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Masters Degrees (Ecology)

Permanent URI for this collectionhttps://hdl.handle.net/10413/7488

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Browsing Masters Degrees (Ecology) by SDG "SDG15"

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    Community diversity and composition of ground-dwelling arthropods in major habitat types of the KwaZulu-Natal Sandstone Sourveld.
    (2023) Mhlongo, Nokukhanya.; Tsvuura, Zivanai.; Munyai, Thinandavha Caswell.
    Grasslands constitute over 25% of the global land surface and close to one-third of southern Africa. Natural and semi-natural grasslands are recognized globally for their high biodiversity value and their important contribution to the provision of ecosystem services, including provisioning services such as carbon sequestration, water catchments, and grazing for livestock and wildlife. Nonetheless, grasslands are consistently reduced and threatened by anthropogenic activities and invasive alien plants. Invasive alien plants may hinder the growth of natural vegetation by overconsumption of resources. The impact of invasive alien plants on natural vegetation may indirectly affect plant-to-animal interactions such as specialized pollination and seed dispersal syndromes which may ultimately disturb ecosystem processes. The Sandstone Sourveld in KwaZulu-Natal province of South Africa is a threatened grassland ecosystem as a result of various anthropogenic disturbances. Knowledge of arthropod response to differences in habitat types may be essential for an improved understanding of the structure and functioning of ecosystems, which is relevant for informing conservation practice. The aim of this study was to investigate the composition and diversity patterns of ground-dwelling arthropods (ants, beetles, Orthopterans, and spiders) in three habitat types (forest, intact grassland, and disturbed grassland) at Springside and Tanglewood Nature Reserves, which occur in the KwaZulu-Natal Sandstone Sourveld (KZNSS). The objectives were: (i) to document the response of the ground-dwelling arthropod community in different habitat types, (ii) to determine the impacts of seasonal change on the abundance and richness of ground-dwelling arthropods at the two sites, and (iii) to determine the correlation between the distribution of ground-dwelling arthropods and soil characteristics in the KZNSS. Ground-dwelling arthropods were sampled in Springside and Tanglewood Nature Reserves using pitfall traps in each habitat type. Soil parameters in the habitats were also assessed. Analysis of variance was used to test for differences in arthropod morphospecies richness and abundance viii across the habitat types and between seasons. The Shannon-Weiner diversity index was computed and used to compare the diversity of ground-dwelling arthropods between the two sites and among habitat types. Ground-dwelling arthropods showed varying patterns in response to habitat characteristics and the disturbance gradient at Springside and Tanglewood. Intact grassland was the most diverse habitat in both Springside and Tanglewood. In Tanglewood, the abundance of ants was greater in disturbed grassland which consisted of a variety of alien invasive shrubs, the high abundance was explained by the “intermediate disturbance hypothesis”. However, alien invasion showed more negative than positive impacts on the abundance and composition of ground-dwelling arthropods when there was a significant decrease in the abundance and composition of ants, beetles and spiders. Species richness of ants and beetles was higher in the wet than dry season whereas Orthopterans and spiders showed no significant difference between seasons. In all arthropod groups, a greater number of species were correlated to soil potassium, soil pH, and soil bulk density. Overall, the intact grassland had the highest species richness and abundance followed by the forest and lastly the disturbed grassland. The greater abundance of ants, beetles, and spiders in the pristine grasslands of KZNSS shows that there is still a need to conserve the remnants of the KZNSS vegetation. Therefore, the conservancy management is urged to consider the eradication of alien invasive plants. Future studies are recommended to consider the volant and vegetation canopy arthropods as they are all interdependent with ground-dwelling arthropods to form a whole community of arthropods in an ecosystem.
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    The impact of land-use change on arthropod diversity along an arid elevational gradient.
    (2022) Mkhungo, S'phesihle.; Munyai, Thinandavha Caswell.; Foord, Stefan Hendrik.
    Land-use change is a major threat to global biodiversity. The rapid growth of the human population has resulted in increased landscape modifications and habitat loss. The impact includes reduced species diversity, ecosystem instability, altered species interactions and altered food webs. Land-use has increased drastically in mountainous areas, mainly through agriculture and human settlements. Mountains support approximately one-third of the terrestrial diversity and host half of the global biodiversity hotspots. The high variation in habitat structure and microclimates, within short distances allows mountains to support high species diversity. This study aimed to investigate the impact of increasing land-use change, elevation, and season on selected arthropod diversity, and community composition along the Western Soutpansberg mountain range in Limpopo province of South Africa. The objectives of the study were to determine spider and ant diversity patterns along the mountain. Secondly, to determine the role of land-use, elevation, and season in structuring the diversity of both taxa. Lastly, to compare the composition of spider and ant assemblages across the various sites and identify indicator species for monitoring land-use change in the study area. A standardized pitfall trap survey was used to sample ants and spiders along an elevational transect that stretches across the southern and northern aspects of the mountain. The elevational transect (800 m a. s. l – 1700 m a. s. l) was made up of 18 sites, some of which have undergone human transformation mainly through agriculture and settlements. Sampling took place during the dry season (September 2019) and wet season (January 2020). Generalized linear mixed models with Poisson error distributions were used to determine the impact of land-use, elevation, season on spider and ant species richness and activity. Community composition was analyzed using NMDS (non-metric multidimensional scaling), PERMANOVA and ANOSIM analyses. Land-use had a positive effect on spider and ant diversity as the transformed sites had significantly higher species richness and activity for both taxa, particularly the agricultural sites and human settlement. However, species evenness was significantly lower in the transformed sites and higher in the natural sites. Species richness and activities for both taxa were highest at the low elevations. Spider diversity was higher in the dry season, but ants peaked in the wet season. Spider and ant assemblages were highly distinct between the land-use types and elevations. Ant assemblages remained similar between the seasons, while spider composition was slightly different across the two seasons. Spider and ant assemblages in the transformed sites were highly uneven which indicates a large disproportion in the number of individuals within the species found in transformed sites. It also indicates high species dominance, which is driven by the disturbance-tolerant species. One spider species, Copa flavoplumosa, was identified as an indicator species for the Eucalyptus plantations. All land-use types had an ant indicator species, which was either Monomorium damarense and/or Lepisiota sp.02 (spinosior gp.). High species dominance displayed by spider and ant assemblages in the modified habitats might have adverse effects on native and endemic communities. Because dominant and disturbance-tolerant species are likely to increase if more natural land is converted. This study was the first to investigate the impact of land-use changes at the Soutpansberg mountain range. The results indicate that landuse change had a positive effect on arthropod species richness and activity. However, species evenness was negatively affected. Although the land-use changes at Soutpansberg can increase the diversity of certain species, the potential to sustain the populations over the long term is unknown. Therefore, further assessments and monitoring of diversity in the region is recommended to understand the long-term impact of land-use and for informed decision making and strategy in conservation efforts.