (mammals, reptiles including birds) exhibit wide diversity in egg/offspring size relatively to female body size. This study reviews mechanisms determining size of propagules (such as morphological or physiological constraints, trade-off between size versus number etc.). Particular attention is paid to comparison of allometric relationship in egg/offspring size among individual amniotic lineages.
Relationship between developmental rate and egg size in reptiles
Mrskočová, Jana ; Kratochvíl, Lukáš (advisor) ; Hořák, David (referee)
Existing analyses indicate that there is a positive relationship between egg mass and incubation period at large taxonomical scales. This suggests that animals are able to solve the trade-off between egg mass and developmental rate. However, some studies (not only reptile- focused) prove that this relationship is taxon-specific. Studies performed at the intraspecific level differ in the conclusion whether such relationship actually exists. Moreover, there are many factors which complicate these analyses (for example the ontogenetic shift at the time of oviposition, presence of diapause during the embryonic development, synchronization of the time of hatching, temperature and humidity). I suggest that the main factor is temperature that has been filtered out by various authors by means which I find unsatisfactory. This thesis attempts to prove that the relationship between egg mass and incubation period is not sufficiently and explicitly explained and to discuss the complications regarding its research.
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...

National Repository of Grey Literature : 110 records found   1 - 10nextend  jump to record:
See also: similar author names
1 Kratochvíl, Leoš
2 Kratochvíl, Lubomír
5 Kratochvíl, Lukáš
2 Kratochvíl, Lumír
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