Browsing by Author "Spear, Dian"

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    Alien species in South Africa’s national parks
    (AOSIS OpenJournals, 2011-08) Spear, Dian; McGeoch, Melodie A.; Foxcroft, Llewellyn C.; Bezuidenhout, Hugo
    Invasive alien species (IAS) are one of the major threats to biodiversity in protected areas and pose a significant management challenge (see Allen, Brown & Stohlgren 2009; Pyšek, Jarošík & Kučera 2002). One of the first steps towards managing IAS in protected areas is establishing which alien species are present, followed by ongoing surveillance and prevention efforts to combat new introductions (Foxcroft et al. 2009). Information on the identity and traits of alien species is needed for conducting risk assessments and prioritising species for control, as well as for monitoring management effectiveness in preventing new introductions (McGeoch et al. 2010). It also provides a first step towards monitoring the extent of occurrence of alien species in national parks.
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    Assessing the association between pathways of alien plant invaders and their impacts in protected areas
    (Pensoft Publishers, 2019-03-05) Foxcroft, Llewellyn C.; Spear, Dian; Van Wilgen, Nicola J.; McGeoch, Melodie A.
    Protected areas face mounting pressures, including invasion by alien plant species. Scientifically sound information is required to advise invasive species management strategies, where early detection and rapid response is particularly important. One approach to this is to determine: (i) the relative importance of pathways of invasion by which a species is introduced, (ii) the range of likely impacts associated with each species, and (iii) the relationship between pathways and impacts, to assess the relative threats posed by different pathways of alien species introductions. This assessment was performed on 139 alien plants that are invasive across the South African National Parks (19 national parks, covering ~39,000 km2), and based on available literature and expert opinion, known to have negative ecological impacts. For each species the likelihood of being introduced by each of eight pathways, and of having negative impacts in each of 13 identified impact categories, was assessed. The similarity of impact and pathway types between species was assessed using the Jaccard index and cladograms. Differences in the prevalence of impacts and pathways and relationships between these were assessed using a Chi-squared contingency and Generalised Linear Model. Nearly 80% of the species are ornamental plants and about 60% are also dispersed by rivers, highlighting the importance of managing ornamental species and surveillance along rivers in preventing future invasions. As to the impacts, ~95% of the species compete directly with native species and 70% change the physical structure of the environment. The majority of species exert multiple impacts, with 70% of species assessed having five or more impacts. There was a significant positive relationship between the number of pathways via which a species can be introduced into an area and the number of potential impacts they can have. This suggests that species using multiple pathways reach a wider range of suitable habitats, increasing the potential for different kinds of impacts over a wider area.
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    An assessment of the information content of South African alien species databases
    (http://www.aosis.co.za/, 2015-05) Faulkner, Katelyn T.; Spear, Dian; Robertson, Mark P.; Rouget, Mathieu; Wilson, John R. U.
    National alien species databases indicate the state of a country’s biodiversity and provide useful data for research on invasion biology and the management of invasions. In South Africa there are several different published alien species databases, but these databases were created for different purposes and vary in completeness and information content. We assessed the information content of published South African alien species databases in the context of other such databases globally, and evaluated how the information content of South African databases varies across taxonomic groups. Although introduction pathway, date of introduction, region of origin and current broad-scale distribution data are available for most taxonomic groups assessed (60% – 90%), data on invasion status, introduction effort and introduction source are available for few taxonomic groups (5% – 18%). South African alien species databases have lower information content than the detailed databases available in other parts of the world and thus cannot be utilised to the same extent. We conclude with 11 recommendations for improving South African alien species databases. In particular, we highlight the data types that should be incorporated in future databases and argue that existing data should be collated in a single, standardised meta-database to facilitate cross-taxon comparisons, highlight gaps in effort, and inform managers and policy makers concerned with alien species.
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    The extent and impacts of ungulate translocations : South Africa in a global context
    (Elsevier, 2009-02) Spear, Dian; Chown, Steven L.
