ORCID Profile
0000-0002-8216-5639
Current Organisations
Princeton University
,
Cornell University
,
Arizona State University
,
Cornell Univesity
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Publisher: Proceedings of the National Academy of Sciences
Date: 05-08-2016
Abstract: The ability to navigate is a hallmark of living systems, from single cells to higher animals. Searching for targets, such as food or mates in particular, is one of the fundamental navigational tasks many organisms must execute to survive and reproduce. Here, we argue that a recent surge of studies of the proximate mechanisms that underlie search behavior offers a new opportunity to integrate the biophysics and neuroscience of sensory systems with ecological and evolutionary processes, closing a feedback loop that promises exciting new avenues of scientific exploration at the frontier of systems biology.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-09-2021
Abstract: A triumph that has emerged from the catastrophe of the severe acute respiratory syndrome coronavirus 2 pandemic has been the rapid development of several potent vaccines. However, 18 months into the pandemic and more than 6 months after vaccine approval, wealthy countries remain the major beneficiaries. Wagner et al . model the consequences of vaccine stockpiling in affluent countries on disease rates in lower- and middle-income countries and the consequences for the eruption of new variants that could jeopardize the early success of vaccines. For countries that can readily access vaccines, it would be better to share vaccines equitably to lower disease burdens in countries with less access, reduce the cost of having to be constantly vigilant for case imports, and minimize virus evolution. —CA
Publisher: Elsevier BV
Date: 04-2021
Publisher: Wiley
Date: 22-12-2021
DOI: 10.1002/FSH.10695
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-04-1995
Publisher: Cambridge University Press (CUP)
Date: 27-11-2012
DOI: 10.1017/S1355770X12000460
Abstract: Systems linking people and nature, known as social-ecological systems, are increasingly understood as complex adaptive systems. Essential features of these complex adaptive systems – such as nonlinear feedbacks, strategic interactions, in idual and spatial heterogeneity, and varying time scales – pose substantial challenges for modeling. However, ignoring these characteristics can distort our picture of how these systems work, causing policies to be less effective or even counterproductive. In this paper we present recent developments in modeling social-ecological systems, illustrate some of these challenges with ex les related to coral reefs and grasslands, and identify the implications for economic and policy analysis.
Publisher: Proceedings of the National Academy of Sciences
Date: 04-09-2001
Abstract: Bio ersity plays a vital role for ecosystem functioning in a changing environment. Yet theoretical approaches that incorporate ersity into classical ecosystem theory do not provide a general dynamic theory based on mechanistic principles. In this paper, we suggest that approaches developed for quantitative genetics can be extended to ecosystem functioning by modeling the means and variances of phenotypes within a group of species. We present a framework that suggests that phenotypic variance within functional groups is linearly related to their ability to respond to environmental changes. As a result, the long-term productivity for a group of species with high phenotypic variance may be higher than for the best single species, even though high phenotypic variance decreases productivity in the short term, because suboptimal species are present. In addition, we find that in the case of accelerating environmental change, species succession in a changing environment may become discontinuous. Our work suggests that this phenomenon is related to ersity as well as to the environmental disturbance regime, both of which are affected by anthropogenic activities. By introducing new techniques for modeling the aggregate behavior of groups of species, the present approach may provide a new avenue for ecosystem analysis.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-04-2021
Abstract: For two-dose vaccines against severe acute respiratory syndrome coronavirus 2, some jurisdictions have decided to delay the second dose to rapidly get the vaccine into more people. The consequences of deviating from manufacturer-prescribed dosing regimens are unknown but will depend on the strength of immune responses to the vaccines. Saad-Roy et al. took a modeling approach to tackling the inevitable uncertainties facing vaccine rollout. The authors found that although one-dose strategies generally reduce infections in the short term, in the long term, the outcome depends on immune robustness. A one-dose strategy may increase the potential for antigenic evolution if immune responses are suboptimal and the virus continues to replicate in some vaccinated people, potentially leading to immune-escape mutations. It is critical to gather serological data from vaccinated people and, to avoid negative outcomes, to r up vaccination efforts worldwide. Science , this issue p. 363
Publisher: Public Library of Science (PLoS)
Date: 21-11-2022
Publisher: MDPI AG
Date: 09-06-2020
DOI: 10.3390/SU12114714
Publisher: Wiley
Date: 07-02-2020
DOI: 10.1111/GCB.14972
Abstract: In light of rapid environmental change, quantifying the contribution of regional- and local-scale drivers of coral persistence is necessary to characterize fully the resilience of coral reef systems. To assess multiscale responses to thermal perturbation of corals in the Coral Triangle (CT), we developed a spatially explicit metacommunity model with coral-algal competition, including seasonal larval dispersal and external spatiotemporal forcing. We tested coral sensitivity in 2,083 reefs across the CT region and surrounding areas under potential future temperature regimes, with and without interannual climate variability, exploring a range of 0.5-2.0°C overall increase in temperature in the system by 2054. We found that among future projections, reef survival probability and mean percent coral cover over time were largely determined by the presence or absence of interannual sea surface temperature (SST) extremes as well as absolute temperature increase. Overall, reefs that experienced SST time series that were filtered to remove interannual variability had approximately double the chance of survival than reefs subjected to unfiltered SST. By the end of the forecast period, the inclusion of thermal anomalies was equivalent to an increase of at least 0.5°C in SST projections without anomalies. Change in percent coral cover varied widely across the region within temperature scenarios, with some reefs experiencing local extinction while others remaining relatively unchanged. Sink strength and current thermal stress threshold were found to be significant drivers of these patterns, highlighting the importance of processes that underlie larval connectivity and bleaching sensitivity in coral networks.
