1. Disturbance

2. Hypotheses Equilibrium Dynamic Equilibrium Intermediate Disturbance
Island biogeography
Robert MacArthur and E. O. Wilson
Dynamic Equilibrium
Michael Huston 1979
Intermediate Disturbance
Joe Connell 1978 and earlier (+ Hutchinson, etc.)
Wayne Sousa (< 1984)
Colin Townsend et al. 1997

3. Ward

7. Perturbation = disturbance + response
Disturbance = the “force”
Physical
Biological?
Response
Biological
Community/Assemblage
Population
Physical as well

8. From Sousa (1984)

9. Downes et al. 2002

10. Press vs. Pulse
Downes et al. 2002

11. What Level of Biological Organization Responds
Can be any
Community
Assemblage
Grouped
Taxonomic
FFGs
Population
Organism

12. When push comes to shove
Population
When push comes to shove

13. Population Growth Concepts
Exponential  Malthus
Non-overlapping (i.e., most bugs)
Nt+1 = NtR (R = offspring/survivor)
Or  dN/dt = rN
r = birth - death
Logistic  Verhulst-Pearl: limiting factors
Nt+1 = Nt * exp [R0 * (1- Nt/K)]
Or  dN/dt = rN * [(K-N)/K]

14. Possible Outcomes Parameter r is: 1. Malthusian parameter
2. Intrinsic rate of increase
3. Population growth rate
And represents r = birth - death
r > 0
r = 0
r < 0
Alexei Sharov

15. But also – What limits K (carrying capacity)
Many interactions within and between:
Abiotic (resources and constraints)
Habitat (temperature, space, etc.)
Biotic (resources and constraints)
Food
Competition/Predation

16. What We Really Need To Do
Better understand those factors responsible for mortality
Key factor analysis
Morris (and Miller)
K-factor analysis
Varley and Gradwell
Used in forestry and agricultural settings

17. Survivorship

18. Cumulative Numbers
Hynes 1970

19. In “reality” What factors may influence the estimates?
Variable time/instar within population
Spatial variability
Sampling error
Benke 1984

20. Growth
Benke 1984

21. Temperature
Sweeney 1984