Ch. 12 Interspecific Competition

Competition

interactions between individuals that have a negative effect on the fitness of the interacting individuals

interspecific

between species

Resource competition

competition for a limited resource such as food, space, or nesting sites

Interference competition

When species engage in direct antagonism/direct aggressive acts

Allopathic activity

secreting secondary chemicals that are antagonistic to other plants (Active carbon binds allelochemicals

Competitive exclusion principle

different species cannot coexist in a community if they are competing for all the same resources (Population that uses the resources more efficiently will have a reproductive advantage and eliminate the other population)

Models of competition

dN/dt-=rN(K-N)/K : describers population growth rates at any point in time

competition coefficients

the per capita competitive effect of one species on the other

a₁₂

Per capita competitive effect of species 2 on species 1

Model of competition with interspecific competition

dN₁/dt = r₁N₁(K₁-N₁-a₁₂*N₂)/K₁

Small a value

(<1) stronger infraspecific competition than interspecific competition

large a value

(>1) stronger interspecific competition than intraspecific competition

Zero net growth isocline (ZNGI)

line of equilibrium that describes dynamics of competition

dN/dt = 0

Values of N₁ and N₂ that yield zero population growth for both species

Lotka-Volterra model

add two isoclines to the same figure, predicts which species will win in a competition

assumptions of constant values of r, k, and a, does not take into account the mechanism of competition

Factors favoring coexistence

Environmental variation, niche partitioning, and niche shift

niche partitioning

ecologically similar species coexisting by using different resources or specializing in different factors in the environment

niche shift

adaptive change in one or more niche dimensions

Apparent competition

indirect interaction, each prey species has an indirect negative effect on the other by having a positive effect on the predator