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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.
1

The status of <i>Desmognathus welteri</i> Barbour (Caudata: plethodontidae) and a comparison with two sympatric congeners

Juterbock, Jan Eric January 1975 (has links)
No description available.
2

Progressive microscopical changes in wood caused by a white-rot and a brown-rot fungus

Wilcox, W. Wayne. January 1965 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. Includes bibliographical references (leaves 121-127).
3

The ecology and conservation of blue duiker and red duiker in Natal.

Bowland, Anthony Ernest. January 1990 (has links)
The ecology of blue duikers Philantomba monticola and red duikers Cephalophus natalensis was studied in three lowland coastal evergreen forests in Natal. Variation in population densities, estimated with numerous census techniques and between and within study areas permitted comparisons of habitat parameters. Both species are strictly diurnal, and are active between 18 and 40% of the nycthemeral cycle. Usually a pair of blue duikers occupy a permanent territory of about 0,7ha while red duiker home ranges, between 2 and 15ha, overlap extensively with each other and those of blue duikers. Habitat quality of both species is determined by canopy cover (stem densities, spatial patterning, and, diversity of the tree and shrub layers), tree to shrub ratios, and, bedsites. The main dietary item, freshly fallen leaves, is not that of a highconcentrate feeder as hypothesised. Food appears to be abundant while condensed tannins have no influence on duiker densities. Management recommendations include land acquisition, forest ecology research, monitoring interaction with other species, genetic aspects, translocations and captive propagation. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1990.
4

Correlates of rarity in UK bumblebee (Bombus spp.) populations

Rustage, Sarah Elizabeth January 2015 (has links)
The decline of bumblebee (Bombus spp.) populations in the UK and worldwide has been well reported. It has been generally assumed that such declines result in the genetic impoverishment of some species, potentially leading to reduced fitness and increased extinction risk. This study tested the fundamental assumption linking population fragmentation with fitness, in a model system of two Bombus species native to the UK. Bombus monticola has declined significantly in range across the UK in recent years and occupies fragmented upland areas, while Bombus pratorum has remained abundant and widespread over many habitat types. The effects of genetic diversity on fitness have been addressed in wild Bombus species, but this is the first study to explicitly compare data from species of differing levels of population connectivity and hence test the assumptions of traditional population genetic theory. As genetic diversity has often been linked with immunocompetence, aspects of the innate immune response were quantified, together with parasite load. These empirical measures of fitness showed lower than expected variability between the two study species, and no evidence was found to support the theory of lower fitness in fragmented populations. However, the considerable variability between sample sites in both species for all parameters measured raised interesting questions as to the underlying evolutionary processes; it is postulated that B. monticola populations may maintain a higher than expected Ne, despite their fragmented distribution. This study also provided methodological developments. An alternative method for the quantification of wing wear as a proxy for age was proposed, which could be easily applied to other Bombus species and possibly adapted for use in other flying insects. In addition possible sources of error in AFLP analysis were highlighted which have not been adequately discussed in the current literature, namely the effects of sample storage. Given the utility of AFLPs for non-model species, this is an important avenue for future research, and would be applicable to studies in other systems. Overall, the data presented here emphasise the challenges of studying fitness in wild populations, and underline the requirement for research into the fundamental principles underlying many assumptions made by conservation genetic theory.
5

Influencia del vaporizado sobre la resistencia a la pudrición de madera de renoval de roble (Nothofagus obliqua (Mirb.) Oerst)

