National Repository of Grey Literature 26 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Phylogeny and evolution of the family Megastigmidae (Hymenoptera: Chalcidoidea)
Böhmová, Julie ; Janšta, Petr (advisor) ; Opatová, Věra (referee)
The family Megastigmidae (Hymenoptera: Chalcidoidea), one of the hymenopteran parasitoid families, is unique in containing many species with phytophagous larval feeding strategy. A number of species of different genera are seed-feeders and the genus Bortesia is even capable of inducing galls. The family Megastigmidae is found mainly in the Australian region but a few genera/species groups are widespread throughout different areas, mainly in the Oriental and the Holarctic region. The main goal of this study was to map phylogenetic relationships among genera and clarify the following: the overall number of transitions between a parasitoid and a phytophagous way of life, the ancestral feeding strategy of the family, the evolution of feeding strategies in the genus Megastigmus, and the geographical area of origin of the family. The questions were tested based on a phylogeny reconstructed by a state-of-the-art method - sequencing of "Ultra-Conserved Elements (UCEs)" - using 100 specimens of Megastigmidae from 11 out of 12 currently valid genera selected taking into consideration their feeding strategy and biogeographical origin. The final dataset contains 1210 loci (570,000 base pairs in length) and most nodes are supported by bootstrap value 100. The results show that the family can be divided into 3...
Genome size in the evolution of cockroaches
Stuchlíková, Magdalena ; Janšta, Petr (advisor) ; Vít, Petr (referee)
Genome size or nuclear DNA content is a a trait which varies greatly among living organisms, with no apparent relashionship between genome size and organismal complexity. It is usually described using the C-value as either a number of base pairs or picograms of DNA. Unresolved questions regarding mechanisms influencing genome size and relationships between genome size and other organismal traits are together known as the C-value enigma. Genome size is known to positively correlate with cell size and negatively with developmental and cell division rate. A maximum constraint of 2 pg has also been proposed for haploid genome sizes of holometabolous insects. Despite the fact that there are about one million described insect species, genome sizes are only known in a fraction of them. This thesis thus aims to extend the dataset of known insect genome sizes by as many species of cockroaches (Blattodea) as possible. Another aim is to compare results with known phylogeny and also to compare difference in genome size between sexes. Flow cytometry was used for genome size estimations, which is a rapid, simple and effective method, also suitable for study of ploidy levels and other cellular charasteristics.
Mimicry of hoverflies (Diptera: Syrphidae) in the context of selection pressures from predators, thermoregulation and sexual selection
Daňková, Klára ; Janšta, Petr (advisor) ; Pekár, Stanislav (referee)
Thermoregulation plays an important role in organisms' lives during foraging, escaping from predators, sexual selection or overwintering. Moreover, pressure on efficient thermoregulation could affect species on an evolutionary level and was recently hypothesized to maintain imperfect mimicry in hoverflies (Diptera, Syrphidae). We set these two aims: 1) to study relationships between thermoregulation, mimicry accuracy and resembled model, 2) to closely study effect of developmental temperature in an intermediately accurate honeybee mimic, Eristalis tenax. In the first part of the project, we examined temperature excess of 566 specimens in 47 species of hoverflies in the field. We did not find significant effect of mimicry accuracy on temperature excess in our data. However, we found a strong sexual dimorphism. Females had lower temperature excess, which was very resilient to internal and external factors, whereas males had higher temperature excess, influenced by activity at time of capture (flying > sitting) and resembled model (bumblebee-mimics > honeybee- mimics > wasp-mimics > solitary bee-mimics). We suggest, that males are pushed to higher temperature excess by sexual selection within lekking. In the second part of the project, we reared E. tenax in three different temperatures in laboratory...
Parasitic wasps Anaphes flavipes Förster, 1841 (Hymenoptera: Mymaridae) as model for parasitoid-host interactions study
Samková, Alena ; Janšta, Petr (advisor) ; Honěk, Alois (referee) ; Hrček, Jan (referee)
Parasitic wasps have a wide range of specific developmental interactions with their hosts due to a close "parasitoid-host" relationship and that allows the study of many ecological and evolutionary questions. In our work, we focused on the parasitoid-host interactions in the parasitic wasp Anaphes flavipes (Förster, 1841) (Hymenoptera: Mymaridae). Because A. flavipes show a high variability of morphology and size, they have been repeatedly described as a new species in the past. Thus, we first redescribed the species and we compared the variability of some morphological structures for wasps from different localities (Paper 1). The high variability of the body size of wasps is reviewed in the second article, where we propose that females of A. flavipes do not decide according to the generally known "trade-off" scheme, if they will have more smaller offspring or fewer bigger offspring. In fact, the number of offspring depends on the body size of the female ("body size-fitness" hypothesis), which determines the variable reproductive strategies of mothers (the number of individuals that are laid into one host by a single female) (Paper 2). The third manuscript deals with the reproductive strategy of gregarious parasitoids. The reproductive strategy does not have to be stable; in the case of A....
