BioND — Dynamics of Biological Networks

Pattern formation in ecology and epidemiology

Ecology is all about patterns. Patterns, or in other words repeated themes, are found everywhere in nature. Prominent examples include vegetation patters, patterns of succession of species, recurrent food web architectures, large-scale laws describing the distribution and abundance of different species and also temporal patterns such as coevolutionary cycles.

Over the past years we have made contributions in several of these areas. One intriguing pattern that is found in ecology is evident in species-abundance-relationships, which describe the probability of finding a species comprising a given number of individuals. Population dynamical models predict that competing species should have a comparable size with high probability. However, empirical data consistently shows that species-abundance curves follow power-laws, so that that there many rare species for every common one. In a recent paper we showed that this dilemma is resolved if weakly nonlinear mortality terms are included in models. Although weakly nonlinear mortality is almost indistinguishable from linear mortality in direct observations, it may open up an "invisible" niche allowing very rare competitors to survive.

Ecological patterns are not always abstract, but can sometimes be observed directly. For instance in certain marine sediments microorganisms are found in macroscopic dot or stripe patterns. Using the approach of generalized modeling we showed that these patterns can emerge due to predator-prey interactions and diffusion (Baurmann et al. 2007). This work also identified a parameter range in which particularly complex dynamics occurs. The precise behavior of systems in this parameter range is presently explored in an ongoing series of simulations, which are run and visualized in real time by an art installation, presently shown in the permanent exhibition of the Universum Science Center in Bremen.

Another repeated theme in ecology is the Redfield ratio, the specific ratio between carbon, phosphorus, and nitrogen, which is similar in all higher organisms. The need to maintain this ratio, despite potential fluctuations in the nitrogen and phosphorus content of available resources introduces stoichiometric constraints on the growth of organisms. In the past, several modeling approaches have been proposed for including the effect of such constraints in population dynamical models. While starting from very similar hypothesis the different modeling approaches result sometimes in very different dynamical behavior. In a recent work (Stiefs et al. 2010) we showed that five major modeling approaches that have been proposed are actually special cases of one generalized model. The generalized stoichiometric model can thus serve as a unifying framework that reveals differences and commonalities between the previously proposed approaches.

Other recent and ongoing work on patterns in ecology involves modeling the vertical distribution of plankton in the water column, the effects of enrichment and predator interference in predator-prey systems, and the development of a new modeling approach for individual-based spatial vegetation models.

Key Publications

A general consumer-resource population model
Kevin Lafferty, Giulio DeLeo, Cheryl J. Briggs, Andrew P. Dobson, Thilo Gross, and Armand M. Kuris
Science 349(6250), 854-857, 2015.
(abstract) (supporting material) (link to publisher) (media coverage)

Fission yeast does not age under favorable conditions, but does so after stress
Miguel Coelho, Aygül Dereli, Anett Haese, Sebastian Kühn, Liliana Malinovska, Morgan E. de Santis, James Shorter, Simon Alberti, Thilo Gross, and Iva M. Tolic-Nørrelykke
Current Biology 23(19), 1844-1852, 2013.
(abstract) (link to publisher) (media coverage)

Coordination, differentiation, and fairness in a population of cooperating agents
Anne-Ly Do, Lars Rudolf, and Thilo Gross
Games 3, 30-40, 2012.
(abstract) (link to publisher) (arXiv) (download preprint)

Uninformed individuals promote democratic consensus in animal groups
Iain D. Couzin, Christos C. Ioannou, Güven Demirel, Thilo Gross, Colin J. Torney, Andrew Hartnett, Larissa Conradt, Simon A Levin, and Naomi E. Leonard
Science 334(6206), 1578-1580 , 2011.
(abstract) (supporting material) (link to publisher) (media coverage)

Stability in networks of delay-coupled delay oscillators
Johannes M. Hoefener, Gautam Sethia, and Thilo Gross
Europhysics Letters 95, 40002, 2011.
(abstract) (link to publisher) (arXiv) (download preprint)

Food quality in producer-grazer models - A generalized analysis
Dirk Stiefs, George A. K. van Voorn, Bob W. Kooi, Ulrike Feudel, and Thilo Gross
The American Naturalist 176, 367–380, 2010.
(abstract) (supporting material) (link to publisher) (arXiv) (download preprint) (media coverage)

The invisible niche: Weakly density-dependent mortality and the coexistence of species
Thilo Gross, Andrew M. Edwards, and Ulrike Feudel
Journal of Theoretical Biology 258(1), 148-155, 2009.
(abstract) (supporting material) (link to publisher) (download preprint)

