• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 49
  • 9
  • 8
  • 2
  • 1
  • 1
  • Tagged with
  • 80
  • 80
  • 27
  • 17
  • 16
  • 16
  • 11
  • 11
  • 10
  • 10
  • 9
  • 9
  • 8
  • 8
  • 7
  • 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.
31

Tree holes as habitat for aquatic and terrestrial invertebrates in mixed broadleaf-podocarp rainforest, New Zealand

Blakely, Tanya Jillaine January 2008 (has links)
Little is known about the spatial distribution and abundance of tree holes in New Zealand’s native forests, or the invertebrate communities that they support. I found that tree holes were common on five endemic tree species, belonging to the families Fagaceae and Podocarpaceae in the mixed broadleaf-podocarp rainforest of Orikaka Ecological Area, Buller District, New Zealand. However, tree holes were not uniformly distributed throughout the forest, with more holes found on the three podocarp species, Prumnopitys ferruginea, P. taxifolia and Dacrycarpus dacrydioides, than on Nothofagus fusca or N. menziesii. Nevertheless, Nothofagus fusca had the largest holes of any of the tree species sampled and larger trees generally had larger holes. Large, hole-bearing Nothofagus fusca trees support a specialist hole-dwelling vertebrate fauna in New Zealand and worldwide, tree holes provide habitat for a range of invertebrate species. Using specially-designed emergence traps, I collected invertebrates emerging from naturally-occurring dry tree holes and compared this assemblage with invertebrates inhabiting leaf litter on the forest floor and those dispersing aerially throughout the study area. At the higher taxonomic resolution (i.e., Order or Class), community composition within the tree holes was highly variable, and there was no strong distinction between invertebrates from tree holes, leaf litter or Malaise traps. Moreover, although some beetle species emerging from tree holes were found exclusively in tree holes, most of these were represented by a single individual. Consequently, only minor differences in species composition were detected between beetle assemblages from tree holes, leaf-litter and those aerially dispersing throughout the forest. In contrast, the aquatic invertebrate assemblage within water-filled tree holes was highly distinctive from that in ground-based freshwater ecosystems, with only six aquatic taxa in common between all freshwater habitats. Using experimental water-filled tree-hole microcosms, I found that species richness and community composition within these microcosms were primarily driven by resource concentration, although habitat quality (i.e., water chemistry parameters) was also an important determinant of the identity and composition of colonising species. Overall, my study has shown that tree holes are common in the study area, and are likely to be more abundant in New Zealand’s indigenous forests than previously thought. Moreover, these generally small, discrete forest ecosystems support a diverse array of terrestrial invertebrates as well as a distinctive aquatic invertebrate community that is primarily structured by organic matter resource availability. These findings not only represent an important advance in our knowledge of New Zealand’s freshwater invertebrate biodiversity, but also highlight the need for further investigation into these unique forest canopy habitats which may well be at risk from deforestation and land use change.
32

Cellular Basis of Sponge-Sponge Associations

Unknown Date (has links)
Marine sponges interact and coexist with many different organisms. A two-sponge association between Amphimedon erina and Geodia gibberosa commonly occurs in the Florida Keys. Previous studies have only focused on the ecological influence of the association; they did not examine the cellular basis of the association. This association between A. erina and G. gibberosa was used in the development of an in vitro model to further the understanding of the cellular basis of natural sponge-sponge associations. In this study, sponge cells were cultured individually and in co-cultures and their responses related to apoptosis, cell death, and proliferation were monitored using high content imaging. Co-cultured cells of species that form sponge-sponge associations did not have the same cellular responses compared to co-cultured cells of species that do not form sponge-sponge associations. Protein expression analyses demonstrated that the model that was established does not mimic the cellular response of the association in nature, but this model can be used to test in vitro cellular interactions of sponge species that do not form associations in nature. In addition, the protein expression data that were obtained revealed that sponges use similar apoptotic pathways as humans and suggest that sponge cells may shut down cell cycling in order to repair damaged DNA. This research is a small piece to the puzzle that is sponge cell culture research. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
33

Quantifying changes in ecological function of headwater catchments following large-scale surface mining in southern West Virginia

Gingerich, Gretchen Anne. January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xvii, 195 p. : ill. (some col.), col. map. Includes abstract. Includes bibliographical references (p. 58-90).
34

Characterization of aquatic macroinvertebrate communities within the Obed Wild and Scenic River system a thesis presented to the faculty of the Graduate School, Tennessee Technological University /

Hutton, Benjamin, January 2009 (has links)
Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Mar. 3, 2010) Bibliography: leaves 39-48.
35

Tree holes as habitat for aquatic and terrestrial invertebrates in mixed broadleaf-podocarp rainforest, New Zealand

