Publications by authors named "Melodie A McGeoch"

48 Publications

Country Compendium of the Global Register of Introduced and Invasive Species.

Sci Data 2022 07 9;9(1):391. Epub 2022 Jul 9.

IUCN SSC Invasive Species Specialist Group, Auckland, New Zealand.

The Country Compendium of the Global Register of Introduced and Invasive Species (GRIIS) is a collation of data across 196 individual country checklists of alien species, along with a designation of those species with evidence of impact at a country level. The Compendium provides a baseline for monitoring the distribution and invasion status of all major taxonomic groups, and can be used for the purpose of global analyses of introduced (alien, non-native, exotic) and invasive species (invasive alien species), including regional, single and multi-species taxon assessments and comparisons. It enables exploration of gaps and inferred absences of species across countries, and also provides one means for updating individual GRIIS Checklists. The Country Compendium is, for example, instrumental, along with data on first records of introduction, for assessing and reporting on invasive alien species targets, including for the Convention on Biological Diversity and Sustainable Development Goals. The GRIIS Country Compendium provides a baseline and mechanism for tracking the spread of introduced and invasive alien species across countries globally. Design Type(s) Data integration objective ● Observation design Measurement Type(s) Alien species occurrence ● Evidence of impact invasive alien species assessment objective Technology Type(s) Agent expert ● Data collation Factor Type(s) Geographic location ● Origin / provenance ● Habitat Sample Characteristics - Organism Animalia ● Bacteria ● Chromista ● Fungi ● Plantae ● Protista (Protozoa) ● Viruses Sample Characteristics - Location Global countries.
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http://dx.doi.org/10.1038/s41597-022-01514-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9271038PMC
July 2022

A framework to integrate innovations in invasion science for proactive management.

Biol Rev Camb Philos Soc 2022 08 22;97(4):1712-1735. Epub 2022 Apr 22.

Flathead Lake Biological Station, University of Montana, 32125 Bio Station Lane, Polson, MT, 59860, U.S.A.

Invasive alien species (IAS) are a rising threat to biodiversity, national security, and regional economies, with impacts in the hundreds of billions of U.S. dollars annually. Proactive or predictive approaches guided by scientific knowledge are essential to keeping pace with growing impacts of invasions under climate change. Although the rapid development of diverse technologies and approaches has produced tools with the potential to greatly accelerate invasion research and management, innovation has far outpaced implementation and coordination. Technological and methodological syntheses are urgently needed to close the growing implementation gap and facilitate interdisciplinary collaboration and synergy among evolving disciplines. A broad review is necessary to demonstrate the utility and relevance of work in diverse fields to generate actionable science for the ongoing invasion crisis. Here, we review such advances in relevant fields including remote sensing, epidemiology, big data analytics, environmental DNA (eDNA) sampling, genomics, and others, and present a generalized framework for distilling existing and emerging data into products for proactive IAS research and management. This integrated workflow provides a pathway for scientists and practitioners in diverse disciplines to contribute to applied invasion biology in a coordinated, synergistic, and scalable manner.
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http://dx.doi.org/10.1111/brv.12859DOI Listing
August 2022

Mechanistic reconciliation of community and invasion ecology.

Ecosphere 2021 Feb 10;12(2):e03359. Epub 2021 Feb 10.

Centre for Invasion Biology Department of Mathematical Sciences Stellenbosch University Stellenbosch 7600 South Africa.

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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http://dx.doi.org/10.1002/ecs2.3359DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8647914PMC
February 2021

A multi-site method to capture turnover in rare to common interactions in bipartite species networks.

J Anim Ecol 2022 02 28;91(2):404-416. Epub 2021 Nov 28.

School of Biological Sciences, Monash University, Clayton, Vic., Australia.

Ecological network structure is maintained by a generalist core of common species. However, rare species contribute substantially to both the species and functional diversity of networks. Capturing changes in species composition and interactions, measured as turnover, is central to understanding the contribution of rare and common species and their interactions. Due to a large contribution of rare interactions, the pairwise metrics used to quantify interaction turnover are, however, sensitive to compositional change in the interactions of, often rare, peripheral specialists rather than common generalists in the network. Here we expand on pairwise interaction turnover using a multi-site metric that enables quantifying turnover in rare to common interactions (in terms of occurrence of interactions). The metric further separates this turnover into interaction turnover due to species turnover and interaction rewiring. We demonstrate the application and value of this method using a host-parasitoid system sampled along gradients of environmental modification. In the study system, both the type and amount of habitat needed to maintain interaction composition depended on the properties of the interactions considered, that is, from rare to common. The analyses further revealed the potential of host switching to prevent or delay species loss, and thereby buffer the system from perturbation. Multi-site interaction turnover provides a comprehensive measure of network change that can, for example, detect ecological thresholds to habitat loss for rare to common interactions. Accurate description of turnover in common, in addition to rare, species and their interactions is particularly relevant for understanding how network structure and function can be maintained.
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http://dx.doi.org/10.1111/1365-2656.13639DOI Listing
February 2022

Combating ecosystem collapse from the tropics to the Antarctic.