Seasonal forcing drives spatio-temporal pattern formation in rabies epidemics
Niels von Festenberg, Thilo Gross, and Bernd Blasius
Mathematical Modeling of Natural Phenomena 2(4), 63-73, 2007.
(abstract) (download preprint)

Instabilities in spatially extended predator-prey systems: spatio-temporal patterns in the neighborhood of Turing-Hopf bifurcations
Martin Baurmann, Thilo Gross, and Ulrike Feudel
Journal of Theoretical Biology 245(2), 220-229, 2007.
(abstract) (link to publisher) (download preprint)

Additional Publications

The influence of dispersal on a predator-prey system with two habitats
Philipp Gramlich, Sebastian Plitzko, Lars Rudolf, Barbara Drossel, and Thilo Gross
Journal of Theoretical Biology 398, 150, 2016.
(abstract) (link to publisher) (arXiv) (download preprint)

Meta-food-chains as a many-layer epidemic process on networks
Edmund Barter and Thilo Gross
Physical Review E 93, 022303, 2016.
(abstract) (link to publisher) (arXiv)

Fusion leads to effective segregation of damage during cell division: an analytical treatment
Steven J. Lade, Miguel Coelho, Iva Tolic, and Thilo Gross
Journal of Theoretical Biology 378, 47–55, 2015.
(abstract) (link to publisher)

Fusion of protein aggregates facilitates asymmetric damage segregation
Miguel Coelho, Stephen J. Lade, Simon Alberti, Thilo Gross, and Iva M. Tolic
PLoS Biology 12(6), e1001885, 2014.
(abstract) (link to publisher) (download preprint) (media coverage)

Amplitude death in networks of delay-coupled delay oscillators
Johannes Höfener, Gautam Sethia, and Thilo Gross
Philosophical Transactions of the Royal Society A 371, 20120462, 2013.
(abstract) (link to publisher) (arXiv) (download preprint)

Fragmentation transitions in multi-state voter models
Gesa A. Böhme and Thilo Gross
Physical Review E 85, 066117-10, 2012.
(abstract) (link to publisher) (arXiv) (download preprint)

Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer
Alexei B. Ryabov, Lars Rudolf, and Bernd Blasius
Journal of Theoretical Biology 263(1), 120-133, 2010.
(abstract) (link to publisher) (arXiv) (download preprint)

Dynamical phase coexistence: A simple solution to the savanna problem
Federico Vazquez, Christobal Lopez, Justin M. Calabrese, and Miguel A. Munoz
Journal of Theoretical Biology 264(2), 360-366, 2010.
(abstract) (link to publisher) (arXiv) (download preprint)

Effects of zooplankton diel vertical migration on a phytoplankton community: a scenario analysis of the underlying mechanisms
Thomas Petzold, Lars Rudolf, Karsten Rinke, and Jürgen Benndorf
Ecological Modelling 220(9-10), 1358-1368 , 2009.
(abstract) (link to publisher) (download preprint)

Stabilization due to predator interference: Comparison of different analysis approaches
George A. K. van Voorn, Dirk Stiefs, Thilo Gross, Bob W. Kooi, Ulrike Feudel, and Sebastiaan A. L. M. Kooijman
Mathematical Biosciences and Engineering 5(3), 567 –583, 2008.
(abstract) (download preprint)

Enrichment and foodchain stability: the impact of different functional forms
Thilo Gross, Wolfgang Ebenhöh, and Ulrike Feudel
Journal of Theoretical Biology 227(3), 349-358, 2004.
(abstract) (link to publisher) (download preprint)

Media Coverage

Kevin Knudson, Forbes, 2015-10-15
Scientists love unifying theories – a single equation (or set of equations) that explains everything in the discipline. Physicists have been searching for theirs for decades, running into difficulty unifying quantum theory with relativity. Economists work very hard at trying to model the global economy via complicated regression models. Until recently, however, ecologists thought that different food webs operated under distinct conditions. That is, the dynamics of foxes and squirrels must be different from those of parasites eating hosts.
(more)

Just Cebrian, Science Magazines, 2015-09-04
All organisms in an ecosystem can be placed on a trophic level, depending on whether they are producers or consumers of energy within the food chain (see the photo). Ecologists have long debated what regulates the trophic structure and dynamics of ecosystems (1). This is important because trophic structure and dynamics regulate many of the goods and services that ecosystems provide to wildlife and humankind, such as the production of harvestable food and energy, carbon sequestration and modulation of climate change, and nutrient uptake and control of global biogeochemical cycles (2). A study by Hatton et al. on page 1070 of this issue (3) and a recent report by Lafferty et al. (4) represent important advances toward a unified theory of trophic structure that captures observed trends across all ecosystems.
(more)

