Landscape genetics of highly disturbed arable systems : insights gained from investigating a small mammal species

A large proportion of the earth’s surface is dedicated to food production, and agriculture is widely acknowledged to influence local biodiversity via habitat loss and degradation. Landscape genetics is an emerging field which can provide detailed understanding of how wildlife populations are influenced by landscape configuration and composition but the approach is yet to be fully integrated with agroecology. When addressing landscape genetics questions, small mammals may provide insight; they may act as model organisms, they are abundant, they are relatively easy to sample and they may have important ecological roles within arable ecosystems. This thesis merged the study of arable landscapes, landscape genetics and small mammals, to develop what is known about the landscape genetics of wild species in this dynamic habitat type. To decide upon a study organism, small mammals were surveyed at an example arable field site. Wood mice (Apodemus sylvaticus) were found to be the most abundant species and a microsatellite marker multiplex was developed for genotyping individuals. Two aspects of their landscape genetics in arable habitat were investigated. First, the possibility of temporal patterns in fine scale genetic structure of arable populations was explored, since this had not been investigated previously. Next, inter-population genetic differentiation was examined to determine whether arable habitat acted as a barrier to gene flow for this species. At the fine scale, three genetically distinct clusters of wood mice were identified and temporal variation in the spatial pattern was confirmed. There was no evidence that arable habitat acted as a barrier to gene flow for this species in comparison to populations in urban habitat, which showed significant differentiation. It is hoped that the landscape genetic insights provided by this thesis will encourage greater momentum for conducting landscape genetics studies in agricultural habitat

The Functional, Ecological, and Evolutionary Morphology of Sea Lampreys (Petromyzon marinus)

Lampreys (Petromyzontiformes) are jawless vertebrates with an evolutionary history lasting at least 360 million years and are often used in comparisons with jawed vertebrates because some of their morphological aspects, such as the segmented trunk musculature with curved myosepta and a non-mineralized skeleton fibrous skeleton, are thought to resemble the condition of early vertebrates before the evolution of jaws. Although earlier authors studied the morphology of the skeleto-muscular system of the trunk of lampreys, their studies are not detailed and complete enough to allow a functional and biomechanical analysis that is needed as a basis for modeling the mechanics of lamprey locomotion and for understanding the causal roles played by the anatomical structures within the trunk. Questions remain, such as what is the architecture of the trunk fibroskeleton, and how does it function with the musculature to bend the trunk? This dissertation studied the functional, ecological and evolutionary morphology of the trunk of Sea Lampreys (Petromyzon marinus) as well as its relevance in understanding the environmental history of landlocked lamprey populations. Functional morphology revealed that the fibroskeleton of the trunk is a self-supporting concatenated system of fibers, which creates a scaffold for the musculature and transmits forces to bend the trunk during swimming. Ecological morphology demonstrated the adaptive advantage of the fibroskeleton’s architecture, which enables the movements that are performed during migration and spawning and gives lampreys the capacity to colonize upstream realms. These results help explain the evolutionary morphology of lampreys, which likely originated in freshwater as algal feeders and evolved into parasites after going through an intermediary scavenging stage. When these insights are applied to the evolution of landlocked Sea Lampreys, it becomes evident that their entry into freshwater lakes occurred as soon as they were able to reach them and that populations likely became established in Lake Ontario, Lake Champlain, and the Finger Lakes thousands of years ago. This insight undermines the current status of landlocked Sea Lampreys as invasive species in these lakes and the case for their eradication. Hence, this dissertation provides a comprehensive and integrative analysis of lamprey biology from their anatomy to environmental policy

Blending by rational canal and ringed surfaces

této práci studujeme racionální techniky vhodné pro výpočet přesných/přibližných parametrizací kanálových a prstencových ploch. V první části práce se soustředíme na implicitně zadané kanálové plochy navržený přístup je založen na výpočtu přibližné parametrizace tak zvaných obrysových křivek na zadané kanálové ploše. Tato metoda může být přímo aplikována na praktické problémy parametrizace implicitních přechodových ploch sestávajících z částí kanálových (nebo přibližně kanálových) ploch. V druhé části práce studujeme podmínku zajišťující racionalitu obrysových křivek na kanálových plochách zadaných pomocí střední osy a poloměrové funkce. Tyto křivky jsou poté použity k výpočtu racionální parametrizace kanálových ploch s pythagorejskými normálami. Použití obrysových křivek v algoritmu parametrizace dovoluje v jednom kroku zkonstruovat celou třídu racionálních kanálových (přechodových) ploch, což je speciálně výhodné pro konstruování přechodových ploch splňujících jistá omezení, např. pokud je požadováno, aby se daná plocha vyhnula překážkám. Poslední část této práce je věnována racionálním prstencovým plochám, pomocí nichž je navržena metoda konstrukce přechodových ploch mezi dvěma prstencovými plochami. Tato metoda může být použita pro konstrukci přechodových ploch, které se mají vyhnout jistým překážkám nebo pro konstrukci přechodových ploch mezi několika prstencovými plochami.Katedra matematikyObhájenoIn this thesis we study rational techniques for computing exact/approximate parameterizations of canal and ringed surfaces. In the first part of the thesis we focus on canal surfaces given implicitly the designed approach is based on computing approximate topology-based parameterizations of the so called contour curves on the given canal surface. The method can be directly applied on the practical problem of parameterizing implicit blends consisting of parts of canal (or canal-surface-like) surfaces. In the second part of the thesis we study a condition guaranteeing the rationality of the contour curves on canal surfaces given by medial axis transforms. These curves are then used for a computation of rational parameterizations of canal surfaces with Pythagorean normals. Using the contour curves the parameterization algorithm enables us to construct the whole family of rational canal (blending) surfaces sharing the same silhouette at once, which is especially useful for constructing blends satisfying certain constrains, e.g. when avoiding obstacles or bypassing other objects is required. The last part of the thesis is devoted to rational ringed surfaces we design the algorithm for blending by these surfaces between two ringed surfaces which can be adjusted for constructing blends avoiding obstacles or for constructing general n-way blends between several ringed surfaces