Glob Chang Biol 2021 05 25;27(9):1692-1703. Epub 2021 Feb 25.

School of Biological Sciences, Monash University, Clayton, Vic., Australia.

Globally, collapse of ecosystems-potentially irreversible change to ecosystem structure, composition and function-imperils biodiversity, human health and well-being. We examine the current state and recent trajectories of 19 ecosystems, spanning 58° of latitude across 7.7 M km , from Australia's coral reefs to terrestrial Antarctica. Pressures from global climate change and regional human impacts, occurring as chronic 'presses' and/or acute 'pulses', drive ecosystem collapse. Ecosystem responses to 5-17 pressures were categorised as four collapse profiles-abrupt, smooth, stepped and fluctuating. The manifestation of widespread ecosystem collapse is a stark warning of the necessity to take action. We present a three-step assessment and management framework (3As Pathway Awareness, Anticipation and Action) to aid strategic and effective mitigation to alleviate further degradation to help secure our future.
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http://dx.doi.org/10.1111/gcb.15539DOI Listing
May 2021

Interspecific facilitation mediates the outcome of intraspecific interactions across an elevational gradient.

Ecology 2021 01 28;102(1):e03200. Epub 2020 Oct 28.

Department of Plant and Soil Sciences, University of Pretoria, Private Bag X20, Pretoria, 0002, South Africa.

Where interspecific facilitation favors the establishment of high densities of a beneficiary species, strong intraspecific competition may subsequently impede beneficiary performance. Consequently, the negative influence of intraspecific competition between beneficiary individuals could potentially outweigh the positive influence of interspecific facilitation when, for example, higher densities of a beneficiary are negated by the negative effect of crowding on beneficiary reproduction. The aim of this study was, therefore, to examine the impact of an interspecific interaction on the outcome of intraspecific interactions within the context of plant-plant facilitation. We used the cushion-forming Azorella selago and a commonly co-occurring dominant perennial grass species, Agrostis magellanica, on sub-Antarctic Marion Island as a model system. We assessed the impact of an interspecific interaction (between A. selago and A. magellanica) on the outcome of intraspecific interactions (between A. magellanica individuals), by testing if the impact of A. magellanica density on A. magellanica performance is mediated by its interaction with A. selago. We observed evidence for competition among A. magellanica conspecifics, with a decreasing proportion of A. magellanica individuals being reproductive under higher conspecific density. This negative intraspecific effect was greater on A. selago than on the adjacent substrate, suggesting that the facilitative effect of A. selago changes the intensity of intraspecific interactions between A. magellanica individuals. However, experimentally reducing A. magellanica density did not affect the species' performance. We also observed that the effect of A. selago on A. magellanica was positive, and despite the negative effect of intraspecific density on the proportion of reproductive A. magellanica individuals, the net reproductive effort of A. magellanica (i.e., the density of reproductive individuals) was significantly greater on A. selago than on the adjacent substrate. These results highlight that, in abiotically severe environments, the positive effects of interspecific facilitation by a benefactor species may outweigh the negative effects of intraspecific competition among beneficiaries. More broadly, these results suggest that both positive inter- and intraspecific biotic interactions may be key to consider when examining spatial and temporal variation in species' performance.
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http://dx.doi.org/10.1002/ecy.3200DOI Listing
January 2021

Soil Bacterial Communities Exhibit Strong Biogeographic Patterns at Fine Taxonomic Resolution.

mSystems 2020 Jul 21;5(4). Epub 2020 Jul 21.

School of Biological Sciences, Monash University, Clayton, VIC, Australia

Bacteria have been inferred to exhibit relatively weak biogeographic patterns. To what extent such findings reflect true biological phenomena or methodological artifacts remains unclear. Here, we addressed this question by analyzing the turnover of soil bacterial communities from three data sets. We applied three methodological innovations: (i) design of a hierarchical sampling scheme to disentangle environmental from spatial factors driving turnover; (ii) resolution of 16S rRNA gene amplicon sequence variants to enable higher-resolution community profiling; and (iii) application of the new metric zeta diversity to analyze multisite turnover and drivers. At fine taxonomic resolution, rapid compositional turnover was observed across multiple spatial scales. Turnover was overwhelmingly driven by deterministic processes and influenced by the rare biosphere. The communities also exhibited strong distance decay patterns and taxon-area relationships, with values within the interquartile range reported for macroorganisms. These biogeographical patterns were weakened upon applying two standard approaches to process community sequencing data: clustering sequences at 97% identity threshold and/or filtering the rare biosphere (sequences lower than 0.05% relative abundance). Comparable findings were made across local, regional, and global data sets and when using shotgun metagenomic markers. Altogether, these findings suggest that bacteria exhibit strong biogeographic patterns, but these signals can be obscured by methodological limitations. We advocate various innovations, including using zeta diversity, to advance the study of microbial biogeography. It is commonly thought that bacterial distributions show lower spatial variation than for multicellular organisms. In this article, we present evidence that these inferences are artifacts caused by methodological limitations. Through leveraging innovations in sampling design, sequence processing, and diversity analysis, we provide multifaceted evidence that bacterial communities in fact exhibit strong distribution patterns. This is driven by selection due to factors such as local soil characteristics. Altogether, these findings suggest that the processes underpinning diversity patterns are more unified across all domains of life than previously thought, which has broad implications for the understanding and management of soil biodiversity.
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http://dx.doi.org/10.1128/mSystems.00540-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7566276PMC
July 2020

Basal tolerance but not plasticity gives invasive springtails the advantage in an assemblage setting.

