This dissertation presents research on the value of using different sources of data to
explore the factors determining invasiveness of introduced species. The research draws upon
the availability of data on the historical trial plantings of alien species and other sources. The
focus of the study is on Australian Acacia species as a taxon introduced into southern Africa
(Lesotho, South Africa and Swaziland). The first component of the study focused on
understanding the factors determining introduction outcome of species in historical trial
plantings and invasion success of Australian Acacia species using Species Distribution
Models (SDMs) and classification tree techniques. SDMs were calibrated using the native
range occurrence records (Australia) and were validated using results of 150 years of South
African government forestry trial planting records and invaded range data from the Southern
African Plant Invaders Atlas. To understand factors associated with survival (‘trial success’)
or failure to survive (‘trial failure’) of species in historical trial plantings, classification and
regression tree analysis was used. The results indicate climate as one of the factors that
explains introduction and/or invasion success of Australian Acacia species in southern Africa. However, the results also indicate that for ‘trial failures’ there are factors other than climate
that could have influenced the trial outcome. This study emphasizes the need to integrate data on whether the species has been recorded to be invasive elsewhere with climate matching for
invasion risk assessment.
The second component of the study focused on understanding the distribution patterns of
Australian Acacia species that are not known as invasive in southern Africa. The specific
aims were to determine which species still exist at previously recorded sites and determine
the current invasion status. This was done by collating data from different sources that list
species introduced into southern Africa and then conducting revisits. For the purpose of this
study, revisits means conducting field surveys based on recorded occurrences of introduced
species. The known occurrence data for species on the list were obtained from different data
sources and various invasion biology experts. As it was not practical to do revisits for all
species on the list, three ornamental species (Acacia floribunda, A. pendula and A. retinodes)
were selected as part of the pilot study for the conducted revisits in this study. Acacia
retinodes trees were not found during the revisits. The results provided data that could be
used to characterize species based on the Blackburn et al., (2011) scheme. However, it is not clear whether observed Acacia pendula or A. floribunda trees will spread away from the sites
hence the need to continuously monitor sites for spread. The methods used in this research
establish a protocol for future work on conducting revisits at known localities of introduced
species to determine their population dynamics and thereby characterize the species
according to the scheme for management purposes. / Dissertation (MSc)--University of Pretoria, 2014. / National Research Foundation (NRF) / Zoology and Entomology / MSc (Zoology) / Unrestricted
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:up/oai:repository.up.ac.za:2263/79720 |
| Date | 06 1900 |
| Creators | Motloung, Rethabile Frangenie |
| Contributors | Robertson, Mark P., mrobertson@zoology.up.ac.za, Rouget, M., Wilson, J.R.U. |
| Publisher | University of Pretoria |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | © 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
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