Vishwesha Guttal

Vishwesha Guttal
Indian Institute of Science | IISC · Centre for Ecological Sciences

PhD

About

34
Publications
9,141
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2,417
Citations

Publications

Publications (34)
Article
Full-text available
Globally, forests and savannah are shown to be alternative stable states for intermediate rainfall regimes. This has implications for how these ecosystems respond to changing rainfall conditions. However, we know little about the occurrence of alternative stable states in forest ecosystems in India. In this study, we investigate the possibility of...
Preprint
Full-text available
Most real-world ecological dynamics, ranging from ecosystem dynamics to collective animal movement, are inherently stochastic in nature. Stochastic differential equations (SDEs) are a popular modelling framework to model dynamics with intrinsic randomness. Here, we focus on the inverse question: If one has empirically measured time-series data from...
Article
Full-text available
Classic computational models of collective motion suggest that simple local averaging rules can promote many observed group-level patterns. Recent studies, however, suggest that rules simpler than local averaging may be at play in real organisms; for example, fish stochastically align towards only one randomly chosen neighbour and yet the schools a...
Article
Strong positive feedback is considered a necessary condition to observe abrupt shifts in ecosystems. A few previous studies have shown that demographic noise—arising from the probabilistic and discrete nature of birth and death processes in finite systems—makes the transitions gradual. In this paper, we investigate the impact of demographic noise o...
Preprint
Full-text available
Strong positive feedback is considered a necessary condition to observe abrupt shifts of ecosystems. A few previous studies have shown that demographic noise -- arising from the probabilistic and discrete nature of birth and death processes in finite systems -- makes the transitions gradual or continuous. In this paper, we show that demographic noi...
Article
Ecosystems can undergo abrupt transitions between alternative stable states when the driver crosses a critical threshold. Dynamical systems theory shows that when ecosystems approach the point of loss of stability associated with these transitions, they take a long time to recover from perturbations, a phenomenon known as critical slowing down. Thi...
Preprint
Diverse ecosystems exhibit clusters that follow scale-free size distributions and lack a characteristic scale. In phase-transition theory, it is well known that scale-free behaviours arise at critical points. Scale-free behaviours, therefore, typically indicate a lack of resilience. Yet, many ecological studies associate loss of scale-free clusteri...
Preprint
Full-text available
Ecosystems can undergo abrupt transitions from one state to an alternative stable state when the driver crosses a threshold or a critical point. Dynamical systems theory suggests that systems take long to recover from perturbations near such transitions. This leads to characteristic changes in the dynamics of the system, which can be used as early...
Article
Full-text available
Complex systems inspired analysis suggests a hypothesis that financial meltdowns are abrupt critical transitions that occur when the system reaches a tipping point. Theoretical and empirical studies on climatic and ecological dynamical systems have shown that approach to tipping points is preceded by a generic phenomenon called critical slowing dow...
Article
Full-text available
Classroom In this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. " Classroom " is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learni...
Article
Full-text available
The paper sets up a model of economic crisis by investigating the role played by movement in asset price as a driver of the dynamic interaction between the real and the financial sectors. Such movement influences income determination in the real economy in the short period through aggregate demand leading to the emergence of two macroeconomic regim...
Article
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Common people and even scientists think of ecology as a discipline that exclusively studies wildlife and topics related to environmental pollution. My friends both within and outside the scientific community are often ba2ed when they hear that I am a physicist doing research in ecology. The aim of this series of articles is to emphasize the less kn...
Article
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A number of ecosystems can exhibit abrupt shifts between alternative stable states. Because of their important ecological and economic consequences, recent research has focused on devising early warning signals for anticipating such abrupt ecological transitions. In particular, theoretical studies show that changes in spatial characteristics of the...
Article
Full-text available
Various ecological and other complex dynamical systems may exhibit abrupt regime shifts or critical transitions, wherein they reorganize from one stable state to another over relatively short time scales. Because of potential losses to ecosystem services, forecasting such unexpected shifts would be valuable. Using mathematical models of regime shif...
Article
Full-text available
Intraspecific competition is a key factor shaping space-use strategies and movement decisions in many species, yet how and when neighbors utilize shared areas while exhibiting active avoidance of one another is largely unknown. Here we investigated temporal landscape partitioning in a population of wild baboons (Papio cynocephalus). We used global...
Article
Full-text available
Movement in animal groups is highly varied and ranges from seemingly disordered motion in swarms to coordinated aligned motion in flocks and schools. These social interactions are often thought to reduce risk from predators, despite a lack of direct evidence. We investigated risk-related selection for collective motion by allowing real predators (b...
Article
Full-text available
During outbreaks, locust swarms can contain millions of insects travelling thousands of kilometers while devastating vegetation and crops. Such large-scale spatial organization is preceded locally by a dramatic density-dependent phenotypic transition in multiple traits. Behaviourally, low-density 'solitarious' individuals avoid contact with one ano...
Article
Full-text available
Many dynamical systems, including lakes, organisms, ocean circulation patterns, or financial markets, are now thought to have tipping points where critical transitions to a contrasting state can happen. Because critical transitions can occur unexpectedly and are difficult to manage, there is a need for methods that can be used to identify when a cr...
Data
Spectral densities and spectral exponent for the critical slowing down and flickering datasets. (TIF)
Data
Rolling Window Metrics: Autocorrelation at-lag-1 (ACF(1) and AR(1)), Spectral ratio, Return rate, Standard Deviation, Coefficient of Variation, Skewness, Kurtosis for the filtered critical slowing down dataset. (TIF)
Data
Rolling Window Metrics: Autocorrelation at-lag-1 (ACF(1) and AR(1)), Spectral ratio, Return rate, Standard Deviation, Coefficient of Variation, Skewness, Kurtosis for the unfiltered (original) critical slowing down dataset. (TIF)
Data
Wavelet analysis for the critical slowing down and flickering datasets. (TIF)
Article
Full-text available
Long-distance dispersal (LDD) events, although rare for most plant species, can strongly influence population and community dynamics. Animals function as a key biotic vector of seeds and thus, a mechanistic and quantitative understanding of how individual animal behaviors scale to dispersal patterns at different spatial scales is a question of crit...
Article
Full-text available
Migration is a hallmark life history strategy of a diverse range of organisms, and also ubiquitous in ontogenic processes including normal embryonic development as well as tumor progression. In such scenarios, individual organisms/cells typically respond to long range (and often noisy) environmental cues. In addition, individuals may interact socia...
Article
Full-text available
Migration of organisms (or cells) is typically an adaptive response to spatiotemporal variation in resources that requires individuals to detect and respond to long-range and noisy environmental gradients. Many organisms, from wildebeest to bacteria, migrate en masse in a process that can involve a vast number of individuals. Despite the ubiquity o...
Article
Empirical evidence for large-scale abrupt changes in ecosystems such as lakes and vegetation of semi-arid regions is growing. Such changes, called regime shifts, can lead to degradation of ecological services. We study simple ecological models that show a catastrophic transition as a control parameter is varied and propose a novel early warning sig...
Article
Full-text available
Ecosystems can undergo large-scale changes in their states, known as catastrophic regime shifts, leading to substantial losses to services they provide to humans. These shifts occur rapidly and are difficult to predict. Several early warning signals of such transitions have recently been developed using simple models. These studies typically ignore...
Article
Spatial self-organization including striking vegetation patterns observed in arid ecosystems has been studied in models with uniform rainfall. In this paper, we present a fully seasonal rainfall model that produces vegetation patterns found in nature by including the natural adaptation of plants to scarcity of water and the consequent seasonal vari...
Article
The existence and implications of alternative stable states in ecological systems have been studied extensively within deterministic models. In this paper, we study the influence of random fluctuations in environmental parameters (e.g. nutrient input and rainfall) on the behavior of two simple bistable, ecological models with a single dynamical var...
Article
Full-text available
We calculate the transverse magnetoresistance (TMR) and Hall coefficient RH of a three-dimensional composite medium with both positive and negative charge carriers, using the effective-medium approximation. The composite is assumed to be composed of two types of small crystallites, in which the charge carriers are either all electrons or all holes....
Article
Full-text available
We study the statistical mechanics of RNA secondary structures designed to have an attraction between two different types of structures as a model system for heteropolymer aggregation. The competition between the branching entropy of the secondary structure and the energy gained by pairing drives the RNA to undergo a "temperature independent" secon...
Article
Full-text available
We calculate the effective resistivity of a macroscopically disordered two dimensional conductor consisting of two components in a perpendicular magnetic field. When two components have equal area fractions, we use a duality theorem to show that the magnetoresistance is non-saturating and at high fields varies exactly linearly with magnetic field....
Article
Full-text available
Generically, in models of driven interacting particles the average speed of the particles decreases monotonically with increasing density. We propose a counter-example, motivated by the motion of ants in a trail, where the average speed of the particles varies {\it non-monotonically} with their density because of the coupling of their dynamics with...
Article
Full-text available
Ecological systems such as forest and lakes can exhibit multiple stable states, abrupt transitions and self-organization as a control parameter is varied. Understanding the dynamics of these systems and devising easily quantifiable measures with predictive capabilities using the theoretical tools of stochastic dynamics and nonequilibrium statistica...

