Ecological Networks

Question 1

Interspecific interactions are important for?

Answer 1

Structuring community via selection

Ecological functions/process e.g. nutrient cycling

Response to perturbation

Question 2

Name 2 types of network

Answer 2

Mutualistic networks

Multiplex networks

Question 3

Bipartite network?

Answer 3

Organisms split into two groups

Species can only belong to one h

Question 4

3 ways you could record interactions

Answer 4

Take a transects and record the number of certain interactions there

Take certain individuals from one species and record how many times they interact with other species

If looking at diet, could dissect and investigate gut contents (easier if they eat vertebrates…bones)

Question 5

What are the different levels of describing networks

Answer 5

1. Network level
   - species richness
   - food chain length
   - connect at
2. Species level
   - degree and diversity of link
3. Link-level
   - interaction strength and frequency

Question 6

Link degree=?

Answer 6

How many species they interact with

Question 7

Link diversity=?

Answer 7

Is their relationship equally spread across species.

Or strong with one and weak with others

Question 8

What’s a null model?

Answer 8

Ignores all known traits about species
Predicts how often interactions should occur based purely on species abundance
Red = stronger, blue= weaker, white = equal

Question 9

Link between body size and food webs

Answer 9

Size + optimality = allometric diet breadth model (Petchey et al 2008)
- species feed on smaller
Trade off between prey size and handling time
Needs to be energy efficient
- often correctly predicts food webs

Question 10

Practical applications of network

Answer 10

• Can investigate indirect inter-specific effects e.g. trophic cascades
• see broader ramifications of individ species changes
• investigate effects of invasions and extinctions

Question 11

Network level effects of extinctions

Answer 11

local scale extinctions can be frequent

• may not be long term but a species decline for certain year potential impacts on ecological processes & ecosystem services
• can model the effects with networks: using computer system that removes species on by one

Question 12

What can change the impact of extinctions on networks

Answer 12

• Robustness a.k.a number of secondary extinctions
• if extinct species a specialist or generalist
• order you remove species (least to most connected increases robustness)
• the number of connections in network

Question 13

The ways to cope with species loss

Answer 13

Rewiring: interacting with new species

Re-weighting: existing weak links strengthen

Question 14

What information can you gain from next-gen robustness models

Answer 14

Urban plant-pollinator networks
Landscape scape networks
Processes inc. rewiring and dispersal among habitats
Relationships between robustness and increasing habitat area

Question 15

How to build a network

Answer 15

1. Record interactions
2. Build a matrix (pairwise comparison of species)
   - interaction = 1
   - no interaction = 0
   - info read into computer to create network

Question 16

Weakness of connectance networks

Answer 16

Don’t quantity the strength of the links 
Cannot tell:
- main energy/nutrient channels 
- affect of links on stability 
- key diet of predators