Explicit Consideration (explicit + consideration)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Cascading top-down effects of changing oceanic predator abundances

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2009
Julia K. Baum
Summary 1Top-down control can be an important determinant of ecosystem structure and function, but in oceanic ecosystems, where cascading effects of predator depletions, recoveries, and invasions could be significant, such effects had rarely been demonstrated until recently. 2Here we synthesize the evidence for oceanic top-down control that has emerged over the last decade, focusing on large, high trophic-level predators inhabiting continental shelves, seas, and the open ocean. 3In these ecosystems, where controlled manipulations are largely infeasible, ,pseudo-experimental' analyses of predator,prey interactions that treat independent predator populations as ,replicates', and temporal or spatial contrasts in predator populations and climate as ,treatments', are increasingly employed to help disentangle predator effects from environmental variation and noise. 4Substantial reductions in marine mammals, sharks, and piscivorous fishes have led to mesopredator and invertebrate predator increases. Conversely, abundant oceanic predators have suppressed prey abundances. Predation has also inhibited recovery of depleted species, sometimes through predator,prey role reversals. Trophic cascades have been initiated by oceanic predators linking to neritic food webs, but seem inconsistent in the pelagic realm with effects often attenuating at plankton. 5Top-down control is not uniformly strong in the ocean, and appears contingent on the intensity and nature of perturbations to predator abundances. Predator diversity may dampen cascading effects except where nonselective fisheries deplete entire predator functional groups. In other cases, simultaneous exploitation of predator and prey can inhibit prey responses. Explicit consideration of anthropogenic modifications to oceanic foodwebs should help inform predictions about trophic control. 6Synthesis and applications. Oceanic top-down control can have important socio-economic, conservation, and management implications as mesopredators and invertebrates assume dominance, and recovery of overexploited predators is impaired. Continued research aimed at integrating across trophic levels is needed to understand and forecast the ecosystem effects of changing oceanic predator abundances, the relative strength of top-down and bottom-up control, and interactions with intensifying anthropogenic stressors such as climate change. [source]


A two-phase analysis of solute partitioning into the stratum corneum

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2006
Johannes M. Nitsche
Abstract An analysis is presented of partition coefficients KSC/w describing solute distribution into fully hydrated stratum corneum (SC) from dilute aqueous solution (w). A comprehensive database is compiled from the experimental literature covering more than eight decades in the octanol/water partition coefficient Ko/w. It is analyzed according to a two-phase model following that of Anderson, Raykar, and coworkers (1988, 1989), which accounts for uptake by intercellular lipid and corneocyte (keratin plus water) phases having inherently different lipophilicities, as characterized by an SC lipid/water partition coefficient Klip/w and a partition coefficient PCpro/w quantifying cornoeocyte-phase binding. Regression of 72 data points yields useful best-fit recalibrations of power laws (or linear free energy relationships) giving Klip/w and PCpro/w as functions of Ko/w. The specific conclusions of the analysis are as follows: (i) The two-phase model offers substantial improvements over previously proposed analytical representations of KSC/w, yielding an rms error in log10KSC/w of 0.30 limited by the scatter in the data. (ii) The best-fit description of the lipid phase is given by the power law Klip/w,=,0.43 (Ko/w)0.81, suggesting about half the absolute value of Klip/w relative to previous estimates. (iii) The best-fit description of corneocyte-phase binding differs negligibly from the correlation found by Anderson, Raykar, and coworkers for the more limited set of compounds studied by them. Explicit consideration of the two-phase nature of the SC also furnishes a rational basis for predicting the effects of varying hydration state upon KSC/w. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:649,666, 2006 [source]


An Examination of Key Factors of Influence in the Development Process of Credit Union Industries

ANNALS OF PUBLIC AND COOPERATIVE ECONOMICS, Issue 3 2002
Alexander Sibbald
The aim of this paper is to analyse credit union industries within a development framework. Explicit consideration is given to credit union industries in four countries , Great Britain, Ireland, New Zealand and the United States. It is argued that in terms of a developmental typology the credit union industry in Great Britain is at a nascent stage of development, the industries in Ireland and New Zealand are at a transition stage while the US credit union industry is mature in nature. In progression between stages the analysis considers the influence of factors such as situational leadership, the complexion of trade associations, professionalisation, regulatory and legislative initiatives and technology. The analysis concluded that while there was a substantial commonality of experience, there were also significant differences in the impact of these factors. This consequently encouraged the recognition of the existence of ,a variety of the species' in respect of credit union development. [source]