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Projects

Projects (3)
Project
We are investigating the fascinating collective movement patterns of blackbuck herds in their natural habitat. One of the specific goals is to understand how individuals within animal groups transfer information and respond collectively to predation-like events. We are using state-of-the art technology involving aerial videography of controlled behavioural experiments in the wild, and machine-learning based image processing techniques to analyse the recorded videos. To capture fine-scale movement patterns, we need to extract relative positions of all individuals at every frame of the video. I have tried tracking animals based on standard image processing techniques (e.g, image subtraction and particle image velocimetry). However since the environment is often heterogeneous and dynamic, standard algorithms that work well under laboratory conditions do not give accurate detections. Therefore, we are using advanced Computer Vision methods based on machine learning algorithms, which have shown the promise in resolving the technical challenges associated with complex Computer Vision problems. In this part of our work, we have specifically investigated which methods are most appropriate to analyse videographic data of fine-scale movement and interactions. We compared three computer vision techniques, motion detection, colour segmentation and convolutional neural networks, to get individuals’ trajectories in various datasets.
Project
Territorial blackbuck males display an array of social behaviours. Some populations of blackbuck exhibit a very rare and fascinating reproductive strategy called Lek mating . Lek-territoriality is an aggregation of males defending small and clustered territories in an area usually devoid of resources and females visit the leks for the sole purpose of finding a mate. We are looking at the spatio-temporal dynamics of male territories and female movement on the lek. Before choosing a male to mate, females move around the lek examining different territories. Their movement is affected by their interactions with males as well as position of other females. We want to test female copying hypothesis of mate-selection using aerial videos which record fine-scale movements and interactions on the lek. The ease of the video recording through drones, ensures we have high-resolution data, unparalleled to what is captured at ground level, without man-made disturbance to the lekking process and migration of these antelopes.
Project
Our main aim is to understand the movement dynamics of Fish groups. For this we do experiments, record movement and then analyse the data. We also build models that capture certain key features of the data.