| Summary: | Thesis (MSc)--Stellenbosch University, 2019. ENGLISH ABSTRACT: Invasive species have been intentionally and accidentally introduced globally to both mainland and isolated island ecosystems, with the effects more harmful on islands given their isolation and high endemism of species. Several sub-Antarctic islands have been invaded by plants, animals and insects, mostly of European origin. Marion Island forms part of the Prince Edward Islands and has been invaded by species over time. Vascular plants, mainly from the families Poaceae, Caryophyllaceae and Juncaceae from Europe, have successfully established on the island due to their broad environmental tolerance and have managed to dominate most of the six habitat community complexes on Marion Island. Springtails found on Marion Island occupy all of the six habitat complexes, where they are amongst the most abundant invertebrates. In this study, I investigated the influence of vegetation on the distribution and abundance of springtail species on Marion Island specifically. I found that springtails on Marion Island are associated with both invasive and native vegetation, with invasive springtails preferring habitats in lower lying coastal sites where native Poa cookii and Cotula plumosa, and invasive Poa annua, Agrostis stolonifera and Sagina procumbens dominate. However, this coastal vegetation was dominated by the presence and abundance of invasive springtail species such as Isotomurus maculatus and Ceratophysella denticulata. Ceratophysella denticulata occurs in very high abundance when present, thus this species may have displaced native springtails, such as observed for Hypogastrura viatica, which is invasive on other sub-Antarctic islands. Furthermore, C. denticulata may potentially reduce native species richness on these islands. While most invasive springtails prefer warmer coastal habitats, Pogonognathellus flavescens and Megalothorax minimus were found in higher altitudinal habitat. The presence of P. flavescens at this higher altitude is surprising, as ...
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