Browsing by Author "Wilson, J. R. U."

Now showing 1 - 5 of 5
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    Does origin determine environmental impacts? Not for bamboos
    (New Phytologist Trust, 2019) Canavan, S.; Kumschick, S.; Le Roux, J. J.; Richardson, D. M.; Wilson, J. R. U.
    Societal Impact Statement: Non‐native species can cause considerable negative impacts in natural ecosystems. Such impacts often are directly due to the fact that these species occur in habitats where they did not evolve. We explored this for bamboos and found that, contrary to the situation in many other plant groups, biogeographic origin was not a strong predictor of the type and severity of environmental impacts caused. We argue that impacts from bamboos are a response to land transformation and disturbance of forest habitats by humans. Therefore, the threats posed by bamboos to highly disturbed forest systems should be the same wherever bamboos are present or planted, and management should adopt similar approaches. Summary • Negative environmental impacts can result from the human‐mediated breakdown of biogeographic boundaries that historically shaped species distributions leading to rapid population expansions, that is, from biological invasions. However, the alteration of natural ecosystems by humans has created opportunities for both native and non‐native species to become weedy. We assessed whether origin status (native or non‐native) matters for the type and magnitude of environmental impacts caused by bamboos (Poaceae: Bambusoideae). • We used a systematic global literature search and the International Union for Conservation of Nature's (IUCN) Environmental Impact Classification of Alien Taxa (EICAT) scheme as the basis for scoring impacts of bamboo species. • We found that the type and severity of recorded impacts were similar in the native and non‐native ranges of weedy bamboos, and that the habitats in which impacts are most often reported (i.e., temperate and tropical forests) were also the same. • Origin was not a strong predictor of environmental impacts for bamboos. Rather, impacts are likely to be a response to human‐mediated land transformation and disturbance of forests. Further research on the mechanisms whereby bamboos impact other species is needed to guide management strategies in their native ranges and as input to risk assessments for new introductions and plantings.
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    A four-component classification of uncertainties in biological invasions : implications for management
    (John Wiley & Sons, Inc, 2019) Latombe, G.; Canavan, S.; Hirsch, H.; Hui, C.; Kumschick, S.; Nsikani, M. N.; Potgieter, L. J.; Robinson, T. B.; Saul, W.-C.; Turner, S. C.; Wilson, J. R. U.; Yannelli, F. A.; Richardson, D. M.
    Although uncertainty is an integral part of any science, it raises doubts in public perception about scientific evidence, is exploited by denialists, and therefore potentially hinders the implementation of management actions. As a relatively young field of study, invasion science contains many uncertainties. This may explain why, despite international policies aimed at mitigating biological invasions, the implementation of national- and regional-scale measures to prevent or control alien species has done little to slow the increase in extent of invasions and the magnitude of impacts. Uncertainty is therefore a critical aspect of invasion science that should be addressed to enable the field to progress further. To improve how uncertainties in invasion science are captured and characterized, we propose a framework, which is also applicable to other applied research fields such as climate and conservation science, divided into four components: the need (1) to clearly circumscribe the phenomenon, (2) to measure and provide evidence for the phenomenon (i.e., confirmation), (3) to understand the mechanisms that cause the phenomenon, and (4) to understand the mechanisms through which the phenomenon results in consequences. We link these issues to three major types of uncertainty: linguistic, psychological, and epistemic. The application of this framework shows that the four components tend to be characterized by different types of uncertainty in invasion science.We explain how these uncertainties can be detrimental to the implementation of management measures and propose ways to reduce them. Since biological invasions are increasingly tightly embedded in complex socio-ecological systems, many problems associated with these uncertainties have convoluted solutions. They demand the consensus of many stakeholders to define and frame the dimensions of the phenomenon, and to decide on appropriate actions. While many of the uncertainties cannot be eliminated completely, we believe that using this framework to explicitly identify and communicate them will help to improve collaboration between researchers and managers, increase scientific, political, and public support for invasion research, and provide a stronger foundation for sustainable management strategies.
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    Improving Darwin Core for research and management of alien species
    (Pensoft, 2019-10-10) Groom, Q.; Desmet, P.; Reyserhove, L.; Adriaens, T.; Oldoni, D.; Vanderhoeven, S.; Baskauf, S. J.; Chapman, A.; McGeoch, M.; Walls, R.; Wieczorek, J.; Wilson, J. R. U.; Zermoglio, P. F. F.; Simpson, A.