    Despite the apparent risks of the introduction of non-indigenous ungulates to biodiversity, relatively little is known globally about the pathways of introduction, propagule pressure and realized impacts of ungulate introductions. These issues were examined here by investigating ungulate introductions to South Africa within a global context. Across countries globally, introduced ungulate richness is not related to indigenous ungulate richness, and several countries are clear outliers. South Africa is second only to the USA in the number of ungulate species introduced to date. Zoos have traded more ungulate species and individuals to non-zoo recipients than to other zoos, highlighting the tensions that exist between in situ and ex situ conservation goals. Introductions to, and extralimital introductions within South Africa have increased through time, with propagule pressure being highest in areas with high human population density. The long distances ungulates have been translocated raise concerns for genetic homogenization. Translocations of indigenous ungulate species extralimitally have significantly altered range sizes, typically to a greater extent than is expected from range shifts associated with global climate change. Although ungulate introductions and translocations are likely to have impacts on biodiversity, evidence for such impacts in South Africa, and elsewhere, is limited. Whilst arguments may be made for a precautionary approach to ungulate introductions, an evidence-based one is much more likely to deliver efficient and convincing conservation decision-making. © 2008 Elsevier Ltd. All rights reserved.
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    The extent, impact and management of ungulate translocations
    (Stellenbosch : Stellenbosch University, 2008-12) Spear, Dian; Chown, Steven L.; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: The worldwide movement of biota is of substantial concern for the conservation of biodiversity. The movement of species takes place at three different scales. These are translocations of indigenous species within their natural distribution ranges, the translocation of species outside their natural distribution ranges within geopolitical boundaries (i.e. extralimital introductions) and the translocation of species outside geopolitical boundaries and their natural distribution ranges (i.e. extraregional introductions). Ungulates are extensively translocated at each of these scales and each scale of translocation is expected to have different impacts on biodiversity. Ungulates are translocated for conservation purposes such as reintroducing species to places where they have previously gone extinct and to mitigate inbreeding in small, isolated populations. Ungulates are also extensively translocated for economic and recreational reasons, such as for sport hunting. Translocations for sport hunting include indigenous, extralimital and extraregional species. Concerns for translocations of indigenous species are largely for the loss of genetic diversity through the mixing of genetically distinct populations, and concerns for extralimital and extraregional translocations are for impacts on indigenous biodiversity such as through herbivory, competition, hybridization and disease transmission. This thesis investigates the extent of ungulate introductions globally and at a finer resolution in South Africa. It investigates the pathways, drivers and impacts of ungulate introductions and it also investigates the use of surrogates for genetic distinctiveness for advising the translocation of indigenous ungulates. The study finds that ungulate translocations have been extensive and have lead to the homogenization of ungulate assemblages in countries globally and at a quarter-degree grid-cell resolution in South Africa. Zoos were identified as a potential introduction pathway for extraregional ungulates globally and in South Africa extraregional introductions have made ungulate assemblages more different; whereas large numbers of extralimital introductions have made ungulate assemblages more similar. The homogenization of ungulate species in South Africa has increased with time, due to increased numbers of translocations, particularly of extralimital species. In South Africa translocations have most recently been made to high-income areas with high human population density and high livestock density; whereas in the 1960s ungulates were introduced to areas species poor for indigenous ungulates and marginal for livestock. In South Africa, long distance translocations of indigenous species extralimitally has resulted in extensive range expansions of a magnitude greater than predicted range changes as a result of predicted climate change. When the use of surrogates of genetic distinctiveness for advising translocations was investigated for Africa, the East African rift valley was found to be important in delineating genetic distinctiveness and translocations across this feature should be prevented. Major rivers in Africa also showed potential for delineating genetic distinctiveness in ungulates, but relevant phylogeographic data are needed to confirm this. Sufficient evidence for the impacts of non-indigenous ungulates on biodiversity both in South Africa and globally is lacking despite substantial concern for their impacts. It is suggested that to demonstrate the impacts of non-indigenous ungulates exclosure and enclosure experiments should be used and population declines in indigenous species should be shown.