FROM DISCRETE-TIME MODELS TO CONTINUOUS-TIME, ASYNCHRONOUS MODELING OF FINANCIAL MARKETS

COMPUTATIONAL INTELLIGENCE, Issue 2 2007
Katalin Boer
Most agent-based simulation models of financial markets are discrete-time in nature. In this paper, we investigate to what degree such models are extensible to continuous-time, asynchronous modeling of financial markets. We study the behavior of a learning market maker in a market with information asymmetry, and investigate the difference caused in the market dynamics between the discrete-time simulation and continuous-time, asynchronous simulation. We show that the characteristics of the market prices are different in the two cases, and observe that additional information is being revealed in the continuous-time, asynchronous models, which can be acted upon by the agents in such models. Because most financial markets are continuous and asynchronous in nature, our results indicate that explicit consideration of this fundamental characteristic of financial markets cannot be ignored in their agent-based modeling. [source]


Patient-assessed health outcome measures for diabetes: a structured review

DIABETIC MEDICINE, Issue 1 2002
A. M. Garratt
Abstract Aims To identify available disease-specific measures of health-related quality of life (HRQL) for diabetes and to review evidence for the reliability, validity and responsiveness of instruments. Methods Systematic searches were used to identify instruments. Instruments were assessed against predefined inclusion and exclusion criteria. Letters were sent to authors requesting details of further instrument evaluation. Information relating to instrument content, patients, reliability, validity and responsiveness to change was extracted from published papers. Results The search produced 252 references. Nine instruments met the inclusion criteria: Appraisal of Diabetes Scale (ADS), Audit of Diabetes-Dependent Quality of Life (ADDQoL), Diabetes Health Profile (DHP-1, DHP-18), Diabetes Impact Measurement Scales (DIMS), Diabetes Quality of Life Measure (DQOL), Diabetes-Specific Quality of Life Scale (DSQOLS), Questionnaire on Stress in Diabetic Patients-Revised (QSD-R), Diabetes-39 (D-39) and Well-being Enquiry for Diabetics (WED). The shortest instrument (ADS) has seven items and the longest (WED) has 50 items. The ADS and ADDQoL are single-index measures. The seven multidimensional instruments have dimensions covering psychological well-being and social functioning but vary in the remainder of their content. The DHP-1 and DSQOLS are specific to Type 1 diabetes patients. The DHP-18 is specific to Type 2 diabetes patients. The DIMS and DQOL have weaker evidence for reliability and internal construct validity. Patients contributed to the content of the ADDQoL, DHP-1/18, DQOL, DSQOLS, D-39, QSD-R and WED. The authors of the ADDQoL, DHP-1/18, DQOL, DSQOLS gave explicit consideration to content validity. The construct validity of instruments was assessed through comparisons with instruments measuring related constructs and clinical and sociodemographic variables. None of the instruments has been formally assessed for responsiveness to changes in health. Conclusions Five of the diabetes-specific instruments have good evidence for reliability and internal and external construct validity: the ADDQoL, DHP-1/18, DSQOLS, D-39 and QSD-R. Instrument content should be assessed for relevance before application. The instruments should be evaluated concurrently for validity and responsiveness to important changes in health. [source]


Detecting spatial hot spots in landscape ecology

ECOGRAPHY, Issue 5 2008
Trisalyn A. Nelson
Hot spots are typically locations of abundant phenomena. In ecology, hot spots are often detected with a spatially global threshold, where a value for a given observation is compared with all values in a data set. When spatial relationships are important, spatially local definitions , those that compare the value for a given observation with locations in the vicinity, or the neighbourhood of the observation , provide a more explicit consideration of space. Here we outline spatial methods for hot spot detection: kernel estimation and local measures of spatial autocorrelation. To demonstrate these approaches, hot spots are detected in landscape level data on the magnitude of mountain pine beetle infestations. Using kernel estimators, we explore how selection of the neighbourhood size (,) and hot spot threshold impact hot spot detection. We found that as , increases, hot spots are larger and fewer; as the hot spot threshold increases, hot spots become larger and more plentiful and hot spots will reflect coarser scale spatial processes. The impact of spatial neighbourhood definitions on the delineation of hot spots identified with local measures of spatial autocorrelation was also investigated. In general, the larger the spatial neighbourhood used for analysis, the larger the area, or greater the number of areas, identified as hot spots. [source]


Do biotic interactions shape both sides of the humped-back model of species richness in plant communities?

