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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

Evaluation of methods and approaches for surveying savanna invertebrates.

Lovell, Saskie Joanne. January 2006 (has links)
The savanna is an important biome, which is under threat from land transformation, and it is therefore a focus for conservation planning. Yet, the invertebrate fauna of this biome is poorly documented and hence there is a need to provide baseline data for this component of biodiversity. This project aimed to provide relevant information that can be used by conservation planners and ecologists, by recommending a sampling strategy for the collection of specific taxa for savanna invertebrate surveys. The effectiveness and efficiency of a sampling strategy using passive and active sampling methods was assessed to provide recommendations for a multi-taxa approach to sampling invertebrates in a savanna ecosystem. In the collection of data, volunteers assisted and they were evaluated in comparison with experienced researchers to assess the effectiveness, efficiency and benefits of using volunteers to carry out multi-taxa invertebrate surveys. In addition, cross-taxon congruency and congruency across taxonomic levels were assessed between nine invertebrate taxa, to select potential surrogates to reduce biodiversity survey costs for conservation planning. Fieldwork was carried out in the Mkhuze Game Reserve (27.67°S:32.27°E, 400km2 ), Phinda Private Game Reserve (27.78°S:32.35°E, 140km2 ) and False Bay Park (27.94°S:32.38°E, 25km2 ) in north-eastern Kwazulu-Natal, South Africa. Forty-three different sites were sampled between November 2002 and March 2005 (summer months). Twenty of these sites were re-sampled across years and in different months during the summer season, giving 77 sampling events. Fifty-four volunteers recruited by the Earthwatch Institute assisted in the collection of data. Lepidoptera, Hymenoptera (Apoidea), Diptera (Asilidae, Bombyliidae), Neuroptera, Odonata, Hemiptera (Cicadellidae), Coleoptera (Cetoniinae, Scarabaeinae), Orthoptera, Blattodea, Isoptera, Araneae (Araneidae, Thomisidae, Oxyopidae), Scorpionida, Myriapoda (Diplopoda, Chilopoda), Mollusca and Annelida were sampled using four active searching methods (transects, tree beating, leaf litter and sweep sampling) and two passive methods (pan traps and baited traps). In its entirety, this project sampled 50 558 individuals from 797 invertebrate species and an extensive database consisting of 33 257 records now exists. A standardised sampling protocol is described for the effective sampling of multiple invertebrate taxa in a savanna biome and recommendations are made for improving the efficacy and completeness of invertebrate surveys based on the application of species accumulation models. Restrictive active searching methods (quadrats) were found to be more effective for sampling epigaeic invertebrates and should be used in conjunction with leaf litter samples. Flying and plant-dwelling invertebrates should be sampled using a range of sampling methods which include baited, malaise and pan traps, active searching along transects and vacuum sampling. I suggest over 75% of the Lovel/, s.1. - MSc. Thesis i ii total estimated fauna to be a satisfactory and realistic level of inventory completeness for making valid comparisons between regions and across sites. Volunteers sampled lower rates of species accumulation, species richness and unique species when using timed, active search methods. Nevertheless, volunteers and researchers were shown to perform equally well when using un-timed, active searching methods. Previous experience or knowledge of scientific method was beneficial when researchers assessed the perceived usefulness of volunteers to researchers for carrying out fieldwork. The project experience raised the volunteers' environmental awareness, knowledge about biodiversity, invertebrates and conservation research, and enabled volunteers to participate in or design locally relevant conservation based projects on their return home. Cross-taxon congruencies were observed. However, relationships were weak and potential surrogates could not be selected. The use of higher taxonomic levels to represent species shows good potential as a surrogate but only in species-poor genera or families. The use of species density to determine congruency and select surrogates is likely to produce different results to those produced by community similarity. Furthermore, when selecting surrogates from congruency assessments an optimal p-value greater than 0.75 should be required. Below this value, the relationship is likely to be weak and if used as a surrogate misinterpretation may occur. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
2

Invertebrate diversity in afrotemperate forests : spatial and seasonal changes and implications for conservation.

