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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Divergent natural selection alters male sperm competition success in Drosophila melanogaster

Dobler, Ralph, Charette, Marc, Kaplan, Katrin, Turnell, Biz R., Reinhardt, Klaus 20 March 2024 (has links)
Sexually selected traits may also be subject to non-sexual selection. If optimal trait values depend on environmental conditions, then “narrow sense” (i.e., non-sexual) natural selection can lead to local adaptation, with fitness in a certain environment being highest among individuals selected under that environment. Such adaptation can, in turn, drive ecological speciation via sexual selection. To date, most research on the effect of narrow-sense natural selection on sexually selected traits has focused on precopulatory measures like mating success. However, postcopulatory traits, such as sperm function, can also be under non-sexual selection, and have the potential to contribute to population divergence between different environments. Here, we investigate the effects of narrow-sense natural selection on male postcopulatory success in Drosophila melanogaster. We chose two extreme environments, low oxygen (10%, hypoxic) or high CO₂ (5%, hypercapnic) to detect small effects. We measured the sperm defensive (P1) and offensive (P2) capabilities of selected and control males in the corresponding selection environment and under control conditions. Overall, selection under hypoxia decreased both P1 and P2, while selection under hypercapnia had no effect. Surprisingly, P1 for both selected and control males was higher under both ambient hypoxia and ambient hypercapnia, compared to control conditions, while P2 was lower under hypoxia. We found limited evidence for local adaptation: the positive environmental effect of hypoxia on P1 was greater in hypoxia-selected males than in controls. We discuss the implications of our findings for the evolution of postcopulatory traits in response to non-sexual and sexual selection.
12

Syndrom karotického pahýlu / The Carotid Stump Syndrome

Hrbáč, Tomáš January 2012 (has links)
Introduction: Internal Carotid Stump Syndrome may be one of the possible causes of ischemic stroke (iCMP), as well as retinal infarction (RI). Syndrome of the occluded internal carotid (ACI) (stump syndrome) is a nosological unit, which is characterized by an onset of ipsilateral iCMP or RI of thromboembolic ethiology in patients with occlusion of ACI via the externa carotid or arteria ophthalmica. In my thesis, I have concentrated upon the specification of the stump syndrome, its diagnostics and treatment; furthermore I have assessed the appropriateness of surgical approach in comparison with conservative approach. Material and methods: A total of 621 patients with occlusion were treated in two centres in the course of five years. In a group of 40 patients, the ACI occlusion was detected sonographically, the length of the occluded ACI being >5 mm, with normal vasoreactivity based upon SPECT CO2 and excluded cardiogenic cause of iCMP. The patients were divided in two groups - surgical and conservative. Patients were monitored in 6-month intervals for the total period of four years. Results: No RI or iCMP were detected in the surgical group; one patient died six months after surgery. We observed one case of amaurosis fugax in the conservative group. Conclusion: Ultrasound examination is a fully sufficient...
13

Syndrom karotického pahýlu / The Carotid Stump Syndrome

Hrbáč, Tomáš January 2012 (has links)
Introduction: Internal Carotid Stump Syndrome may be one of the possible causes of ischemic stroke (iCMP), as well as retinal infarction (RI). Syndrome of the occluded internal carotid (ACI) (stump syndrome) is a nosological unit, which is characterized by an onset of ipsilateral iCMP or RI of thromboembolic ethiology in patients with occlusion of ACI via the externa carotid or arteria ophthalmica. In my thesis, I have concentrated upon the specification of the stump syndrome, its diagnostics and treatment; furthermore I have assessed the appropriateness of surgical approach in comparison with conservative approach. Material and methods: A total of 621 patients with occlusion were treated in two centres in the course of five years. In a group of 40 patients, the ACI occlusion was detected sonographically, the length of the occluded ACI being >5 mm, with normal vasoreactivity based upon SPECT CO2 and excluded cardiogenic cause of iCMP. The patients were divided in two groups - surgical and conservative. Patients were monitored in 6-month intervals for the total period of four years. Results: No RI or iCMP were detected in the surgical group; one patient died six months after surgery. We observed one case of amaurosis fugax in the conservative group. Conclusion: Ultrasound examination is a fully sufficient...

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