Browsing by Author "McGeoch, Melodie A."

Now showing 1 - 12 of 12
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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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    A biodiversity monitoring framework for South Africa : progress and directions
    (Academy of Science of South Africa, 2007) Reyers, Belinda; McGeoch, Melodie A.
    Global declines in biodiversity, and the associated impacts on human wellbeing, have triggered national and international agreements to reduce or halt these trends. The Convention on Biological Diversity's 2002 commitment, 'to achieve, by 2010, a significant reduction in the current rate of biodiversity loss....', is an often cited example and has caused a flurry of activity in the development of biodiversity monitoring systems. At a national scale, South Africa's National Environmental Management: Biodiversity Act and associated legislation have highlighted the need for a national biodiversity monitoring framework. The National Biodiversity Strategy and Action Plan makes a significant contribution to the development of this framework. As South Africa begins to implement the action plan, a review of existing national monitoring programmes in terms of global and national biodiversity monitoring requirements is important. This paper presents the results of a review of these national programmes, to provide a broad overview, assess alignment with national and global requirements, evaluate gaps and discuss a way forward in the devising of a national biodiversity monitoring framework. We find that the National Biodiversity Strategy and Action Plan aligns well with the Convention on Biological Diversity's 2010 target objectives, but differs in terms of the indicators proposed. Existing national biodiversity monitoring programmes also exhibit these indicator differences and show several gaps in indicator development and data collation. These gaps raise concern around the country's ability to report on the Convention on Biological Diversity's 2010 target, but together with the sound platform provided by the National Biodiversity Strategy and Action Plan, provide a good indication of national priorities and a way forward through a combination of short-term achievable tasks and longer-term development of programmes.
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    A conceptual map of invasion biology : integrating hypotheses into a consensus network
    (Wiley, 2020-03-25) Enders, Martin; Havemann, Frank; Ruland, Florian; Bernard-Verdier, Maud; Catford, Jane A.; Gomez-Aparicio, Lorena; Haider, Sylvia; Heger, Tina; Kueffer, Christoph; Kuh, Ingolf; Meyerson, Laura A.; Musseau, Camille; Novoa, Ana; Ricciardi, Anthony; Sagouis, Alban; Schittko, Conrad; Strayer, David L.; Vilà, Montserrat; Essl, Franz; Hulme, Philip E.; Van Kleunen, Mark; Kumschick, Sabrina; Lockwood, Julie L.; Mabey, Abigail L.; McGeoch, Melodie A.; Estibaliz, Palma; Pysek, Petr; Saul, Wolf-Christian; Yannelli, Florencia A.; Jeschke, Jonathan M.
    Background and aims: Since its emergence in the mid-20th century, invasion biology has matured into a productive research field addressing questions of fundamental and applied importance. Not only has the number of empirical studies increased through time, but also has the number of competing, overlapping and, in some cases, contradictory hypotheses about biological invasions. To make these contradictions and redundancies explicit, and to gain insight into the field’s current theoretical structure, we developed and applied a Delphi approach to create a consensus network of 39 existing invasion hypotheses. Results: The resulting network was analysed with a link-clustering algorithm that revealed five concept clusters (resource availability, biotic interaction, propagule, trait and Darwin’s clusters) representing complementary areas in the theory of invasion biology. The network also displays hypotheses that link two or more clusters, called connecting hypotheses, which are important in determining network structure. The network indicates hypotheses that are logically linked either positively (77 connections of support) or negatively (that is, they contradict each other; 6 connections). Significance: The network visually synthesizes how invasion biology’s predominant hypotheses are conceptually related to each other, and thus, reveals an emergent structure – a conceptual map – that can serve as a navigation tool for scholars, practitioners and students, both inside and outside of the field of invasion biology, and guide the development of a more coherent foundation of theory. Additionally, the outlined approach can be more widely applied to create a conceptual map for the larger fields of ecology and biogeography.
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    The effect of cross-boundary management on the trajectory to commonness in biological invasions
    (Pensoft, 2020-10-15) Latombe, Guillaume; Essl, Franz; McGeoch, Melodie A.