Uys, Charmaine Janet. January 2006 (has links)
Forests in the Drakensberg Mountains, although generally small and fragmented, represent a wealth of globally significant biodiversity. This is especially true of the invertebrate fauna, which includes a range of localized endemic species. Ground dwelling, flightless invertebrates living in forests show relative immobility and poor dispersal abilities compared to birds, butterflies and other animal taxa. The naturally fragmented state of Afrotemperate forests also geographically isolates these taxa. No quantified, systematic surveys of flightless invertebrates have been conducted in Afrotemperate forests in the Drakensberg Mountains. This means that, to date, invertebrates have not been considered in the management of these habitats. However, invertebrates are vitally important in ecosystem functioning and maintenance and must be included in management plans. This study quantified flightless invertebrate diversity in Afrotemperate forest patches in the Drakensberg by investigating spatial patterns and seasonal changes in invertebrate diversity. The broad objectives were to: 1) Determine the appropriate spatial scale at which conservation of flightless invertebrates should be implemented; 2) Determine which season, taxa and sampling methods are most suitable for biodiversity assessment and monitoring in Afrotemperate forest; and 3) Investigate methods of prioritizing Afrotemperate forests for conservation of flightless invertebrate diversity. Seventeen forest patches in six valleys in four Drakensberg reserves (Rugged Glen Nature Reserve, Royal Natal National Park, Cathedral Peak and Injisuthi) were sampled in the summer of 2004/2005. In addition, three forests at Injisuthi were sampled in March, June, September and December 2004 to enable seasonal comparisons. Sampling methods included soil samples, leaf litter samples, pitfall traps, active search quadrats and tree beats. The study focused on terrestrial molluscs (Class Gastropoda), earthworms (Class Annelida), onychophorans (Class Onychophora), centipedes (Class Chilopoda), millipedes (Class Diplopoda) and ants (Class Insecta). Target taxa were sorted to morphospecies and then identified to species by taxonomic experts. Seventy-two species and a total of 5261 individual specimens from the six target taxa were collected. Species composition of sites varied along the north-south gradient, and species turnover (beta diversity) was related to the distance between sites. Flightless invertebrate species richness and community structure fluctuated seasonally. Therefore, I recommend that sampling should take place during the wet season (summer months). Molluscs were the most suitable taxon among those surveyed to represent flightless invertebrate diversity and leaf litter samples and active search quadrats are the most suitable sampling methods for flightless invertebrates in forest. This study compared approaches to prioritizing Afrotemperate forests in terms of their invertebrate diversity using ranked species richness with complementarity indices of species presence/absence, taxonomic distinctness (orders, families and genera) and endemicity. There was no consistent spatial trend in the priority ranking of forests based on species richness. Complementarity based on species richness only required eight out of 17 forests to represent all 62 species. Although complementarity based on taxonomic distinctness and endemicity required fewer sites, not all species were represented. The minimum set of sites identified using complementarity based on species richness and augmented with information on taxa of conservation importance (local endemic and threatened species) was the most rigorous approach to prioritizing Afrotemperate forest patches in the Drakensberg for flightless invertebrate conservation. Urgent conservation interventions are required because invertebrates play a critical role in ecosystem functioning. As many forest patches and invertebrate populations as possible should be protected to conserve the full complement of invertebrate species of the region. Special management attention should be paid to the eight forests identified as priority sites in the complementarity analyses. Forest patches cannot survive in isolation, so it is important to manage the grassland, riverine vegetation, forest ecotone and forests holistically. Provisional targets were set for the conservation of flightless invertebrates, based on estimates of the requirements for persistence of invertebrates in Afrotemperate forest, made within the constraints of available information and expert opinion. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
3

The effect of habitat alteration by elephants on invertebrate diversity in two small reserves in South Africa.

Govender, Navashni. January 2005 (has links)
Balancing increasing elephant numbers with biodiversity conservation in small reserves has become a concern for many protected area managers. Elephants are considered important agents of disturbance creating heterogeneity and thus contributing to the maintenance of biodiversity. However elephants also damage vegetation through their destructive feeding habits, and this has led to pressure to reduce elephant populations in many reserves. Quantitative data on the impact of elephants on invertebrates, the main component of biodiversity at the species level, are lacking. The aim of this project was to assess the effect that habitat alteration by elephants has on the diversity of selected ground-dwelling invertebrates (ants, centipedes, millipedes, spiders, scorpions and termites) through the provision of logs and dung as a potential refuge niche for these invertebrate communities, and to determine the effect of spatial (vegetation types) and temporal (season and age of dung) variation on the invertebrates using these refugia. Variation in impacts was considered important because savanna is not homogenous and the impact of the refugia is likely to be dynamic in terms of seasonal trends in invertebrate populations, and in terms of changes in the environmental conditions offered by the refugia. Elephant impact on vegetation, quantity of refugia (logs and dung) produced and invertebrate diversity associated with refugia were determined for 115 transects within Madikwe Game Reserve in the North Western Province, South Africa. Invertebrate abundance, species richness and diversity were always higher under refugia than in areas without refugia. Vegetation utilisation, frequency of refugia production and invertebrate diversity showed strong temporal variation (seasonal); elephant impact and production of logs were higher in winter than in summer because elephants are more likely to feed on woody vegetation in winter when grass nutrient levels are low. Invertebrate diversity under the logs was higher in summer than in winter, and this probably reflected the higher abundance and diversity of invertebrates that are usually associated with the warmer, wetter summer months. The effect of adding refugia to three vegetation types on invertebrate diversity was tested experimentally at Makalali Private Game Reserve in the Limpopo Province, South Africa. Logs and elephant dung were set out in five plots each measuring 20m x 20m within Govender - iii mixed bushveld, riverine and mopane woodland. Significant differences were observed in invertebrate abundance, species richness and diversity between the refugia and control plots that lacked refugia and between the three vegetation types sampled. Similarity between invertebrate communities utilising the different refugia types and between the three different vegetation types were tested using the Jaccard similarity coefficient. The three vegetation types shared fewer than 50% of their species, as did the logs, dung and control sites. However the results obtained do illustrate a higher degree of similarity between the refugia substrates (logs and dung) than the control sites and between the more heterogeneous vegetation types (mixed bushveld and riverine) than the mopane veld. This indicated that invertebrate communities associated with refugia were not uniform, but were influenced by vegetation type. An experimental test of temporal changes in invertebrate community composition illustrated the importance of elephant dung as a microhabitat for different invertebrate groups over different ages of dung (three days, two, four, 12 and 32 weeks old). Colonisation of the dung, by dung beetles was immediate but as the microclimate of the dung changed with time, the new conditions were ideal for other invertebrate taxa. Over a period of eight months, the change of invertebrate communities utilising the dung included dung beetles, followed by millipedes and [mally ant and termite communities. The results of this study illustrated the importance of refugia (logs and dung) produced by elephants for ground-dwelling invertebrate species in the savanna environment. The extent of the influence of the refugia varied both spatially and temporally and this should be considered in future monitoring or in measuring impacts. While further research on a broader range of organisms and at larger scales is necessary, elephants do have a positive impact on at least some components of biodiversity, through the process of facilitation of refugia. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

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