Population Interactions

Trophic Interactions

Predation

Herbivory

Parasitism

Competition

Commensalism

Mutualism

Interspecific Competition

Classic Competition Theory

Lotka-Volterra

Start with the Logisitc model

DN₁/dt =r₁N₁(K₁-N₁-µN₂)/K₁

DN₂/dt =r₂N₂(K₂-N₂-µN₁)/K₂

Figure 14.1

a, b absence of competion

c, d: species with higher K always wins

e: iosclines cross, each

species inhibits other (interspecific)

more than self (intraspecific)

f: interspecific < intraspecific

Assumptions of the models

1) environment is homogeneous and stable

2) migrtion unimportant

3) competition effect is instantaneous

4) coexistance requires a stable equilibrium point

5) competition only biological interaction

Ecological Niche: multidimensional space

Fundamental niche, realized niche

Competitive Exclusion (Figure c, d)

Gause’s competitve exclusion priniciple

Easy to demonastrate in the lab

Paramecium Fig 14.4; diatoms Figure 14.5

Difficult to find evidence in nature

Golden navel Scale suckers

Corals

Black Ducks Fig 14.7

Resource partitioning and niche overlap

Character Displacement: Weasels, Finches

Shrimp

Niche as a dynamic concept:Mar. Biol. 1995. 124:341-