    ENGLISH ABSTRACT: The number of alien species introduced and undergoing range expansion in novel environments is steadily increasing, with important consequences for native ecosystems. The efficacy of management planning and decision making to limit such invasions can be improved by understanding how interventions will impact the population dynamics of recently introduced species. To do so, here we expand on a typological framework that enables the classification of populations over time into 10 categories of commonness, and apply it to a spatially discrete metapopulation with heterogeneous abundance across spatial units (patches). We use this framework to assess the effect of cross-boundary management on the capacity of a metapopulation with different demographic and dispersal characteristics, including time lags in population growth, to become common. We demonstrate this framework by simulating a simple theoretical metapopulation model capable of exploring a range of environments, species characteristics, and management actions. Management can vary in the efficacy of propagule interception between patches, and in the synchronisation of the implementation of these measures across patches (i.e. if management is implemented simultaneously across patches). Simulations show that poor interception efficacy that only modestly reduces the number of propagules entering a given spatial unit cannot be compensated for by strong management synchronisation between spatial units. Management synchronisation will nonetheless result in a reduction in rates of spread once a critical threshold of interception efficacy has been met. Finally, time lags in population growth that may result in delayed spread are an important aspect to be considered in management as they can amplify the efficacy of management. Our results demonstrate how a typological framework of categories of commonness can be used to provide practical insights for the management of biological invasions.
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    Framing the concept of satellite remote sensing essential biodiversity variables : challenges and future directions
    (John Wiley & Sons Ltd., 2016-03) Pettorelli, Nathalie; Wegmann, Martin; Skidmore, Andrew; Mucher, Sander; Dawson, Terence P.; Fernandez, Miguel; Lucas, Richard; Schaepman, Michael E.; Wang, Tiejun; O’Connor, Brian; Jongman, Robert H. G.; Kempeneers, Pieter; Sonnenschein, Ruth; Leidner, Allison K.; Bohm, Monika; He, Kate S.; Nagendra, Harini; Dubois, Gregoire; Fatoyinbo, Temilola; Hansen, Matthew C.; Paganini, Marc; De Klerk, Helen Margaret; Asner, Gregory P.; Kerr, Jeremy T.; Estes, Anna B.; Schmeller, Dirk S.; Heiden, Uta; Rocchini, Duccio; Pereira, Henrique M.; Turak, Eren; Fernandez, Nestor; Lausch, Angela; Cho, Moses A.; Alcaraz-Segura, Domingo; McGeoch, Melodie A.; Turner, Woody; Mueller, Andreas; St-Louis, Veronique; Penner, Johannes; Vihervaara, Petteri; Belward, Alan; Reyers, Belinda; Geller, Gary N.
    Although satellite-based variables have for long been expected to be key components to a unified and global biodiversity monitoring strategy, a definitive and agreed list of these variables still remains elusive. The growth of interest in biodiversity variables observable from space has been partly underpinned by the development of the essential biodiversity variable (EBV) framework by the Group on Earth Observations – Biodiversity Observation Network, which itself was guided by the process of identifying essential climate variables. This contribution aims to advance the development of a global biodiversity monitoring strategy by updating the previously published definition of EBV, providing a definition of satellite remote sensing (SRS) EBVs and introducing a set of principles that are believed to be necessary if ecologists and space agencies are to agree on a list of EBVs that can be routinely monitored from space. Progress toward the identification of SRS-EBVs will require a clear understanding of what makes a biodiversity variable essential, as well as agreement on who the users of the SRS-EBVs are. Technological and algorithmic developments are rapidly expanding the set of opportunities for SRS in monitoring biodiversity, and so the list of SRS-EBVs is likely to evolve over time. This means that a clear and common platform for data providers, ecologists, environmental managers, policy makers and remote sensing experts to interact and share ideas needs to be identified to support long-term coordinated actions.
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    Measures, perceptions and scaling patterns of aggregated species distributions
    (Nordic Society Oikos, 2010) Hui, Cang; Veldtman, Ruan; McGeoch, Melodie A.
    Non-random (aggregated) species distributions arise from habitat heterogeneity and nonlinear biotic processes. A comprehensive understanding of the concept of aggregation, as well as its measurement, is pivotal to our understanding of species distributions and macroecological patterns. Here, using an individual-based model, we analyzed opinions on the concept of aggregation from the public and experts (trained ecologists), in addition to those calculated from a variety of aggregation indices. Three forms of scaling patterns (logarithmic, power-law and lognormal) and four groups of scaling trajectories emerged. The experts showed no significant difference from the public, although with a much lower deviation. The public opinion was partially influenced by the abundance of individuals in the spatial map, which was not found in the experts. With the increase of resolution (decrease of grain), aggregation indices showed a general trend from significantly different to significantly similar to the expert opinion. The over-dispersion index (i.e. the clumping parameter k in the negative binomial distribution) performed, at certain scales, as the closest index to the expert opinion. Examining performance of aggregation measures from different groups of scaling patterns was proposed as a practical way of analyzing spatial structures. The categorization of the scaling patterns of aggregation measures, as well as their over- and in-sensitivity towards spatial structures, thus not only provides a potential solution to the modifiable areal unit problem, but also unveils the interrelationship among the concept, measures and perceptions of aggregated species distributions.