Conserv Physiol 2020 15;8(1):coaa049. Epub 2020 Jun 15.

School of Biological Sciences, Monash University, Victoria 3800, Australia.

As global climates change, alien species are anticipated to have a growing advantage relative to their indigenous counterparts, mediated through consistent trait differences between the groups. These insights have largely been developed based on interspecific comparisons using multiple species examined from different locations. Whether such consistent physiological trait differences are present within assemblages is not well understood, especially for animals. Yet, it is at the assemblage level that interactions play out. Here, we examine whether physiological trait differences observed at the interspecific level are also applicable to assemblages. We focus on the Collembola, an important component of the soil fauna characterized by invasions globally, and five traits related to fitness: critical thermal maximum, minimum and range, desiccation resistance and egg development rate. We test the predictions that the alien component of a local assemblage has greater basal physiological tolerances or higher rates, and more pronounced phenotypic plasticity than the indigenous component. Basal critical thermal maximum, thermal tolerance range, desiccation resistance, optimum temperature for egg development, the rate of development at that optimum and the upper temperature limiting egg hatching success are all significantly higher, on average, for the alien than the indigenous components of the assemblage. Outcomes for critical thermal minimum are variable. No significant differences in phenotypic plasticity exist between the alien and indigenous components of the assemblage. These results are consistent with previous interspecific studies investigating basal thermal tolerance limits and development rates and their phenotypic plasticity, in arthropods, but are inconsistent with results from previous work on desiccation resistance. Thus, for the Collembola, the anticipated advantage of alien over indigenous species under warming and drying is likely to be manifest in local assemblages, globally.
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http://dx.doi.org/10.1093/conphys/coaa049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7294889PMC
June 2020

A conceptual map of invasion biology: Integrating hypotheses into a consensus network.

Glob Ecol Biogeogr 2020 Jun 25;29(6):978-991. Epub 2020 Mar 25.

Department of Biology, Chemistry, Pharmacy Institute of Biology Freie Universität Berlin Berlin Germany.

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 (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 , 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 - 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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http://dx.doi.org/10.1111/geb.13082DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8647925PMC
June 2020

Measuring continuous compositional change using decline and decay in zeta diversity.

Ecology 2019 11 14;100(11):e02832. Epub 2019 Aug 14.

Centre for Invasion Biology, Department of Mathematical Sciences, Stellenbosch University, Matieland, 7602, South Africa.

Incidence, or compositional, matrices are generated for a broad range of research applications in biology. Zeta diversity provides a common currency and conceptual framework that links incidence-based metrics with multiple patterns of interest in biology, ecology, and biodiversity science. It quantifies the variation in species (or OTU) composition of multiple assemblages (or cases) in space or time, to capture the contribution of the full suite of narrow, intermediate, and wide-ranging species to biotic heterogeneity. Here we provide a conceptual framework for the application and interpretation of patterns of continuous change in compositional diversity using zeta diversity. This includes consideration of the survey design context, and the multiple ways in which zeta diversity decline and decay can be used to examine and test turnover in the identity of elements across space and time. We introduce the zeta ratio-based retention rate curve to quantify rates of compositional change. We illustrate these applications using 11 empirical data sets from a broad range of taxa, scales, and levels of biological organization-from DNA molecules and microbes to communities and interaction networks-including one of the original data sets used to express compositional change and distance decay in ecology. We show (1) how different sample selection schemes used during the calculation of compositional change are appropriate for different data types and questions, (2) how higher orders of zeta may in some cases better detect shifts and transitions, and (3) the relative roles of rare vs. common species in driving patterns of compositional change. By exploring the application of zeta diversity decline and decay, including the retention rate, across this broad range of contexts, we demonstrate its application for understanding continuous turnover in biological systems.
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http://dx.doi.org/10.1002/ecy.2832DOI Listing
November 2019

The influence of landscape, climate and history on spatial genetic patterns in keystone plants (Azorella) on sub-Antarctic islands.

Mol Ecol 2019 07 10;28(14):3291-3305. Epub 2019 Jul 10.

Department of Zoology, Centre for Ecological Genomics and Wildlife Conservation, University of Johannesburg, Auckland Park, South Africa.