Roland G. Roberts, PloS Biology Synopsis, 2014-06-17
We all pass unwanted stuff on to our children—emotional baggage, peculiar habits, unfashionable furniture. Cells do the same thing when they divide; along with their newly replicated genomes andthe vital cellular organelles, they also pass on a lifetime’s worth of accrued rubbish. An important component of this is the legacy of insoluble aggregated protein that the parent cell has failed to deal with by the normal processes of degradation, and the amount that’s passed on can affect the lifespan and wellbeing of the daughter cells.
(more) (pdf)

Phil Hammond, BBC Radio Bristol, 2013-09-21
The only place where you can book a regular appointment with a GP on a Saturday.
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PA, Huffington Post, 2013-09-14
For lessons in anti-ageing, we need look no further than celebrities who are obsessed with youth and suffer disastrous consequences at the end of a plastic surgeon's knife. However, could there finally be a solution in nature for a more natural-looking method of anti-ageing?
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2013-09-13, The Herald, 2013-09-13
The yeast microbe, called S. pombe, is said to be immune to ageing, as it rejuvenates every time it reproduces.
(more)

VLM, Evening Gazette (Croatia), 2013-09-13
Istraživa?ki tim pokazao je da su stanice pivskog kvasca Schizosaccharomyces pombe imune na starenje kada se reproduciraju i rastu pod odre?enim uvjetima.
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Claudia Lord, Bild, 2013-09-13
Es ist ein Menschheitstraum – die ewige Jugend! Jetzt kam Dr. Iva Tolic-Nørrelykke (39) vom Max-Planck-Institut für Molekulare Zellbiologie und Genetik dem Geheimnis ein großes Stück näher!
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The Scotsman, 2013-09-13
A MICROBE that stays forever young and could help unlock the secrets of ageing has been discovered by scientists.
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Western Daily Press, 2013-09-12
A microbe that stays forever young and could help unlock the secrets of ageing has been discovered by scientists.
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Guernsey Press, 2013-09-12
A microbe that stays forever young and could help unlock the secrets of ageing has been discovered by scientists.
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Norbert Lossau, Die Welt, 2013-09-12
Seegurken, Süßwasserpolypen oder Pilze machen es uns vor: Sie können offenbar ewig leben. Eine Hefe-Art aber treibt es auf die Spitze: Sie verjüngt sich sogar.
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Chris Löwer, P.M., 2013-02-01
Nur scheinbar eine einförmige Masse: Fische im Schwarm sind nicht alle gleich – es gibt „meinungsbildende“ und Mitläufer.
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Manuela Lenzen, Frankfurter Allgemeine Zeitung, 2012-03-14
Ignoranten sind eine Gefahr für die Demokratie. Wie leicht könnten sie in ihrer Ahnungslosigkeit dem erstbesten Demagogen aufsitzen! Stimmt nicht, sagen Ian D. Couzin und Mitautoren: Uninformierte Individuen befördern den demokratischen Konsens - jedenfalls bei Notemigonus crysoleucas, einem schwarmbildenden Süßwasserfisch.
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CBC Radio, 2011-12-19
We journalists like to think that what we do is vital for democracy. That keeping the people informed of a complex world empowers each individual, and helps people make the best choices for the whole of society. According to a new study published in the journal Science, however, we've got it all backwards. The conclusion of the study is that the health of a democracy is dependent on keeping people UN-informed. Or some of them, anyway.
(more)

