Nikunj Goel wins Volterra Award and Damman Award at ESA 2016

Nikunj Goel has won two awards at the Ecological Society of America (ESA) 2016 Annual Meeting, Volterra Award by the Theoretical Ecology section and Ton Damman award from the Vegetation section. He was given these for his excellent presentation titled “Spatiotemporal dynamics of savanna-forest distribution”. Both of these awards are given to best graduate student presentation at the Annual meetings of ESA.

Congratulations to Nikunj!

Nikunj graduated with BSc(Research) from IISc in 2015 and worked in our lab for his final year project working on early warning signals of financial meltdowns that resulted in a publication. He is currently a PhD student with Dr Carla Staver at Yale University. We continue to collaborate after he has moved to Yale and I serve on his PhD thesis committee.

Our new paper testing theory of spatial indicators of ecological transitions published in Global Ecology and Biogeography

We are happy to announce that our new paper on testing theory of spatial indicators of critical slowing down and ecological transitions has appeared in the online early version of the journal Global Ecology and Biogeography.

Congratulations to Amit Agrawal (former project assistant of our lab) and Sabiha Majumder (PhD student) for their first research publication! This project began during conversations between Stephanie Eby, Andrew P. Dobson and myself. That was back in 2010, when I was a post-doc at Princeton. They had this excellent high resolution data that made sense in the context of a theory paper from my thesis in 2009.

So what is this paper about? 

Ecosystems like clear lakes or forests can abruptly collapse to ‘unhealthy’ states like toxic-turbid lakes or deserts with low vegetation. Our lab uses ideas from physics of phase transitions (e.g., water boiling to become vapour) to develop statistical tools of early warnings of such abrupt transitions. For example, two papers of my PhD thesis (Guttal and Jayaprakash 2008 and 2009) were on developing such tools to analyse time series and spatial data from ecosystems. The underlying theory is now popularly known as ‘Early warning signals of critical transitions’, “Theory of Critical slowing down”, etc.

In this paper, we were testing such tools using spatial data of large scale ecosystems. There were earlier efforts to test these quantitative tools, but mostly in simple laboratory conditions or controlled lake experiments.

Specifically, we test the prediction that the following metrics show stronger signatures of transitions ‘before a collapse of an ecosystem’

(A) Spatial variance (proposed in Guttal and Jayaprakash, 2009)

(B) Spatial skewness (proposed in Guttal and Jayaprakash, 2009)

(C) Spatial autocorrelation (proposed in Dakos et al 2010)

(D) Spatial spectra (proposed in Carpenter and Brock 2010).

This graph below shows how theoretical predictions and real data match.

spatial-csd-theory-data-comparison

There were a few subtle and insightful aspects related to analysing this dataset. First, we didn’t have an ideal dataset, so we had to make an approximation called ‘space-for-time substitution’ to compare theory with real data. We justified this approach using a model. Second, the data were discrete-state (occupied/unoccupied), unlike what the models typically assumes continuous variables (like biomass density) in each of the above papers. We developed a data preprocessing method called coarse-graining, inspired from the physics literature. We thought the method to be sufficiently important and hence the details of the method will be published separately. Analysing this dataset has motivated various thesis chapters in our lab’s PhD student Sabiha Majumder, who is from Physics department and works jointly with me and Prof. Sriram Ramaswamy.

I should add that reviewers gave detailed comments that helped the manuscript a lot. This was also our first manuscript where we used services of Axios.

All codes and some data associated with this manuscript are available on our Github page: https://github.com/tee-lab/spacetime-csd

ISRO meeting and poster award

The National Centre for Remote Sensing at Hyderabad, an ISRO centre focussing exclusively on remote sensing related activities, organised a one day ‘Academica and student interaction meeting’ on 5th Feb 2015. Myself and my PhD student Sumithra Sankaran attended this meeting.

We had very good interactions with scientists at NRSC. We discussed our requirement of high resolution data of various ecosystems for our research work for which they offered lot of support. We hope to build strong collaborations with the ISRO scientists.

Congratulations to Sumithra Sankaran who won a best poster award for her poster on ‘Characterising vegetation of semi-arid ecosystems’. She presented her modelling work on based on simple cellular automata models and how one can use spatial metrics of remote sensing data to infer ecological features underlying the system.

Student updates: collaborations, conferences and interns

A bunch of student related updates.

