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INSECT POPULATION ECOLOGY

READ: T&J pp 95-97

REFERENCES:

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.

 

Potential for population increase - link to my population ecology page

r = instantaneous birth rate Ė instantaneous death rate (% increase)

R0 = net replacement rate (daughters/female/generation) determined by survivorship and maternal frequency

doubling time

Population growth

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

Factors limiting insect populations & determining commonness or rarity

Limiting or controlling factors must be density-dependent

resource competition

food - quantity, quality

space

enemies

Effects of weather & climate

donít 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