The distribution of genetic variation in species is governed by factors that act differently across spatial scales. To tease apart the contribution of different processes, especially at intermediate spatial scales, it is useful to study simple ecosystems such as those on sub-Antarctic oceanic islands. In this study, we characterize spatial genetic patterns of two keystone plant species, Azorella selago on sub-Antarctic Marion Island and Azorella macquariensis on sub-Antarctic Macquarie Island. Although both islands experience a similar climate and have a similar vegetation structure, they differ significantly in topography and geological history. We genotyped six microsatellites for 1,149 individuals from 123 sites across Marion Island and 372 individuals from 42 sites across Macquarie Island. We tested for spatial patterns in genetic diversity, including correlation with elevation and vegetation type, and clines in different directional bearings. We also examined genetic differentiation within islands, isolation-by-distance with and without accounting for direction, and signals of demographic change. Marion Island was found to have a distinct northwest-southeast divide, with lower genetic diversity and more sites with a signal of population expansion in the northwest. We attribute this to asymmetric seed dispersal by the dominant northwesterly winds, and to population persistence in a southwestern refugium during the Last Glacial Maximum. No apparent spatial pattern, but greater genetic diversity and differentiation between sites, was found on Macquarie Island, which may be due to the narrow length of the island in the direction of the dominant winds and longer population persistence permitted by the lack of extensive glaciation on the island. Together, our results clearly illustrate the implications of island shape and geography, and the importance of direction-dependent drivers, in shaping spatial genetic structure.
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http://dx.doi.org/10.1111/mec.15147DOI Listing
July 2019

Essential biodiversity variables for mapping and monitoring species populations.

Nat Ecol Evol 2019 04 11;3(4):539-551. Epub 2019 Mar 11.

NSW Office of Environment & Heritage, Sydney, New South Wales, Australia.

Species distributions and abundances are undergoing rapid changes worldwide. This highlights the significance of reliable, integrated information for guiding and assessing actions and policies aimed at managing and sustaining the many functions and benefits of species. Here we synthesize the types of data and approaches that are required to achieve such an integration and conceptualize 'essential biodiversity variables' (EBVs) for a unified global capture of species populations in space and time. The inherent heterogeneity and sparseness of raw biodiversity data are overcome by the use of models and remotely sensed covariates to inform predictions that are contiguous in space and time and global in extent. We define the species population EBVs as a space-time-species-gram (cube) that simultaneously addresses the distribution or abundance of multiple species, with its resolution adjusted to represent available evidence and acceptable levels of uncertainty. This essential information enables the monitoring of single or aggregate spatial or taxonomic units at scales relevant to research and decision-making. When combined with ancillary environmental or species data, this fundamental species population information directly underpins a range of biodiversity and ecosystem function indicators. The unified concept we present links disparate data to downstream uses and informs a vision for species population monitoring in which data collection is closely integrated with models and infrastructure to support effective biodiversity assessment.
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http://dx.doi.org/10.1038/s41559-019-0826-1DOI Listing
April 2019

The effect of network size and sampling completeness in depauperate networks.

J Anim Ecol 2019 02 2;88(2):211-222. Epub 2018 Nov 2.

School of Biological Sciences, Monash University, Clayton, Vic., Australia.

The accurate estimation of interaction network structure is essential for understanding network stability and function. A growing number of studies evaluate under-sampling as the degree of sampling completeness (proportional richness observed). How the relationship between network structural metrics and sampling completeness varies across networks of different sizes remains unclear, but this relationship has implications for the within- and between-system comparability of network structure. Here, we test the combined effects of network size and sampling completeness on the structure of spatially distinct networks (i.e., subwebs) in a host-parasitoid model system to better understand the within-system variability in metric bias. Richness estimates were used to quantify a gradient of sampling completeness of species and interactions across randomly subsampled subwebs. The combined impacts of network size and sampling completeness on the estimated values of twelve unweighted and weighted network metrics were tested. The robustness of network metrics to under-sampling was strongly related to network size, and sampling completeness of interactions were generally a better predictor of metric bias than sampling completeness of species. Weighted metrics often performed better than unweighted metrics at low sampling completeness; however, this was mainly evident at large rather than small subweb size. These outcomes highlight the significance of under-sampling for the comparability of both unweighted and weighted network metrics when networks are small and vary in size. This has implications for within-system comparability of species-poor networks and, more generally, reveals problems with under-sampling ecological networks that may otherwise be difficult to detect in species-rich networks. To mitigate the impacts of under-sampling, more careful considerations of system-specific variation in metric bias are needed.
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http://dx.doi.org/10.1111/1365-2656.12912DOI Listing
February 2019

Conserving the abundance of nonthreatened species.

Conserv Biol 2019 04 24;33(2):319-328. Epub 2018 Oct 24.

School of Biological Sciences, Monash University, Clayton, VIC, 3800, Australia.

Human modification of the environment is driving declines in population size and distributional extent of much of the world's biota. These declines extend to many of the most abundant and widespread species, for which proportionally small declines can result in the loss of vast numbers of individuals, biomass, and interactions. These losses could have major localized effects on ecological and cultural processes and services without elevating a species' global extinction risk. Although most conservation effort is directed at species threatened with extinction in the very near term, the value of retaining abundance regardless of global extinction risk is justifiable based on many biodiversity or ecosystem service metrics, including cultural services, at scales from local to global. The challenges of identifying conservation priorities for widespread and abundant species include quantifying the effects of species' abundance on services and understanding how these effects are realized as populations decline. Negative effects of population declines may be disconnected from the threat processes driving declines because of species movements and environment flows (e.g., hydrology). Conservation prioritization for these species shares greater similarity with invasive species risk assessments than extinction risk assessments because of the importance of local context and per capita effects of abundance on other species. Because conservation priorities usually focus on preventing the extinction of threatened species, the rationale and objectives for incorporating declines of nonthreatened species must be clearly articulated, going beyond extinction risk to encompass the range of likely harmful effects (e.g., secondary extinctions, loss of ecosystem services) if declines persist or are not reversed. Research should focus on characterizing the effects of local declines in species that are not threatened globally across a range of ecosystem services and quantifying the spatial distribution of these effects through the distribution of abundance. The case for conserving abundance in nonthreatened species can be made most powerfully when the costs of losing this abundance are better understood.
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http://dx.doi.org/10.1111/cobi.13197DOI Listing
April 2019

Introducing the Global Register of Introduced and Invasive Species.