Rob Waugh, Daily Mail Online, 2011-12-19
A well-informed, interested public is often hailed as the 'ideal' of democracy. But a new Princeton study suggests that the opposite could be the case - and that people who have no interest at all could be vital to the working of a democratic society.
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Scinexx, 2011-12-19
Ob in einem Fischschwarm oder in einer menschlichen Gesellschaft: Soziale Lebewesen müssen gemeinsam Entscheidungen treffen. Nicht immer setzt sich dabei die Mehrheit durch. In manchen Fällen gelingt es einer zielstrebigen kleinen Gruppe, die ganze Gemeinschaft in ihrem Sinne zu beeinflussen. Ein Forscherteam hat jetzt anhand von Computermodellen und Verhaltensstudien an Fischen herausgefunden, dass uninformierte Individuen die Entscheidung einer Mehrheit unterstützen und verhindern können, dass sich eine besonders entschlossene Minderheit durchsetzt.
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PTI, Firstpost, 2011-12-19
Ignorance is bliss, it’s often said, but it seems it can also promote democracy, a new study based on animal behaviour says.
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Jeffrey Kluger , Time, 2011-12-19
The Tea Party and the Occupy Wall Streeters owe a lot to a little fish called the golden shiner.
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Jürgen Schönstein, Science Blogs, 2011-12-19
Auf diesen knappen Nenner lassen sich die Ergenisse des Papers Uninformed Individuals Promote Democratic Consensus in Animal Groups bringen, das in der aktuellen Ausgabe von Science erschienen ist.
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Christopher Shea, Wall Street Journal, 2011-12-19
Computer models and experiments with shiners, a kind of fish, demonstrate that, within groups, members with weak preferences can prevent minorities with strongly held views from getting their way.
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Christine Lepisto, Treehugger, 2011-12-18
First of all, kudos to Iain Couzin and his team at Princeton for an elegant bit of research using shiner fish to validate computer models exploring the effect of the uninformed population on consensus when opposing minority interests threaten to doom decision making.
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Brunei Times, 2011-12-17
It might sound fishy, but researchers at Princeton University say minnows make perfect lab rats when it comes to exploring the surprising power of the uninformed in group decision-making.
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Eberhard Lauth, The European, 2011-12-17
Uninformierte und Ungebildete können sich jederzeit von Modernisierungsverlierern zum entscheidenden Faktor für Umbrüche entwickeln. Das ist gerade jetzt wichtig. Und die Fische machen es vor.
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St. Albert Gazette, 2011-12-17
A new study suggests that uninformed voters may help, not hinder, democratic decisions.
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Gill Eapen , Scientific Sense, 2011-12-16
A recent study shows that some percentage of uninformed (ignorant) individuals promote democratic consensus in animal groups. This is a very interesting finding as the same appears to be true in complex human societies as well. Through theory and experiments, the article demonstrates that the presence of uninformed individuals inhibit the process of domination by a strongly opinionated minority. If the strongly opinionated minority is pushing toward an optimal outcome for the system, ignorant participants will slow them down.
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Kate Shaw, Wired, 2011-12-16
How do groups of animals make collective decisions? Last week, we learned that bees reach consensus by headbutting those with opposing views. But in many other species, the decision-making process is a bit more democratic. In cases where social animals are unrelated and have different self-interests (such as our own), contrasting opinions are common. But it can be just as common for individuals to either be uninformed about the options, or simply not care much about the decision.
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BBC.co.uk, 2011-12-16
Disinterested individuals are vital for achieving a democratic consensus, according to a study in the journal Science.
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Emily Badger, Miller-McCune, 2011-12-15
In a lesson taught by schools of fish, researchers determine that uninformed individuals are actually a benefit to democracy by sanding off extreme views.
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Susan Milius, ScienceNews, 2011-12-15
Decisions can be more democratic when individuals with no preset preference join a group
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Paul Basken, The Cronicle of higher education, 2011-12-15
As Congress proves itself increasingly dysfunctional and captive to extremists, lots of people may be asking themselves: What kind of fish-brained voters keep electing these guys?
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AFP, ABC Science, 2011-12-15
It might sound fishy, but US researchers say minnows make perfect lab rats when it comes to exploring the surprising power of the uninformed in group decision-making.
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Science Daily, 2011-12-15
Contrary to the ideal of a completely engaged electorate, individuals who have the least interest in a specific outcome can actually be vital to achieving a democratic consensus.
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Eva Obermüller, ORF.at, 2011-12-15
Der mündige und informierte Bürger ist Grundlage jeder funktionierenden Demokratie, so die gängige Annahme. Eine Studie besagt hingegen: Unwissende, interesselose Individuen sind ebenso wichtig für den demokratischen Konsens.
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Joseph Castro, LiveScience, 2011-12-15
Ignorance can be bliss, but it seems it can also promote democracy.
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Joseph Castro, MSNBC.com, 2011-12-15
Minority can persuade majority, until the unknowing come along, study finds.
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AFP, Ottawa Citizen, 2011-12-15
It might sound fishy, but researchers at Princeton University say minnows make perfect lab rats when it comes to exploring the surprising power of the uninformed in group decision-making.
(more)

Improbable Research, 2011-12-15
A democracy without a substantial number of uninformed individuals, may not know what it’s doing, metaphorically speaking. So implies this new study
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Sabiene Sütterlin, Science Blogs, 2010-08-26
Seit ich mit der Netzwerk-Gruppe zu tun habe, sehe ich überall Netzwerke. Die Leser dieses Blogs sind teilweise untereinander vernetzt, zum Beispiel. Und die Nervenzellen in unseren Gehirnen knüpfen stets neue Verbindungen
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