ECOLOGY LETTERS, Issue 7 2006
Richard Michalet
Abstract A humped-back relationship between species richness and community biomass has frequently been observed in plant communities, at both local and regional scales, although often improperly called a productivity,diversity relationship. Explanations for this relationship have emphasized the role of competitive exclusion, probably because at the time when the relationship was first examined, competition was considered to be the significant biotic filter structuring plant communities. However, over the last 15 years there has been a renewed interest in facilitation and this research has shown a clear link between the role of facilitation in structuring communities and both community biomass and the severity of the environment. Although facilitation may enlarge the realized niche of species and increase community richness in stressful environments, there has only been one previous attempt to revisit the humped-back model of species richness and to include facilitative processes. However, to date, no model has explored whether biotic interactions can potentially shape both sides of the humped-back model for species richness commonly detected in plant communities. Here, we propose a revision of Grime's original model that incorporates a new understanding of the role of facilitative interactions in plant communities. In this revised model, facilitation promotes diversity at medium to high environmental severity levels, by expanding the realized niche of stress-intolerant competitive species into harsh physical conditions. However, when environmental conditions become extremely severe the positive effects of the benefactors wane (as supported by recent research on facilitative interactions in extremely severe environments) and diversity is reduced. Conversely, with decreasing stress along the biomass gradient, facilitation decreases because stress-intolerant species become able to exist away from the canopy of the stress-tolerant species (as proposed by facilitation theory). At the same time competition increases for stress-tolerant species, reducing diversity in the most benign conditions (as proposed by models of competition theory). In this way our inclusion of facilitation into the classic model of plant species diversity and community biomass generates a more powerful and richer predictive framework for understanding the role of plant interactions in changing diversity. We then use our revised model to explain both the observed discrepancies between natural patterns of species richness and community biomass and the results of experimental studies of the impact of biodiversity on the productivity of herbaceous communities. It is clear that explicit consideration of concurrent changes in stress-tolerant and competitive species enhances our capacity to explain and interpret patterns in plant community diversity with respect to environmental severity. [source]


Real options for precautionary fisheries management

FISH AND FISHERIES, Issue 2 2008
Eli P Fenichel
Abstract The 1996 Food and Agriculture Organization's (FAO) ,Guidelines on the Precautionary Approach to Fisheries and Species Introduction' raise important issues for fisheries managers, but fail to prescribe an approach for risk management. The distinguishing characteristics of the ,precautionary approach' are the inclusion of uncertainty and ,an elaboration on the burden of proof'. The FAO precautionary approach emphasizes that managers should be risk-averse, but does not provide tools for determining the appropriate degree of risk aversion. Consequently, application of the precautionary approach often leads to decision-making based on ad hoc safety margins. These safety margins are seldom chosen with explicit consideration of trade-offs. If the emphasis was shifted to choosing between competing uncertainties, then managers could manage risk. By attempting to avoid risk, managers may gain exposure to other risks and perhaps miss valuable opportunities. We place fishery management problems within the rubric of ,real investment' problems, and compare and contrast the consideration of risk by alternative investment frameworks. We show that traditional investment frameworks are inappropriate for fishery management, and furthermore, that traditional precautionary approaches are arbitrary and without basis in decision theory. Quantitative decision-making techniques, such as formal decision analysis (FDA), enable integration of competing hypotheses that help alleviate burden-of-proof issues. These techniques help analysts consider sources of uncertainty. FDA, however, can still be subject to arbitrary safety margins because such analyses often focus on determining which strategies best achieve, or avoid, targets that have been established without complete consideration of trade-offs. A managerial finance approach, real options analysis (ROA), is an alternative and complementary decision-making technique that enables managers to compute precautionary adjustments that couple the size of the ,safety margin' with the amount of uncertainty, thereby optimizing risk exposure and avoiding the need for arbitrary safety margins. We illustrate the advantages of an approach that combines FDA and ROA, using a heuristic example about a decision to re-introduce Atlantic salmon (Salmo salar L.) into Lake Ontario. Finally, we provide guidance on applying ROA to other fishery problems. The precautionary approach requires that managers consider risk, but considering risk is not the same as managing it. Here ROA is useful. [source]