Sci Data 2018 01 23;5:170202. Epub 2018 Jan 23.

IUCN SSC Invasive Species Specialist Group, 00144 Rome, Italy.

Harmonised, representative data on the state of biological invasions remain inadequate at country and global scales, particularly for taxa that affect biodiversity and ecosystems. Information is not readily available in a form suitable for policy and reporting. The Global Register of Introduced and Invasive Species (GRIIS) provides the first country-wise checklists of introduced (naturalised) and invasive species. GRIIS was conceived to provide a sustainable platform for information delivery to support national governments. We outline the rationale and methods underpinning GRIIS, to facilitate transparent, repeatable analysis and reporting. Twenty country checklists are presented as exemplars; GRIIS Checklists for close to all countries globally will be submitted through the same process shortly. Over 11000 species records are currently in the 20 country exemplars alone, with environmental impact evidence for just over 20% of these. GRIIS provides significant support for countries to identify and prioritise invasive alien species, and establishes national and global baselines. In future this will enable a global system for sustainable monitoring of trends in biological invasions that affect the environment.
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http://dx.doi.org/10.1038/sdata.2017.202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779068PMC
January 2018

Antarctica and the strategic plan for biodiversity.

PLoS Biol 2017 03 28;15(3):e2001656. Epub 2017 Mar 28.

School of Biological Sciences, Monash University, Melbourne, Victoria, Australia.

The Strategic Plan for Biodiversity, adopted under the auspices of the Convention on Biological Diversity, provides the basis for taking effective action to curb biodiversity loss across the planet by 2020-an urgent imperative. Yet, Antarctica and the Southern Ocean, which encompass 10% of the planet's surface, are excluded from assessments of progress against the Strategic Plan. The situation is a lost opportunity for biodiversity conservation globally. We provide such an assessment. Our evidence suggests, surprisingly, that for a region so remote and apparently pristine as the Antarctic, the biodiversity outlook is similar to that for the rest of the planet. Promisingly, however, much scope for remedial action exists.
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http://dx.doi.org/10.1371/journal.pbio.2001656DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5369689PMC
March 2017

Quantifying the extent of protected-area downgrading, downsizing, and degazettement in Australia.

Conserv Biol 2017 10 9;31(5):1039-1052. Epub 2017 Jun 9.

School of Biological Sciences, Monash University, Clayton, VIC, 3800, Australia.

The use of total area protected as the predominant indicator of progress in building protected area (PA) networks is receiving growing criticism. Documenting the full dynamics of PA networks, both in terms of the gains and losses in protection, provides a much more informative approach to tracking progress. To this end, documentation of PA downgrading, downsizing, and degazettement (PADDD) has increased. Studies of PADDD events generally fail to place these losses in the context of gains in protection; therefore, they omit important elements of PA network dynamics. To address this limitation, we used a spatially explicit approach to identify every parcel of land added to and excised from the Australian terrestrial PA network and PAs that had their level of protection changed over 17 years (1997-2014). By quantifying changes in the spatial configuration of the PA network with time-series data (spatial layers for nine separate time steps), ours is the first assessment of the dynamics (increases and decreases in area and level of protection) of a PA network and the first comprehensive assessment of PADDD in a developed country. We found that the Australian network was highly dynamic; there were 5233 changes in area or level of protection over 17 years. Against a background of enormous increases in area protected, we identified over 1500 PADDD events, which affected over one-third of the network, which were largely the result of widespread downgrading of protection. We believe our approach provides a mechanism for robust tracking of trends in the world's PAs through the use of data from the World Database on Protected Areas. However, this will require greater transparency and improved data standards in reporting changes to PAs.
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http://dx.doi.org/10.1111/cobi.12904DOI Listing
October 2017

Beyond the continuum: a multi-dimensional phase space for neutral-niche community assembly.

Proc Biol Sci 2015 Dec;282(1821):20152417

School of Biological Sciences, Monash University, Melbourne 3800, Australia.