Phd Students:  Sumithra Sankaran and Sabiha Sachdeva both visited Montpellier, France to initiate collaboration with Dr Sonia Kefi on an Indo-French grant supported by IFCAM. They spent around a month in Montpellier (I was there for the initial one week) and have started working on an interesting collaborative project on spatial patterns in vegetation and other ecological systems. As of today, they finished attending a three day conference in Paris on Mathematical Models in Ecology and Evolution, 2015 with a distinguished list of speakers from various parts of the world. They too gave talks on their ongoing phd thesis work. They are expected to be back in town by the end of this month.

Jaideep Joshi is having great fun at IIASA, Austria at their annual Young Scientist Summer Program. For three months (June-Aug 2015), he will be working with Ake Bronstrom and Ulf Dieckmann, leading theoretical evolutionary biologists, on a spatial model of public goods dilemma.

Interns: Somewhat surprisingly, I ended up accepting quite a few interns this summer! They have all been fantastic.

The first intern was Arpitha who is doing her MSc in math from Christ University. She did a reading project on the evolution of cooperation in networks and also did various simulations related to that. In the process, I got to learn a few basic terminologies of network theory.

Sampada, a fourth year IISc UG student from math department did a simulational project on merge-split models of swarms.

Gokul Nair, a second year IISc UG student wrote efficient codes on swarming using net-logo which are now being used for the experimental work.

Poornima, a second year student from IISER Pune did a reading project on super organisms.

Hans Kaliaden, a third year IISc UG student majoring in biology read about and wrote a net-logo code on vegetation pattern dynamics that has both individual based and reaction-diffusion based dynamics.

Varsha Shenoy, a second year MSc student from Mysore Univerisity is also working on a short project on vegetation pattern formation!

Science is Fun with so many young students around!

Jaideep Joshi has been selected for Young Scientists Summer Program, IIASA, Austria

We are delighted that Jaideep Joshi, a third year PhD student in our lab, has been selected for Young Scientists Summer Program, at IIASA, Austria. This is a highly competitive and prestigious summer program for those working in theoretical ecology and evolution. He will be working on a research project in collaboration with Dr Ulf Dieckmann and Dr. Ack Brannstrom. All the best to Jaideep!

Lab Updates: Summer conferences, 3rd year lab anniversary and new members.

It’s been a really long time since we have updated any news about the lab. So here goes:

Summer and conferences*: We did lot of conference travel in the summer. Jaideep Joshi, going-from-second-to-third-year PhD student of the lab, tops the list by attending three major international conferences: Evolution 2014 at Rayleigh, North Carolina followed by ISBE 2014 (International Society for Behavioural Ecology) meeting at New York, and then finally ABS 2014 (American Behavioral Society) annual meeting at Princeton. He presented his work on the Coevolution of cooperation with collective movement and got some really useful feedback that will help us in writing the manuscript.

Sabiha Majumder, an Integrated PhD student from Physics & working jointly with me and Sriram Ramaswamy, and Sumithra Sankaran, now a second year PhD student, both presented their work at the 99th Annual meeting of Ecological Society of America at Sacramento, USA. For both of them it was their first major international conference!

Finally, I myself went to visit Princeton for a few days to attend couple of days atAmerican Behaviour Society (ABS) meeting and then three days at Sacramento to give a short contributed talk at the Ecological Society of America (ESA) annual meeting. I was visiting US after three years, and it was great to meet friends andformer colleagues, including Simon Levin and Iain Couzin, at Princeton, and then a host of others at the ESA meeting.

3rd Lab Anniversary: On Sept 5th 2014, we celebrated 3rd lab anniversary, which incidentally is also celebrated as Teachers day in India. I can only hope that all the hard work that has gone in various projects will see their light (i.e., get published) before we celebrate the 4th anniversary!

New members:

Several old members have now left the lab. Nitin (who did so many things other than his own project for smooth functioning of the the lab), Aishwariya, Pradeeksha and Ravi Ranjan have all moved on. All the best for their future careers.

We welcome four IISc UG students who will work on their final year projects with us: Nikunj Goel (Physics major), Amitabh Srivastava (Physics major), Visweswaran (Bio major, working jointly with Prof. Dipshikha Chakravorty, MCBL) and Athmanathan (Math major, working jointly with Prof. Srikanth Iyer, Math dept). We are excited that this is opening up opportunities for collaborations outside our lab and department.

We also have visitor from France, Quentin Hoarau, a physics masters student at Ecole Normale Supérieure of Cachan. He is our first international student visitor and will be working with us until the end of Feb 2015.

Kartik Azhagesan, who has a BTech from Biotechnology and has deep interest in computational ecology, has joined the lab from Sept.