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    Mechanistic reconciliation of community and invasion ecology
    (Ecological Society of America, 2021-02) Latombe, Guillaume; Richardson, David M.; McGeoch, Melodie A.; Altwegg, Res; Catford, Jane A.; Chase, Jonathan M.; Courchamp, Franck; Esler, , Karen J.; Jeschke, Jonathan M.; Landi, Pietro; Measey, John; Midgley, Guy F.; Minoarivelo, Henintsoa O.; Rodger, James G.; Hui, Cang
    Community and invasion ecology have mostly grown independently. There is substantial overlap in the processes captured by different models in the two fields, and various frameworks have been developed to reduce this redundancy and synthesize information content. Despite broad recognition that community and invasion ecology are interconnected, a process‐based framework synthesizing models across these two fields is lacking. Here we review 65 representative community and invasion models and propose a common framework articulated around six processes (dispersal, drift, abiotic interactions, within‐guild interactions, cross‐guild interactions, and genetic changes). The framework is designed to synthesize the content of the two fields, provide a general perspective on their development, and enable their comparison. The application of this framework and of a novel method based on network theory reveals some lack of coherence between the two fields, despite some historical similarities. Community ecology models are characterized by combinations of multiple processes, likely reflecting the search for an overarching theory to explain community assembly and structure, drawing predominantly on interaction processes, but also accounting largely for the other processes. In contrast, most models in invasion ecology invoke fewer processes and focus more on interactions between introduced species and their novel biotic and abiotic environment. The historical dominance of interaction processes and their independent developments in the two fields is also reflected in the lower level of coherence for models involving interactions, compared to models involving dispersal, drift, and genetic changes. It appears that community ecology, with a longer history than invasion ecology, has transitioned from the search for single explanations for patterns observed in nature to investigate how processes may interact mechanistically, thereby generating and testing hypotheses. Our framework paves the way for a similar transition in invasion ecology, to better capture the dynamics of multiple alien species introduced in complex communities. Reciprocally, applying insights from invasion to community ecology will help us understand and predict the future of ecological communities in the Anthropocene, in which human activities are weakening species’ natural boundaries. Ultimately, the successful integration of the two fields could advance a predictive ecology that is urgently required in a rapidly changing world.
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    Niche shift and resource supplementation facilitate an amphibian range expansion
    (Wiley, 2019) Davies, Sarah J.; Hill, Matthew P.; McGeoch, Melodie A.; Clusella-Trullas, Susana
    Aim: To determine whether recent range expansion of small- bodied arboreal frogs, Hyperolius marmoratus Rapp, is accompanied by changes in species–environment re- lationships and whether its historical range was constrained by climate, availability of water bodies or topographic variables. We test if artificial water bodies in the novel range have facilitated niche shift by increasing available habitats for frog establishment. Location: Western Cape Province, South Africa, with reference to the broader spe- cies range in southeastern Africa. Methods: We build species distribution models using occurrence data from the his- torical and novel ranges and reciprocally project them to highlight areas of putative niche change. We test for niche shift through ordination- based approaches to disen- tangle how species–environment relationships may have altered and whether climate or landscape features (artificial water bodies and topography) are more strongly as- sociated with the identified change. We further decompose niche change into areas of expansion and unfilling to quantify niche shift and describe potential future spread. Results: We observed niche expansion into novel environmental space, with 21% of niche space in the invaded range composed of environments that were not occupied in the native range. We also observed 16% niche unfilling, signifying range disequilib- rium and potential for further spread. Mean annual precipitation and proximity to water bodies were more influential in models constructed in the novel range than in historical or combined range models, suggesting that presence of artificial water bodies in the landscape ameliorates novel range conditions. Together, these metrics suggest that range expansion may be ongoing based on climate and water body availability. Main conclusions: Our analyses identify a realised niche shift that has allowed painted reed frogs to occupy drier and more thermally variable habitats in their novel (invaded) range. This shift may be mediated by artificial water bodies that provide additional buffered habitats, a key resource supplement for these small- bodied tropi- cal frogs.
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    Options for reducing uncertainty in impact classification for alien species
    (2021) Clarke, David A.; Palmer, David J.; McGrannachan, Chris; Burgess, Treena I.; Chown, Steven L.; Clarke, Rohan H.; Kumschick, Sabrina; Lach, Lori; Liebhold, Andrew M.; Roy, Helen E.; Saunders, Manu E.; Yeates, David K.; Zalucki, Myron P.; McGeoch, Melodie A.