Neutral and niche processes are generally considered to interact in natural communities along a continuum, exhibiting community patterns bounded by pure neutral and pure niche processes. The continuum concept uses niche separation, an attribute of the community, to test the hypothesis that communities are bounded by pure niche or pure neutral conditions. It does not accommodate interactions via feedback between processes and the environment. By contrast, we introduce the Community Assembly Phase Space (CAPS), a multi-dimensional space that uses community processes (such as dispersal and niche selection) to define the limiting neutral and niche conditions and to test the continuum hypothesis. We compare the outputs of modelled communities in a heterogeneous landscape, assembled by pure neutral, pure niche and composite processes. Differences in patterns under different combinations of processes in CAPS reveal hidden complexity in neutral-niche community dynamics. The neutral-niche continuum only holds for strong dispersal limitation and niche separation. For weaker dispersal limitation and niche separation, neutral and niche processes amplify each other via feedback with the environment. This generates patterns that lie well beyond those predicted by a continuum. Inferences drawn from patterns about community assembly processes can therefore be misguided when based on the continuum perspective. CAPS also demonstrates the complementary information value of different patterns for inferring community processes and captures the complexity of community assembly. It provides a general tool for studying the processes structuring communities and can be applied to address a range of questions in community and metacommunity ecology.
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http://dx.doi.org/10.1098/rspb.2015.2417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4707763PMC
December 2015

A bust but no boom: responses of floodplain bird assemblages during and after prolonged drought.

J Anim Ecol 2015 11 4;84(6):1700-10. Epub 2015 Sep 4.

Institute for Applied Ecology, The University of Canberra, Bruce, ACT, 2617, Australia.

Climate change alters the frequency and severity of extreme events, such as drought. Such events will be increasingly important in shaping communities as climate change intensifies. The ability of species to withstand extreme events (resistance) and to recover once adverse conditions abate (resilience) will determine their persistence. We estimated the resistance and resilience of bird species during and after a 13-year drought (the 'Big Dry') in floodplain forests in south-eastern Australia. We conducted bird surveys at the beginning and end of the Big Dry, and after the abrupt end to the drought (the 'Big Wet'), to evaluate species-specific changes in reporting rates among the three periods. We assessed changes in bird-breeding activity before and after the Big Wet to estimate demographic resilience based on breeding. Between the start and the end of the Big Dry (1998 vs. 2009), 37 of 67 species declined substantially. Of those, only two had increased reporting rates after the Big Wet (2009 vs. 2013) that were equal to or larger than their declines, while three partially recovered. All other declining species showed low resilience: 25 showed no change in reporting rates and seven declined further. The number of breeding species and total breeding activity of all species declined after the Big Wet, and there was no change in the number of young produced. The Big Dry caused widespread declines in the floodplain avifauna. Despite the drought being broken by 2 years of well-above-average rainfall and subsequent near-average rainfall, most species showed low resilience and there was little indication that overall breeding had increased. The effects of drought appeared to be pervasive for much of the floodplain avifauna, regardless of species traits (species body mass, fecundity, mobility or diet). Ecosystems such as these are likely to require active management and restoration, including reinstatement of natural flooding regimes, to improve ecological condition, to enhance resistance and resilience to extreme climate events.
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http://dx.doi.org/10.1111/1365-2656.12424DOI Listing
November 2015

Plasticity of thermal tolerance and metabolism but not water loss in an invasive reed frog.

Comp Biochem Physiol A Mol Integr Physiol 2015 Nov 8;189:11-20. Epub 2015 Jul 8.

DST-NRF Centre of Excellence for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.

Phenotypic plasticity may buffer the selection pressures on organisms that inhabit novel or rapidly-changing environments. We investigated plasticity of thermal tolerance, energetic and water loss traits and their interaction with behaviour in a small-bodied, arboreal anuran (Hyperolius marmoratus Rapp, Hyperoliidae) undergoing rapid range expansion into the winter rainfall region of South Africa. After short-term exposure to three temperatures (acclimation treatments) commonly encountered in their historical and novel ranges, frogs exhibited a broad thermal tolerance range (mean±s.d.: 42.1±2.9 °C) and higher plasticity in CTmax than in CTmin. Resting metabolic rate was lowest in cold-acclimated animals, while active metabolic rates were lowest in warm-acclimated frogs, likely reflecting compensation towards energy conservation. Evaporative water loss was not significantly altered by the acclimation treatments in either resting or active animals, indicating limited plasticity in this trait compared to metabolism. Our results suggest that plasticity of temperature limits and metabolism may benefit this species in variable environments such as those encountered in its expanded range. Lack of plasticity in water loss during resting and activity suggests that these frogs rely on their high cutaneous resistance and behavioural means to buffer climate variation. This study highlights the importance of synergistic interactions between physiology and behaviour in determining amphibian responses to temperature variation.
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http://dx.doi.org/10.1016/j.cbpa.2015.06.033DOI Listing
November 2015

The changing form of Antarctic biodiversity.

Nature 2015 Jun;522(7557):431-8

School of Biological Sciences, Monash University, Victoria 3800, Australia.

Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. Understanding of how this diversity is distributed in marine and terrestrial systems, the mechanisms underlying its spatial variation, and the significance of the microbiota is growing rapidly. Broadly recognizable drivers of diversity variation include energy availability and historical refugia. The impacts of local human activities and global environmental change nonetheless pose challenges to the current and future understanding of Antarctic biodiversity. Life in the Antarctic and the Southern Ocean is surprisingly rich, and as much at risk from environmental change as it is elsewhere.
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http://dx.doi.org/10.1038/nature14505DOI Listing
June 2015

The role and value of conservation agency research.

