Browsing by Author "Adedoja, Opeyemi Adebayo"

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    Response of plant-pollinator interactions to landscape transformations in the Greater Cape Floristic Region (GCFR) biodiversity hotspot
    (Stellenbosch : Stellenbosch University, 2019-12) Adedoja, Opeyemi Adebayo; Samways, Michael J.; Kehinde, T. O.; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Landscape transformation is one of the leading causes of global biodiversity decline. This decline is seen in terms of loss of species of ecological importance, and the collapse of important ecological interactions in terrestrial ecosystems. Ecological interactions are highly sensitive to environmental changes, as they are more vulnerable to disruptions than the species involved. Understanding the stability of these interactions in the face of growing environmental changes is key to identifying suitable conservation strategies for ameliorating species loss in transformed landscapes. This is of major conservation concern for the Greater Cape Floristic Region (GCFR), a globally important biodiversity hotspot and rich floral kingdom, which is home to many endemic species. I assessed here the response of plant-pollinator interaction networks to landscape transformation in the GCFR. I examined the influence of changing abiotic and biotic conditions across elevation zones, and I further investigated the influence of fire and invasive alien trees as drivers of environmental change on plant-pollinator interactions. I used a multi-taxon approach to highlight the effects of these drivers on these interactions. I sampled insects and flowering plants, as well as their interactions in areas impacted differentially by fire, invaded areas, and in areas with stratified elevation zones. My results showed a significant response of bees and beetles to environmental factors influencing species distribution across elevation gradients. Ecotones were an area of high conservation interest, as they were the most diverse in terms of species abundance and richness, although there was a mismatch between bees and flowering plant abundance peaks. Furthermore, species restricted to the highest elevation, peak zone are most at risk of local extinction, especially for the insect pollinators, as shown by interaction networks here having the lowest Shannon diversity index, generality, and interaction evenness. Fire influences plant-pollinator interactions and species dispersion patterns through its direct effect on flower abundance and nest provision. Bees were the only group associated with flower abundance. Results showed the importance of flower-rich fire refuges for the persistence of insect pollinators, especially the specialized species during fire events. Finally, increases in alien pine tree age and density were associated with a decline in plant-pollinator interactions, species abundance, and richness. However, dense, tall pine tree patches supported unique interactions involving large-sized pollinators. Overall, this study highlights the important response of plant-pollinator interaction networks to different drivers of environmental change. Habitat physical structure that sustains plant-pollinator interactions, especially those involving specialized species, holds important solutions for conservation action in this region. Controlled burning of overgrown areas should be encouraged for the proliferation of flowering plants. In addition, careful consideration should be given to trade-offs when instigating important conservation actions, such as restoration, especially when these actions can lead to local loss of some endemic species.