Download Predator-Prey Experiments

Experimental Ecology
Controls
Manipulation
Replicates
Pseudoreplication
Rocky Intertidal Space Limited System
Paine’s Pisaster removal experiment
Connell: Balanus and Chthamalus
Menge’s Leptasterias and Pisaster experiment
Dunham’s Big Bend saxicolous lizards
Brown’s Seed Predation experiments
R. T. Paine
(1966)
Joseph Connell
(1961)
Bruce Menge
(1972)
Menge 1972
Bruce Menge
Grapevine Hills, Big Bend National Park
Sceloporus merriami and Urosaurus ornatus
Arthur Dunham
Six rocky outcrops: 2 controls, 2 Sceloporus removal
plots and 2 Urosaurus removal areas.
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4 year study: 2 wet and 2 dry: insect abundances
Monitored density, feeding success, growth rates, body weights, survival, lipid
levels
Urosaurus removal did not effect Sceloporus density
No effects during wet years (insect food plentiful)
Insects scarce during dry years: Urosaurus growth and survival
was higher on Sceloporus removal plots
James Brown
Experimental Design of Seed Predation in the Chihuahuan Desert
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Plots
Treatments
___________________________________________________
11,14 Controls
6,13
Seed addition, large seeds, constant rate
2,22
Seed addition, small seeds, constant rate
9,20
Seed addition, mixed seeds, constant rate
1,18
Seed addition, mixed seeds, temporal pulse
5,24
Rodent removal, Dipodomys spectabilis (largest kangaroo rat)
15,21 Rodent removal, all Dipodomys species (kangaroo rats)
7,16
Rodent removal, all seed-eating rodents
8,12
Pogonomyrmex harvester ants
4,17
All seed-eating ants
3,19
All Dipodomys plus Pogonomyrmex ants
10,23 All seed-eating rodents plus all seed-eating ants
___________________________________________________________
Munger, J. C. and J. H. Brown. 1981. Competition in desert rodents: an experiment
with semipermeable enclosures. Science 211: 510-512.
open circles =
rodents removed
solid circles =
controls
Simberloff and Wilson 1970
Evidence for Stability of Trophic Structure? First number is the number
of species before defaunation, second in parentheses is the number after
_____________________________________________________________________________
Trophic Classes
____________________________________________________________
Island
H
S
D
W
A
C
P
?
Total
_____________________________________________________________________________
E1
9 (7) 1 (0)
3 (2)
0 (0)
3 (0)
2 (1)
2 (1)
0 (0)
20 (11)
E2
11 (15) 2 (2)
2 (1)
2 (2)
7 (4)
9 (4)
3 (0)
0 (1)
36 (29)
E3
7 (10) 1 (2)
3 (2)
2 (0)
5 (6)
3 (4)
2 (2)
0 (0)
23 (26)
ST2
7 (6) 1 (1)
2 (1)
1 (0)
6 (5)
5 (4)
2 (1)
1 (0)
25 (18)
E7
9 (10) 1 (0)
2 (1)
1 (2)
5 (3)
4 (8)
1 (2)
0 (1)
23 (27)
E9
12 (7) 1 (0)
1 (1)
2 (2)
6 (5)
13 (10) 2 (3)
0 (1)
37 (29)
Totals 55 (55) 7 (5) 13 (8)
8 (6) 32 (23)
36 (31) 12 (9)
1 (3) 164 (140)
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H = herbivore
S = scavenger
D = detritus feeder
W = wood borer
A = ant
C = carnivorous predator
? = undetermined
Wilson 1969
Predation and Parasitism
Predator-Prey Experiments
Georgii F. Gause
Predator-Prey Experiments
Georgii F. Gause
Predator-Prey Experiments
Georgii F. Gause
Lotka-Volterra
Predation Equations
coefficients of predation,
p1 and p2
Alfred Lotka
Vito Volterra
dN1 /dt = r1 N1 – p1 N1 N2
dN2 /dt = p2 N1 N2 – d2 N2
No self damping (no density dependence)
dN1 /dt = 0 when r1 = p1 N2 or N2 = r1 / p1
dN2 /dt = 0 when p2 N1 = d2 or N1 = d2 / p2