Browsing by Author "Khan, Zahra"

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    The effects of landscape transformation, isolation, and habitat quality on plant-pollinator interactions in conservation corridors
    (Stellenbosch : Stellenbosch University, 2024-03) Khan, Zahra; Pryke, James; Gaigher, Rene; Van Schalkwyk, Julia; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: The KwaZulu Natal Midland’s natural areas are comprised mainly of grasslands, wetlands, and indigenous forest which are highly threatened by agricultural expansion and commercial forestry. Many endemic plant and animal taxa occur in this region and require protection due to competing land uses. To mitigate biodiversity loss in these rich landscapes, conservation corridors have been implemented creating habitat and conduits for dispersal across the harsh matrix of alien trees. While corridors fulfil the functions of habitat and conduits for dispersal, there is significant fragmentation and habitat loss to forestry which are known to be the drivers of biodiversity loss worldwide. In light of this, my study explores plant-pollinator interactions to determine whether corridors are effectively preserving biodiversity and its function. I first explored the differences in plant-pollinator interaction networks between four different landscape contexts within conservation corridors. Interactions between flowering plants and flower visitors were observed in each landscape context and local environmental variables measuring habitat quality, (provision of food for the pollinators) and landscape variables measuring isolation (the amount of natural/semi-natural habitat in the broader landscape) and landscape transformation (the amount of habitat loss to afforestation in the immediate surroundings) were measured. Habitat quality was found to be the most important for the presence of flower visitors and facilitating plant-pollinator interactions. Isolation and landscape transformation played smaller roles and often had interactive effects on plant-pollinator biodiversity. I also investigated the functional traits of flowering plants and flower visitors to understand the traits that underpin the interactions observed. Flower visitor functional dispersion and dissimilarity were most affected by environmental conditions and the interactions between seasonality and landscape variables. However, again local environmental conditions were the main variable affecting flower visitor presence and functional dispersion and dissimilarity. Season, isolation, and landscape transformation also had individual and interactive effects on flower visitor and flowering plant assemblage composition along with environmental variables. Although landscape transformation and season had limited effects on flower visitor functional dissimilarity and dispersion, flower visitor traits differed distinctly between high and low levels of landscape transformation and season. Flowering plant traits also displayed some differences between season and landscape transformation, but these were not as distinct as with flower visitors. Low levels of isolation were found to be beneficial to plant- pollinator biodiversity even under high landscape transformation. In conclusion, landscape transformation had negative effects on flowering plant and flower visitor biodiversity, but conservation corridors helped ameliorate these effects. Habitat quality and condition (here vegetation height was used as a proxy for grassland condition) were most important for the presence of flower visitors and facilitating interactions between flower visitors and flowering plants. Results suggest that corridors are providing connectivity and habitat for flower visitors due to the diverse flower visitor traits found in different landscape contexts, however, isolation still negatively impacts biodiversity in some areas. Conservation efforts should focus mainly on improving habitat quality for flower visitors. This entails the effective control of invasive plants within corridors, the introduction of appropriate indigenous flora, and establishing appropriate disturbance regimes. Achieving connectivity should still be a focus of management to allow for rescue effects in the event of species loss, however, this should not overshadow habitat quality management.