    To improve the suitability of the Darwin Core standard for the research and management of alien species, the standard needs to express the native status of organisms, how well established they are and how they came to occupy a location. To facilitate this, we propose: 1. To adopt a controlled vocabulary for the existing Darwin Core term dwc:establishmentMeans 2. To elevate the pathway term from the Invasive Species Pathways extension to become a new Darwin Core term dwc:pathway maintained as part of the Darwin Core standard 3. To adopt a new Darwin Core term dwc:degreeOfEstablishment with an associated controlled vocabulary These changes to the standard will allow users to clearly state whether an occurrence of a species is native to a location or not, how it got there (pathway), and to what extent the species has become a permanent feature of the location. By improving Darwin Core for capturing and sharing these data, we aim to improve the quality of occurrence and checklist data in general and to increase the number of potential uses of these data.
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    Melaleuca parvistaminea Byrnes (Myrtaceae) in South Africa : invasion risk and feasibility of eradication
    (Elsevier, 2014) Jacobs, L. E. O; Richardson, D. M.; Wilson, J. R. U.
    ENGLISH ABSTRACT: We document and assess management options for the first reported invasion of Melaleuca parvistaminea Byrnes (initially identified asM. ericifolia) in the world, in the context of a South African wetland ecosystem. Delimitation surveys indicate that the entire invasion is restricted to three sites between Tulbagh and Wolseley and that populations are only associated with areas currently or previously covered by pine plantations (primarily Pinus radiata). To estimate abundance we surveyed 42% of the three identified areas and found ~26,000 plants over 1800 ha (condensed canopy area of 1.15 ha). At least 63% of recorded plants were seedlings or juveniles, mostly <4 yrs old, and most occurred in seasonally inundated (but not waterlogged) habitats. M. parvistaminea creates monospecific stands that overtop the native shrubland vegetation (Breede Shale Renosterveld) and is thus considered a potential transformer species. Species distribution modelling also revealed large areas of climatically suitable habitat in the Western Cape, pointing to substantial invasion debt for the species in South Africa. Felling triggers seed release from serotinous capsules, resulting in prolific seedling recruitment after winter rains (up to ~18,000 seedlings/m2). No evidence of a soil-stored seed bank was found, and when plants are cut at ground level or treated with herbicide after cutting, plants do not resprout. The invasive populations of this water-dispersed species are close to major rivers (the Berg and Breede), but the intervening countryside is largely transformed and is unfavourable for establishment. Much of the area downstream from the invaded area is open vegetation that is unsuitable for major recruitment but easy to survey and detect small plants. Consequently, although the extent of invasion is large (potentially 9185 ha), the invasion can be delimited with some confidence, and eradication is considered achievable since seeds only survive for about a year, seedlings achieve maturity after 4 years, and because the species is an obligate reseeder. Given the threats posed, eradication is desirable and M. parvistaminea should be listed as a category-1a invader (requiring compulsory control) under the proposed invasive species regulations under South Africa's National Environmental Management: Biodiversity Act (10/2004).We estimate that search and destroy operations could eradicate the species by 2021 at a cost of ZAR 3 475 000 (US$ 355 400).
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    Propagule pressure helps overcome adverse environmental conditions during population establishment
    (Elsevier, 2021) Saccaggi, D. L.; Wilson, J. R. U.; Terblanche, J. S.
    ENGLISH ABSTRACT: The establishment success of a population is a function of abiotic and biotic factors and introduction dynamics. Understanding how these factors interact has direct consequences for understanding and managing biological invasions and for applied ecology more generally. Here we use a mesocosm approach to explore how the size of founding populations and the number of introduction events interact with environmental conditions (temperature) to determine the establishment success of laboratory-reared Drosophila melanogaster. We found that temperature played the biggest role in establishment success, eclipsing the role of the other experimental factors when viewed overall. Under optimal temperature conditions propagule pressure was of negligible importance to establishment success.  At adverse temperatures, however, establishment success increased with the total founding population size. This effect was considerably stronger at the cold than at the hot extreme. Whether the population was introduced all at once or by increments (changing the number of introduction events) had a negligible global effect. However, once again, a stronger effect of increasing number of introduction events was seen at adverse temperatures, with hot and cold extremes revealing opposite effects: adding flies incrementally decreased their establishment success at the hot extreme, but increased it at the cold extreme. These differing effects at hot and cold thermal extremes implies that different establishment mechanisms are at play at either extreme. These results suggest that the effort required to prevent (or conversely, to facilitate) the establishment of populations varies with the environment in ways that can be complicated but predictable.