The volatile constituents of frankincense , a review

FLAVOUR AND FRAGRANCE JOURNAL, Issue 6 2009
Michaela Mertens
Abstract The smell of frankincense resin and powder, as well as burned frankincense, has been linked to a series of health effects since ancient times. Additionally, frankincense and its fumes are used as a means to induce positive psychophysical effects and well-being, not only in an ecclesiastical setting but also in traditional medical applications. This review aims to provide an overview of current knowledge of the volatile constituents of frankincense, with explicit consideration concerning the diverse Boswellia varieties. Altogether, more than 300 volatiles in frankincense have been reported in the literature. In particular, a broad diversity has been found in the qualitative and quantitative composition of the volatiles with respect to different varieties of Boswellia. A detailed discussion of the various analytical approaches applied to isolating and analysing the volatile fractions of frankincense is also presented. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Area-to-Point Prediction Under Boundary Conditions

GEOGRAPHICAL ANALYSIS, Issue 4 2008
E. -H.
This article proposes a geostatistical solution for area-to-point spatial prediction (downscaling) taking into account boundary effects. Such effects are often poorly considered in downscaling, even though they often have significant impact on the results. The geostatistical approach proposed in this article considers two types of boundary conditions (BC), that is, a Dirichlet-type condition and a Neumann-type condition, while satisfying several critical issues in downscaling: the coherence of predictions, the explicit consideration of support differences, and the assessment of uncertainty regarding the point predictions. An updating algorithm is used to reduce the computational cost of area-to-point prediction under a given BC. In a case study, area-to-point prediction under a Dirichlet-type BC and a Neumann-type BC is illustrated using simulated data, and the resulting predictions and error variances are compared with those obtained without considering such conditions. [source]


Hydrologic sources of carbon cycling uncertainty throughout the terrestrial,aquatic continuum

GLOBAL CHANGE BIOLOGY, Issue 11 2005
G. Darrel Jenerette
Abstract Linking hydrologic interactions with global carbon cycling will reduce the uncertainty associated with scaling-up empirical studies and facilitate the incorporation of terrestrial,aquatic linkages within global and regional change models. Much of the uncertainty in estimates of carbon fluxes associated with precipitation and hydrologic transport results from the extensive spatial and temporal heterogeneity in both intrinsic functioning and anthropogenic modification of hydrological cycles. To better understand this variation we developed a landscape ecological approach to coupled hydrologic,carbon cycling that merges local mechanisms with multiple-scale spatial heterogeneity. This spatially explicit framework is applied to examine variability in hydrologic influences on carbon cycling along a continental scale water availability gradient with an explicit consideration of human sources of variability. Hydrologic variation is an important component of the uncertainty in carbon cycling; accounting for this variation will improve understanding of current conditions and projections of future ecosystem responses to global change. [source]


A double structure generalized plasticity model for expansive materials

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2005
Marcelo Sánchez
Abstract The constitutive model presented in this work is built on a conceptual approach for unsaturated expansive soils in which the fundamental characteristic is the explicit consideration of two pore levels. The distinction between the macro- and microstructure provides the opportunity to take into account the dominant phenomena that affect the behaviour of each structural level and the main interactions between them. The microstructure is associated with the active clay minerals, while the macrostructure accounts for the larger-scale structure of the material. The model has been formulated considering concepts of classical and generalized plasticity theories. The generalized stress,strain rate equations are derived within a framework of multidissipative materials, which provides a consistent and formal approach when there are several sources of energy dissipation. The model is formulated in the space of stresses, suction and temperature; and has been implemented in a finite element code. The approach has been applied to explaining and reproducing the behaviour of expansive soils in a variety of problems for which experimental data are available. Three application cases are presented in this paper. Of particular interest is the modelling of an accidental overheating, that took place in a large-scale heating test. This test allows the capabilities of the model to be checked when a complex thermo-hydro-mechanical (THM) path is followed. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Reduction and identification methods for Markovian control systems, with application to thin film deposition

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 2 2004
Martha A. Gallivan
Abstract Dynamic models of nanometer-scale phenomena often require an explicit consideration of interactions among a large number of atoms or molecules. The corresponding mathematical representation may thus be high dimensional, nonlinear, and stochastic, incompatible with tools in nonlinear control theory that are designed for low-dimensional deterministic equations. We consider here a general class of probabilistic systems that are linear in the state, but whose input enters as a function multiplying the state vector. Model reduction is accomplished by grouping probabilities that evolve together, and truncating states that are unlikely to be accessed. An error bound for this reduction is also derived. A system identification approach that exploits the inherent linearity is then developed, which generates all coefficients in either a full or reduced model. These concepts are then extended to extremely high-dimensional systems, in which kinetic Monte Carlo (KMC) simulations provide the input,output data. This work was motivated by our interest in thin film deposition. We demonstrate the approaches developed in the paper on a KMC simulation of surface evolution during film growth, and use the reduced model to compute optimal temperature profiles that minimize surface roughness. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Priority research areas for ecosystem services in a changing world