    ENGLISH ABSTRACT: Impact assessment is an important and cost-effective tool for assisting in the identification and prioritization of invasive alien species. With the number of alien and invasive alien species expected to increase, reliance on impact assessment tools for the identification of species that pose the greatest threats will continue to grow. Given the importance of such assessments for management and resource allocation, it is critical to understand the uncertainty involved and what effect this may have on the outcome. Using an uncertainty typology and insects as a model taxon, we identified and classified the causes and types of uncertainty when performing impact assessments on alien species. We assessed 100 alien insect species across two rounds of assessments with each species independently assessed by two assessors. Agreement between assessors was relatively low for all three impact classification components (mechanism, severity, and confidence) after the first round of assessments. For the second round, we revised guidelines and gave assessors access to each other’s assessments which improved agreement by between 20% and 30% for impact mechanism, severity, and confidence. Of the 12 potential reasons for assessment discrepancies identified a priori, 11 were found to occur. The most frequent causes (and types) of uncertainty (i.e., differences between assessment outcomes for the same species) were as follows: incomplete information searches (systematic error), unclear mechanism and/or extent of impact (subjective judgment due to a lack of knowledge), and limitations of the assessment framework (context dependence). In response to these findings, we identify actions that may reduce uncertainty in the impact assessment process, particularly for assessing speciose taxa with diverse life histories such as Insects. Evidence of environmental impact was available for most insect species, and (of the non-random original subset of species assessed) 14 of those with evidence were identified as high impact species (with either major or massive impact). Although uncertainty in risk assessment, including impact assessments, can never be eliminated, identifying, and communicating its cause and variety is a first step toward its reduction and a more reliable assessment outcome, regardless of the taxa being assessed.
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    A vision for global monitoring of biological invasions
    (Elsevier Ltd., 2017) Latombe, Guillaume; Pysek, Petr; Jeschke, Jonathan M.; Blackburn, Tim M.; Bacher, Sven; Capinha, Cesar; Costello, Mark J.; Fernandez, Miguel; Gregory, Richard D.; Hobern, Donald; Hui, Cang; Jetz, Walter; Kumschick, Sabrina; McGrannachan, Chris; Pergl, Jan; Roy, Helen E.; Scalera, Riccardo; Squires, Zoe E.; Wilson, John R. U.; Winter, Marten; Genovesi, Piero; McGeoch, Melodie A.
    ENGLISH ABSTRACT: Managing biological invasions relies on good global coverage of species distributions. Accurate information on alien species distributions, obtained from international policy and cross-border co-operation, is required to evaluate trans-boundary and trading partnership risks. However, a standardized approach for systematically monitoring alien species and tracking biological invasions is still lacking. This Perspective presents a vision for global observation and monitoring of biological invasions. We show how the architecture for tracking biological invasions is provided by a minimum information set of Essential Variables, global collaboration on data sharing and infrastructure, and strategic contributions by countries. We show how this novel, synthetic approach to an observation system for alien species provides a tangible and attainable solution to delivering the information needed to slow the rate of new incursions and reduce the impacts of invaders. We identify three Essential Variables for Invasion Monitoring; alien species occurrence, species alien status and alien species impact. We outline how delivery of thisminimum information set by joint, complementary contributions from countries and global community initiatives is possible. Country contributions are made feasible using a modular approach where all countries are able to participate and strategically build their contributions to a global information set over time. The vision we outline will deliver wide-ranging benefits to countries and international efforts to slow the rate of biological invasions and minimize their environmental impacts. These benefits will accrue over time as global coverage and information on alien species increases.
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    Zeta diversity as a concept and metric that unifies incidence-based biodiversity patterns
    (The University of Chicago Press, 2014-11) Hui, Cang; McGeoch, Melodie A.
    Patterns in species incidence and compositional turnover are central to understanding what drives biodiversity. Here we propose zeta (ζ) diversity, the number of species shared by multiple assemblages, as a concept and metric that unifies incidence-based diversity measures, patterns, and relationships. Unlike other measures of species compositional turnover, zeta diversity partitioning quantifies the complete set of diversity components for multiple assemblages, comprehensively representing the spatial structure of multispecies distributions. To illustrate the application and ecological value of zeta diversity, we show how it scales with sample number, grain, and distance. Zeta diversity reconciles several different biodiversity patterns, including the species accumulation curve, the species-area relationship, multispecies occupancy patterns, and scaling of species endemism. Exponential and power-law forms of zeta diversity are associated with stochastic versus niche assembly processes. Zeta diversity may provide new insights on biodiversity patterns, the processes driving them, and their response to environmental change.