Blakely, Tanya Jillaine January 2008 (has links)
Little is known about the spatial distribution and abundance of tree holes in New Zealand’s native forests, or the invertebrate communities that they support. I found that tree holes were common on five endemic tree species, belonging to the families Fagaceae and Podocarpaceae in the mixed broadleaf-podocarp rainforest of Orikaka Ecological Area, Buller District, New Zealand. However, tree holes were not uniformly distributed throughout the forest, with more holes found on the three podocarp species, Prumnopitys ferruginea, P. taxifolia and Dacrycarpus dacrydioides, than on Nothofagus fusca or N. menziesii. Nevertheless, Nothofagus fusca had the largest holes of any of the tree species sampled and larger trees generally had larger holes. Large, hole-bearing Nothofagus fusca trees support a specialist hole-dwelling vertebrate fauna in New Zealand and worldwide, tree holes provide habitat for a range of invertebrate species. Using specially-designed emergence traps, I collected invertebrates emerging from naturally-occurring dry tree holes and compared this assemblage with invertebrates inhabiting leaf litter on the forest floor and those dispersing aerially throughout the study area. At the higher taxonomic resolution (i.e., Order or Class), community composition within the tree holes was highly variable, and there was no strong distinction between invertebrates from tree holes, leaf litter or Malaise traps. Moreover, although some beetle species emerging from tree holes were found exclusively in tree holes, most of these were represented by a single individual. Consequently, only minor differences in species composition were detected between beetle assemblages from tree holes, leaf-litter and those aerially dispersing throughout the forest. In contrast, the aquatic invertebrate assemblage within water-filled tree holes was highly distinctive from that in ground-based freshwater ecosystems, with only six aquatic taxa in common between all freshwater habitats. Using experimental water-filled tree-hole microcosms, I found that species richness and community composition within these microcosms were primarily driven by resource concentration, although habitat quality (i.e., water chemistry parameters) was also an important determinant of the identity and composition of colonising species. Overall, my study has shown that tree holes are common in the study area, and are likely to be more abundant in New Zealand’s indigenous forests than previously thought. Moreover, these generally small, discrete forest ecosystems support a diverse array of terrestrial invertebrates as well as a distinctive aquatic invertebrate community that is primarily structured by organic matter resource availability. These findings not only represent an important advance in our knowledge of New Zealand’s freshwater invertebrate biodiversity, but also highlight the need for further investigation into these unique forest canopy habitats which may well be at risk from deforestation and land use change.
36

Assessment of aquatic invertebrate communities of tributaries of the Buffalo River, Arkansas, and evaluation of indices of community integrity /

Mixon-Hinsey, Janice Arlene, January 1900 (has links)
Thesis (M.S.)--Missouri State University, 2008. / "December 2008." Includes bibliographical references (leaves 63-74). Also available online.
37

Associations between stream macroinvertebrate communities and surface substrate size distributions /

Stamp, Jennifer D. January 2004 (has links)
Thesis (M.S.)--Ohio University, August, 2004. / Includes bibliographical references (p. 71-73).
38

Associations between stream macroinvertebrate communities and surface substrate size distributions

Stamp, Jennifer D. January 2004 (has links)
Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 71-73)
39

Efeito da retirada da mata ripária sobre a estrutura dos grupos funcionais de alimentação em assembleias de macroinvertebrados bentônicos

Ono, Erika Ramos January 2018 (has links)
Orientador: Virginia Sanches Uieda / Resumo: Macroinvertebrados bentônicos são comumente utilizados como bioindicadores da qualidade do habitat em riachos. Estes estudos podem ser realizados através de uma abordagem taxonômica ou funcional da comunidade. Na abordagem funcional, a classificação em grupos funcionais de alimentação (FFG - Functional Feeding Groups) baseia-se nos mecanismos de apreensão do alimento e nos recursos consumidos. O estudo teve o objetivo de verificar o efeito de alterações na mata ripária sobre a estrutura dos FFG em comunidades de macroinvertebrados bentônicos. Estudamos 36 riachos, separados em três tipos de entorno: com mata ripária nas duas margens (florestado), com mata em uma das margens e pastagem na outra (intermediário) e sem mata nas duas margens (pastagem). A análise das variáveis ambientais indicou uma diferenciação dos riachos florestados e da maioria dos intermediários devido a maiores valores de material alóctone e oxigênio dissolvido e menores de vegetação nas margens e substrato fino, quando comparados aos de pastagem. A análise da abundância da fauna em cada FFG indicou uma diferença entre entornos somente para coletores, com valores significativamente menores nos florestados quando comparados aos de pastagem e intermediários. Já a análise aplicada aos dados de presença-ausência mostrou diferença entre entornos somente para os predadores, indicando diferença significativa na composição entre riachos florestados e de pastagem. A análise da diferenciação dos entornos considerando... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Benthic macroinvertebrates are commonly used as bioindicators of the habitat quality in streams. These studies may be carried out through analyzes with taxonomic or functional approach of the assemblage. In the functional approach, the classification of macroinvertebrates into Functional Feeding Groups (FFG) is based on the mechanisms of food´s apprehension and the resources consumed. This study aimed to verify the effect of the changes in riparian forest upon the structure of FFG in assemblages of benthic macroinvertebrates. We studied 36 streams, separated in three types of land use: with riparian forest on both banks (forest), with forest on one of the banks and pasture on another (intermediate) and without forest on both banks (pasture). The analysis of environmental variables showed a differentiation of the forest and most of the intermediate streams due to high values of allochthonous material and dissolved oxygen and low amounts of vegetation on the banks and unconsolidated substrate, when compared to pasture streams. The analysis of the abundance of the fauna in each FFG indicated a difference between types of land use only for gathering collectors, with significantly low abundance in forested streams when compared to pasture and intermediate ones. On the other hand, analysis applied to the presence-absence data showed distinction between land uses only for predators, indicating significant difference in the composition of forest and pasture streams. The analysis of t... (Complete abstract click electronic access below) / Mestre
40