Publisher: University of Chicago Press
Date: 2013
DOI: 10.1086/668572
Abstract: Plant pathogens often respond sensitively to changes in their environmental conditions and consequently represent a potentially important ecological response to global change. Although several studies have considered the effects of increased temperature and CO(2) concentrations on plant pathogen risk, the effects of changing precipitation regimes have drawn less attention. Many classes of plant pathogen, however, are sensitive to changes in the water potential of their local environment. This study applied existing ecohydrological frameworks to connect precipitation, soil, and host properties with scenarios of pathogen risk, focusing on two water-sensitive pathogens: Phytophthora cinnamomi and Botryosphaeria doithidea. Simple models were developed to link the dynamics of these pathogens to water potentials. Model results demonstrated that the risk of host plants being colonized by the pathogens varied sensitively with soil and climate. The model was used to predict the distribution of Phytophthora in Western Australia and the severity of disease in horticultural blueberry trials with variable irrigation rates, illustrating potential applications of the framework. Extending the modeling framework to include spatial variation in hydrology, epidemic progression, and feedbacks between pathogens and soil moisture conditions may be needed to reproduce detailed spatial patterns of disease. At regional scales, the proposed modeling approach provides a tractable framework for coupling climatic drivers to ecosystem response while accounting for the probabilistic and variable nature of disease.
Publisher: MyJove Corporation
Date: 31-01-2020
DOI: 10.3791/60589
Publisher: The Royal Society
Date: 2016
Abstract: Many chemotactic bacteria inhabit environments in which chemicals appear as localized pulses and evolve by processes such as diffusion and mixing. We show that, in such environments, physical limits on the accuracy of temporal gradient sensing govern when and where bacteria can accurately measure the cues they use to navigate. Chemical pulses are surrounded by a predictable dynamic region, outside which bacterial cells cannot resolve gradients above noise. The outer boundary of this region initially expands in proportion to the square root of time before rapidly contracting. Our analysis also reveals how chemokinesis—the increase in swimming speed many bacteria exhibit when absolute chemical concentration exceeds a threshold—may serve to enhance chemotactic accuracy and sensitivity when the chemical landscape is dynamic. More generally, our framework provides a rigorous method for partitioning bacteria into populations that are ‘near’ and ‘far’ from chemical hotspots in complex, rapidly evolving environments such as those that dominate aquatic ecosystems.
Publisher: IOP Publishing
Date: 03-2021
Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.JTBI.2010.02.030
Abstract: We propose a (time) multiscale method for the coarse-grained analysis of collective motion and decision-making in self-propelled particle models of swarms comprising a mixture of 'naïve' and 'informed' in iduals. The method is based on projecting the particle configuration onto a single 'meta-particle' that consists of the elongation of the flock together with the mean group velocity and position. We find that the collective states can be associated with the transient and asymptotic transport properties of the random walk followed by the meta-particle, which we assume follows a continuous time random walk (CTRW). These properties can be accurately predicted at the macroscopic level by an advection-diffusion equation with memory (ADEM) whose parameters are obtained from a mean group velocity time series obtained from a single simulation run of the in idual-based model.
Publisher: Springer Science and Business Media LLC
Date: 16-08-2009
DOI: 10.1007/S00267-008-9187-2
Abstract: Current ecological thinking emphasizes that systems are complex, dynamic, and unpredictable across space and time. What is the ersity in interpretation of these ideas among today's ecologists, and what does this mean for environmental management? This study used a Policy Delphi survey of ecologists to explore their perspectives on a number of current topics in ecology. The results showed general concurrence with nonequilibrium views. There was agreement that disturbance is a widespread, normal feature of ecosystems with historically contingent responses. The importance of recognizing multiple levels of organization and the role of functional ersity in environmental change were also widely acknowledged. Views differed regarding the predictability of successional development, whether "patchiness" is a useful concept, and the benefits of shifting the focus from species to ecosystem processes. Because of their centrality to environmental management, these different views warrant special attention from both managers and ecologists. Such ergence is particularly problematic given widespread concerns regarding the poor linkages between science (here, ecology) and environmental policy and management, which have been attributed to scientific uncertainty and a lack of consensus among scientists, both jeopardizing the transfer of science into management. Several suggestions to help managers deal with these differences are provided, especially the need to interpret broader theory in the context of place-based assessments. The uncertainty created by these differences requires a proactive approach to environmental management, including clearly identifying environmental objectives, careful experimental design, and effective monitoring.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2008
Publisher: Informa UK Limited
Date: 12-2006
Publisher: Proceedings of the National Academy of Sciences
Date: 16-05-2019
Abstract: The limited precision of sensory organs places fundamental constraints on organismal performance. An open question, however, is whether organisms are routinely pushed to these limits and how limits might influence interactions between populations of organisms and their environment. By combining a method to generate dynamic, replicable resource landscapes, high-speed tracking of freely moving bacteria, a mathematical theory, and agent-based simulations, we show that sensory noise ultimately limits when and where bacteria can detect and climb chemical gradients. Our results suggest that the typical chemical landscapes bacteria inhabit are dominated by noise that masks shallow gradients and that the spatiotemporal dynamics of bacterial aggregations can be predicted by mapping the region where gradient signal rises above noise.