JOURNAL OF APPLIED ECOLOGY, Issue 6 2009
Emily Nicholson
Summary 1.,Ecosystem services are the benefits humans obtain from ecosystems. The importance of research into ecosystem services has been widely recognized, and rapid progress is being made. However, the prevailing approach to quantifying ecosystem services is still based on static analyses and single services, ignoring system dynamics, uncertainty and feedbacks. This is not only partly due to a lack of mechanistic understanding of processes and a dearth of empirical data, but also due to a failure to engage fully with the interdisciplinarity of the problem. 2.,We argue that there is a tendency to ignore the feedbacks between and within both social and ecological systems, and a lack of explicit consideration of uncertainty. Metrics need to be developed that can predict thresholds, which requires strong linkages to underlying processes, while the development of policy for management of ecosystem services needs to be based on a broader understanding of value and drivers of human well-being. 3.,We highlight the complexities, gaps in current knowledge and research, and the potentially promising avenues for future investigation in four priority research areas: agendas, processes, metrics and uncertainty. 4.,Synthesis and applications. The research interest in the field of ecosystem services is rapidly expanding, and can contribute significantly to the sustainable management of natural resources. However, a narrow disciplinary approach, or an approach which does not consider feedbacks within and between ecological and social systems, has the potential to produce dangerously misleading policy recommendations. In contrast, if we explicitly acknowledge and address uncertainties and complexities in the provision of ecosystem services, progress may appear slower but our models will be substantially more robust and informative about the effects of environmental change. [source]


Living outside the system?

LEGAL STUDIES, Issue 2 2007
The (im)morality of urban squatting after the Land Registration Act 200
The Land Registration Act 2002 (LRA 2002) has effectively curtailed the law permitting the acquisition of title through adverse possession in relation to most types of adverse possessor, including the paradigmatic urban squatter. While the traditional principles for the acquisition of title through adverse possession enabled a squatter to secure rights in land ,automatically' after 12 years, under the LRA 2002 an urban squatter seeking to defend their possession of land in this way must now apply to the Land Registry, who will serve a notice on the registered proprietor alerting them to his or her presence. This procedure provides the landowner with an opportunity to recover possession of the property before the squatter's occupation has given rise to any claim on the title to the land. On the whole, these reforms have been presented as, and accepted as being, wholly justified in the context of a modern regime of ,title by registration'. This paper argues, however, that the reform of adverse possession also implements a contentious moral agenda in relation to advertent squatters and to absent landowners. While these provisions of the LRA 2002 will have important practical and philosophical consequences, the Law Commission has attempted to close off any prospect of further debate on the subject, without explicit consideration of current social and housing issues associated with urban squatting, or of the matrix of moral issues at stake in such cases. [source]


Scale as a lurking factor: incorporating scale-dependence in experimental ecology

OIKOS, Issue 9 2009
Brody Sandel
Ecologists have recognized for decades the importance of spatial scale in ecological processes and patterns, as well as the complications scale poses for understanding ecological mechanisms. Here we highlight the opportunity attention to scale offers experimental ecology. Despite many advantages to considering scale, a review of the literature indicates that multi-scale experimental studies are rare. Although much work has focused on scale as a primary factor (e.g. island size), we draw attention to scale as a ,lurking' variable: one which influences the relationship between two or more variables that are not usually understood to be scale-dependent. We highlight three basic observations from which scale-dependence arises: abundance increases with area, environmental conditions vary across space, and the effect of an organism on its environment is spatially limited. From these arise first-order scale-dependence, which relates an ecological variable of interest to a measure of scale. Combining first-order relationships together, we can produce second-order scale-dependencies, which occur when the relationship between two or more variables is mediated by scale. It is these relationships that are of particular interest, as they have the potential to confound experimental results. Most ecological experiments have incorporated scale either implicitly or not at all. We suggest that an explicit consideration of scale could help resolve some long-standing debates when scale is turned from a lurking variable into a working variable. Finally, we review and evaluate four different experimental sampling designs and corresponding statistical analyses that can be used to address the effects of scale in ecological experiments. [source]


