One organism inhibits another by consuming a shared nutrient resource
Consumptive
One organism occupies space, preventing another from having it
Preemptive
One organism grows directly over another.
Overgrowth
Chemical warfare between competitors
Chemical (allelopathy)
Aggressive behavioral exclusion of an organism from another’s defended territory
Territorial
non-territorial encounters reducing growth.
Encounter
The outcome of competition is often determined by
competition for the limiting resource
limitations on growth determined by the availability of the scarcest resource
Liebig’s law of the minimum
resources species could utilize in the absence of other species
niche absent of competition
Fundamental niche
resources actually utilized by the species after the effects of all species
niche with competition
Realized niche
The greater the niche overlap between two competitors the
Fig 14.3
greater the competition
The lower the abundance of the resources the
Fig 14.3
greater the competition
The effects of competing species are not equal
interaction betw 2 species (ammensalism)
Asymmetric competition
Stems from Asymmetric competition: one species is affected negatively and the other isnt
Amensalism
Experiment 1: with P Caudatum and P. Bursaria that were grown both together and isolated demonstrated
Fig 14.9
Competitive coexistence
Why did competitive coexistence happen between those two?
Fig 14.9
P. caudatum consumed only bacteria while P. bursaria was able to consume both bacteria and yeast.
Experiment 2: P. caudatum and P. aurelia were grown both in isolation and together, demonstrated
Fig 14.9
competitive exclusion
Why did competitive exclusion happen between those two?
Fig 14.9
P. caudatum and P. auralia both consumed only bacteria, and P. auralia was the superior competitor for bacteria
Modified version of Gause: Competitive exclusion principle
Resource partitioning (niche partitioning)
- Ex. Anolis Lizards
Competitors that use a limiting resource in the same cannot coexist
Lotka and Volterra modified logistic equation
dN/dt = rN(K– N)/K
r= maximum growth rate
N= actual population size
K= carrying capacity
What does Lotka Volterra model tell us about competitive coexistence?
Competing species coexist when they do not compete with each other
SLIDE 30 Equation
XXXX READ SLIDES XXXX
If α > 1.0, then sp. 2 individuals carry
greater weight than
sp. 1 individuals.
If α = 1.0, then sp. 2 individuals
carry
the same weight as sp. 1 individuals.
If α < 1.0,
then sp. 2 individuals carry
less weight than sp. 1 individuals.
Zero growth isocline tells us that
On the isocline, dN 1/dt= 0,
so N 1 does not change.
• In
the blue zone, dN 1/dt is
negative, so N 1 decreases.
• In
the yellow zone, dN 1/dt is
positive, so N 1 increases
G. Tansley Experiment with Galium saxatile and Galium sylvestre resulted in
Each species was at a disadvantage in competition when not grown on their preferred soil type.
Takeaway: The outcome of competition between species can depend on the environment.