Publisher: Proceedings of the National Academy of Sciences
Date: 07-02-2010
Publisher: Wiley
Date: 10-02-2014
DOI: 10.1111/GCB.12463
Abstract: Global change will simultaneously impact many aspects of climate, with the potential to exacerbate the risks posed by plant pathogens to agriculture and the natural environment yet, most studies that explore climate impacts on plant pathogen ranges consider in idual climatic factors separately. In this study, we adopt a stochastic modeling approach to address multiple pathways by which climate can constrain the range of the generalist plant pathogen Phytophthora cinnamomi (Pc): through changing winter soil temperatures affecting pathogen survival spring soil temperatures and thus pathogen metabolic rates and changing spring soil moisture conditions and thus pathogen growth rates through host root systems. We apply this model to the southwestern USA for contemporary and plausible future climate scenarios and evaluate the changes in the potential range of Pc. The results indicate that the plausible range of this pathogen in the southwestern USA extends over approximately 200,000 km(2) under contemporary conditions. While warming temperatures as projected by the IPCC A2 and B1 emissions scenarios greatly expand the range over which the pathogen can survive winter, projected reductions in spring rainfall reduce its feasible habitat, leading to spatially complex patterns of changing risk. The study demonstrates that temperature and rainfall changes associated with possible climate futures in the southwestern USA have confounding impacts on the range of Pc, suggesting that projections of future pathogen dynamics and ranges should account for multiple pathways of climate-pathogen interaction.
Publisher: Springer Science and Business Media LLC
Date: 28-02-2020
Publisher: The Royal Society
Date: 06-2022
DOI: 10.1098/RSOS.211515
Publisher: Springer Science and Business Media LLC
Date: 18-02-2015
Publisher: Cambridge University Press (CUP)
Date: 2022
Publisher: Elsevier BV
Date: 11-1995
Publisher: Proceedings of the National Academy of Sciences
Date: 05-12-2011
Abstract: The metabolic machinery of marine microbes can be remarkably plastic, allowing organisms to persist under extreme nutrient limitation. With some exceptions, most theoretical approaches to nutrient uptake in phytoplankton are largely dominated by the classic Michaelis–Menten (MM) uptake functional form, whose constant parameters cannot account for the observed plasticity in the uptake apparatus. Following seminal ideas by earlier researchers, we propose a simple cell-level model based on a dynamic view of the uptake process whereby the cell can regulate the synthesis of uptake proteins in response to changes in both internal and external nutrient concentrations. In our flexible approach, the maximum uptake rate and nutrient affinity increase monotonically as the external nutrient concentration decreases. For low to medium nutrient availability, our model predicts uptake and growth rates larger than the classic MM counterparts, while matching the classic MM results for large nutrient concentrations. These results have important consequences for global coupled models of ocean circulation and biogeochemistry, which lack this regulatory mechanism and are thus likely to underestimate phytoplankton abundances and growth rates in oligotrophic regions of the ocean.
Publisher: Springer Science and Business Media LLC
Date: 05-04-2022
DOI: 10.1007/S13280-022-01721-3
Abstract: Transformation toward a sustainable future requires an earth stewardship approach to shift society from its current goal of increasing material wealth to a vision of sustaining built, natural, human, and social capital—equitably distributed across society, within and among nations. Widespread concern about earth’s current trajectory and support for actions that would foster more sustainable pathways suggests potential social tipping points in public demand for an earth stewardship vision. Here, we draw on empirical studies and theory to show that movement toward a stewardship vision can be facilitated by changes in either policy incentives or social norms. Our novel contribution is to point out that both norms and incentives must change and can do so interactively. This can be facilitated through leverage points and complementarities across policy areas, based on values, system design, and agency. Potential catalysts include novel democratic institutions and engagement of non-governmental actors, such as businesses, civic leaders, and social movements as agents for redistribution of power. Because no single intervention will transform the world, a key challenge is to align actions to be synergistic, persistent, and scalable.
Publisher: Wiley
Date: 08-01-2015
DOI: 10.1111/CONL.12156
Publisher: Springer Science and Business Media LLC
Date: 30-01-2023
No related grants have been discovered for Simon Levin.