Guzmán Santibáñez, Diego Ignacio January 2017 (has links)
Memoria para optar al Título Profesional de Ingeniero de la Madera / Nothofagus obliqua (Mirb.) Oerst (roble o pellín), es una especie que se distribuye desde la Región de Valparaíso hasta la Región de Los Lagos; también habita en Argentina. Esta especie se caracteriza por la alta durabilidad natural que presenta su madera en individuos adultos. Sin embargo, para la madera proveniente de renovales, con diferentes características de color y densidad, no existen antecedentes sobre su comportamiento frente al ataque de hongos de pudrición u otros agentes de biodeterioro. Actualmente, la madera de renovales de roble es sometida a un tratamiento de “vaporizado”, el que tiene como objetivo igualar el color rosado a rojizo del duramen de la madera de renoval, con el rojo oscuro del duramen de roble pellín, mucho más apreciado en el mercado. Con el objetivo de proporcionar antecedentes sobre la durabilidad natural de la madera de renoval de roble y de la influencia del tratamiento de cambio de color (vaporizado), se evaluó la resistencia de estas maderas frente a la acción de hongos de pudrición mediante la pérdida de peso, solubilidad en soda y el % de lignina. Para realizar el estudio se utilizó madera de renoval de roble, empleándose 40 probetas de albura y 40 de duramen. Se aplicó el proceso de vaporizado a 20 probetas de cada grupo, de manera de compararlas con el comportamiento de la madera sin vaporizar frente al ataque del hongo de pudrición blanca Polystictus versicolor y de pudrición café Poria monticola, utilizando además, 20 probetas de roble adulto como testigo. La mitad de las probetas de cada conjunto fue evaluada a los 2 meses (T1) y el resto a los 4 meses (T2) desde el inicio del ataque fúngico. Los resultados indicaron que el vaporizado no tuvo influencia sobre la resistencia de la madera de renoval frente al ataque de P. versicolor, que generó el %PP más alto para todos los tipos de madera a los 2 meses de acción fúngica. Así mismo, el % de solubilidad en soda indicó que el hongo de pudricion blanca provocó el mayor biodeterioro en comparación con el hongo de pudricion café. Para el caso de P. monticola, se observó que el vaporizado tampoco tuvo efecto sobre la resistencia al ataque de pudrición, generándose el mayor biodeterioro a los 4 meses (T2) que a los 2 meses (T1). Esto señaló finalmente, que la madera de renoval de roble no es una madera durable, considerando su resistencia frente al ataque de hongos de pudrición. / Nothofagus obliqua (Mirb.) Oerst (roble o pellín), is a specie allocated from Valparaiso Region to Los Lagos Region, Chile, also it can be found in Argentina. This kind is characterised by its high natural durability of its wood in adults members. Nevertheless, there are not history, for wood from secondary forests, with different characteristics of color and density, about its behaviour against the fungal attack or other biodeterioration agents. Nowadays, the roble wood from secondary forests is subjected to a “steaming” treatment, which aims to equalize pink to reddish heartwood color of the wood from secondary forests, with the dark red of the roble pellin heartwood, much more appreciated in the market. In order to provide history about the natural durability of the roble secondary forest wood, and of the influence of the color change treatment (steaming), the resistance of these woods against the action of fungal through weightloss, soda solubility and the lignin percentage was evaluated. Roble wood (renoval) was used to carry out the research, using 40 test tubes for sapwood and 40 test tubes for heartwood. Steaming process was tested in 20 test tubes of each group to do the comparison with those samples that were not under the process but under the white rot fungi attack Polystictus versicolor and the brown fungi Poria monticola. Also 20 test tubes of old roble were used as reference sample. Half of the samples of each group was checked at two months (T1) and the remaining samples at four months (T2) since the attacks of fungi started. The results shown that the steaming did not affect the wood resistance against the attack of P. versicolor produced the highest %PP for all the samples at 2 months of the test. Moreover, the %S indicated that the white fungi produced a bigger biodeterioration than the brown one. In the case of P. Monticola, it was observed that the steaming had no effect neither about the resistance of fungal attack, generating the greatest deterioration at 4 months (T2) than 2 months (T1). This finally pointed that the roble secondary forest wood is not a durable one, considering its resistance against the fungal attack
6

Genetic patterns in forest antelope populations : implications for the conservation of key species in the Udzungwa Mountains, Tanzania

Bowkett, Andrew Edward January 2012 (has links)
The field of conservation genetics, in combination with non-invasive sampling, provides a powerful set of tools for investigating the conservation status and natural history of rare species that are otherwise difficult to study. A systematic literature review demonstrated that this is certainly the case for many forest associated antelope species, which are poorly studied and yet constitute some of the most heavily hunted wildlife in Africa. The aim of the present study was to use non-invasive sampling to investigate genetic patterns in forest antelope populations in the high-biodiversity Udzungwa Mountains, Tanzania, within the context of the conservation of these species and the wider ecosystem. Genetic information was derived from faecal samples collected across the Udzungwa landscape and assigned to five antelope species (N = 618, collected 2006-09). Faecal pellet length was measured for a subset of samples but statistical assignment to species by this method proved unreliable. Phylogenetic analysis using mitochondrial control region sequences unexpectedly revealed that Harvey’s duiker within the Udzungwas are paraphyletic with respect to sequences from a putative sister species from southern Africa. However, there was no corresponding pattern in the microsatellite dataset suggesting that these mitochondrial lineages do not represent contemporary genetic isolation. Instead, Harvey’s duiker nuclear variation is shaped both by isolation by distance, due to positive spatial autocorrelation at short distances, and clustering of distinct genotypes from western outlying forests. These forests also harbour the endangered Abbott’s duiker and therefore require effective conservation management. Despite being detected throughout the Udzungwas, genetic diversity in Abbott’s duiker was very low in comparison to other species. These results suggest several promising research directions but also have significant conservation implications that will be disseminated to the Tanzanian wildlife authorities and the wider conservation community.

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