Benthic assemblage structure, and the feeding biology of sixteen macroinvertebrate taxa from the Buffalo River, Eastern Cape, South Africa

Palmer, C G (Carolyn Gay) January 1992 (has links)
The River continuum concept (RCC) (Vannote et al. 1980) attempted to provide a unifying theory of river function. The Functional Feeding Group (FFG) concept (Cummins 1973, 1974) became a major component of the RCC. The FFG concept provides testable hypotheses about the changes in proportions of FFGs along a downstream gradient in a river, in response to the changing nature of food resources. The following short-comings of the FFG concept have been identified: 1) the variability of macroinvertebrate feeding, 2) problems with gut analysis as a method for assigning taxa to FFGs, and 3) inconsistent criteria defining FFGs. The objective of this study was to investigate the macroinvertebrate fauna of the Buffalo River in order to assess the applicability of aspects of the RCC and the FFG concept. The specific aims of the study were: 1) to describe the distribution of macroinvertebrate assemblages in the Buffalo River; 2) to clarify aspects of the FFG concept listed above; 3) to establish whether selected taxa could be assigned to FFGs; 4) to assess whether the proportions of different FFGs in successive reaches of a southern African river conformed to the predictions of the RCC; and 5) to test whether a functional classification is a useful alternative to a taxonomic classification. Macroinvertebrates were collected seasonally from a variety of biotopes at three sites, one each in the upper, middle and lower reaches. Riffles were sampled in summer at 16 sites. Over 100 taxa were identified and an hierarchical classification was prepared using two-way indicator species analysis. Invertebrate assemblages in the narrow headwater stream were taxonomically distinct from those of the middle/lower reaches and were not positively associated with subjectively identified biotopes. Biotopes were characterised by distinct assemblages in the wider middle/lower reaches. Sixteen abundant taxa whose feeding had not been previously investigated were selected for feeding studies, four from the headwaters and 12 from the middle/lower reaches. Methods used included gut content analysis, behavioural observations, food choice experiments and morphological studies using scanning electron microscopy. Three aspects of the functional feeding group concept were clarified. 1) Dietary variability was assessed using gut contents as an index of diet. The gut contents of both early (small) and late (large) instar larvae of all 16 taxa collected from different sites and biotopes, and in different seasons were compared using a multifactor analysis of variance. For all taxa the most consistently significant differences in gut contents were between large and small larvae. These were due to differences in the amount of material in the gut and in varying amounts of rarer dietary items. Dietary variability did not prevent taxa from being assigned to FFGs. 2) Gut content analysis satisfactorily provided basic information about the feeding biology of taxa but proved to be an inadequate single method for positively assigning taxa to FFGs. 3) Before taxa could be assigned to FFGs the definitions for some FFG categories had to be described clearly. It is suggested that the term shredder be based on the observation of shredding and a predominance of leaf fragments in the foregut. The presence of algae was not diagnostic of scrapers and a morphological basis is suggested. A morphological basis for the brusher FFG is described for the first time. All 16 taxa were assigned to FFGs. Three headwater taxa were shredders ((Goerodes caffrariae (Lepidostomatidae), Dyschimus ensifer (Pisulidae), Afronemoura spp. (Notonemouridae)) and one was a collector:brusher (Adenophlebia auriculata (Leptophlebiidae). These results were consistent with RCC predictions. All 12 of the taxa from the middle/lower reaches were filterers or collectors and this result was also consistent with RCC predictions. The Hydropsychidae, Cheumtopsyche afra and Macrostemum capense, were passive net filterers; Neurocaenis reticulatus (Tricorythidae) was a passive setal filterer; Caenidae sp. Band Pseudocloeon maculosum (Baetidae) were active filterers; caenidae sp. A, and the Baetidae, Baetis harrisoni, Centroptilum excisum and Cloeon africanum, were collector: gatherers; the Leptophlebiidae, Choroterpes elegans and Choroterpes nigrescens, were collector:brushers; and Afronurus harrisoni (Heptageniidae) was a scraper. Gut content analyses alone were insufficient to assign taxa to FFGs, but when augmented by morphological and/or behavioural data, taxa could be assigned to FFGs with confidence. In all cases the FFG designation referred to the most frequent style of feeding. N. reticulatus, A. harrisoni and A. auriculata were particularly flexible in their feeding behaviour. A functional classification of macro invertebrates in the Buffalo River was compared with a taxonomic classification. In both cases similar groups were identified, but their taxonomic and functional descriptions yielded different information. It is suggested that functional and taxonomic classifications should be viewed as complementary rather than alternative options.

Page generated in 0.1057 seconds