• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 17
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 21
  • 21
  • 6
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 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 impact of the European honey bee (Apis mellifera) on Australian native bees /

Paini, Dean. January 2004 (has links)
Thesis (Ph.D)--University of Western Australia, 2004. / "This thesis is presented for the degree of Doctor of Philosophy. University of Western Australia, School of Animal Biology, Faculty of Natural and Agricultural Sciences, 2004" Bibliography: leaves 94-110.
2

Experimental investigation of a vacuum apparatus for zebra mussel control in closed conduits

Bartrand, Timothy A. January 1997 (has links)
Thesis (M.S.)--Ohio University, November, 1997. / Title from PDF t.p.
3

The ecology of large herbivores native to the coastal lowlands of the fynbos biome in the Western Cape, South Africa /

Radloff, Frans Gustav Theodor. January 2008 (has links)
Dissertation (DSc)--University of Stellenbosch, 2008. / Bibliography. Also available vir the Internet.
4

The extent, impact and management of ungulate translocations

Spear, Dian 12 1900 (has links)
Thesis (PhD (Botany and Zoology))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: The worldwide movement of biota is of substantial concern for the conservation of biodiversity. The movement of species takes place at three different scales. These are translocations of indigenous species within their natural distribution ranges, the translocation of species outside their natural distribution ranges within geopolitical boundaries (i.e. extralimital introductions) and the translocation of species outside geopolitical boundaries and their natural distribution ranges (i.e. extraregional introductions). Ungulates are extensively translocated at each of these scales and each scale of translocation is expected to have different impacts on biodiversity. Ungulates are translocated for conservation purposes such as reintroducing species to places where they have previously gone extinct and to mitigate inbreeding in small, isolated populations. Ungulates are also extensively translocated for economic and recreational reasons, such as for sport hunting. Translocations for sport hunting include indigenous, extralimital and extraregional species. Concerns for translocations of indigenous species are largely for the loss of genetic diversity through the mixing of genetically distinct populations, and concerns for extralimital and extraregional translocations are for impacts on indigenous biodiversity such as through herbivory, competition, hybridization and disease transmission. This thesis investigates the extent of ungulate introductions globally and at a finer resolution in South Africa. It investigates the pathways, drivers and impacts of ungulate introductions and it also investigates the use of surrogates for genetic distinctiveness for advising the translocation of indigenous ungulates. The study finds that ungulate translocations have been extensive and have lead to the homogenization of ungulate assemblages in countries globally and at a quarter-degree grid-cell resolution in South Africa. Zoos were identified as a potential introduction pathway for extraregional ungulates globally and in South Africa extraregional introductions have made ungulate assemblages more different; whereas large numbers of extralimital introductions have made ungulate assemblages more similar. The homogenization of ungulate species in South Africa has increased with time, due to increased numbers of translocations, particularly of extralimital species. In South Africa translocations have most recently been made to high-income areas with high human population density and high livestock density; whereas in the 1960s ungulates were introduced to areas species poor for indigenous ungulates and marginal for livestock. In South Africa, long distance translocations of indigenous species extralimitally has resulted in extensive range expansions of a magnitude greater than predicted range changes as a result of predicted climate change. When the use of surrogates of genetic distinctiveness for advising translocations was investigated for Africa, the East African rift valley was found to be important in delineating genetic distinctiveness and translocations across this feature should be prevented. Major rivers in Africa also showed potential for delineating genetic distinctiveness in ungulates, but relevant phylogeographic data are needed to confirm this. Sufficient evidence for the impacts of non-indigenous ungulates on biodiversity both in South Africa and globally is lacking despite substantial concern for their impacts. It is suggested that to demonstrate the impacts of non-indigenous ungulates exclosure and enclosure experiments should be used and population declines in indigenous species should be shown. / AFRIKAANSE OPSOMMING: Verskuiwing van plante en diere wêreldwyd lei tot groot kommer in gevolge die bewaring van biodiversiteit. Verskuiwings vind op drie skale plaas, naamlik, die verskuiwing van inheemse spesies binne hulle natuurlike verspreidingsgebied, die verskuiwing van spesies buite hul natuurlike verspreidingsgebied maar binne landsgrense (d.w.s. buite limiet verskuiwings), en die verskuiwing van spesies buite hul natuurlike verspreidingsgebied en buite landsgrense (d.w.s. buite grondgebied verskuiwings). Grootskaalse verskuiwing van hoefdiere vind op al drie skale plaas. Verskuiwing op elk van die skale sal na verwagting biodiversiteit verskillend beïnvloed. Hoefdiere word ook vir bewaringsdoeleindes verskuif, bv. die herbevolking van ‘n gebied waar die spesies uitgesterf het, asook om genetiese probleme wat gepaardgaan met klein bevolkingsgroottes te vermy. Hoefdiere word ook verskuif vir ekonomiese- en ontspannings redes, o.a. vir sportjag, en sluit verskuiwings op al drie skale in. Kommer oor verskuiwings binne ‘n spesies se verspreidingsgebied rus hoofsaaklik op die verlies van genetiese diversiteit a.g.v. die vermenging van vorig genetiese eiensoortige bevolkings, terwyl op die ander twee skale kommer hoofsaaklik gebaseer is op die impakte van kompetisie, interteling, predasie, herbivoor effek, en die verspreiding van parasiete op inheemse biodiversiteit. Hierdie proefskrif ondersoek die omvang van hoefdier verskuiwings globaal asook in Suid Afrika. Die verskuiwingsweë, oorsake en impakte van verskuiwings word hier ondersoek, asook die maatstawwe van genetiese eiensoortigheid om advies oor verskuiwings te verskaf. Die bevindings toon op ekstensiewe verskuiwing van hoefdiere wat eenvormigheid van hoefdier spesiesamestellings wêreldwyd bevorder het, sowel as op ‘n kwartgraad skaal in Suid Afrika. Dieretuine is geïdentifiseer as ‘n potensiële bron van buite grondgebied verskuiwings. In Suid Afrika het buite grondgebied verskuiwings hoefdier spesiesamestellings minder eenvormig gemaak, terwyl buite limiet verskuiwings hoefdier samestellings binne Suid Afrika meer eenvormig gemaak het. Eenvormigheid in hoefdier spesiesamestellings het met tyd in Suid Afrika toegeneem as gevolg van ‘n toename in veral buite limiet verskuiwings. In Suid Afrika is verskuiwings mees onlangs na hoë-inkomste gebiede met hoë menslike bevolkingsen veëdigthede gemaak. In die sestiger jare is hoefdiere egter verskuif na gebiede waar min inheemse hoefdiere voorgekom het en wat marginaal was vir veëboerdery. In Suid Afrika het langafstand buite limiet verskuiwings versoorsaak dat die verspreidingsgebiede van sekere hoefdier spesies groter is as wat die geval sal wees met voorspelde klimaatsveranderinge. Waneer surogaat inligting gebruik word om genetiese verskille tussen bevolkings te identifiseer om verskuiwings te adviseer, word die Oos Afrika Rift vallei geïdentifiseer as ‘n belangrike breuk tussen bevolkings. Verskuiwings oor die vallei moet verkieslik nie plaasvind nie. Groot riviere in Afrika speel ‘n soortgelyke rol, maar verdere genetiese inligting is nodig om dit te bevestig. Alhoewel kommer oor die impak van verskuiwings groot en teoreties verdedigbaar is, bestaan daar te min konkrete bewyse vir die impakte in Suid Afrika. Daar word voorgestel dat manipuleringseksperimente uitgevoer moet word om impakte te demonstreer, en dat aandag veral gegee moet word aan die demonstrasie van impakte op inheemse spesies.
5

