ORCID Profile
0000-0002-1376-1058
Current Organisation
UNSW Sydney
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Informa UK Limited
Date: 06-04-2023
Publisher: Wiley
Date: 20-04-2023
Abstract: S le size estimation through power analysis is a fundamental tool in planning an ecological study, yet there are currently no well‐established procedures for when multivariate abundances are to be collected. A power analysis procedure would need to address three challenges: designing a parsimonious simulation model that captures key community data properties measuring effect size in a realistic yet interpretable fashion and ensuring computational feasibility when simulation is used both for power estimation and significance testing. Here, we propose a power analysis procedure that addresses these three challenges by: using for simulation a Gaussian copula model with factor analytical structure, fitted to pilot data assuming a common effect size across all taxa, but applied in different directions according to expert opinion (to “increaser”, “decreaser” or “no effect” taxa) using a critical value approach to estimate power, which reduces computation time by a factor of 500 (if we would otherwise use 999 res les to estimate each p ‐value) with minor loss of accuracy. The procedure is demonstrated on pilot data from fish assemblages in a restoration study, where it was found that the planned study design would only be capable of detecting relatively large effects (change in abundance by a factor of 1.7 or more). The methods outlined in this paper are available in accompanying R software (the ecopower package), which allows researchers with pilot data to answer a wide range of design questions to assist them in planning their studies.
Publisher: Public Library of Science (PLoS)
Date: 23-07-2019
Publisher: Wiley
Date: 09-09-2023
Publisher: Wiley
Date: 24-07-2019
Abstract: Ecologists often investigate co‐occurrence patterns in multi‐species data in order to gain insight into the ecological causes of observed co‐occurrences. Apart from direct associations between the two species of interest, they may co‐occur because of indirect effects, where both species respond to another variable, whether environmental or biotic (e.g. a mediator species). A wide variety of methods are now available for modelling how environmental filtering drives species distributions. In contrast, methods for studying other causes of co‐occurence are much more limited. “Graphical” methods, which can be used to study how mediator species impact co‐occurrence patterns, have recently been proposed for use in ecology. However, available methods are limited to presence/absence data or methods assuming multivariate normality, which is problematic when analysing abundances. We propose Gaussian copula graphical models (GCGMs) for studying the effect of mediator species on co‐occurence patterns. GCGMs are a flexible type of graphical model which naturally accommodates all data types , for ex le binary (presence/absence), counts, as well as ordinal data and biomass, in a unified framework. Simulations demonstrate that GCGMs can be applied to a much broader range of data types than the methods currently used in ecology, and perform as well as or better than existing methods in many settings. We apply GCGMs to counts of hunting spiders, in order to visualise associations between species. We also analyse abundance data of New Zealand native forest cover (on an ordinal scale) to show how GCGMs can be used analyse large and complex datasets. In these data, we were able to reproduce known species relationships as well as generate new ecological hypotheses about species associations.
Publisher: Cold Spring Harbor Laboratory
Date: 19-11-2018
DOI: 10.1101/470161
Abstract: Ecologists often investigate co-occurrence patterns in multi-species data in order to gain insight into the ecological causes of observed co-occurrences. Apart from direct associations between two species, two species may co-occur because they both respond in similar ways to environmental variables, or due to the presence of other (mediator) species. A wide variety of methods are now available for modelling how environmental filtering drives species distributions. In contrast, methods for studying other causes of co-occurence are much more limited. “Graphical” methods, which can be used to study how mediator species impact co-occurrence patterns, have recently been proposed for use in ecology. However, available methods are limited to presence/absence data and methods assuming multivariate normality, which is problematic when analysing abundances. We propose Gaussian copula graphical models (GCGMs) for studying the effect of mediator species on co-occurence patterns. GCGMs are a flexible type of graphical model which naturally accommodates all data types – binary (presence/absence), counts, as well as ordinal data and biomass, in a unified framework. Simulations for count data demonstrate that GCGMs are better able to distinguish effects of mediator species from direct associations than using existing methods designed for multivariate normal data. We apply GCGMs to counts of hunting spiders, in order to visualise associations between species. We then analyze abundance data of New Zealand native forest cover (on an ordinal scale) to show how GCGMs can be used analyze large and complex datasets. In these data, we were able to reproduce known species relationships as well as generate new ecological hypotheses about species associations.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Wiley
Date: 26-12-2022
DOI: 10.1002/CNCR.34582
Abstract: Cyclin E1 (CCNE1) is a potential predictive marker and therapeutic target in tubo‐ovarian high‐grade serous carcinoma (HGSC). Smaller studies have revealed unfavorable associations for CCNE1 lification and CCNE1 overexpression with survival, but to date no large‐scale, histotype‐specific validation has been performed. The hypothesis was that high‐level lification of CCNE1 and CCNE1 overexpression, as well as a combination of the two, are linked to shorter overall survival in HGSC. Within the Ovarian Tumor Tissue Analysis consortium, lification status and protein level in 3029 HGSC cases and mRNA expression in 2419 s les were investigated. High‐level lification ( copies by chromogenic in situ hybridization) was found in 8.6% of HGSC and overexpression ( % with at least 5% demonstrating strong intensity by immunohistochemistry) was found in 22.4%. CCNE1 high‐level lification and overexpression both were linked to shorter overall survival in multivariate survival analysis adjusted for age and stage, with hazard stratification by study (hazard ratio [HR], 1.26 95% CI, 1.08‐1.47, p = .034, and HR, 1.18 95% CI, 1.05‐1.32, p = .015, respectively). This was also true for cases with combined high‐level lification/overexpression (HR, 1.26 95% CI, 1.09‐1.47, p = .033). CCNE1 mRNA expression was not associated with overall survival (HR, 1.00 per 1‐SD increase 95% CI, 0.94‐1.06 p = .58). CCNE1 high‐level lification is mutually exclusive with the presence of germline BRCA1/2 pathogenic variants and shows an inverse association to RB1 loss. This study provides large‐scale validation that CCNE1 high‐level lification is associated with shorter survival, supporting its utility as a prognostic biomarker in HGSC.
