READ: T&J pp 95-97
Carey, James R.. 1993. Applied Demography for Biologists. New York. Oxford Univ. Press. 206pp.
Day, W.H.. 1994. Estimating mortality caused by parasites and diseases of insects.... Environ. Entomol. 23: 543-550.
Dwyer, G. et al. 2004. The combined effects of pathogens and predators on insect outbreaks. Nature 430, 341 - 345 (15 July)
Gaston, K.J. 1988. The intrinsic rates of increase of insects of different sizes. Ecological Entomology 14: 399-409
Meyers. J. 1998. Synchrony in outbreaks of forest lepidoptera... Ecology 79: 1111-1117.
Miller, W. 1996. Population behavior and adult feeding capability in lepidoptera. Environ Entomol 25: 213-226.
Price, P.W. Insect Ecology various editions (on reserve)
Roland, J. 1994. After the decline: what maintains low winter moth density... J Anim Ecol 63: 392-398.
r = instantaneous birth rate – instantaneous death rate (% increase)
R0 = net replacement rate (daughters/female/generation) determined by survivorship and maternal frequency
doubling time
In unlimited environment, populations grow exponentially
Nt = N0ert
POPULATION STATISTICS FOR VARIOUS SPECIES
Odum, E.P. 1971. Fundamentals of Ecology. Philadelphia. Saunders. p 182.
|
Organism & environment |
Rate of Increase (r) |
Mean Generation time (weeks) |
Net reproductive rate (Ro) |
Finite rate of increase ( l) |
Doubling time |
||
|
|
per wk |
per yr |
|
|
per wk |
per yr |
|
|
Rice weevil Calandra 23oC |
0.43 |
22.4 |
10.6 |
96.58 |
1.54 |
5.34x108 |
1.61wk |
|
29oC |
0.76 |
39.6 |
6.2 |
113.56 |
2.14 |
1.58x1016 |
0.91wk |
|
33.5oC |
0.12 |
6.2 |
9.2 |
3.38 |
1.13 |
493 |
5.78wk |
|
Flour beetle Tribolium |
0.71 |
36.8 |
7.9 |
275 |
2.03 |
1.06x1015 |
0.96wk |
|
Human louse Pediculus |
0.78 |
40.6 |
4.4 |
30.93 |
2.18 |
4.27x1016 |
0.88wk |
|
Vole Microtus
|
0.088 |
5.4 |
20.2 |
5.9 |
1.09 |
90 |
7.90wk |
|
Brown rat Rattus |
0.104 |
5.4 |
31.1 |
25.66 |
1.11 |
221 |
6.76wk |
|
Human World 1968 |
|
0.02 |
|
|
|
1.202 |
34.7yr |
Social insect colonies do not grow exponentially
limited birth rate - only one reproducing individual
must look at dynamics of number of colonies
Limiting or controlling factors must be density-dependent
resource competition
food - quantity, quality
space
enemies
Effects of weather & climate
don’t directly limit
may impose large, non-regulatory mortality
Factors which set (legislate) resource levels are the ultimate determinates of commonness and rarity of species
Risk accepting vs. risk avoiding - all eggs in one basket?
eruptive species often risk takers
species that spread risk show less fluctuation
Do insect populations exhibit chaotic dynamics?
Gypsy moth, and many other insects - very unstable behavior if r is large