Environ Manage 2015 Jun 4;55(6):1232-45. Epub 2015 Apr 4.

Scientific Services, South African National Parks, Private Bag X6531, George, 6530, South Africa,

Governments charge their conservation agencies to safeguard biodiversity through protected areas and threat mitigation. Increasingly, conservation management and policy need to be supported by rigorous evidence provided by science. As such, institutional arrangements should consider and enable effective scientific research and information dissemination. What role can in-house agency research play in responding to this challenge? We examined the research capabilities of three conservation agencies from Australia, South Africa, and United States. Seven indicators were used to characterize the reliability and relevance of agency research. We found similarities among agencies in their patterns of peer-reviewed publication, cultures of research collaboration, and tendencies to align research with organizational objectives. Among the many and diverse activities that constitute the role of a contemporary agency researcher, we emphasize two key research dimensions: reliability, achieved through peer-reviewed research output, and relevance, achieved through active stakeholder engagement. Amid increasingly challenging realities for conservation of ecosystems, agency science functions are vital to providing the evidence base required for effective management and policy development.
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http://dx.doi.org/10.1007/s00267-015-0473-5DOI Listing
June 2015

Zeta diversity as a concept and metric that unifies incidence-based biodiversity patterns.

Am Nat 2014 Nov 24;184(5):684-94. Epub 2014 Sep 24.

Centre for Invasion Biology, Department of Mathematical Sciences, Stellenbosch University, Matieland 7602, South Africa; and African Institute for Mathematical Sciences, Muizenberg 7945, South Africa.

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.
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http://dx.doi.org/10.1086/678125DOI Listing
November 2014

The effects of climate change and land-use change on demographic rates and population viability.

Biol Rev Camb Philos Soc 2015 Aug 25;90(3):837-53. Epub 2014 Aug 25.

Institute for Applied Ecology, The University of Canberra, Bruce, Australian Capital Territory, 2617, Australia.

Understanding the processes that lead to species extinctions is vital for lessening pressures on biodiversity. While species diversity, presence and abundance are most commonly used to measure the effects of human pressures, demographic responses give a more proximal indication of how pressures affect population viability and contribute to extinction risk. We reviewed how demographic rates are affected by the major anthropogenic pressures, changed landscape condition caused by human land use, and climate change. We synthesized the results of 147 empirical studies to compare the relative effect size of climate and landscape condition on birth, death, immigration and emigration rates in plant and animal populations. While changed landscape condition is recognized as the major driver of species declines and losses worldwide, we found that, on average, climate variables had equally strong effects on demographic rates in plant and animal populations. This is significant given that the pressures of climate change will continue to intensify in coming decades. The effects of climate change on some populations may be underestimated because changes in climate conditions during critical windows of species life cycles may have disproportionate effects on demographic rates. The combined pressures of land-use change and climate change may result in species declines and extinctions occurring faster than otherwise predicted, particularly if their effects are multiplicative.
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http://dx.doi.org/10.1111/brv.12136DOI Listing
August 2015

Accommodating the human response for realistic adaptation planning: response to Watson and Segan.

Trends Ecol Evol 2013 Oct 14;28(10):574-5. Epub 2013 Aug 14.

School of Biological Sciences, Monash University, Clayton, VIC 3800, Australia.

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http://dx.doi.org/10.1016/j.tree.2013.07.001DOI Listing
October 2013

Accommodating climate change contingencies in conservation strategy.

Trends Ecol Evol 2013 Mar 9;28(3):135-42. Epub 2012 Nov 9.

Plant Conservation Unit, Botany Department, Private Bag X3, University of Cape Town, Rondebosch 7701, South Africa.

Species ranges are seldom at equilibrium with climate, because several interacting factors determine distribution, including demographic processes, dispersal, land use, disturbance (e.g., fire), and biotic interactions. Conservation strategies in a changing climate therefore cannot be based only on predicted climate-driven range shifts. Here, we explore conservation and management options in a framework for prioritizing landscapes based on two 'axes of concern': landscape conservation capacity attributes (percentage of protected area, connectivity, and condition of the matrix) and vulnerability to climate change (climate change velocity and topographic variation). Nine other conservation actions are also presented, from understanding and predicting to planning and managing for climate change. We emphasize the need for adaptation and resilience in populations, ecosystems, and the conservation environment itself.
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http://dx.doi.org/10.1016/j.tree.2012.10.008DOI Listing
March 2013

Climate change and elevational diversity capacity: do weedy species take up the slack?

Biol Lett 2013 Feb 24;9(1):20120806. Epub 2012 Oct 24.

Centre for Invasion Biology, Stellenbosch University, Matieland 7602, South Africa.

