Food webs 2: commmunity ecology and interaction networks Flashcards
What is ecological network analysis?
Study of ecological systems using network models and analysis to characterize their structure, function and evolution
What does a node represent in ecological systems?
individual species or population or functional group
What do links represent in ecological systems?
Interactions between nodes
What are three ways of characterizing links?
1) Topology: how are links arranged
2) Geometry: includes distance between nodes, therefore the importance of the interaction
3) Direction and stregth: differentiates interactions
What are different types of interaction?
1) Presence/absence
2) directed networks
3) interaction sign (+ or -)
4) Weighted networks: strength assigned to links
What is defined by the number of nodes in the foodweb?
Species richness
What defines network complexity?
Connectance and linkage density
What is the ‘proportion of directed links realized out of the maximum number of possible links’ called?
Connectance
What is the ‘number of trophic interactions’ called?
Linkage density
What is the ‘count of number of interactions established by a species’ called?
Degree centrality
What does mean shortest path define in a network?
Stability, shorter chain is more stable
What is vulnerability?
Number of consumers
What is ‘number of resources per taxa’ called?
Generality
What do trophic levels represent?
Energy steps that are taken to reach higher up in the food web
What is omnivory?
Variability in trophic levels of preys
What is degree distribution?
Defines variability of linkage density and how equally distributed connections are in the system
How is a centralized network organized?
Has high degree distribution, with few central nodes with many connections and others with few
What term describes the extent to which the network can be divided into non-overlapping grups of highly interacting species within their local neighborhood?
Modularity
What are the components of node-weighted dynamics?
Connectance, vulnerability, generality, trophic level
What does ‘node-weighted’ mean?
Averaged/weighted by biomass
What is a keystone species?
A species with high centrality in the ecosystem
What is the keystone index?
Indicates how fundamental their role is in the ecosystem as compared to their number
What is ecological resilience?
The amount of disturbance that a system can withstand without changing into an alternate stable state
What is engineering resilience?
Time required for the system to come back to equilibrium or steady state after the system has been perturbed
How is a ‘state’ defined?
COmbination of function, structure, identity and feedbacks
What characterizes most resilient foodwebs?
Abundant weak links and high diversity
What is network robustness used for?
Measure food web resilience. Measures potential impacts of extiction on food webs and proposes an index of resilience
What is the System Omnivory Index?
Index that quantifies the interactions among the trophic levels. High omnivory increases resilience
What determines a major role in pattern and strength of trophic interactions within the foodweb?
Body size
How does climate change impact marine food webs?
Biogeographic shift
Body size
Phenological shift (nature clock)
Average sea level rise