Adaptation of parasitoids used during host utilization in the Chalcidoidea superfamily (Hymenoptera)
Ročková, Lenka ; Janšta, Petr (advisor) ; Holý, Kamil (referee)
The Chalcidoidea superfamily is one of the most diverse groups of parasitic insects. The life strategy prevalent in most species of this superfamily is parasitoidism, which can be used by human as an effective tool in biological control. Parasitoids deal during their reproduction with the fact, that their hosts are often hidden in hardly accessible places. This matter of fact is probably the reason for development of some of the ovipositor's characteristics, that cannot be explained phylogeneticaly. These characteristics are therefore described as adaptations for parasitoid lifestyle. These adaptations mirror the nature of substrate which their hosts inhabitate and where the oviposition is being realised. Species inhabitating the same niche use to show different adaptations of the ovipositor, which could be explained by better distribution of the present resources. It is also considered a speciation factor of sympatric species. Detailed studies of the differences between ovipositor adaptations may simplify the determination procces of life strategies of hymenopteran insects, which could be performed based on ovipositor morphology. Key words: parasitic Hymenoptera, Chalcidoidea, ovipositor structure, hosts seeking, adaptation for host utilization, host discrimination
Evolution of parasitic Hymenoptera hosts specialisation of the genus Torymus
Bubeníková, Kristýna ; Janšta, Petr (advisor) ; Bogusch, Petr (referee)
The genus Torymus (Chalcidoidea: Torymidae) has very diversified parasitic strategies and adaptations to its hosts. Its larvae are ectoparasitoids and attack mostly larvae of various gall wasps (Hymenoptera: Cynipidae) and gall midges (Diptera: Cecidomyiidae). However, few species prefer also other insect groups as a host or are even phytophagous. Many hypotheses concerning evolution of insect host associations were published, but have not been satisfactorily tested using parasitic insects as a model. In this thesis I studied coevolution of the genus Torymus and its hosts. The main questions are what kind of host shifts occurred during the evolution of host strategies and whether sister species of parasitoids are specific to the related hosts/or nonrelated hosts living in the same type of habitat. I also studied changes at morphological adaptations to its hosts. To test critically these hypotheses, I constructed phylogenetic tree of selected Torymus species based on 5 genes and compared their host association within and between clades of Torymus. Key words: Torymus, Chalcidoide, parasitoid, phylogeny, host specialisation
Visualization of insect morphological structures using x-ray microtomography and other modern 3D techniques
Rosová, Kateřina ; Prokop, Jakub (advisor) ; Janšta, Petr (referee)
In my bachelor thesis I describe techniques currently used for 3D visualization of morphological structures of insects. Since X-ray microtomography is currently the most attractive option for visualizing internal insect structures, more space is dedicated to its description, but the work includes more innovative techniques. Traditional techniques used in the past decades are not neglected, since they do not lose their importance in the competition of new methods. In the first part the individual methods are presented in terms of their simplified functional mechanisms and the basic steps of creation of 3D reconstructions are described. Techniques are further compared in the text in terms of their usability on different types and sizes of samples, according to the desired final resolution of the visualization, the time required to complete the observation and final visualization and in terms of invasiveness of the techniques. The last chapter summarizes the possibilities of using these innovative methods in entomology based on available studies. Keywords: Insecta, morphology, 3D visualization, SEM, CLSM, MRI, Micro-CT
Phytophagy as an alternative feeding strategy of parasitic Hymenoptera larvae
Böhmová, Julie ; Janšta, Petr (advisor) ; Skuhrovec, Jiří (referee)
Parasitoidism is considered to be the primary larval feeding strategy of parasitic Hymenoptera (Hymenoptera: Apocrita: Parasitoida). However, many species became secondarily phytophagous, in particular some species of Ichneumonoidea, Cynipoidea and Chalcidoidea. The bachelor thesis summarizes the knowledge about phytophagy in these superfamilies and divides them into four categories. The thesis further evaluates morphological and behavioural adaptations related to this way of life as well as other aspects of their coevolution with host plants.
Flow cytometry and its use for study of insects
Stuchlíková, Magdalena ; Janšta, Petr (advisor) ; Sadílek, David (referee)
Flow cytometry is a modern technique in research, playing a significant role in biomedicine and botanics. Despite its benefits (speed, simplicity, low costs), flow cytometry is currently not used in the study of insects on a large scale. This thesis gives an overview as to how flow cytometry is used in research on insects and summarises the results of such study. This pertains to genome size and its connections to other phenomena. Other focal points of research, such as ploidy and base pair ratios, are addressed to a lesser extent. Key words: flow cytometry, use in study of insects, genome size, ploidy, invertebrates

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