Trophic position in aquatic food webs

Vander Zanden, M. Jake. January 1999 (has links)
No description available.
6

Improving success of translocating southern Idaho ground squirrels (Spermophilus endemicus) /

Busscher, Katie Lea. January 2009 (has links)
Thesis (M.S.)--Boise State University, 2009. / Includes abstract. Includes bibliographical references (leaves 41-45).
7

Trophic position in aquatic food webs

Vander Zanden, M. Jake. January 1999 (has links)
This thesis examines broad-scale patterns in the food web structure of lake ecosystems. The unifying framework for this analysis is the concept of trophic position, which represents the energy-weighted trophic path length leading to a consumer or population. Trophic position was estimated for over 550 populations of fish (16 species) using quantitative dietary data. A method to estimate trophic position of aquatic consumers using stable isotope ratios was developed; this involved correcting for within and among-lake variation in delta15N of primary consumers (organisms used to represent the base of the food web). We report an overall correspondence between dietary and isotopic estimates of trophic position; for each species, trophic position generally ranged the equivalent of one trophic level unit among-populations. The concept of discrete trophic levels provided only a qualitative description of energy flow pathways in aquatic food webs. Among-population variation was much greater than within-population variation in trophic position of lake trout. Long-standing hypotheses about the determinants of food chain length were examined; food chain length was most closely correlated with species richness and lake area. / The trophic position approach was used to examine two separate environmental problems relevant to lakes: the bioaccumulation of persistent contaminants in food chains and the impacts of invasive species. Trophic position was the major determinant of PCB levels in lake trout; these relationships were used to characterize biomagnification factors (BMFs) for this and a number of other contaminants. Furthermore, the introduction of smelt into lakes was linked to increased levels of PCB and Hg contamination in lake trout. Stable isotopes were used to quantify the impacts of smallmouth bass and rock bass invasions on food webs leading to lake trout. Lake trout from invaded lakes exhibited reduced consumption on littoral prey fish; a food web shift that is likely to have detrimental impacts on native lake trout populations.
8

Improving the success of a translocation of black mudfish (Neochanna diversus)

McDonald, Amy Elizabeth. January 2007 (has links)
Thesis (M.Sc. Biological Sciences)--University of Waikato, 2007. / Title from PDF cover (viewed April 7, 2008) Includes bibliographical references (p. 91-101)
9

Ecology of Mediterranean snails in Southern Australian agriculture : a study of Cernuella virgata and Cochlicella acuta on the Yorke Peninsula /

Carne, Vanessa L. January 2003 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2004? / "August 2003." Includes bibliographical references (leaves 294-333).
10

Translocation of the Eastern Bristlebird and factors associated with a successful program

Bain, David. January 2006 (has links)
Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 124-146.

Page generated in 0.0944 seconds