Publisher: Wiley
Date: 21-03-2015
Publisher: Wiley
Date: 11-05-2202
DOI: 10.1111/ANZS.12087
Publisher: Wiley
Date: 19-12-2021
DOI: 10.1111/BCP.14635
Publisher: Elsevier BV
Date: 04-2023
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 07-2018
DOI: 10.1016/J.JAMDA.2018.05.002
Abstract: Despite limited efficacy and significant safety concerns, antipsychotic medications are frequently used to treat behavioral and psychological symptoms of dementia (BPSD) in long-term residential care. This study evaluates the sustained reduction of antipsychotic use for BPSD through a deprescribing intervention and education of health care professionals. Repeated-measures, longitudinal, single-arm study. Long-term residential care of older adults. Nursing staff from 23 nursing homes recruited 139 residents taking regular antipsychotic medication for ≥3 months, without primary psychotic illness, such as schizophrenia or bipolar disorder, or severe BPSD. An antipsychotic deprescribing protocol was established. Education of general practitioners, pharmacists, and residential care nurses focused on nonpharmacological prevention and management of BPSD. The primary outcome was antipsychotic use over 12-month follow-up secondary outcomes were BPSD (Neuropsychiatric Inventory, Cohen-Mansfield Agitation Inventory, and social withdrawal) and adverse outcomes (falls, hospitalizations, and cognitive decline). The number of older adults on regular antipsychotics over 12 months reduced by 81.7% (95% confidence interval: 72.4-89.0). Withdrawal was not accompanied by drug substitution or a significant increase in pro-re-nata antipsychotic or benzodiazepine administration. There was no change in BPSD or in adverse outcomes. In a selected s le of older adults living in long-term residential care, sustained reduction in regular antipsychotic use is feasible without an increase of BPSD.
Publisher: Springer Science and Business Media LLC
Date: 15-11-2021
Publisher: Wiley
Date: 05-07-2022
DOI: 10.1111/AEC.13215
Abstract: Human intervention through damming, ersion and extraction of water resources has created regulated dryland river systems. As a result, connectivity between river channels and floodplain wetlands has diminished. Wetland function is fundamentally linked to water availability: flooding exchanges water, nutrients, sediments and biota with the floodplain. Water allocation for environmental flows may mitigate wetland degradation following river regulation by improving hydrological connectivity between rivers and floodplain wetlands. We report the results (2014–15 to 2018–19) of a vegetation monitoring program in the Macquarie Marshes in north western New South Wales. As part of the long‐term program, we monitored semi‐permanent wetland (Water Couch ( Paspalum distichum ) grassland or sedgeland dominated) and River Red Gum ( Eucalyptus camaldulensis ) forest/woodland communities along with environmental and water resource availability predictors. During the five‐year period, we found linear and nonlinear responses of functional group abundance and species richness to the water year and to time since last inundation. We also found differences in species assemblages in response to the flow and flooding regime, particularly water year and inundation duration. These results indicated that wetlands continued to express dry and wet phase responses. We also observed a depressed response to the large 2016–17 flood event by a subset of semi‐permanent wetland sites that had not been inundated in 3 years, compared with sites that were more recently inundated. This result indicated that environmental water management, along with protection of natural inundation events, may improve the resilience of floodplain wetlands: increased hydrological connectivity may promote a stronger wetland response when floods occur. Our results indicate that inundation, in part comprised of managed environmental flows, is a primary driver of species assemblage and functional group representation in semi‐arid floodplain wetlands.
Publisher: Wiley
Date: 18-11-2021
Abstract: Visualising data is a key step in data analysis, allowing researchers to find patterns, and assess and communicate the results of statistical modelling. In ecology, visualisation is often challenging when there are many variables (often for different species or other taxonomic groups) and they are not normally distributed (often counts or presence–absence data). Ordination is a common and powerful way to overcome this hurdle by reducing data from many response variables to just two or three, to be easily plotted. Ordination is traditionally done using dissimilarity‐based methods, most commonly non‐metric multidimensional scaling (nMDS). In the last decade, however, model‐based methods for unconstrained ordination have gained popularity. These are primarily based on latent variable models, with latent variables estimating the underlying, unobserved ecological gradients. Despite some major benefits, a drawback of model‐based ordination methods is their speed, as they typically take much longer to return a result than dissimilarity‐based methods, especially for large s le sizes. We introduce copula ordination, a new, scalable model‐based approach to unconstrained ordination. This method has all the desirable properties of model‐based ordination methods, with the added advantage that it is computationally far more efficient. In particular, simulations show copula ordination is an order of magnitude faster than current model‐based methods, and can even be faster than nMDS for large s le sizes, while being able to produce similar ordination plots and trends as these methods.