Behavioral intermittence, Lévy patterns, and randomness in animal movement

OIKOS, Issue 4 2009
F. Bartumeus
The recent debate on both the existence and the cause of fractal (Lévy) patterns in animal movement resonates with much deeper and richer problems in movement ecology: (1) establishing mechanistic links between animal behavior and statistical patterns of movement, and (2) understanding what is the role of randomness (stochasticity) in animal motion. Here, the idea of behavioral intermittence is shown to be crucial to establish mechanistic connections between the behavior of organisms and the statistical properties they generate when moving. Attention is drawn to the fact that some random walk modeling procedures can impair the identification of intermittent biological mechanisms which could govern major statistical properties of movement. This fact, together with some misconceptions and prejudices regarding the role of randomness in animal motion may explain why stochastic processes have been disregarded as a potential source of adaptation in animal movement. In the near future, the advances in biotelemetry together with a more explicit consideration of behavioral intermittence, and the development of novel random walk approaches, could help us to set up the bases for a landscape-level behavioral ecology. [source]


Forest Restoration in Urbanizing Landscapes: Interactions Between Land Uses and Exotic Shrubs

RESTORATION ECOLOGY, Issue 2 2005
Kathi L. Borgmann
Abstract Preventing and controlling exotic plants remains a key challenge in any ecological restoration, and most efforts are currently aimed at local scales. We combined local- and landscape-scale approaches to identify factors that were most closely associated with invasion of riparian forests by exotic shrubs (Amur honeysuckle [Lonicera maackii] and Tatarian honeysuckle [L. tatarica]) in Ohio, U.S.A. Twenty sites were selected in mature riparian forests along a rural,urban gradient (<1,47% urban land cover). Within each site, we measured percent cover of Lonicera spp. and native trees and shrubs, percent canopy cover, and facing edge aspect. We then developed 10 a priori models based on local- and landscape-level variables that we hypothesized would influence percent cover of Lonicera spp. within 25 m of the forest edge. To determine which of these models best fit the data, we used an information-theoretic approach and Akaike's information criterion. Percent cover of Lonicera was best explained by the proportion of urban land cover within 1 km of riparian forests. In particular, percent cover of Lonicera was greater in forests within more urban landscapes than in forests within rural landscapes. Results suggest that surrounding land uses influence invasion by exotic shrubs, and explicit consideration of land uses may improve our ability to predict or limit invasion. Moreover, identifying land uses that increase the risk of invasion may inform restoration efforts. [source]


Elevated dominance of extrafloral nectary-bearing plants is associated with increased abundances of an invasive ant and reduced native ant richness

DIVERSITY AND DISTRIBUTIONS, Issue 5 2009
Amy M. Savage
Abstract Aim, Invasive ants can have substantial and detrimental effects on co-occurring community members, especially other ants. However, the ecological factors that promote both their population growth and their negative influences remain elusive. Opportunistic associations between invasive ants and extrafloral nectary (EFN)-bearing plants are common and may fuel population expansion and subsequent impacts of invasive ants on native communities. We examined three predictions of this hypothesis, compared ant assemblages between invaded and uninvaded sites and assessed the extent of this species in Samoa. Location, The Samoan Archipelago (six islands and 35 sites). Methods, We surveyed abundances of the invasive ant Anoplolepis gracilipes, other ant species and EFN-bearing plants. Results,Anoplolepis gracilipes was significantly more widely distributed in 2006 than in 1962, suggesting that the invasion of A. gracilipes in Samoa has progressed. Furthermore, (non- A. gracilipes) ant assemblages differed significantly between invaded and uninvaded sites. Anoplolepis gracilipes workers were found more frequently at nectaries than other plant parts, suggesting that nectar resources were important to this species. There was a strong, positive relationship between the dominance of EFN-bearing plants in the community and A. gracilipes abundance on plants, a relationship that co-occurring ants did not display. High abundances of A. gracilipes at sites dominated by EFN-bearing plants were associated with low species richness of native plant-visiting ant species. Anoplolepis gracilipes did not display any significant relationships with the diversity of other non-native ants. Main conclusions, Together, these data suggest that EFN-bearing plants may promote negative impacts of A. gracilipes on co-occurring ants across broad spatial scales. This study underscores the potential importance of positive interactions in the dynamics of species invasions. Furthermore, they suggest that conservation managers may benefit from explicit considerations of potential positive interactions in predicting the identities of problematic invaders or the outcomes of species invasions. [source]