Climate change leads to species range shifts and consequently to changes in diversity. For many systems, increases in diversity capacity have been forecast, with spare capacity to be taken up by a pool of weedy species moved around by humans. Few tests of this hypothesis have been undertaken, and in many temperate systems, climate change impacts may be confounded by simultaneous increases in human-related disturbance, which also promote weedy species. Areas to which weedy species are being introduced, but with little human disturbance, are therefore ideal for testing the idea. We make predictions about how such diversity capacity increases play out across elevational gradients in non-water-limited systems. Then, using modern and historical data on the elevational range of indigenous and naturalized alien vascular plant species from the relatively undisturbed sub-Antarctic Marion Island, we show that alien species have contributed significantly to filling available diversity capacity and that increases in energy availability rather than disturbance are the probable underlying cause.
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http://dx.doi.org/10.1098/rsbl.2012.0806DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565488PMC
February 2013

Uncertainty in invasive alien species listing.

Ecol Appl 2012 Apr;22(3):959-71

Cape Research Centre, South African National Parks, P.O. Box 216, Steenberg 7947, South Africa.

Lists of invasive alien species (IAS) are essential for preventing, controlling, and reporting on the state of biological invasions. However, these lists suffer from a range of errors, with serious consequences for their use in science, policy, and management. Here we (1) collated and classified errors in IAS listing using a taxonomy of uncertainty; and (2) estimated the size of these errors using data from a completed listing exercise, with the purpose of better understanding, communicating, and dealing with them. Ten errors were identified. Most result from a lack of knowledge or measurement error (epistemic uncertainty), although two were a result of context dependence and vagueness (linguistic uncertainty). Estimates of the size of the effects of these errors were substantial in a number of cases and unknown in others. Most errors, and those with the largest estimated effect, result in underestimates of IAS numbers. However, there are a number of errors where the size and direction of the effect remains poorly understood. The effect of differences in opinion between specialists is potentially large, particularly for data-poor taxa and regions, and does not have a clearly directional or consistent effect on the size and composition of IAS lists. Five tactics emerged as important for reducing uncertainty in IAS lists, and while uncertainty will never be removed entirely, these approaches will significantly improve the transparency, repeatability, and comparability of IAS lists. Understanding the errors and uncertainties that occur during the process of listing invasive species, as well as the potential size and nature of their effects on IAS lists, is key to improving the value of these lists for governments, management agencies, and conservationists. Such understanding is increasingly important given positive trends in biological invasion and the associated risks to biodiversity and biosecurity.
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http://dx.doi.org/10.1890/11-1252.1DOI Listing
April 2012

Plant dispersal in the sub-Antarctic inferred from anisotropic genetic structure.

Mol Ecol 2012 Jan 30;21(1):184-94. Epub 2011 Nov 30.

Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.

Climatic conditions and landscape features often strongly affect species' local distribution patterns, dispersal, reproduction and survival and may therefore have considerable impacts on species' fine-scale spatial genetic structure (SGS). In this study, we demonstrate the efficacy of combining fine-scale SGS analyses with isotropic and anisotropic spatial autocorrelation techniques to infer the impact of wind patterns on plant dispersal processes. We genotyped 1304 Azorella selago (Apiaceae) specimens, a wind-pollinated and wind-dispersed plant, from four populations distributed across sub-Antarctic Marion Island. SGS was variable with Sp values ranging from 0.001 to 0.014, suggesting notable variability in dispersal distance and wind velocities between sites. Nonetheless, the data supported previous hypotheses of a strong NW-SE gradient in wind strength across the island. Anisotropic autocorrelation analyses further suggested that dispersal is strongly directional, but varying between sites depending on the local prevailing winds. Despite the high frequency of gale-force winds on Marion Island, gene dispersal distance estimates (σ) were surprisingly low (<10 m), most probably because of a low pollen dispersal efficiency. An SGS approach in association with isotropic and anisotropic analyses provides a powerful means to assess the relative influence of abiotic factors on dispersal and allow inferences that would not be possible without this combined approach.
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http://dx.doi.org/10.1111/j.1365-294X.2011.05372.xDOI Listing
January 2012

Relative roles of climatic suitability and anthropogenic influence in determining the pattern of spread in a global invader.

Proc Natl Acad Sci U S A 2011 Jan 20;108(1):220-5. Epub 2010 Dec 20.

Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa.

Because invasive species threaten the integrity of natural ecosystems, a major goal in ecology is to develop predictive models to determine which species may become widespread and where they may invade. Indeed, considerable progress has been made in understanding the factors that influence the local pattern of spread for specific invaders and the factors that are correlated with the number of introduced species that have become established in a given region. However, few studies have examined the relative importance of multiple drivers of invasion success for widespread species at global scales. Here, we use a dataset of >5,000 presence/absence records to examine the interplay between climatic suitability, biotic resistance by native taxa, human-aided dispersal, and human modification of habitats, in shaping the distribution of one of the world's most notorious invasive species, the Argentine ant (Linepithema humile). Climatic suitability and the extent of human modification of habitats are primarily responsible for the distribution of this global invader. However, we also found some evidence for biotic resistance by native communities. Somewhat surprisingly, and despite the often cited importance of propagule pressure as a crucial driver of invasions, metrics of the magnitude of international traded commodities among countries were not related to global distribution patterns. Together, our analyses on the global-scale distribution of this invasive species provide strong evidence for the interplay of biotic and abiotic determinants of spread and also highlight the challenges of limiting the spread and subsequent impact of highly invasive species.
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http://dx.doi.org/10.1073/pnas.1011723108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017164PMC
January 2011
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