Publisher: Wiley
Date: 08-02-2023
Abstract: Upland sw s are peat‐accumulating, groundwater‐dependent and fire‐prone wetland ecosystems. Drying caused by anthropogenic processes such as underground mining, ditching and climate change may disrupt surface and groundwater flows and result in bottom‐up controls on wetland expression. Fire is an endogenous, recurring disturbance that drives a top‐down consumptive force in many upland sw systems. When compounded with drying, fire may facilitate permanent community transitions. A dearth of ecological data and temporal lags have h ered our ability to predict risks associated with multiple disturbances in wetland plant communities. We collected intact wetland mesocosms from valley floors and lower slopes of four undisturbed sw sites. We transferred the mesocosms to a glasshouse and established three different soil moisture availability levels to simulate wetland drainage. After 20 months of the hydrological treatment, we simulated a fire event by sequentially applying biomass removal (clipping), heat and smoke to half of the mesocosms. We monitored species biomass, richness and composition over a 3.5‐year time frame. We found evidence of a temporal lag in biomass response to low water availability and synergistic hydrological and fire effects on species richness. In unburnt conditions, richness declined with low water availability but was maintained under high and medium water availability. After simulated fire under medium water availability, however, richness also declined and converged with depauperate low‐water mesocosm richness. Representation by many obligate sw species declined in low compared with high water availability mesocosms over time, an effect that was lified by the fire treatment. Synthesis . Our evidence of lagged effects of hydrological change on wetland vegetation and compounding effects of fire should be considered in impact assessments, monitoring programs and ecosystem management to avoid irreversible wetland change in drying environments.
Publisher: The American Association of Immunologists
Date: 15-10-2022
Abstract: Phagocytic responses by effector cells to opsonized viruses have been recognized to play a key role in antiviral immunity. Limited data on coronavirus disease 2019 suggest that the role of Ab-dependent and -independent phagocytosis may contribute to the observed immunological and inflammatory responses however, their development, duration, and role remain to be fully elucidated. In this study of 62 acute and convalescent patients, we found that patients with acute coronavirus disease 2019 can mount a phagocytic response to autologous plasma-opsonized Spike protein–coated microbeads as early as 10 d after symptom onset, while heat inactivation of this plasma caused 77–95% abrogation of the phagocytic response and preblocking of Fc receptors showed variable 18–60% inhibition. In convalescent patients, phagocytic response significantly correlated with anti-Spike IgG titers and older patients, while patients with severe disease had significantly higher phagocytosis and neutralization functions compared with patients with asymptomatic, mild, or moderate disease. A longitudinal subset of the convalescent patients over 12 mo showed an increase in plasma Ab affinity toward Spike Ag and preservation of phagocytic and neutralization functions, despite a decline in the anti-Spike IgG titers by & %. Our data suggest that early phagocytosis is primarily driven by heat-liable components of the plasma, such as activated complements, while anti-Spike IgG titers account for the majority of observed phagocytosis at convalescence. Longitudinally, a significant increase in the affinity of the anti-Spike Abs was observed that correlated with the maintenance of both the phagocytic and neutralization functions, suggesting an improvement in the quality of the Abs.
Publisher: Frontiers Media SA
Date: 15-06-2021
DOI: 10.3389/FCOSC.2021.669563
Abstract: Evaluating the effectiveness of captive breeding programs is central to improving conservation outcomes in released animals. However, few studies have assessed the impact of the strategies and trade-offs involved in husbandry decisions and the selection of traits on the success of breeding programs. This study evaluated a range of husbandry features including an animal's environment, health, and traits of the released in idual and its parents involved in the zoo-based Regent Honeyeater breed for release program to optimise in idual reproductive success and survivability, leading to improved conservation outcomes in the wild. We analysed 285 birds using a penalised Cox proportional hazard model to assess survival and an ordinal logistic model to evaluate the reproductive success of zoo bred birds released to the wild. Key features identified by the study highlight the importance of having parents that are successful breeders and parents that have an overall higher lifetime reproductive output. However, there were associated quantity-quality trade-offs, as the success of young (i.e., released birds) produced by parents was negatively associated to the number of clutches per year (where one clutch per year was found optimal). The study demonstrated the importance of considering the parental effects on the traits of its offspring beyond its pedigree information and found there was an associated decline in fitness of its offspring with older fathers. Song tutoring using wild Regent Honeyeaters was also important for increased survival post-release. Other important factors are discussed within the review. In general, the study recommended that a multi-faceted approach in the assessment and evaluation of the captive breeding program, to identify markers that will improve conservation outcomes of future releases.
No related grants have been discovered for Gordana Popovic.