- Anusha Uppaluri

1

ContentsProblemProblems ImportanceResearch MethodologyData CollectionConclusionReferencesQuestions

22

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

3

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

44

Research Methodology

Main question: Eliminating what nodes in the food web network would cause the maximum shattering of the networks stability

5

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

7

Random node removal though not of much help might help with new ideas and give the simulation a new direction

8

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

9

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

10

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

11

The answers obtained from the above III steps are analyzed to reach a final conclusion

Any further experimentation is done if needed

12

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

13

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

14

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

15

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

16

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

1717

Questions?

1818