- Anusha Uppaluri
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ContentsProblemProblems ImportanceResearch MethodologyData CollectionConclusionReferencesQuestions
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Problem
Food Webs – Complex networks formed by one species of animals feeding on the other species
Target Groups – Species of animals which when extinct cause the near extinction/ extinction of a large number of species of animals
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Problems ImportanceFood webs make a very complex network and its understanding would be interestingInterdependence of species in food web is important to maintain balanceHelps in understanding the do’s and don'ts in trying to preserve our environment and ecosystem
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Research Methodology
Main question: Eliminating what nodes in the food web network would cause the maximum shattering of the networks stability
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Collect data from recent related literature and recreate network
Pajek can be used for network creation and analysis
Nodes in the network are eliminated according to a certain criteria
Reaction of the remaining network is judged Robustness of the remaining network is
calculated 6
Step I Elimination of nodes can also be done on a
random basis Nodes are removed randomly Network reaction is judged based on
robustness The species that cause the steepest plunge in
robustness can be focused
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Random node removal though not of much help might help with new ideas and give the simulation a new direction
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Step II Nodes can be eliminated on the basis of their
indegree centraility Indegree centrality of all the nodes is calculated The nodes with the highest indegree centrality
are eliminated first and so on After each elimination the robustness of the
remaining network is calculated
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The species that causes the steepest plunge in robustness upon its elimination is zeroed in on
Intuition behind using indegree centrality: if a species is being fed on by many other animals then it is an important part of the network
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Step III Nodes can be eliminated on the basis of their
betweeness centraility aswell Previously mentioned process is eliminated
while considering betweeness centrality The intution behind using betweeness centrality
is, is a node is on several shortest paths between pairs several other nodes => it is important to maintain the balance in the system
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The answers obtained from the above III steps are analyzed to reach a final conclusion
Any further experimentation is done if needed
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Data Collection
Food web data sets The problem is the above data sets are too
small Working with them would give an initial idea of
what the network reacts like and what the answers could be
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Focus on recent sources of data and recent related literature
Older sources of data were found to be weak and incomplete
Main data to be obtained from the literature studied
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Conclusion
Collect data from recent literature and recent data source
Reconstruct the network using Pajek Follow a III step process Eliminate nodes on a random basis and
analyze the reaction of the network Eliminate the nodes on indegree centrality basis
and analyze the reaction of network
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Eliminate the nodes on the basis of betweenness centrality and analyze the reaction of the network
Use the results found in the above III step process to either reach the conclusion or to perform any further experimentation as needed
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ReferencesDunne J. A., Williams R. J., Martinez N. D., “ Food-web structure and network theory: The role of connectance and size”, Proceedings of National Academy of Sciences of United States of America, Vol. 99 No. 20, pp. 12917-12922, 2002Dunne J. A., Williams R. J., Martinez N. D., “ Network structure and biodiversity loss in food webs: robustness increases with connectance”, Ecology Letters, Vol. 5, pp. 558-567, 2002Gilbert A.J., “ Connectance indicates the robustness to food webs when subjected to species loss”, Ecological Indicators, Vol. 9, pp. 72-80, 2009
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Questions?
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